Geminal dihalides hydrolyze to aldehydes positive with Tollens' reagent

Steps:

• Classify each dibromobutane as geminal (both Br on same C) or not.
• Hydrolysis of geminal dihalides (RCHBr₂) yields aldehydes (RCHO); others yield diols or ketones.
• Aldehydes reduce Tollens' reagent (Ag⁺ in NH₃) to Ag mirror; ketones and diols do not.
• Select option producing aldehyde.

Why A is correct:

• 1,1-Dibromobutane (CH₃CH₂CH₂CHBr₂) hydrolyzes to butanal (CH₃CH₂CH₂CHO), an aldehyde that gives silver mirror per Tollens' test definition.

Why the others are wrong:

• B: 1,2-Dibromobutane hydrolyzes to 1,2-butanediol (vicinal diol), which does not form carbonyl.
• C: 1,3-Dibromobutane hydrolyzes to 1,3-butanediol, which does not form carbonyl.
• D: 2,2-Dibromobutane (CH₃CBr₂CH₂CH₃) hydrolyzes to butan-2-one, a ketone that fails Tollens' test.

Final answer: A