By Dr. Nahed Nasser Carboxylic Acids and Their Derivatives

CONTENTS Structure of carboxylic acids Nomenclature Physical properties of carboxylic acids Preparation of carboxylic acids Reaction os carboxylic acids Derivatives of carboxylic acids: a. Acid chlorides b. Esters c. Amides d. Anhydrides Occurrence and uses of carboxylic acids and their derivatives CARBOXYLIC ACIDS

3 STRUCTURE OF CARBOXYLIC ACIDS Carboxylic acids are organic acids contain one or more carboxyl group A carboxyl group is made up of a carbonyl (C=O) group and a hydroxyl (O-H) group It is often written in condensed form as –CO 2 H or –COOH The general formula of a carboxylic acid is R-COOH or Ar-COOH

NOMENCLATURE Of CARBOXYLIC ACIDS IUPAC Nomenclature of carboxylic acids Find the longest continuous carbon chain contains the COOH group to get the name of the parent hydrocarbon, the ending -e is replaced by the suffix –oic acid. Number the chain starting with the carbon of COOH group as C-1 If there are substituents identify their names and positions and list them as prefixes in alphabetical order. Examples: (CH 3 ) 2 CH - CH(CH 3 ) - CH 2 - CH 2 - COOH Examples: (CH 3 ) 2 CH - CH(CH 3 ) - CH 2 - CH 2 - COOH is called 4,5-Dimethylhexanoic acid

5 Cyclic compounds (Aliphatic or aromatic) containing one or more COOH groups attached to the ring are named by identifying the name of the ring followed by the word carboxylic acid or dicarboxylic acids etc. The carbon atom bearing the carboxylic group is numbered 1 and the substituents are numbered relative to it.

6 Common nomenclature of carboxylic acids Some carboxylic acids are called after characteristic properties or their origin. Formula IUPAC name Common name origin of name HCOOH methanoic acid formic acid Latin for ant CH 3 COOH ethanoic acid acetic acid Latin for vinegar CH 3 CH 2 COOH propanoic acid propionic acid Greek for milk CH 3 (CH 2 ) 2 COOH butanoic acidbutyric acid Latin for butter CH 3 (CH 2 ) 3 COOH pentanoic aicvaleric acid valerian root The positions of the carbons present on the acid chain, are located by the Greek letters α indicating the carbon atom next to COOH group (C2), β (C3), γ (C4), δ (C5), etc.

7 Some aromatic acids have common names. common:  -  - Dimethyl butyric acid IUPAC: 2,3-Dimethyl butanoic acid

8 Carboxylic acids are polar, they can form hydrogen bonds with water molecules Smaller carboxylic acids (1 to 4 carbons) are soluble with water Whereas the solubility of bigger carboxylic acids decrease with size due to the increasing hydrophobic nature of the alkyl chain. Aromatic acids are insoluble in water PHYSICAL PROPERTIES OF CARBOXYLIC ACIDS Solubility

Carboxylic acids have exceptionally high boiling points than alcohols of identical relative molecular masses, For example: M.F. M.Wbp / °C 1- PropanolC 3 H 8 O Ethanoic acidC 2 H 4 O This is due to carboxylic acids usually exist as dimeric pairs by forming two intramolecular hydrogen bonds in nonpolar media Boiling Points

Acidity and acid strength Carboxylic acids are the most acidic simple organic compounds (they are stronger acids by over ten powers of ten compared to alcohols of comparable weights); also they are more acidic than phenols However, they are weak acids compared to inorganic acids (HCl or H 2 SO 4 ) nearAdjacent electron withdrawing substituents near the carboxyl group increase the acidity Whereas electron releasing substituents decrease the acidity. 10 HCOOH > CH 3 COOH > CH 3 CH 2 COOH > CH 3 CH 2 CH 2 CH 2 COOH ( size of R group) Cl 3 CCOOH > Cl 2 CHCOOH > ClCH 2 COOH > CH 3 COOH > (OCH 3 )CH 2 COOH ( number of e.w.g. and e.r. g.) CH 3 CH 2 CH 2 CH(Cl)COOH > CH 3 CH 2 CH(Cl)CH 2 COOH > CH 3 CH(Cl)CH 2 CH 2 COOH > CH 2 (Cl)CH 2 CH 2 CH 2 COOH ( position of e.w.g. relative to COOH group)

Preparation of Carboxylic acids 1- Oxidation of primary alcohols or aldehydes 2- Oxidation of Alkylbenzenes

3- Carbonation of Grignard Reagents 4- Hydrolysis of nitriles

Reactions of Carboxylic Acids 1- Salts Formation

2- Substitution of hydroxyl group

Carboxylic Acid Derivatives Acid Chloride Ester Amide acid anhydride 1-Nomenclature of acid chloride Replace the -ic acid ending in the name of the parent acid by –yl chloride IUPAC: Ethanoyl chloride Benzoylchloride Common : Acetyl chloride

Reactions of Acid Chlorides

2- Nomenclature of esters The alkyl group (R’) is named first followed by the name of the parent acid with the ending –ate in place of –ic acid ending e.g.: IUPAC: Ethyl ethanoate Methyl benzoate Common: Ethyl acetate

Reactions of Esters

3- Nomenclature of amides Replace the oic acid ending of the parent acid by amide word IUPAC: Ethanamide Benzamide Common: Acetamide IUPAC: N,N-Dimethylmethamide N-Ethyl-N-methylbenzamide Common:N,N-Dimethylformamide

Reactions of Amides

4- Nomenclature of acid anhydrides An anhydride is named by replacing the word acid by the word anhydride in the name of the parent acid. Ethanoic anhydride Benzoic anhydide Succinic anhydride

Reactions of Acid anhydride

Occurrence and Uses of Carboxylic Acids and their Derivatives Carboxylic acids and their derivatives are widespread in nature 23

Carboxylic acids are used in the production of polymers, pharmaceuticals, solvents, and food additives. Examples 24