rules for iupac nom e nclatu r e -...

RULES FOR IUPAC NOMENCLATURE A

Project Report

For Elective Subject

Submitted

To Hemchandracharya North Gujarat University

Patan.

In Partial Fulfillment of the Requirement for the Degree of

Bachelor of Pharmacy YYeeaarr:: 22000066--22000077

Submitted By,

BHAVESH B. PATEL

Shree S.K.Patel College of Pharmaceutical

Education & Research

Ganpat Vidyanagar,

Kherva-382711 gnu.i

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CERTIFICATE

This is to certify that the project report for the elective subject entitled

‘RULES FOR IUPAC NOMENCLATURE ’ is the bonafide work of

BHAVESH B. PATEL satisfactorily carried under my guidance and

supervision in the Department of Pharmaceutical Chemistry, Shree

S.K.Patel College of Pharmaceutical Education and Research, Ganpat

Vidyanagar, during the academic year 2006-2007.

Guide:

Dr. S.A.Patel M.Pharm,Ph.D. Assistant professor,

Department of Pharmaceutical Chemistry,

Shree S.K. Patel College of Pharmaceutical Education & Research,

Ganpat Vidyanagar.

Head of the department:

Dr. P.U.Patel M.Pharm,Ph.D. Assistant professor,

Department of Pharmaceutical Chemistry,


Ganpat Vidyanagar.

Principal:

Dr. M.M.Patel M.Pharm, Ph.D, LLB, FIC.

Department of Pharmaceutical Technology,


Ganpat Vidyanagar.

Date:

Place:

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ACKNOWLEDGEMENT First I would like to express my salutation to GOD for giving me the

strength, confidence and moral boost to successful completition of this

project.

In preparing this book I have received great help and support from many of

my teachers and my friends in a number of ways. I take this opportunity to

thank all of them but in particular to following:

My guide Dr. S.A.Patel for their encouraging guidance and support. He has

shared thoughts and critical comments on manuscript. He paid his valuable

suggestions on the manuscript.

Hon. HOD Dr. P.U.Patel and other respected teachers for giving me

inspiration and their ideas.

Dr. M.M.Patel, Principal for providing me extraordinary infrastructure and

research facilities at the college.

Librarian Mr.P.I.Patel for their full co-operation and support.

I am thankful to my parents, brothers and sisters in law who led me from

darkness to light, ignorance to enlighten and confusion o clarity throughout

my life.

“Your sorrow get divided and your happiness get multiplied with your friends”

It way all my friends Hardik, Gaurang, Alpesh and Dhaval who help me in

hardship through the sweet fragrance of freinship without which I could

not have won all the battles.

GANPAT VIDYANAGAR BHAVESH B.PATEL 2006-07 FOURTH B.PHARM

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INDEX Sr.No. Title Page

No. 1. 2. 3. 4. 5. 6.

Introduction – Naming organic compound

Recommendations 1979

A. Hydrocarbons

- Acyclic Hydrocarbons

- Monocyclic Hydrocarbons - Fused Polycyclic Hydrocarbons - Bridged Hydrocarbons (Extension of the Von

Baeyer Sistem) - Spiro Hydrocarbons

- Hydrocarbon Ring Assemblies

- Cyclic Hydrocarbons with Side Chains

B. Bridged Heterocyclic Systems


R-1 General Principles of Organic Nomenclature

R-1.2 Nomenclature Operations - R-1.2.1 Substitutive operation

- R-1.2.2 Replacement operation

- R-1.2.3 Additive operation

- R-1.2.4 Conjunctive operation

- R-1.2.5 Subtractive operation

- R-1.2.6 Ring formation or cleavage

Characteristic (Functional) Groups

References

1 10

11. 24. 30 41

43 48 54 57 64 65 65 67 68 69 70 71 74

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Introduction:- Naming Organic Compounds

The increasingly large number of organic compounds identified with each passing

day, together with the fact that many of these compounds are isomers of other compounds,

requires that a systematic nomenclature system be developed. Just as each distinct

compound has a unique molecular structure which can be designated by a structural

formula, each compound must be given a characteristic and unique name.

As organic chemistry grew and developed, many compounds were given trivial names,

which are now commonly used and recognized. Some examples are:

Name Methane Butane Acetone Toluene Acetylene Ethyl Alcohol

Formula CH4 C4H10 CH3COCH2 CH3C6H5 C2H2 C2H5OH

Such common names often have their origin in the history of the science and the natural

sources of specific compounds, but the relationship of these names to each other is

arbitrary, and no rational or systematic principles underly their assignments1

The IUPAC Systematic Approach to Nomenclature

A rational nomenclature system should do at least two things. First, it should

indicate how the carbon atoms of a given compound are bonded together in a characteristic

lattice of chains and rings. Second, it should identify and locate any functional groups

present in the compound. Since hydrogen is such a common component of organic

compounds, its amount and locations can be assumed from the tetravalency of carbon, and

need not be specified in most cases.

The IUPAC nomenclature system is a set of logical rules devised and used by

organic chemists to circumvent problems caused by arbitrary nomenclature. Knowing

these rules and given a structural formula, one should be able to write a unique name for

every distinct compound. Likewise, given a IUPAC name, one should be able to write a

structural formula. In general, an IUPAC name will have three essential features:

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• A root or base indicating a major chain or ring of carbon atoms found in the

molecular structure.

• A suffix or other element(s) designating functional groups that may be present in

the compound.

• Names of substituent groups, other than hydrogen, that complete the molecular

structure.

As an introduction to the IUPAC nomenclature system, we shall first consider

compounds that have no specific functional groups. Such compounds are composed only

of carbon and hydrogen atoms bonded together by sigma bonds (all carbons are sp3

hybridized).

An excellent presentation of organic nomenclature is provided on a Nomenclature

Page. Created by Dave Woodcock. A full presentation of the IUPAC Rules is also

available8.

.

Alkanes

Hydrocarbons having no double or triple bond functional groups are classified as

alkanes or cycloalkanes, depending on whether the carbon atoms of the molecule are

arranged only in chains or also in rings. Although these hydrocarbons have no functional

groups, they constitute the framework on which functional groups are located in other

classes of compounds, and provide an ideal starting point for studying and naming organic

compounds. The alkanes and cycloalkanes are also members of a larger class of

compounds referred to as aliphatic. Simply put, aliphatic compounds are compounds that

do not incorporate any aromatic rings in their molecular structure.

The following table lists the IUPAC names assigned to simple continuous-chain alkanes

from C-1 to C-10. A common "ane" suffix identifies these compounds as alkanes. Longer

chain alkanes are well known, and their names may be found in many reference and text

books. The names methane through decane should be memorized, since they constitute

the root of many IUPAC names. Fortunately, common numerical prefixes are used in

naming chains of five or more carbon atoms.

Name Molecular

Formula

Structural

Formula Isomers Name

Molecular

Formula

Structural

Formula Isomers

methane CH4 CH4 1 hexane C6H14 CH3(CH2)4CH3 5

ethane C2H6 CH3CH3 1 heptane C7H16 CH3(CH2)5CH3 9 gnu.i

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propane C3H8 CH3CH2CH3 1 octane C8H18 CH3(CH2)6CH3 18

butane C4H10 CH3CH2CH2CH3 2 nonane C9H20 CH3(CH2)7CH3 35

pentane C5H12 CH3(CH2)3CH3 3 decane C10H22 CH3(CH2)8CH3 75

Some important behavior trends and terminologies:

(i) The formulas and structures of these alkanes increase uniformally by a CH2

increment.

(ii) A uniform variation of this kind in a series of compounds is called

homologous.

(iii) These formulas all fit the CnH2n+2 rule. This is also the highest possible H/C

ratio for a stable hydrocarbon.

Beginning with butane (C4H10), and becoming more numerous with larger alkanes,

we note the existence of alkane isomers. For example, there are five C6H14 isomers, shown

below as abbreviated line formulas (A through E):

Although these distinct compounds all have the same molecular formula, only one

(A) can be called hexane. How then are we to name the others?

The IUPAC system requires first that we have names for simple unbranched

chains, as noted above, and second that we have names for simple alkyl groups that may be

attached to the chains. Examples of some common alkyl groups are given in the following

table. Note that the "ane" suffix is replaced by "yl" in naming groups. The symbol R is

used to designate a generic (unspecified) alkyl group.

