chem 2412 additional nomenclature
DESCRIPTION
Chem 2412 Additional Nomenclature. The Importance of Carboxylic Acids (RCO 2 H). Starting materials for acyl derivatives (esters, amides, and acid chlorides) Abundant in nature from oxidation of aldehydes and alcohols in metabolism Acetic acid, CH 3 CO 2 H, - vinegar - PowerPoint PPT PresentationTRANSCRIPT
John E. McMurry
www.cengage.com/chemistry/mcmurry
Paul D. Adams • University of Arkansas
Chem 2412 Additional Nomenclature
Starting materials for acyl derivatives (esters, amides, and acid chlorides)
Abundant in nature from oxidation of aldehydes and alcohols in metabolism Acetic acid, CH3CO2H, - vinegar
Butanoic acid, CH3CH2CH2CO2H (rancid butter) Long-chain aliphatic acids from the breakdown of fats
The Importance of Carboxylic Acids (RCO2H)
1. Carboxylic Acids (3 O bonds, 1 OH)
2. Esters (3 O bonds, 1 OR)
3. Amides
4. Nitriles
5. Aldehydes (2 O bonds, 1H)
6. Ketones (2 O bonds)
7. Alcohols (1 O bond, 1 OH)
8. Thiols
9. Amines
10. Alkenes, Alkynes
11. Alkanes
12. Ethers
13. Halides
The parent will be determined based on the highest priority functional group.
O OH
OH
2-ethyl-4-hydroxybutanoic acid
Functional Group Priority
Carboxylic Acids, RCO2H If derived from open-chain alkanes, replace the terminal -
e of the alkane name with -oic acid The carboxyl carbon atom is C1
20.1 Naming Carboxylic Acids and Nitriles
Compounds with –CO2H bonded to a ring are named using the suffix -carboxylic acid
The CO2H carbon is not itself numbered in this system Use common names for formic acid (HCOOH) and
acetic acid (CH3COOH) – see Table 20.1
Alternative Names
Closely related to carboxylic acids named by adding -nitrile as a suffix to the alkane name, with the nitrile carbon numbered C1
Complex nitriles are acids; named as derivatives of carboxylic acids. Replace -ic acid or -oic acid ending with -onitrile
Nitriles, RCN
Carboxyl carbon sp2 hybridized: carboxylic acid groups are planar with C–C=O and O=C–O bond angles of approximately 120°
Carboxylic acids form hydrogen bonds, existing as cyclic dimers held together by two hydrogen bonds
Strong hydrogen bonding causes much higher boiling points than the corresponding alcohols
20.2 Structure and Properties of Carboxylic Acids
Carboxylic acids are proton donors toward weak and strong bases, producing metal carboxylate salts, RCO2
+M
Carboxylic acids with more than six carbons are only slightly soluble in water, but their conjugate base salts are water-soluble
Dissociation of Carboxylic Acids
Carboxylic acids transfer a proton to water to give H3O+ and carboxylate anions, RCO2
, but H3O+ is a much stronger acid
The acidity constant, Ka,, is about 10-5 for a typical carboxylic acid (pKa ~ 5)
Acidity Constant and pKa
Electronegative substituents promote formation of the carboxylate ion
Substituent Effects on Acidity
Fluoroacetic, chloroacetic, bromoacetic, and iodoacetic acids are stronger acids than acetic acid
Multiple electronegative substituents have synergistic effects on acidity
Inductive Effects on Acidity
Acyl group bonded to X, an electronegative atom or leaving group
Includes: X = halide (acid halides), acyloxy (anhydrides), alkoxy (esters), amine (amides), thiolate (thioesters), phosphate (acyl phosphates)
Carboxylic Compounds
Nucleophilic acyl substitution
Why this Chapter?
Carboxylic acids are among the most widespread of molecules.
