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