Carboxylic Acids and its Derivatives

1. Introduction

Carboxylic acids contain the carboxyl group $\ce{-COOH}$ (a carbonyl $\ce{C=O}$ plus a hydroxyl $\ce{-OH}$ on the same carbon). General formula $\ce{R-COOH}$; the simplest is methanoic (formic) acid $\ce{HCOOH}$ and the next is ethanoic (acetic) acid $\ce{CH3COOH}$.

The carboxyl group is the reason these compounds are the most acidic common organic compounds: after losing $\ce{H+}$, the resulting carboxylate ion $\ce{RCOO-}$ is stabilised by resonance (the negative charge is shared equally over the two oxygen atoms), which is why the acid readily gives up its proton.

2. Nomenclature and Isomerism

IUPAC: replace the -e of the parent alkane by -oic acid; the carboxyl carbon is C-1. Aromatic: benzoic acid $\ce{C6H5COOH}$.

They show chain and position isomerism, and are functional isomers of esters ($\ce{C2H4O2}$: acetic acid $\ce{CH3COOH}$ or methyl formate $\ce{HCOOCH3}$).

3. Preparation of Monocarboxylic Acids

3.1 By oxidation of 1 degree alcohols or aldehydes

$\ce{CH3CH2OH + [O] -> CH3CHO + [O] -> CH3COOH}$

3.2 By hydrolysis of nitriles (adds one carbon)

$\ce{CH3CN + 2H2O ->[H+][\Delta] CH3COOH + NH3}$