(A), (B) and (C) are three non-cyclic functional isomers of a carbonyl compound with molecular formula C₄H₈O. Isomers (A) and (C) give positive Tollen's test whereas isomer (B) does not give Tollen's test but gives positive iodoform test. Isomers (A) and (B) on reduction with Zn(Hg)/conc. HCI give the same product (D).

Solution:

• Tollen’s test is given by aldehydes and ketones do not give Tollen's test.
• The iodoform test is given by compounds that have a methyl group attached to a carbonyl carbon.
• The reagent Zn(Hg)/HClZn(Hg)/HClZn(Hg)/HCl is Clemmensen’s reagent and reduces carbonyl carbon into methylene.

Identifying the compound B:

• Compound B does not give Tollen's test but gives the iodoform test.
• So, compound B is a methyl ketone.

Identifying the compound A, C, and D:

• Compound A gives the Tollen's test. So, it is an aldehyde and it also gave the same product on reaction with Clemmenson reagent as given by compound B.
• The compounds B and A gave the same product D on reacting with Clemmensen reagent.
• Compound C is also an aldehyde.

Part b: Which is less reactive towards HCNHCNHCN

• HCN addition reaction to a carbonyl compound is a bimolecular reaction.
• The rate of bimolecular reaction depends upon the steric hindrance.
• So, the compound containing large substituents is less reactive towards HCN addition reaction.
• Hence, ketones are less reactive as compared to aldehyde.
• So, compound B is least reactive towards HCN addition reaction.