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I IUPAC Rules for Alkane Nomenclature

1. Find and name the longest continuous carbon chain.

2. Identify and name groups attached to this chain.

3. Number the chain consecutively, starting at the end nearest a substituent group.

4. Designate the location of each substituent group by an appropriate number and name.

5. Assemble the name, listing groups in alphabetical order.

The prefixes di, tri, tetra etc., used to designate several groups of the same kind, are not considered when alphabetizing.

For the above isomers of hexane the IUPAC names are: B 2-methylpentane C 3-

methylpentane D 2,2-dimethylbutane E 2,3-dimethylbutane

Halogen substituents are easily accomodated, using the names: fluoro (F-), chloro (Cl-),

bromo (Br-) and iodo (I-). For example, (CH3)2CHCH2CH2Br would be named 1-bromo-3-

methylbutane. If the halogen is bonded to a simple alkyl group an alternative "alkyl halide"

name may be used. Thus, C2H5Cl may be named chloroethane (no locator number is

needed for a two carbon chain) or ethyl chloride.

For additional examples of how these rules are used in naming branched alkanes, and

for some sub-rules of nomenclature .

Cycloalkanes

Cycloalkanes have one or more rings of carbon atoms. The simplest examples of this

class consist of a single, unsubstituted carbon ring, and these form a homologous series

similar to the unbranched alkanes. The IUPAC names of the first five members of this

series are given in the following table. The last (yellow shaded) column gives the general

formula for a cycloalkane of any size. If a simple unbranched alkane is converted to a

cycloalkane two hydrogen atoms, one from each end of the chain, must be lost. Hence the

general formula for a cycloalkane composed of n carbons is CnH2n.

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Examples of Simple Cycloalkanes9

Name Cyclopropane Cyclobutane Cyclopentane Cyclohexane Cycloheptane Cycloalkane

Molecular

Formula C3H6 C4H8 C5H10 C6H12 C7H14 CnH2n

Structural

Formula

(CH2)n

Line

Formula

Substituted cycloalkanes are named in a fashion very similar to that used for naming

branched alkanes. The chief difference in the rules and procedures occurs in the numbering

system. Since all the carbons of a ring are equivalent (a ring has no ends like a chain does),

the numbering starts at a substituted ring atom.

Rules for Cycloalkane Nomenclature

1 For a monosubstituted cycloalkane the ring supplies the root name (table above) and the substituent group is

named as usual. A location number is unnecessary.

2. If the alkyl sustituent is large and/or complex, the ring may be named as a substituent group on an alkane.

3. If two different substituents are present on the ring, they are listed in alphabetical order, and the first cited

substituent is assigned to carbon #1. The numbering of ring carbons then continues in a direction (clockwise or

counter-clockwise) that affords the second substituent the lower possible location number.

4. If several substituents are present on the ring, they are listed in alphabetical order. Location numbers are

assigned to the substituents so that one of them is at carbon #1 and the other locations have the lowest possible

numbers, counting in either a clockwise or counter-clockwise direction.

5. The name is assembled, listing groups in alphabetical order and giving each group (if there are two or more) a

location number. The prefixes di, tri, tetra etc., used to designate several groups of the same kind, are not

considered when alphabetizing.

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For examples of how these rules are used in naming substituted cycloalkanes .

Hydrocarbons having more than one ring are common, and are referred to as bicyclic (two rings),

tricyclic (three rings) and in general, polycyclic compounds. The molecular formulas of such compounds

have H/C ratios that decrease with the number of rings. In general, for a hydrocarbon composed of n

carbon atoms associated with m rings the formula is: CnH(2n + 2 - 2m). The structural relationship of rings in

a polycyclic compound can vary. They may be separate and independent, or they may share one or two

common atoms. Some examples of these possible arrangements are shown in the following table.

Examples of Isomeric C8H14 Bicycloalkanes

Isolated Rings Spiro Rings Fused Rings Bridged Rings

No common atoms One common atom One common bond Two common atoms

Alkenes and Alkynes

Alkenes and alkynes are hydrocarbons which respectively have carbon-carbon double

bond and carbon-carbon triple bond functional groups. The molecular formulas of these

unsaturated hydrocarbons reflect the multiple bonding of the functional groups:

Alkane R–CH2–CH2–R CnH2n+2 This is the maximum H/C ratio for a given number of carbon atoms.

Alkene R–CH=CH–R CnH2n Each double bond reduces the number of hydrogen atoms by 2.

Alkyne R–C≡C–R CnH2n-2 Each triple bond reduces the number of hydrogen atoms by 4.

As noted earlier in the Analysis of Molecular Formulas section, the molecular formula of a

hydrocarbon provides information about the possible structural types it may represent. For gnu.i

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IUPAC NOMENCLATURE

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example, consider compounds having the formula C5H8. The formula of the five-carbon

alkane pentane is C5H12 so the difference in hydrogen content is 4. This difference suggests

such compounds may have a triple bond, two double bonds, a ring plus a double bond, or

two rings. Some examples are shown here, and there are at least fourteen others!

IUPAC Rules for Alkyne Nomenclature

1.The yne suffix (ending) indicates an alkyne or cycloalkyne.

2. The longest chain chosen for the root name must include both carbon atoms of the triple bond.

3. The root chain must be numbered from the end nearest a triple bond carbon atom. If the triple bond is in the center of

the chain, the nearest substituent rule is used to determine the end where numbering starts.

4. The smaller of the two numbers designating the carbon atoms of the triple bond is used as the triple bond locator.

5. If several multiple bonds are present, each must be assigned a locator number. Double bonds precede triple bonds in the

IUPAC name, but the chain is numbered from the end nearest a multiple bond, regardless of its nature.

6. Because the triple bond is linear, it can only be accomodated in rings larger than ten carbons. In simple cycloalkynes the

triple bond carbons are assigned ring locations #1 and #2. Which of the two is #1 may be determined by the nearest

substituent rule.

For examples of how these rules are used in naming alkenes, alkynes and cyclic analogs .

Benzene Derivatives

The nomenclature of substituted benzene ring compounds is less systematic than

that of the alkanes, alkenes and alkynes. A few mono-substituted compounds are named by

using a group name as a prefix to "benzene", as shown by the combined names listed

below. A majority of these compounds, however, are referred to by singular names that are

unique. There is no simple alternative to memorization in mastering these names.8 gn

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Two commonly encountered substituent groups that incorporate a benzene ring are

phenyl, abbreviated Ph-, and benzyl, abbreviated Bn-. These are shown here with

examples of their use. Be careful not to confuse a phenyl (pronounced fenyl) group with

the compound phenol (pronounced feenol). A general and useful generic notation that

complements the use of R- for an alkyl group is Ar- for an aryl group (any aromatic ring).

When more than one substituent is present on a benzene ring, the relative locations

of the substituents must be designated by numbering the ring carbons or by some other

notation. In the case of disubstituted benzenes, the prefixes ortho, meta & para are

commonly used to indicate a 1,2- or 1,3- or 1,4- relationship respectively. In the following gnu.i

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examples, the first row of compounds show this usage in red. Some disubstituted toluenes

have singular names (e.g. xylene, cresol & toluidine) and their isomers are normally

designated by the ortho, meta or para prefix. A few disubstituted benzenes have singular

names given to specific isomers (e.g. salicylic acid & resorcinol). Finally, if there are three

or more substituent groups, the ring is numbered in such a way as to assign the substituents

the lowest possible numbers, as illustrated by the last row of examples. The substituents

are listed alphabetically in the final name. If the substitution is symmetrical (third example

from the left) the numbering corresponds to the alphabetical order.

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A. Hydrocarbons 4

* Acyclic Hydrocarbons

* Monocyclic Hydrocarbons

* Fused Polycyclic Hydrocarbons

* Bridged Hydrocarbons (Extension of the Von Baeyer System)

* Spiro Hydrocarbons

* Hydrocarbon Ring Assemblies

* Cyclic Hydrocarbons with Side Chains

* Terpene Hydrocarbons

A. Hydrocarbons Acyclic Hydrocarbons

A-1. Saturated Unbranched-chain Compounds and Univalent Radicals

A-2. Saturated Branched-chain Compounds and Univalent Radicals

A-3. Unsaturated Compounds and Univalent Radicals

A-4. Bivalent and Multivalent Radicals

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Acyclic Hydrocarbons

Rule A-1. Saturated Unbranched-chain Compounds and

Univalent Radicals

1.1 - The first four saturated unbranched acyclic hydrocarbons are called methane, ethane,

propane and butane. Names of the higher members of this series consist of a numerical

term, followed by "-ane" with elision of terminal "a" from the numerical term. Examples of

these names are shown in the table below. The generic name of saturated acyclic

hydrocarbons (branched or unbranched) is "alkane".

