How is acetic acid prepared from

(a) Ethanol

(b) Acetylene

(a) Ethanol under high pressure and low temperature when treated with oxidising agent like acidified potassium dichromate produces ethanoic acid (acetic acid).

$\underset{ \text{ ethanol[ethyl alcohol]}}{\text{C}$2\text{H}5\text{OH}} \xrightarrow[\text{K}2\text{Cr}2\text{O}7]{\text{[O]}} \underset{\text{ethanal [acetaldehyde] }}{\text{CH}3\text{CHO}} \xrightarrow[\text{K}2\text{Cr}2\text{O}7]{\text{[O]}} \underset{ \text{ethanoic acid[acetic acid]} }{\text{CH}3\text{COOH}}

(b) Acetylene is first converted to acetaldehyde by passing it through a 40 percent H₂SO₄ solution at 60°C in the presence of 1% Mercury(II) Sulphate [HgSO₄].

$\underset{\text{acetylene}}{\text{C}$2\text{H}2} + \text{H}2\text{O} \xrightarrow{\text{H}2\text{SO}4\text{(dil) , HgSO}4}\underset{\text{ethanal [acetaldehyde] }}{\text{CH}_3\text{CHO}}

The acetaldehyde is oxidised to acetic acid by passsing a mixture of acetaldehyde vapous and air over manganese acetate at 70°C

$\underset{\text{ethanal [acetaldehyde] }}{2\text{CH}$3\text{CHO}} + \text{O}2 \xrightarrow[\text{Catalyst}]{\Delta} \underset{ \text{ethanoic acid[acetic acid]} }{2\text{CH}_3\text{COOH}}