2013 lect1a naming oc (alkane)

7/29/2019 2013 Lect1a Naming OC (Alkane)

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NAMING ORGANIC COMPOUNDS:

Straight chain (alkanes, alkenes, alkynes) and ring

chain hydrocarbon : rootname, numbering locant,

complex substituent, prioritization of double bond,Halogen, oxygen, nitrogen containing compound :

rootname pattern (prefix, suffix), prioritization of

functional group, numbering locant


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2

This chapter deals with alkanes, compounds

that contain only carbons and hydrogens, allconnected exclusively by single bonds


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ALKANES AND THEIR ISOMERS

Alkanes are compounds with C-C single bonds and C-H bondsonly (no functional groups). The connecting carbons can lead tolarge or small molecules

The formula for an alkane must be CnH2n+2 where the number of

Cs is n Alkanes are saturated with hydrogen (no more can be added.

They are also called aliphatic compounds


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NAMES OF SMALL HYDROCARBONS

No. of Carbons Formula Name (CnH2n+2)

1 Methane CH4

2 Ethane C2H6

3 Propane C3H8

4 Butane C4H10

5 Pentane C5H12

6 Hexane C6H14

7 Heptane C7H16

8 Octane C8H18

9 Nonane C9H20

10 Decane C10

H22

No of

carbons11 12 13 14 15 20 30 40 50

Prefix Undec Dodec Tridec Tetradec Pentadec Eicos Triacont Tetracont Pentacont


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Alkane Isomers

CH4 = methane, C2H6 = ethane, C3H8= propane

The molecular formula of an alkane with more than threecarbons can give more than one structure

C4 (butane) = butane and isobutane

C5 (pentane) = pentane, 2-methylbutane, and 2,2-dimethylpropane

Alkanes with Cs connected to no more than 2 other Csare straight-chain ornormal alkanes

Alkanes with one or more Cs connected to 3 or 4 Cs arebranched-chain alkanes


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ALKYL GROUPS

remove one H from an alkane (a part of a structure)

General abbreviation R (for Radical, the rest of the

molecule)

Name: replace -ane ending of alkane with -ylending

CH3is methyl (from methane)

CH2CH3is ethyl from ethane


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Types of Alkyl groups

Classified by the connection site (See Figure 3.3) a carbon at the end of a chain (primary alkyl group)

a carbon in the middle of a chain (secondary alkyl group)

a carbon with three carbons attached to it (tertiary alkyl

group)


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*

*

**

* Commonly used, should be memorized

Common names


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Also...

or

Phenyl

or C6H5


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Naming Alkanes

Compounds are given systematic names by a process that

uses

Prefix-Parent-Suffix

Follows specific rules

Named as longest possible chain

Carbons in that chain are numbered in sequence

substituents are numbered at their point of attachment

Compound name is one word (German style)

Complex substituents are named as compounds would be


13/59WWU Chemistry

IUPAC nomenclature of alkanes

Single substituent group

identify the longest chain -- parent

number from the end closest to substituent

identify the substituent and number it

combine number and name of substituentwith parent name, separating with hyphen


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longest possible chain =parent

substituen


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CH3

CH2

CH CH3

CH3

Organic nomenclature

4 3 2 1

2-methylbutane


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CH3

CH2

CH CH3

CH2

CH3

Find the longest continuous

carbon chain

1 2 3

4 5

3-methylpentane


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CH3

CH2

CH CH2

CH2

CH3

CH2

CH2

CH3

You must choose the longest

continuous carbon chain

4 3 2 1

5 6 7

4-ethylheptane


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Two different substituents

number chain from end closestto a group,

regardless of alphabetical order

locate where groups are on chain withnumbers

place groups in alphabetical order, with the

appropriate number

assemble the complete name, using hyphens

to separate numbers from text


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WWU Chemistry

CH3

CH2

CH2

CH CH CH2

CH3

CH3

CH2

CH3

Number from the end nearest

the first substituent

7 6 5 4 3 2 1

4-ethyl-3-methylheptane


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WWU Chemistry

CH3 CH2 CH2 CH CH2 CH CH2 CH3

CH2

CH3

CH3


the first substituent

8 7 6 5 4 3 2 1

3-ethyl-5-methyloctane


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WWU Chemistry

Two or more identical substituent

groups for two identical groups, use prefix di with

the name of the group: dimethyl, diethyl etc.