Examples of names:

(n = total number of carbon atoms)

n n

1 Methane 21 Docosane

2 Ethane 22 Tricosane

3 Propane 23 Tetracosane

4 Butane 24 Pentacosane

5 Pentane 25 Hexacosane

6 Hexane 26 Heptacosane

7 Heptane 27 Octacosane

8 Octane 28 Nonacosane

9 Nonane 29 Triacontane

10 Decane 30 Hentriacontane

11 Undecane 31 Dotriacontane

12 Dodecane 33 Tritriacontane

13 Tridecane 40 Tetracontane

14 Tetradecane 50 Pentacontane

15 Pentadecane 60 Hexacontane

16 Hexadecane 70 Heptacontane

17 Heptadecane 80 Octacontane

18 Octadecane 90 Nonacontane

19 Nonadecane 100 Hectane

20 Icosane 132 Dotriacontahectane gnu.i

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1.2 - Univalent radicals derived from saturated unbranched acyclic hydrocarbons by

removal of hydrogen from a terminal carbon atom are named by replacing the ending "-

ane" of the name of the hydrocarbon by "-yl". The carbon atom with the free valence is

numbered as 1. As a class, these radicals are called normal, or unbranched chain, alkyls.

Examples to Rule A-1.2


Rule A-2. Saturated Branched-chain Compounds and

Univalent Radicals

2.1 - A saturated branched acyclic hydrocarbon is named by prefixing the designations of

the side chains to the name of the longest chain present in the formula.

Example to Rule A-2.1

The following names are retained for unsubstituted hydrocarbons only:

Isobutane

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Isopentane

Neopentane

2.2 - The longest chain is numbered from one end to the other by Arabic numerals, the

direction being so chosen as to give the lowest numbers possible to the side chains. When

series of locants containing the same number of terms are compared term by term, that

series is "lowest" which contains the lowest number on the occasion of the first difference.

This principle is applied irrespective of the nature of the substituents.


2.25 - Univalent branched radicals derived from alkanes are named by prefixing the

designation of the side chains to the name of the unbranched alkyl radical possessing the

longest possible chain starting from the carbon atom with the free valence, the said atom

being numbered as 1.

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1-Methylpentyl

2-Methylpentyl

5-Methylhexyl

The following names may be used for the unsubstituted radicals only:

Isopropyl

Isobutyl

sec-Butyl

tert-Butyl

Isopentyl

2.3 - If two or more side chains of different nature are present, they are cited in

alphabetical order.

The alphabetical order is decided as follows:

(i) The names of simple radicals are first alphabetized and the multiplying prefixes are then

inserted.

Examples to Rule A-2.3(i)

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(ii) The name of a complex radical is considered to begin with the first letter of its

complete name.

Examples to Rule A-2.3(ii)

dimethylpentyl (as complete single substituent) is

alphabetized under "d",

thus 7-(1,2-Dimethylpentyl)-5-ethyltridecane

(iii) In cases where names of complex radicals are composed of identical words, priority

for citation is given to that radical which contains the lowest locant at the first cited point

of difference in the radical.

Examples to Rule A-2.3(iii)

2.4 - If two or more side chains are in equivalent positions, the one to be assigned the

lower number is that cited first in the name.

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Examples: to Rule A-2.4

2.5 - The presence of identical unsubstituted radicals is indicated by the appropriate

multiplying prefix di-, tri-, tetra-, penta-, hexa-, hepta-, octa-, nona-, deca-, undeca, etc.

Example to Rule A-2.5(a)

The presence of identical radicals each substituted in the same way may be indicated by

the appropriate multiplying prefix bis-, tris-, tetrakis-, pentakis-, etc. The complete

expression denoting such a side chain may be enclosed in parentheses or the carbon atoms

in side chains may be indicated by primed numbers.

Examples to Rule A-2.5(b)

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(a) Use of parentheses and unprimed numbers:

5,5-Bis(1,1-dimethylpropyl)-2-methyldecane

(b) Use of primes:

5,5-Bis-1',1'-dimethylpropyl-2-methyldecane

(a) Use of parentheses and unprimed numbers:

7-(1,1-Dimethylbutyl)-7-(1,1-dimethylpentyl)tridecane

(b) Use of primes:

7-1',1'-Dimethylbutyl-7-1",1"-dimethylpentyltridecane

2.6 - If chains of equal length are competing for selection as main chain in a saturated

branched acyclic hydrocarbon, then the choice goes in series to:

(a) The chain which has the greatest number of side chains.

Example to Rule A-2.6(a)

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(b) The chain whose side chains have the lowest-numbered locants.

Example to Rule A-2.6(b)

(C) The chain having the least branched side chains.

Example to Rule A-2.6(C)


Rule A-3. Unsaturated Compounds and Univalent

Radicals

3.1 - Unsaturated unbranched acyclic hydrocarbons having one double bond are named by

replacing the ending "-ane" of the name of the corresponding saturated hydrocarbon with

the ending "-ene". If there are two or more double bonds, the ending will be "-adiene", "-

atriene", etc. The generic names of these hydrocarbons (branched or unbranched) are

"alkene", "alkadiene", "alkatriene", etc. The chain is so numbered as to give the lowest

possible numbers to the double bonds. When, in cyclic compounds or their substitution

products, the locants of a double bond differ by unity, only the lower locant is cited in the

name; when they differ by more than unity, one locant is placed in parentheses after the

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2-Hexene

1,4-Hexadiene

The following non-systematic names are retained:

Ethylene

Allene 3.2 - Unsaturated unbranched acyclic hydrocarbons having one triple bond are named by

replacing the ending "-ane" of the name of the corresponding saturated hydrocarbon with

the ending "-yne". If there are two or more triple bonds, the ending will be "-adiyne",

"atriyne", etc. The generic names of these hydrocarbons (branched or unbranched) are

"alkyne", "alkadiyne", "alkatriyne", etcThe chain is so numbered as to give the lowest

possible numbers to the triple bonds. Only the lower locant for a triple bond is cited in the

name of a compound.

The name "acetylene" for is retained.

3.3 - Unsaturated unbranched acyclic hydrocarbons having both double and triple bonds

are named by replacing the ending "-ane" of the name of the corresponding saturated

hydrocarbon with the ending "-enyne", "-adienyne", "-atrienyne", "-enediyne", etcNumbers

as low as possible are given to double and triple bonds even though this may at times give

"-yne" a lower number than "-ene". When there is a choice in numbering, the double bonds

are given the lowest numbers.


1,3-Hexadien-5-yne

3-Penten-1-yne

1-Penten-4-yne

3.4 - Unsaturated branched acyclic hydrocarbons are named as derivatives of the

unbranched hydrocarbons which contain the maximum number of double and triple bonds.

If there are two or more chains competing for selection as the chain with the maximum

number of unsaturated bonds, then the choice goes to (1) that one with the greatest number

of carbon atoms; (2) the number of carbon atoms being equal, that one containing the

maximum number of double bonds. In other respects, the same principles apply as for

naming saturated branched acyclic hydrocarbons. The chain is so numbered as to give the

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The following name is retained for the unsubstituted compound only:

3.5 - The names of univalent radicals derived from unsaturated acyclic hydrocarbons have

the endings "-enyl", "-ynyl", "-dienyl", etc., the positions of the double and triple bonds

being indicated where necessary. The carbon atom with the free valence is numbered as 1.


Ethynyl

2-Propynyl

1-Propenyl

2-Butenyl

1,3-Butadienyl

2-Pentenyl

2-Penten-4-ynyl

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Exceptions:

The following names are retained (for unsubstituted radical only):

Vinyl (for ethenyl)

Allyl (for 2-propenyl)

Isopropenyl(for 1-methylvinyl)

3.6 - When there is a choice for the fundamental chain of a radical, that chain is selected

which contains (1) the maximum number of double and triple bonds; (2) the largest

number of carbon atoms; and (3) the largest number of double bonds.


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Acyclic Hydrocarbons5

Rule A-4. Bivalent and Multivalent Radicals

4.1 - Bivalent and trivalent radicals derived from univalent acyclic hydrocarbon radicals

whose authorized names end in "-yl" by removal of one or two hydrogen atoms from the

carbon atom with the free valences are named by adding "-idene" or "-idyne", respectively,

to the name of the corresponding univalent radical. The carbon atom with the free valence

is numbered as 1.

