Question

CH₃CH₂COOH □(→┴(Cl₂) A □(→┴(alc.KOH) )B. What is B?
(a) CH₃CH₂COCl (b) CH₃CH₂CHO
(c) CH₂=CHCOOH (d) ClCH₂CH₂COOH.

Answer 1

I think the correct answer is (b)

Answer 2

B is

c) CH₂=CHCOOH

When a carboxylic acid reacts with Cl₂ or Br₂ in presence of red phosphorus, the alpha-Hydrogen of the acid gets replaced by the Cl or Br atom accordingly.

So,  CH₃CH₂COOH + Cl₂ → CH₃CH(Cl)COOH

When the resulted compound reacts with alcoholic KOH, alkene is formed (HCl is removed)

CH₃CH(Cl)COOH + alc. KOH → CH₂=CH-COOH + HCl

So, option (c) is correct.