(a) Write a test to distinguish between aldehydes and ketones.
(b) How will you prepare benzaldehyde by Etard's reaction?
(c) How will you bring about the following conversions? (Write the chemical equations)
(i) Ethanol $\to$ Ethanoic acid
(ii) Benzamide $\to$ Benzoic acid
(iii) Benzaldehyde $\to$ Meta-nitrobenzaldehyde.

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Solution

(a) Aadd a few drops of the aldehyde or ketone to the freshly prepared reagent, and warm gently in a hot water bath for a few minutes. The colourless solution produces a grey precipitate of silver or a silver mirror on the test tube. Aldehydes reduce the diamine silver(I) ion to metallic silver.

(b) The Étard reaction is a chemical reaction that involves the direct oxidation of an aromatic or heterocyclic bound methyl group to an aldehyde using chromyl chloride
(c) i)Ethanol on oxidation with strong oxidising agent gives ethanoic acid

ii) $C_{6} H_{5} C O N H_{2} + H^{+} / H_{2} O / h e a t \to C_{6} H_{5} C O O H$

iii) $C_{6} H_{5} C H O + N a N O_{3} / H_{2} S O_{4} \to m - N O_{2} C_{6} H_{4} - C H O$

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How will you bring about the following conversions in not more than two steps?

(i) Propanone to Propene

(ii) Benzoic acid to Benzaldehyde

(iii) Ethanol to 3-Hydroxybutanal

(iv) Benzene to m-Nitroacetophenone

(v) Benzaldehyde to Benzophenone

(vi) Bromobenzene to 1-Phenylethanol

(vii) Benzaldehyde to 3-Phenylpropan-1-ol

(viii) Benazaldehyde to α-Hydroxyphenylacetic acid

(ix) Benzoic acid to m- Nitrobenzyl alcohol

a .

- 2 -

- 3 -

b .

c .

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