(i) Benzoic acid to Benzaldehyde
• Benzoic acid is chlorinated with thinly chloride to obtain Benzoyl chloride.
• Benzoyl chloride is hydrogenated to obtain Benzaldehyde- Rosenmund’s reduction.
(ii) Ethyne to Ethanal
On treating alkynes with H2SO4 and HgSO4 , a molecule of water is added to form aldehydes.
(iii) Acetic acid to methane
• Acetic acid is first converted to its sodium salt.
• Sodium salt of acetic acid is heated with sodium hydroxide & calcium oxide to form methane. In this process a molecule of CO2 is lost.
(i) Stephen Reaction
• On treating nitriles with stannous chloride in the presence of HCl, it is reduced to imine.
• Imine when hydrolysed results in aldehydes.
(ii) Wolff Kishner reduction
When a carbonyl compound is treated with hydrazine followed by heating with sodium or potassium hydroxide in boiling solvent like ethylene glycol, it gets reduced to a hydrocarbon. (CO group changes to CH2 group).
(iii) Etard reaction
On treating Toluene with chromyl chloride, methyl groul is oxidized to a chromium complex which on hydrolysis results in benzaldehyde.
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