Q.How will you prepare propan-1-amine from

Step 1. i) Butanenitrile, CH3CH2CH2-CN, has FOUR carbons -- one more than the 3-carbon target, propan-1-amine -- so a simple direct reduction (which would give butan-1-amine) is the wrong route. Instead, PARTIAL hydrolysis (H2O2/OH-) stops the nitrile at the amide stage, giving butanamide, CH3CH2CH2-CONH2 (still 4 carbons); Hofmann bromamide degradation (Br2/KOH) then removes exactly the carbonyl carbon, giving propan-1-amine, CH3CH2CH2-NH2 (3 carbons) -- the carbon-shortening step that a direct nitrile reduction could never achieve.

Step 2. ii) Propanamide, CH3CH2-CONH2, already has THREE carbons, matching the target exactly. LiAlH4 reduction of an amide keeps the SAME carbon count (the carbonyl carbon becomes a CH2, it is not lost as CO2 the way Hofmann degradation loses it), so propanamide --LiAlH4--> propan-1-amine directly, with no carbon-count adjustment needed.

Step 3. iii) 1-Nitropropane, CH3CH2CH2-NO2, also already has three carbons. The unit's standard nitro-to-amine reduction (Sn/HCl, or catalytic H2/Ni) simply swaps -NO2 for -NH2 on the same carbon skeleton, giving propan-1-amine directly. …

Count the carbons in each starting material FIRST and compare to the 3-carbon target -- a matching count (ii, iii) needs only a direct reduction, while a mismatch (i, one carbon too many) signals …

• Reducing butanenitrile directly (H2/Ni or LiAlH4) and calling the product propan-1-amine -- direct nitrile reduction preserves the full carbon skeleton, giving butan-1-amine (4 carbons), one carbon too many for the st …