dimethyl alphabetized as methyl, notdimethyl

use numbers to locate groups on chain

use commas to separate numbers

prefixes: di = 2 tri = 3

tetra = 4 penta = 5


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WWU Chemistry

CH3 CH CH CH3

CH3

CH3

Use di- with two substituents

1 2 3 4

2,3-dimethylbutane


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WWU Chemistry

CH3 CH2 C CH2 CH2 CH3

CH3

CH3

Every substituent must get a number

1 2 3 4 5 6

3,3-dimethylhexane


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WWU Chemistry

CH3 CH2 CH CH CH2 CH2 CH2 CH2 CH CH3

CH3

CH3

CH3


first substituent

10 9 8 7 6 5 4 3 2 1

2,7,8-trimethyldecane


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WWU Chemistry

CH3 CH2 CH CH CH2 CH2 CH2 CH CH2 CH3

CH3

CH3

CH3

Number from the end which has

the first difference

1 2 3 4 5 6 7 8 9 10

3,4,8-trimethyldecane


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WWU Chemistry

CH3

CH CH2

C CH3

CH3

CH3

CH3

you need numbers, even though it

appears on the same carbon!

5 4 3 2 1

2,2,4-trimethylpentane


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WWU Chemistry

CH3 CH2 CH CH CH2 CH CH2 CH3

CH3

CH3

CH2

CH3


the first difference

1 2 3 4 5 6 7 8

6-ethyl-3,4-dimethyloctane


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WWU Chemistry

CH3

CH2

CH CH2

CH2

CH CH2

CH3

CH3

CH2

CH3

Which end do we number from?

8 7 6 5 4 3 2 1

3-ethyl-6-methyloctane


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WWU Chemistry

If you can name this,

you can name almost anything!

1 2 3 4 5 6

7

8 9

4-isopropyl-2,6,6-trimethylnonane

CH3 CH CH2 CH CH2 C CH3

CH3

CH

CH3

CH3

CH3

CH2

CH2 CH3


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WWU Chemistry

The isopropyl group can be named

as a complex substituent

1-methylethyl

CH3

CH

CH3

2 1


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WWU Chemistry

Now, rename the isopropyl group.

Notice the alphabetical order!

1 2 3 4 5 6

7

8 9

2,6,6-trimethyl-4-(1-methylethyl)nonane

CH3 CH CH2 CH CH2 C CH3

CH3

CH

CH3

CH3

CH3

CH2

CH2 CH3


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WWU Chemistry

Naming complex substituents -- this

one is aphabetized under d

1,3-dimethylbutyl

CH3 CH CH2 CH

CH3

CH3

4 3 2 1


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WWU Chemistry

deciding on alphabetical order for

complex groups Complex groups are alphabetized under the

first letter of the name

(1,3-dimethylbutyl) = d

(1,1,2-trimethylpropyl) = t

(1-ethyl-1,2-dimethylbutyl) = e


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WWU Chemistry

Naming complex substituents

2-ethyl-1,1-dimethylbutyl

CH3 C CH CH2 CH3

CH3

CH2

CH3

1 2 3 4


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WWU Chemistry

CH3

CH2

CH2

CH2

C CH2

CH2

CH2

CH3

C

CH2

CH2

CH3

CH3

CH2

CH2

CH3

CH3

Name this compound!

1 2 3

1 2 3 4 5 6 7 8 9

5-(1-ethyl-1-methylpropyl)-5-propylnonane

hi ( h l


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WWU Chemistry

CH2CH2

CH2CHCH2

CH3

C CH2CH

2CH3

CH2

CH3

CH3

CCH3

CH3

CH3

name this two ways -- (the complex

group)

7-(1,1-dimethylethyl)-3-ethyl-7-methyldecane

7-tert-butyl-3-ethyl-7-methyldecane


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Illustration 3(CH3)2CH2CH(C2H5)C(CH3)3

3-ethyl-2,2,5-trimethylhexane


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Illustration 4.