The name "methylene" is retained for the radical


Methylidyne

Ethylidene

Ethylidyne

Vinylidene

Isopropylidene

4.2 - The names of bivalent radicals derived from normal alkanes by removal of a

hydrogen atom from each of the two terminal carbon atoms of the chain are ethylene,

trimethylene, tetramethylene, etc.


Pentamethylene

Hexamethylene

Names of the substituted bivalent radicals are derived in accordance with Rules A-2.2 and

A-2.25.

Example to Rule A-4.2a

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The following name is retained:

4.3 - Bivalent radicals similarly derived from unbranched alkenes, alkadienes, alkynes,

etc., by removing a hydrogen atom from each of the terminal carbon atoms are named by

replacing the endings "-ene", "-diene", "-yne", etc., of the hydrocarbon name by "-

enylene", "-dienylene", "-ynylene", etc., the positions of the double and triple bonds being

indicated where necessary.


The following name is retained:

Names of the substituted bivalent radicals are derived in accordance with Rule A-3.4.


4.4 - Trivalent, quadrivalent and higher-valent acyclic hydrocarbon radicals of two or more

carbon atoms with the free valences at each end of a chain are named by adding to the

hydrocarbon name the terminations "-yl" for a single free valence, "-ylidene" for a double,

and "-ylidyne" for a triple free valence on the same atom (the final "e" in the name of the

hydrocarbon is elided when followed by a suffix beginning with "-yl"). If different types

are present in the same radical, they are cited and numbered in the order "-yl", "-ylidene",

"-ylidyne".


Butanediylidene

Butanediylidyne

1-Propanyl-3-ylidene

Propadienediylidene gn

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A. Hydrocarbons Monocyclic Hydrocarbons

A-11. Unsubstituted Compounds and Radicals

A-12. Substituted Aromatic Compounds

A-13. Substituted Aromatic Radicals

Monocyclic Hydrocarbons

Rule A-11. Unsubstituted Compounds and Radicals

11.1 - The names of saturated monocyclic hydrocarbons (with no side chains) are formed

by attaching the prefix "cyclo" to the name of the acyclic saturated unbranched

hydrocarbon with the same number of carbon atoms. The generic name of saturated

monocyclic hydrocarbons (with or without side chains) is "cycloalkane".


11.2 - Univalent radicals derived from cycloalkanes (with no side chains) are named by

replacing the ending "-ane" of the hydrocarbon name by "-yl", the carbon atom with the

free valence being numbered as 1. The generic name of these radicals is "cycloalkyl".

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11.3 - The names of unsaturated monocyclic hydrocarbons (with no side chains) are

formed by substituting "-ene", "-adiene", "-atriene", "-yne", "-adiyne", etc., for "-ane" in

the name of the corresponding cycloalkane. The double and triple bonds are given numbers

as low as possible as in Rule A-3.3.


The name "benzene" is retained.

11.4 - The names of univalent radicals derived from unsaturated monocyclic hydrocarbons

have the endings "-enyl", "-ynyl", "-dienyl", etc., the positions of the double and triple

bonds being indicated according to the principles of Rule A-3.3. The carbon atom with the

free valence is numbered as 1, except as stated in the rules for terpenes (see Rules A-72 to

A-75).

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The radical name "phenyl" is retained.

11.5 - Names of bivalent radicals derived from saturated or unsaturated monocyclic

hydrocarbons by removal of two atoms of hydrogen from the same carbon atom of the ring

are obtained by replacing the endings "-ane", "-ene", "-yne", by "-ylidene", "-enylidene"

and "-ynylidene", respectively. The carbon atom with the free valences is numbered as 1

except as stated in the rules for terpenes.


11.6 - Bivalent radicals derived from saturated or unsaturated monocyclic hydrocarbons by

removing a hydrogen atom from each of two different :carbon atoms of the ring are named

by replacing the endings "-ane", "-ene", "-diene", "-yne", etc., of the hydrocarbon name by

"-ylene", "-enylene", "-dienylene", "-ynylene", etc., the positions of the double and triple

bonds and of the points of attachment being indicated. Preference n lowest numbers is

given to the carbon atoms having the free valences. Examples to Rule A-11.6

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:


Rule A-12. Substituted Aromatic Compounds

12.1 - The following names for monocyclic substituted aromatic hydro carbons are

retained:


12.2 - Other monocyclic substituted aromatic hydrocarbons are named as derivatives of

benzene or of one of the compounds listed in Part .1 of this rule. However, if the

substituent introduced into such a compound is identical with one already present in that

compound, then the substituted compound is named as a derivative of benzene (see Rule

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12.3 - The position of substituents is indicated by numbers except that o- (ortho), m-

(meta) and p- (para) may be used in place of 1,2-, 1,3-, and 1,4-, respectively, when only

two substituents are present. The lowest numbers possible are given to substituents, choice

between alternatives being governed by Rule A-2 so far as applicable except that when

names are based on those of compounds listed in Part .1 of this rule the first priority for

lowest numbers is given to the substituent(s) already present in those compounds.


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Rule A-13. Substituted Aromatic Radicals

13.1 - Univalent radicals derived from monocyclic substituted aromatic hydrocarbons and

having the free valence at a ring atom are given the names listed below. Such radicals not

listed below are named as substituted phenyl radicals. The carbon atom having the free

valence is numbered as 1.


13.2 - Since the name phenylene (o-, m- or p-) is retained for the radical (exception

to Rule A-11.6), bivalent radicals formed from substituted benzene derivatives and having

the free valences at ring atoms are named as substituted phenylene radicals. The carbon

atoms having the free valences are numbered 1,2-, 1,3- or 1,4- as appropriate.

13.3-The following trivial names for radicals having a single free valence in the side chain

are retained:


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A. Hydrocarbons Fused Polycyclic Hydrocarbons

A-21. Trivial and Semi-trivial names

A-22. Numbering

A-23. Hydrogenated Compounds

A-24. Radical Names from Trivial and Semi-trivial Names

A-28. Radical Names for Fused Cyclic Systems with Side Chains

Fused Polycyclic Hydrocarbons

Rule A-21. Trivial and Semi-trivial names

21.1 - The names of polycyclic hydrocarbons with maximum number of non-cumulative

double bonds end in "-ene". The following list contains the names of polycyclic

hydrocarbons which are retained. This list is not limiting.


(1) Pentalene

(2) Indene

(3) Naphthalene

(4) Azulene

21.2 - The names of hydrocarbons containing five or more fused benzene rings in a straight

linear arrangement are formed from a numerical prefix as specified in Rule A-1.1

followedby "-acene". gnu.i

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21.3 - "Ortho-fused" or "ortho- and peri-fused" polycyclic hydrocarbons with maximum

number of non-cumulative double bonds which contain at least two rings of five or more

members and which have no accepted trivial name such as those of Part .1 of this rule, are

named by prefixing to the name of a component ring or ring system (the base component)

designations of the other components. The base component should contain as many rings

as possible (provided it has a trivial name), and should occur as far as possible from the

beginning of the list of Rule A-21.1. The attached components should be as simple as

possible.


(not Naphthophenanthrene: benzo is "simpler" than

naphtho, even through there are two benzo rings and

only one naphto)

21.4 - The prefixes designating attached components are formed by changing the ending "-

ene" of the name of the component hydrocarbon into "-eno"; e.g., "pyreno" (from pyrene).

When more than one prefix is present, they are arranged in alphabetical order. The

following common abbreviated prefixes are recognized (see list in Part.1 of this rule):

Acenaphtho from Acenaphthylelle

Anthra from Anthracene

Benzo from Benzene

Naphtho from Naphthalene

Perylo from Perylene gnu.i

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For monocyclic prefixes other than "benzo" the following names are recognized, each to

represent the form with the maximum number of non-cumulative double bonds:

cyclopenta, cyclohepta, cycloocta, cyclonona, etcWhen the base component is a

monocyclic system, the ending "-ene" signifies the maximum number of non-cumulative

double bonds and thus does not denote one double bond only.


21.5 - Isomers are distinguished by lettering the peripheral sides of the base component a,

b, c, etc., beginning with "a" for the side "1,2", "b" for "2,3" (or in certain cases "2,2a")

and lettering every side around the periphery. To the letter as early in the alphabet as

possible, denoting the side where fusion occurs, are prefixed, if necessary, the numbers of

the positions of attachment of the other component. These numbers are chosen to be as low

as is consistent with the numbering of the component, and their order conforms to the

direction of lettering of the base component. When two or more prefixes refer to equivalent

positions so that there is a choice of letters, the prefixes are cited in alphabetical order

according to Rule A-21.4 and the location of the first cited prefix is indicated by a letter as

early as possible in the alphabet. The numbers and letters are enclosed in square brackets

and placed immediately after the designation of the attached component. This expression

merely defines the manner of fusion of the components.


