question_answer

  (a) An organic compound (A) with the molecular formula forms 2, 4-DNP derivative reduces Tollen's reagent and undergoes Cannizzaro reaction. On vigorous oxidation it gives 1,2-benzene dicarboxylic acid. Identify the compound (A). (b) Give simple chemical tests to distinguish between the following pairs of compounds. (i) Phenol and benzoic acid                          (ii) Benzaldehyde and acetophenone.                                    [3 + 3] Or (a) Predict the products of the following reactions.   (i)     (ii)   (iii)       (b) Describe the following giving linked chemical equations. (i) Aldol condensation                                                    (ii) Stephen reaction                                                                       [3 + 2]

Answer:

  (a)

Properties	Conclusion
(A) from 2, 4,-DNP derivatives	(A) Has carbonyl group
(A) reduces Tollen's reagent	Carbonyl group is ?CHO
(A) gives Cannizzaro reaction	(A) Has-CHO group attached towithout any H
(A)gives, 1,2-benzene dicarboxylic acid	(A)Has benzene nucleus with ?CHO group and alkyl group in 1,2-position

Thus, (A) is Since, (A) is Hence, R. is (by difference) (A) is                    Reactions   [3]

(i)		Phenol	Benoic acid
(p)	Add neutral solution Addsolution	Violet colour	Buff coloured ppt
(q)	Add	No reaction	Brisk [1] Effervescence
(ii)		Benzaldehyde	Acetophenone
(p)	Iodoform test with	No yellow ppt	Yellow ppt of
(p)	Tollen's reagent test	Silver mirror is formed	No reaction [1]

lodoform test Silver mirror test Or   (a)    (i) (ii) [1] (iii) (b) (i) Aldehydes and ketones with at least one condenses in presence of base forming a product having ?OH and carbonyl group. This product is called aldol and reaction is called aldol condensation. Aldol on heating changes to enol.               [1] (ii) Stephen reaction Nitriles can be converted aldehydes by reduction using This is called Stephen reaction.