(a) Illustrate the following name reactions by giving example :
(i) Cannizzaro's reaction
(ii) Clemmensen reduction
(b) An organic compound A contains `69.77`% carbon , `11.63` % hydrogen and rest oxygen .
The molecular mass of the compound is 86. it does not reduce Tollen's reagent but forms an addition compound with sodium hydrogen sulphite and give positive iodoform test.
On vigorous oxidation it gives ethanoic and propanoic acid. Derive the possible structure of compound A .

Explanation

(a) (i) Cannizaro's Reaction : Aldehydes which do not contain any `alpha`-hydrogen atom such as formaldehyde HCHO and benzaldehyde `C_(6)H_(5)CHO` undergo self oxidation and reduction reaction on treatment with concentrated alkali . A mixture of an alcohol and a salt of a carboxylic acid is formed.
`underset("Methanal")(HCHO) + HCHO overset(NaOH)(to) underset("Methanol")(CH_(3)OH) + underset("Sod. formate")(HCOONa)`
(ii) Clemmensen reduction : The carbonyl group of aldehyde and ketones is reduced to `CH_(2)` group on treatment with zinc amalgam and concentrated hydrochloric acid.

(b) (a) Calculation for molecular formula
C = 69.77% . H = 11.63 %
`therefore O = 100-(69.77 + 11.63) = 18.6`%

Emperical formula of given compound = `C_(5)H_(10)O`
Emperical formula mass = `5 xx 12 + 10 xx 1 + 1 xx 16 = 86`
Given molar mass = 86
`therefore " " n = (86)/(86) = 1`
Molecular formula of the given compound = ` 1 xx (C_(5)H_(10)O) = (C_(5)H_(10)O)`
Determination of structure : Since the compound does not reduce Tollen's reagent and gives a positive iodoform test . So the given compound is ketone and not aldehyde .
Since the given compound on vigorous oxidation gives a mixture of ethanoic acid and propanoic acid . Therefore , given Organic compound is methyl ketone and its structure would be `CH_(3)COCH_(2)CH_(2)CH_(3)`.
`underset("Pentan-2-one(Methyl Ketone)")(CH_(3)COCH_(2)CH_(3)) overset(K_(2)Cr_(2)O_(7))underset(H_(2)SO_(4))(to) underset("Ethanoic acid")(CH_(3)COOH) + CH_(3)underset("Propanoic acid")(CH_(2)COOH)`