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The completed system consisting of the base component and the other components is then

renumbered according to Rule A-22, the enumeration of the component parts being

ignored.6


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Rule A-22. Numbering

22.1 - For the purposes of numbering, the individual rings of a polycyclic "ortho-fused" or

"ortho- and peri-fused" hydrocarbon system are normally drawn as follows:

and the polycyclic system is oriented so that (a) the greatest number of rings are in a

horizontal row and (b) a maximum number of rings are above and to the right of the

horizontal row (upper right quadrant). If two or more orientations meet these requirements,

the one is chosen which has as few rings as possible in the lower left quadrant.

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The system thus oriented is numbered in a clockwise direction commencing with the

carbon atom not engaged in ring-fusion in the most counter-clockwise position of the

uppermost ring, or if there is a choice, of the uppermost ring farthest to the right, and

omitting atoms common to two or more rings.


22.2 - Atoms common to two or more rings are designated by adding roman letters "a",

"b", "c", etc., to the number of the position immediately preceding. Interior atoms follow

the highest number, taking clockwise sequence wherever there is a choice.

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22.3 - When there is a choice, carbon atoms common to two or more rings follow the

lowest possible numbers.


Notes:

I 4, 4, 8, 9 is lower than 4, 5, 9, 9.

II 2, 5, 8 is lower than 3, 5, 8.

22.4 - When there is a choice, the carbon atoms which carry an indicated hydrogen atom

are numbered as low as possible.

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22.5 - The following are recommended exceptions to the above rules on numbering:


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Rule A-23. Hydrogenated Compounds

23.1 - The names of "ortho-fused" or "ortho- and peri-fused" polycyclic hydrocarbons with

less than maximum number of non-cumulative double bonds are formed from a prefix

"dihydro-", "tetrahydro-", etc., followed by the name of the corresponding unreduced

hydrocarbon. The prefix "perhydro-" signifies full hydrogenation. When there is a choice

for H used for indicated hydrogen it is assigned the lowest available number.


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23.2 - When there is a choice, the carbon atoms to which hydrogen atoms are added are

numbered as low as possible.


23.3 - Substituted polycyclic hydrocarbons are named according to the same principles as

substituted monocyclic hydrocarbons (see Rules A-12 and A-61).

23.5 (Alternate to part of Rule A-23.1) - The names of "ortho-fused" polycyclic

hydrocarbons which have (a) less than the maximum number of non-cumulative double

bonds, (b) at least one terminal unit which is most conveniently named as an unsaturated

cycloalkane derivative, and (c) a double bond at the positions where rings are fused

together, may be derived by joining the name of the terminal unit to that of the other

component by means of a letter "o" with elision of a terminal "e". The abbreviations for

fused aromatic systems laid down in Rule A-21.4 are used, and the exceptions of Rule A-

23.1 apply.


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Table 22 Polycyclic hydrocarbon substituent prefixes.19

Type 1-Unlimited substitution

Adamantyl (2-isomer shown)

Anthryl (2-isomer shown)

(An exception to systematic numbering)

Naphthyl (2-isomer shown)

Phenanthryl (2-isomer shown)

(An exception to systematic numbering)

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A. Hydrocarbons 4

Bridged Hydrocarbons (Extension of the Von Baeyer Sistem)

A-31. Bicyclic Systems

A-32. Polycyclic Systems

A-34. Hydrocarbon Bridges

Bridged Hydrocarbons

Rule A-31. Bicyclic Systems

31.1 - Saturated alicyclic hydrocarbon systems consisting of two rings only, having two or

more atoms in common, take the name of an open chain hydrocarbon containing the same

total number of carbon atoms preceded by the prefix "bicyclo-". The number of carbon

atoms in each of the three bridges connecting the two tertiary carbon atoms is indicated in

brackets in descending order.


31.2 - The system is numbered commencing with one of the bridgeheads, numbering

proceeding by the longest possible path to the second bridgehead; numbering is then

continued from this atom by the longer unnumbered path back to the first bridgehead and

is completed by the shortest path from the atom next to the first bridgehead. gnu.i

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31.3 - Unsaturated hydrocarbons are named in accordance with the principles set forth in

Rule A-11.3 When after applying Rule A-31.2 a choice in numbering remains unsaturation

is given the lowest numbers.


31.4 - Radicals derived from bridged hydrocarbons are named in accordance with the

principles set forth in Rule A-11 The numbering of the hydrocarbon is retained and the

point or points of attachment are given numbers as low as is consistent with the fixed

numbering of the saturated hydrocarbon.

.

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A. Hydrocarbons

Spiro Hydrocarbons 7

Spiro Hydrocarbons

A-41. Compounds: Method 1

A-42. Compounds: Method 2

A-43. Radicals

Spiro Hydrocarbons

A "spiro union" is one formed by a single atom which is the only common member of two

rings. A "free spiro union" is one constituting the only union direct or indirect between two

rings senior.. The common atom is designated as the "spiro atom". According to the

number of spiro atoms present, the compounds are distinguished as monospiro-, dispiro-,

trispirocompounds, etc. The following rules apply to the naming of compounds containing

free spiro unions.

Spiro Hydrocarbons

Rule A-41. Compounds: Method 1

41.1 - Monospiro compounds consisting of only two alicyclic rings as components are

named by placing "spiro" before the name of the normal acyclic hydrocarbon of the same

total number of carbon atoms. The number of carbon atoms linked to the spiro atom in gnu.i

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each ring is indicated in ascending order in brackets placed between the spiro prefix and

the hydrocarbon name.


41.2 - The carbon atoms in monospiro hydrocarbons are numbered consecutively starting

with a ring atom next to the spiro atom, first through the smaller ring (if such be present)

and then through the spiro atom and around the second ring.

Example A-41.2

41.3 - When unsaturation is present, the same enumeration pattern is maintained, but in

such a direction around the rings that the double and triple bonds receive numbers as low

as possible in accordance with Rule A-11.

Example A-41.3

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41.4 - If one or both components of the monospiro compound are fused polycyclic

systems, "spiro" is placed before the names of the components arranged in alphabetical

order and enclosed in brackets. Established numbering of the individual components is

retained. The lowest possible number is given to the spiro atom, and the numbers of the

second component are marked with primes. The position of the spiro atom is indicated by

placing the appropriate numbers between the names of the two components.

Example A-41.4

41.5 - Monospiro compounds containing two similar polycyclic components are named by

placing the prefix "spirobi" before the name of the component ring system. Established

enumeration of the polycyclic system is maintained and the numbers of one component are

distinguished by primes. The position of the spiro atom is indicated in the name of the

spiro compound by placing the appropriate locants before the name.

Example A-41.5

.

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Spiro Hydrocarbons

Rule A-42. Compounds: Method 2

42.1 - (Alternate to Rules A-41.1 and A-41.2) - When two dissimilar cyclic components

are united by a spiro union, the name of the larger component is followed by the affix

"spiro" which, in turn, is followed by the name of the smaller component. Between the

affix "spiro" and the name of each component system is inserted the number denoting the

spiro position in the appropriate ring system, these numbers being as low as permitted by

any fixed enumeration of the component. The components retain their respective

enumerations but numerals for the component mentioned second are primed. Numerals I

may be omitted when a free choice is available for a component.

Examples A-42.1

.

42.2 - (Alternate to A-41.3) - Rule A-41.3 applies also with appropriate different

enumeration, where nomenclature is according to Rule A-42.1, but the spiro junction has

priority for lowest numbers over unsaturation.

Example A-42.2

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.

Spiro Hydrocarbons

Rule A-43. Radicals

43.1 - Radicals derived from spiro hydrocarbons are named according to the principles set

forth in Rules A-11 and A-24

Examples A-43.1

.

.

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Recommendations 1979 Hydrocarbon Ring Assemblies

A-51. Definition

A-52. Two Identical Ring Systems

A-53. Non-identical Ring Systems

A-54. Three or More Identical Ring Systems

A-55. Radicals for Identical Ring Systems

A-56. Radicals for Non-benzenoid Ring Systems

Hydrocarbon Ring Assemblies

Rule A-51. Definition

51.1 - Two or more cyclic systems (single rings or fused systems) which are directly joined

to each other by double or single bonds are named "ring assemblies" when the number of

such direct ring junctions is one less than the number of cyclic systems involved.