A study of them and their primary reaction “nucleophilic acyl substitution” is fundamental to understanding organic chemistry
General Reaction Pattern
Acid Halides, RCOX Derived from the carboxylic acid name by replacing the -ic
acid ending with -yl or the -carboxylic acid ending with –carbonyl and specifying the halide
21.1 Naming Carboxylic Acid Derivatives
If symmetrical replace “acid” with “anhydride” based on the related carboxylic acid
Unsymmetrical anhydrides— cite the two acids alphabetically
Naming Acid Anhydrides, RCO2COR'
With unsubstituted NH2 group. replace -oic acid or -ic acid with -amide, or by replacing the -carboxylic acid ending with –carboxamide
If the N is further substituted, identify the substituent groups (preceded by “N”) and then the parent amide
Naming Amides, RCONH2
Naming Amides
N,N-dimethylethanamide
CH3
CH3
CH3
O
N
CH3
CH3CH3
H
O
N
N-isobutylmethylbutanamide
CH3
O
N
N-ethyl-N-phenylbenzamide
CH3
CH3
O
NH
N,2-dimethylbenzamide
Name R’ and then, after a space, the carboxylic acid (RCOOH), with the “-ic acid” ending replaced by “-ate”
Naming Esters, RCO2R’
Naming Esters Esters may have common or IUPAC names The first word of the name of an ester is the name of alkyl or aromatic group (R) Change the –ic acid ending of the acid name to –ate (like naming carboxylic acid salts) Parent contains the –COO group
methyl ethanoate phenyl butanoate ethyl benzoate
isopropyl methanoate
methyl benzoate
O
CH3
OCH3
CH3
O O O
O CH3
CH3
CH3O
H
O
O
OCH3
For simple amines, the suffix -amine is added to the name of the alkyl substituent
IUPAC Names – Simple Amines
IUPAC Names – “-amine” Suffix
Replace –e in alkane with –amine. Number position of amino group lowest on parent chain. If substituent on nitrogen, prefixed with N.
3-Pentanamine
NH2
CH3CH3
3-Methyl-1-butanamine
NH2
CH3
CH3
CH3NH
CH3
CH3
N-Methyl-2-butanamine
NH2
CH3
CH3
2-Hexanamine
CH3
NH
CH3
CH3
CH3 CH3
N
CH3
CH3
N-Methyl-2-hexanamine N,N-Dimethyl-2-hexanamine
CH3CH3
N
CH3
CH3
NH2
NH2
CH3
CH3NH2
N-Ethyl-N-methyl-2-hexanamine 2,5-hexanediamine cyclohexylamine
Consider the –NH2 as an amino substituent on the parent molecule
IUPAC Names – Amines with More Than One Functional Group
Symmetrical secondary and tertiary amines are named by adding the prefix di- or tri- to the alkyl group
IUPAC Names – Multiple Alkyl Groups
Named as N-substituted primary amines Largest alkyl group is the parent name, and other
alkyl groups are considered N-substituents
IUPAC Names – Multiple, Different Alkyl Groups
If the nitrogen atom occurs as part of a ring, the compound is designated as being heterocyclic
Each ring system has its own parent name
Common Names of Heterocyclic Amines
Many common names (toluene = methylbenzene; aniline = aminobenzene)
Monosubstituted benzenes systematic names as hydrocarbons with –benzene C6H5Br = bromobenzene C6H5NO2 = nitrobenzene, and C6H5CH2CH2CH3 is
propylbenzene
15.1 Naming Aromatic Compounds
6 C ring structures with alternating double bonds (benzene). Everything that is not aromatic, is aliphatic (alkanes, alkenes,
alkynes). Early problem chemists found was that benzene was not reactive
(recall that alkenes are reactive due to double bond). Kekule proposed that double bonds alternated between 2
equivalent structures electrons move around a conjugated pi bond system of rings Stabilizes structure and makes it less reactive.
Aromatics
1. For single replacement (H some FG), cmpd named as a benzene derivative.
CH3
N+ O
-O
CH3 OH
CH3CH3OHO
propylbenzene nitrobenzene methylbenzene hydroxybenzene
isopropylbenzene carboxybenzene
Naming Benzene Derivatives
Some common names are IUPAC-accepted and used preferentially.
Naming Benzene Derivatives (Continued)
With only 2 groups on benzene ring, can use o, m, p (ortho, meta, para) nomenclature.
CH3
CH3
CH3
CH3
CH3
CH3
o- m- p-
p-methylanilinep-aminotoluene
m-dichlorobenzeneo-nitrotoluene
CH3 N+
O-
OCl
Cl
NH2
CH3
Naming Benzene Derivatives (Continued)
Choose numbers to get lowest possible values List substituents alphabetically with hyphenated numbers Common names, such as “toluene” can serve as root name (as in TNT)
Naming Benzenes with More Than Two Substituents
When a benzene ring is a substituent, the term phenyl is used (for C6H5
?)
You may also see “Ph” or “” in place of “C6H5”
“Benzyl” refers to “C6H5CH2?”
The Phenyl Group
• The benzene ring can also be an attached substituent group.
CH3 CH3
4-phenylheptane 1,1-diphenylcyclobutane
Benzene as a Phenyl group