Write a structural formula for the compound

3,4-dichloro-4-ethyl-5-methylheptane

CH3CH2CHClCCl(C2H5)CH(CH3)CH2CH3 orC2H5CHClCCl(C2H5)CH(CH3)C2H5


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Give another example


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Naming Cycloalkanes

Count the number of carbon atoms in the ring and the numberin the largest substituent chain. If the number of carbon atomsin the ring is equal to or greater than the number in thesubstituent, the compound is named as an alkyl-substituted

cycloalkane

For an alkyl- orhalo-substituted cycloalkane, start at a pointof attachment as C1 and number the substituents on the ringso that the secondsubstituenthasas low a numberas possible.

Numberthe substituents and write the name

See text for more details and examples


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1,3-dimethylcyclohexane

methylcyclopentane

1,2-dimethylcyclobutane

CH3

CH3

CH3

CH3

CH3


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WWU Chemistry

Two ways of naming this

1-isopropyl-2-methylcyclohexane

1-methyl-2-(1-methylethyl)cyclohexane

CH3

CH

CH3

CH3


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WWU Chemistry

Cycloalkyl groups

Cyclopropyl Cyclobutyl

Cyclopentyl Cyclohexyl


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monosubstituted cycloalkanes

highly substituted cycloalkanes

Illustration 5.


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Illustration 6.


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C C C A A S


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BICYCLIC ALKANES. One Ring Carbon Common

(rings sharing only one carbon)

the two rings are not in the same plane, in fact they are at right angles to

each other at the common carbon

spiro[4.4]nonane spiro[3.5]nonane spiro[2.6]nonane

To name these compounds, the root name is taken from the totalnumber of carbons in both rings

leading to the name spirononane

they are constitutional isomers (differing in atom connectivity) of each other.


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Numbering for positioning ring substituents

numbering of the rings starts in the small ring next to the ring junction,

passes round this ring and through the ring junction into the larger ring.The numbering goes round the two rings in the direction whichproduces

substituents with the lowest numbers in each ring.

2,6-dimethylspiro[4.5]decane 2,6-dimethylspiro[3.3]heptane.

1,2,4,8-tetramethylspiro[2.5]octane


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two carbons common

the carbon atoms labeled a and b are the

carbons common to the two rings, often

refered to asbridgehead carbons,

and the three different paths between a and b

contain 1,2 and 4 intervening carbon atoms

bicyclo[4.2.1]nonane

bicyclo[2.2.1]heptane


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bicyclo[4.3.2]undecane bicyclo[4.1.0]heptane

bicyclo[4.4.0]decane

decalin


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Numbering the ring systems for substituent positioning

Start with one ofthe bridgehead carbons and number it 1.

Proceed round the longest chain of carbons to the secondbridgehead.

Number the second bridgehead carbon and continue on roundthe next longest chain of carbons back towards the firstbridgehead carbon.

Pass over the first bridgehead carbon (it already has thenumber 1) and along the shortest chain of carbons to the secondbridgehead carbon again.

bicyclo[4.1.0]heptane


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7,7-dimethylbicyclo[2.2.1]heptane

4-ethyl-2-isopropylbicyclo[4.1.0]heptane

1-methyl-8-propylbicyclo[4.3.0]nonane

1,9-dimethylbicyclo[4.2.1]nonane

2,6,6-trimethylbicyclo[3.1.1]heptane


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WWU Chemistry

Alkene nomenclature

ending is ene

identify the longest chain with the C=C

number from the end closest to the C=C and

assign a number - - i.e. 2-pentene

C=C is more important than groups!!

now number the attached groups


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WWU Chemistry

Nomenclature of alkynes

similar system used as with alkenes

ending is yne

identify the longest chain with the triple

bond

everything else is the same as alkenes


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2013 lect1a naming oc (alkane)

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