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Rule A-52. Two Identical Ring Systems

52.1 - Assemblies of two identical cyclic hydrocarbon systems are named in either of two

ways: (a) by placing the prefix "bi-" before the name of the corresponding radical, or (b)

for systems joined by a single bond by placing the prefix "bi-" before the name of the

corresponding hydrocarbon. In each case, the numbering of the assembly is that of the

corresponding radical or hydrocarbon, one system being assigned unprimed numbers and

the other primed numbers. The points of attachment are indicated by placing the

appropriate locants before the name.


52.2 - If there is a choice in numbering, unprimed numbers are assigned to the system

which has the lower-numbered point of attachment.


52.3 - If two identical hydrocarbon systems have the same point of attachment and contain

substituents at different positions, the locants of these substituents are assigned according

to Rule A-2.2; for this purpose an unprimed number is considered lower than the same

number when primed. Assemblies of primed and unprimed numbers are arranged in

ascending numerical order.

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.

52.4 - The name "biphenyl" is used for the assembly consisting of two benzene rings.



Rule A-53. Non-identical Ring Systems

53.1 - Other hydrocarbon ring assemblies are named by selecting one ring system as the

base component and considering the other systems as substituents of the base component.

Such substituents are arranged in alphabetical order. The base component is assigned

unprimed numbers and the substituents are assigned numbers with primes. .

53.2 - The base component is chosen by considering the following characteristics in turn

until a decision is reached: .

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(a) The system containing the larger number of rings.

Examples to Rule A-53.2(a)

.

(b) The system containing the larger ring.

Examples to Rule A-53.2(b)

.

(c) The system in the lowest state of hydrogenation (see also Part .3 of this rule).

Example to Rule A-53.2(c)

..

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Rule A-54. Three or More Identical Ring Systems

54.1 - Unbranched assemblies consisting of three or more identical hydrocarbon ring

systems are named by placing an appropriate numerical prefix before the name of the

hydrocarbon corresponding to the repetitive unit. The following numerical prefixes are

used:

3. ter- 7. septi-

4. quater- 8. octi-

5. quinque- 9. novi-

6. sexi- 10. deci-


54.2 - Unprimed numbers are assigned to one of the terminal systems, the other systems

being primed serially. Points of attachment are assigned the lowest numbers possible.


.

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.


Rule A-55. Radicals for Identical Ring Systems

(Alternative in part to Rule A-56.1)

55.1 - Univalent and multivalent radicals derived from assemblies of identical hydrocarbon

ring systems are named by adding "-yl", "-ylene" or "-diyl", "-triyl", etc., to the name of

the ring assembly.


.

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Cyclic Hydrocarbons with Side Chains

A-61. General Principles

Cyclic Hydrocarbons with Side Chains

Rule A-61. General Principles

61.1 - Hydrocarbons more complex then those envisioned in Rule A-12, composed of

cyclic nuclei and aliphatic chains, are named according to one of the methods given below.

Choice is made so as to provide the name which is the simplest permissible or the most

appropriate for the chemical intent.

61.2 - When there is no generally recognized trivial name for the hydrocarbon, then (1) the

radical name denoting the aliphatic chain is prefixed to the name of the cyclic

hydrocarbon, or (2) the radical name for the cyclic hydrocarbon is prefixed to the name of

the aliphatic compound. Choice between these methods is made according to the more

appropriate of the following principles: (a) the maximum number of substitutions into a

single unit of structure; (b) treatment of a smaller of structure as a substituent into a larger.

Numbering of double and triple bonds in chains or non-aromatic rings is assigned

according to the principles of Rule A-3; numbering and citation of substituents are effected

as described in Rule A-2.

61.3 - In accordance with the principle (a) of Part .2 of this rule, hydrocarbons containing

several chains attached to one cyclic nucleus are generally named as derivatives of the

cyclic compound; and compounds containing several side chains and/or cyclic radicals

attached to one chain are named as derivatives of the acyclic compound.


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61.4 - In accordance with the principle (b) of Part .2 of this rule, a hydrocarbon containing

a small cyclic nucleus attached to a long chain is generally named as a derivative of the

acyclic hydrocarbon; and a hydrocarbon containing a small group attached to a large cyclic

nucleus is generally named as a derivative of the cyclic hydrocarbon.


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.

.

Acyclic and monocyclic hydrocarbons. Parent

hydrocarbons.

Type 1-Unlimited substitution

CH4

Methane

Ethane

Acetylene

Propane

Allene

Butane

Benzene

Type 2-Limited substitution (ring only)

Toluene., .

Styrene., .

Stilbene., .

Type 3-No substitution

Isobutane

Isopentane

Neopentane

Isoprene

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B. Fundamental Heterocyclic Systems 14

* Specialist Heterocyclic Nomenclature

* Heterocyclic Spiro Compounds

* Heterocyclic Ring Assemblies

* Bridged Heterocyclic Systems

Heterocyclic Systems

Rule B-1. Extension of Hantzsch-Widman System .

1.1 - Monocyclic compounds containing one or more hetero atoms in a three- to ten-

membered ring are named by combining the appropriate prefix or prefixes from Table B-I

(eliding "a" where necessary) with a stem from Table B-II. The state of hydrogenation is

indicated either in the stem, as shown in Table B-II , or by the prefixes "dihydro-",

"tetrahydro-'', etc., according to Rule B-1.2.

Examples to Rule B-1.1

1.2 - Heterocyclic systems whose unsaturation is less than the one corresponding to the

maximum number of non-cumulative double bonds are named by using the prefixes

"dihydro-", "tetrahydro-", etc.

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58

In the case of 4- and 5-membered rings, a special termination is used for the structures

containing one double bond, when there can be more than one non-cumulative double

bond.

No. of members

of the partly

saturated rings

Rings

containing

nitrogen

Rings

containing

no nitrogen

4 -etine -etene

5 -oline -olene


.

1.3 - Multiplicity of the same hetero atom is indicated by a prefix "di-", "tri-", etc., placed

before the appropriate "a" term (Table B-I).

Example to Rule B-1.3

1.4 - If two or more kinds of "a" terms occur in the same name, their order of citation is in

order of their appearance in Table B-I of Rule B-1.1..


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.

Heterocyclic Systems14

Rule B-2. Trivial and Semi-trivial Names

2.11 - The following trivial and semi-trivial names constitute a partial list of such names

which are retained for the compound and as a basis of fusion names. The names of the

radicals shown are formed according to Rule B-5.

.

2.12 - The following trivial and semi-trivial names are retained but are not recommended

for use in fusion names. The names of the radicals shown are formed according to Rule B-

5.


Rule B-3. Fused Heterocyclic Systems

3.1 - "Ortho-fused" and "ortho- and peri-fused" ring compounds containing hetero atoms

are named according to the fusion principle described in Rule A-21 for hydrocarbons. The

components are named according to Rules A-21, B-1 and B-2. When the name of a

component in a fusion name contains locants (numerals or letters) that do not apply also to

the numbering of the fused system, these locants are placed in square brackets (as are also

the locants for fusion positions required by Rule A-21.5). The base component should be a

heterocyclic system. If there is a choice, the base component should be, by order of

preference:

(a) A nitrogen-containing component.

Example to Rule B-3.1(a)

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(b) A component containing a heteroatom (in the absence of nitrogen) as high as possible

in Table B-I.

Example to Rule B-3.1(b)

Thieno[2,3-b]furan

not Furo[2,3-b]thiophene

.

3.2 - If a position of fusion is occupied by a hetero atom, the names of the component rings

to be fused are so chosen as both to contain the hetero atom.


Imidazo[2,1-b]thiazole

3.3 - The following contracted fusion prefixes may be used: furo, imidazo, isoquino,

pyrido, pyrimido, quino and thieno.


Furo[3,4-c]cinnoline

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Rule B-4. Replacement Nomenclature (also known as

"a" Nomenclature)

4.1 - Names of monocyclic hetero compounds may be formed by prefixing "a" terms (see

Table B-I), preceded by their locants, to the name of the corresponding hydrocarbon..

Numbering is assigned so as to give locant 1 to the hetero atom listed earlier in Table B-I,

next to hetero atoms as a complete set, and then to hetero atoms in order of Table B-I. If a

further choice is possible, numbering is assigned according to Rule C-0.15.


