RI 2023 Carboxylic Acids and Derivatives

RAFFLES INSTITUTION YEAR 6 H2 CHEMISTRY 2023 Lecture Notes 18 - Carboxylic Acids & Derivatives A Content I Carboxylic acids {exemplified by ethanoic acid and benzoic acid) {i) Formation from primary alcohols and nitriles {ii) Salt, ester and acyl chloride formation II Acyl chlorides {exemplified by ethanoyl chloride) {i) Ease of hydrolysis compared with alkyl and aryl chlorides {ii) Reaction with alcohols, phenols and primary amines Ill Esters {exemplified by ethyl ethanoate and phenyl benzoate) {i) Formation from carboxylic acids and from acyl chlorides {ii) Hydrolysis {under acidic and under basic conditions) B Learning outcomes Candidates should be able to: {a) describe the formation of carboxylic acids from alcohols, aldehydes and nitrites {b) describe the reactions of carboxylic acids in the formation of {i) salts {ii) esters on condensation with alcohols, using ethyl ethanoate as an example {iii) acyl chlorides, using ethanoyl chloride as an example {iv) primary alcohols, via reduction with lithium aluminium hydride, using ethanol as an example {c) explain the acidity of carboxylic acids and of chlorine-substituted ethanoic acids in terms of their structures {d) describe the hydrolysis of acyl chlorides (e) describe the condensation reactions of acyl chlorides with alcohols, phenols and primary amines (f) explain the relative ease of hydrolysis of acyl chlorides, alkyl chlorides and aryl chlorides (g) describe the formation of esters from the condensation reaction of acyl chlorides, using phenyl benzoate as an example (h) describe the acid and base hydrolyses of esters C References and Websites 1 A-Level Chemistry (by Ramsden) 2 Organic Chemistry (by David Klein) 3 www.chemguide.co.uk

.. CARBOXYLIC ACIDS 1.1 Structure Carboxylic acids may be represented as RCOOH, , where R is Hor alkyl or aryl group. R-c-o-H The functional group of carboxylic acids: carboxyl group (-COOH). The name is a combination of the carbonyl and the hydroxy/ groups. Carboxyl carbon atom is sp2 hybridised • 3 x sp2 hybrid orbitals form cr bonds with the 2 oxygen atoms and the C atom of the R group or H atom. • 1 x unhybridised p-orbital forms a n bond with the p-orbital of O atom of the C=O The molecule is trigonal planar with respect to the carboxyl carbon. 1.2 Nomenclature Carboxylic acids are named by taking the name of the appropriate hydrocarbon, dropping the -e and adding the suffix -oic acid. The longest chain bearing the carboxyl group is considered the parent structure. Numbering of the carbon chain starts from the carboxyl carbon (principal functional group). When two carboxyl groups are present, the sutfix-dioic acid is used. e.g. HOOC-COOH ethanedioic acid HOOCCH2COOH propanedioic acid Ex amp es: 0 0 0 HC g g g 2 -=::-c,,.. 'OH H,,.. 'OH H3C,.,, ' OH methanoic acid ethanoic acid propenoic acid (formic acid) (acetic acid) (acrylic acid) 0 0 II g CH3, /C...._ CH OH O('OH I OH H02C-C02H 2-hy