.

Sila-2,4-cyclopentadiene

Sila-1,3-cyclopentadiene ..

4.2 - Fused heterocyclic systems may be named by prefixing "a" terms preceded by their

locants, to the name of the corresponding hydrocarbon. The numbering of the

corresponding hydrocarbon is retained, irrespective of the position of the hetero atoms;

where there is a choice, low numbers are assigned in the following order: first to hetero

atoms as a complete set, next to hetero atoms in order of Table B-I, and then to multiple

bonds in the heterocyclic compound according to the principles of Rule A-11.3. These

principles are applied in one of two ways, as follows:

(a) When the corresponding hydrocarbon does not contain the maximum number of non-

cumulative double bonds and can be named without the use of hydro prefixes, as for indan,

then the hydrocarbon is named in that state of hydrogenation.

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Example to Rule B-4.2(a)

2,3-Dithia-1,5-diazaindan

(b) When the two conditions of paragraph (a) are not fulfilled, positions in the skeleton of

the corresponding hydrocarbon that are occupied by hetero atoms are denoted by "a"

prefixes, and the parent heterocyclic compound is considered to be that which contains the

maximum number of conjugated or isolated.front of the "a" terms.

4H-1,3-Dithianaphthalene

1,4-Dithianaphthalene

2,4,6-Trithia-3a,7a-diazaindene

1H-2-Oxapyrene

2,7,9-Triazaphenanthrene

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Rule B-5. Radicals

5.11 - Univalent radicals derived from heterocyclic compounds by removal of hydrogen

from a ring are in principle named by adding "yl" to the names of the parent compounds

(with elision of final "e", if present).


Indolyl from indole

Pyrrolinyl from pyrroline

Triazolyl from triazole

Triazinyl from triazine

.

The following exceptions are retained: furyl, pyridyl, piperidyl, quinolyl, isoquinolyl and

thienyl (from thiophene) (see also Rule B-2.12). Also retained are furfuryl (for 2-

furylmethyl), furfurylidene (for 2-furylmethylene), furfurylidyne (for 2-furylmethylidyne),

thenyl (for thienylmethyl), thenylidene (for thienylmethylene) and thenylidyne (for

thienylmethylidyne).

As exceptions, the names "piperidino" and "morpholino" are preferred to "1-piperidyl" and

"4-morpholinyl".

5.12 - Bivalent radicals derived from univalent heterocyclic radicals whose names end in "-

yl" by removal of one hydrogen atom from the atom with the free valence are named by

adding "-idene" to the name of the corresponding univalent radical.


.

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Bridged Heterocyclic Systems

Rule B-15. Hetero Bridges11

15.1 - A hetero polycyclic system that contains an "ortho-fused" or an "ortho- and peri-

fused" system according to Rule A-21 or B-3 and has one or more atomic bridges is named

as an "ortho-fused" or "ortho- and peri-fused" system. The atomic bridges are then

indicated by prefixes as exemplified in the annexed Table or by Rule A-31.4. The name of

a bridge containing hetero atoms is constructed from units beginning with the terminal

atom that occurs first in Table B-I, the final "o" of a prefix being elided before a vowel in a

following prefix; to illustrate this, the formulae in the annexed Table are arranged from left

to right in the same order as the prefixes. If bridges of different types are present, they are

cited in alphabetical order. For examples see Rule B-15.2.

Azimino

Azo

Biimino

Epidioxy

Epidithio

Epithio

Epithioximino

Epoxy (see also Rule C212.2)

Epoxyimino

Epoxynitrilo

Epoxythio

Epoxythioxy

Furano (usually 3,4)

Imino (see also Rule C815.2)

Nitrilo

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R-1 General Principles of Organic Nomenclature

R-1.2 Nomenclature Operations R-1.2.1 Substitutive operation

R-1.2.2 Replacement operation

R-1.2.3 Additive operation

R-1.2.4 Conjunctive operation

R-1.2.5 Subtractive operation

R-1.2.6 Ring formation or cleavage

R-1.2.1 Substitutive operation .

The substitutive operation involves the exchange of one or more hydrogen atoms for

another atom or group. This process is expressed by a prefix or suffix denoting the atom or

group being introduced (see R-3.2 and R-4 for lists of prefixes and suffixes).

Examples to R-1.2.1

Cyclohexane

Chlorocyclohexane

(substitutive prefix = chloro)

Ethane

Ethanethiol

(substitutive suffix = thiol)

R-1.2.2 Replacement operation

The replacement operation involves the exchange of one group of atom or a single

nonhydrogen atom for another. This can be expressed in several ways as follow:

R-1.2.2.1 By use of "a" prefixes representing the element(s) being introduced, usually

signifying replacement of carbon (see R-9.3). gnu.i

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Examples to R-1.2.2.1

Cyclohexane

Silacyclohexane

(replacement prefix = sila)

Phenanthrene

2,7,9-Triazaphenanthrene

(replacement prefix = aza)

Note: Except for bismuth, a replacement term for a cationic atom of the nitrogen,

chalcogen or halogen families of elements is denoted by replacing the final "a" of the

corresponding replacement term for the neutral heteroatom by "-onia"; the cationic

replacement term for bismuth, the "a" term for which is "bisma", is "bismuthonia" (see R-

5.8.2).

R-1.2.2.2 By use prefixes or infixes signifying replacement of oxygen atoms or oxygen-containing group (see R-3.4). These affixes represent the group(s) being introduced.


(CH3)2P(O)(OCH3)

Methyl dimethylphosphinate

(CH3)2P(NH)(OCH3)

Methyl P,P-dimethylphosphinimidate

(replacement infix = imid(o))

C6H5P(O)(OH)2

Phenylphosphonic acid

C6H5P(N)(OH)

Phenylphosphononitridic acid

(replacement infix = nitrid(o))

The chalcogen affixes "thio-", "seleno-", and "telluro-" indicate replacement of an oxygen

atom by another chalcogen atom.


Benzoic acid

Selenobenzoic acid

Hexanoic acid

Hexane(dithioic) acid gn

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R-1.2.3 Additive operation

The additive operation involves the formal assembly of a structure from its component

parts without loss of any atoms or groups. This can be expressed in various ways as

follows:

R-1.2.3.1 By use of an additive prefix


Naphthalene

1,2,3,4-Tetrahydronaphthalene

(hydro = addition of one H atom)

(homo = addition of a CH2 (methylene)

group, in this case to expand a ring)

Note: Coordination nomenclature, used extensively in nomenclature for inorganic

compounds, is an additive operation.

.R-1.2.3.2 By use of an additive suffix


Pyridine

Pyridinium

(-ium = addition of one H+)

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R-1.2.4 Conjunctive operation .

The conjunctive operation involves the formal construction of the name of a compound

from those of its components with abstraction of the same number of hydrogen atoms from

each component at each site of conjunction. This operation may be expressed:

R-1.2.4. By juxtaposition of component names. This method is most commonly used

when the two components to be joined are: (a) a ring or a ring system; and (b) carbon chain

(or chains) substituted by a principal characteristic group. In this method, both the

principal characteristic group and the ring or ring system must terminate the chain; the rest

of the structure attached to the chain, if any, is described by substituent prefixes, the

location of which is indicated by Greek letter locants, , , etc., ( designating the atom next

to the principal characteristic group).


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R-1.2.5 Subtractive operation

The subtractive operation involves the removal of an atom, ion, or group implicit in a

name. This can occur with no other change, with exchange for hydrogen, with introduction

of unsaturation, or with bond scission and reformation. The elimination of the elements of

water with concomitant bond formation can also be regarded as a subtractive operation.

Subtraction can be expressed in the following ways:

R-1.2.5.1 By use of a prefix


.

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R-1.2.6 Ring formation or cleavage .

R-1.2.6.1 The prefix cyclo-. The formation of a ring by means of a direct link between any

two atoms of a parent structure, with loss of one hydrogen atom from each, is indicated by

he prefix "cyclo-" followed by the name of the parent structure; when appropriate, this

prefix is preceded by the locants of the positions joined by the new bond and by the Greek

letter ( , , ) denoting the configurations at the ends of the new bond. (See R-2.3.1.1 and

Section F of the 1979 edition of the IUPAC Nomenclature of Organic Chemistry.).


R-1.2.6.2 The prefix seco-. Cleavage of a ring with addition of one or more hydrogen

atoms at each terminal group thus created is indicated by the prefix "seco-" (see also

Section F of the 1979 edition of the IUPAC Nomenclature of Organic Chemistry.).


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R-3 Characteristic (Functional) Groups R-3.0 Introduction

R-3.1 Unsaturation

R-3.2 Specification of Characteristic Groups

R-3.3 Functional Parent Compounds and Derived Substituent Groups


R-3.0 Introduction

The prefixes and/or suffixes attached to a parent name specifying a particular molecular

structure usually represent substituents of various types, which are considered to replace

hydrogen atoms of a parent hydride or parent structure. It has been customary to regard

such substituents as characteristic (or functional) when the link between substituent and

parent is not a carbon-carbon bond, for example, , , and , but many

exceptions are recognized, such as and. It seems appropriate at this time to retain

the general view of functionality as implying the presence of heteroatoms and/or

unsaturation, but it would not be helpful to attempt to define precisely the limits of

application of the term.

Carbon-carbon unsaturation in acyclic species is regarded as a special type of functionality

and it is therefore treated here in Section R-3 rather then in Section R-2 (Parent Hydrides);

however, its presence here (and that of hydrogenation of parent hydrides containing the

maximum number of noncumulative double bonds) is anomalous in that for some

purposes, for example, choice of parent, it can be regarded as part of the parent; but for

others, such as numbering, it is treated like a substituent.

Section R-3 also deals with functional parents, i.e., structures which are treated as parent

structures, having substitutable hydrogen atoms, but which possess the characteristics

normally associated with functionality [e.g., phosphonic acid ].

Although, strictly speaking, ions and radicals do not fall within the concept of

functionality, as described above, an ionic centre or a radical centre is treated like a

function, and this treatment is also included, therefore, here in Section R-3.

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R-3.1 Unsaturation .

As noted above (R-3.0), the treatment of unsaturation (of a saturated parent hydride) or

saturation (of an unsaturated parent hydride) is different from that of other functions. This

difference has implications for choice of parent hydride and for numbering. The following

three subsections describe ways to indicate unsaturation/saturation.


R-3.2.1 Prefixes and suffixes

R-3.2.1.1 The presence of a characteristic group can be denoted by a prefix or suffix

attached to the parent name (with elision of terminal "e", if present). Such prefixes and

suffixes are illustrated in Table 5. Additional details for the use of functional prefixes and

suffixes are found in Section R-4 (Name Construction).

R-3.2.1.2 Affixes used to denote ionic or radical centres in a parent structure, classified

according to the type of formal operation by which the ion or radical may be considered to

be derived (see R-5.8), are given in Table 6. Suffixes are added to the name of a parent

hydride in the customary manner or serve as endings to names of characteristic groups.

When needed, ionic centres are expressed as prefixes that terminate with endings given in

the column labelled "Substituent prefix ending", for example, ethan-1-ylium-1-yl,

pyridinio, sulfonato, and propan-2-id-2-yl; for radical centres, the prefix "ylo-" is added in

front of the name of the substituent prefix, for example, 2-yloethyl. In replacement

nomenclature, the replacement prefixes are modified to end as shown in the column

labelled "Replacement prefix endings", for example, azonia and boranylia.

Two or more such operations are indicated by an appropriate multiplying affix, for

example, "-diide", and "-tris(ylium)". Additional details for the use of ionic prefixes and

suffixes are given in Section R-5.8 and in a separate publication.

R-3.2.2 Functional modifiers

Many derivatives of principal characteristic groups or functional parent compounds (see R-

3.3) may be named by name modifiers which consist of one or more separate words placed

after the name of the parent structure. This method is most useful in an indexing

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Note: For indexing purposes, this method is used in Beilstein for esters, acyl halides,

amides, hydrazides, lactones, lactams and nitrogen derivatives of carbonyl compounds

(oximes, hydrazones, etc.). For indexing purposes, this method is also used in Chemical

Abstracts index nomenclature for anhydrides, esters, hydrazides, hydrazones and oximes.

Examples to R-3.2.2

Propanal

Propanal dimethyl acetal

Propanal oxime

Propanal hydrazone

Propionic acid

Propionic acid methyl ester

Propionic acid hydrazide

Note: The use, in this section and elsewhere in this guide, of systematic names, such as

propanal and propanoic acid, rather than retained names (see R-9.1), such as

propionaldehyde and propionic acid, illustrates that, even though some names are retained,

this does not preclude use of the systematic names.

R-3.3 Functional Parent Compounds and Derived

Substituent Groups

Structures which are treated as parent compounds in substitutive nomenclature although

they have characteristics normally associated with functionality are illustrated in Table 7.

.

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REFERENCES

1. International Union of Pure and Applied Chemistry, Nomenclature of Organic

Chemistry, Sections A, B, C, D, E, F, and H, 1979 edition, Pergamon Press, Oxford, 1979:

[a] p. 53-54; [b] Rule B-1.1, Tables I and II, footnotes, p. 53; [c] Rule B-1.1, Table II,

footnote (d), p. 53; [d] Rule B-1.1, Table I, footnote, p. 53; [e] Rule B-1.1, Table I,

footnote, and Table II, footnote (b), p. 53; [f] Rule B-1.2, exception, p. 54; [g] Rules 1.51,

p. 55; [h] pp. 55-63; [i] p.68.

2. A. Hantzsch and J. H. Weber, Ber. Dtsch. Chem. Ges., 20, 3118-3132 (1887).

3. O. Widman, J. Prakt. Chem., 38, 185-201 (1888)

4. www.acdlabs.com/iupac/nomenclature

5. W. H. Hale, J. Am. Chem. Soc., 41, 370-378 (1919).

6. A. M. Patterson, J. Am. Chem. Soc., 50, 3074-7078 (1938).

7. A. M. Patterson and L. I. Capell, The Ring Index, Reinhold, New York, 1940, pp. 20-21.


Chemistry (1957), Sections A and B, 1st ed., Butterworths, London, 1958: [a] Rule B-1,

pp. 51-53; [b] Rule B-1.1, Table I, p. 51; [c] 2nd ed., Butterworths, London, 1966, Table I,

p. 51.

9. International Union of Pure and Applied Chemistry, Definitive Rules of Organic

Chemistry, J. Am. Chem. Soc., 82, 5545-5574 (1960), Comment to Table I, p. 5566.


Chemistry, Sections A and B, 3rd ed. and Section C, 2nd ed., Butterworths, London, 1971:

[a] Rule B-1.1, Table 1, p. 53; [b] Rule B-1.1, Tables I and II, footnotes, p. 53; [c] Rule B-

1.1, Table I, footnote, p. 53.

11. International Union of Pure and Applied Chemistry, Nomenclature of Organosilicon

Compounds, Compt. Rend. Quinziène Conf., Amsterdam, 1949, pp. 127-132.

12. American Chemical Society, Report of the ACS Nomenclature, Spelling and

Pronunciation Committee for the First Half of 1952. F. Organosilicon Compounds, Chem.

Eng. News, 30, 4517-4522 (1952). gnu.i

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IUPAC NOMENCLATURE

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13. A. M. Patterson, L. T. Capell, and D. F. Walker, The Ring Index, 2nd ed., American

Chemical Society, Washington, D.C., 1960; Supplement I, 1963; Supplement II, 1964;

Supplement III, 1965.

14. International Union of Pure and Applied Chemistry, Revision of the Extended

Hantzsch-Widman System of Nomenclature for Heteromonocycles, Provisional

Recommendations, 1978, Pure Appl. Chem., 51, 1995-2003 (1979).

15. Reference 1, Section C: [a] Rule C-41.2, p. 115; [b] Rule C-32.1, p. 114; [c] Preamble,

Elision of Vowels, p. 83; [d] Rule C-923.1, p. 289; [e] Rule C-13.11(e), footnote, p. 99; [f]

pp. 108, 115-116.

16. Reference 1, Section A, Rule A-21.6, p. 25.

17. International Union of Pure and Applied Chemistry, The Designation of Nonstandard

Classical Valence Bonding in Organic Nomenclature (Provisional), Pure Appl. Chem., 54,

217-227 (1982). Revised version now published as: Treatment of Variable Valency in

Organic Nomenclature (Lambda Convention) (Recommendations 1983), Pure Appl.

Chem., 56, 769-778 (1984).

18. International Union of Pure and Applied Chemistry, Nomenclature of Inorganic

Chemistry (1970), 2nd ed., Butterworths, London, 1971, Table IV, p. 104.

19. Reference 1, Section D, Appendix, Table I, pp. 459-460.

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