Considering the below reactions, the compound 'A' and compound 'B', respectively are:

Step 1: Reaction with AgCN

1-Bromopropane + AgCN → ?

AgCN is covalent (Ag-CN bond):

• Metal bonded to carbon end
• Nucleophile attacks through nitrogen end
• Product: Isocyanide ($\ce{R-NC}$)

$\ce{CH3CH2CH2Br + AgCN -> CH3CH2CH2-NC + AgBr}$

Compound A = 1-Isocyanopropane (propyl isocyanide)

Structure: $\ce{CH3-CH2-CH2-N≡C}$

Step 2: Reaction with NaCN

1-Bromopropane + NaCN → ?

NaCN is ionic (Na⁺ and CN⁻):

• Free $\ce{CN-}$ ion
• Attacks through carbon end (more nucleophilic)
• Product: Nitrile ($\ce{R-CN}$)

$\ce{CH3CH2CH2Br + NaCN -> CH3CH2CH2-CN + NaBr}$

Compound B = Butanenitrile (propyl cyanide)

Structure: $\ce{CH3-CH2-CH2-C≡N}$

Step 3: Match with options

Option (c) shows:

• A = Isocyanide ($\ce{R-NC}$) ✓
• B = Nitrile ($\ce{R-CN}$) ✓

Answer: (c)

Key Distinctions:

| Reagent | Type | Attack Site | Product | Structure | |---------|------|-------------|---------|------------| | AgCN | Covalent | N-attack | Isocyanide | $\ce{R-N≡C}$ | | NaCN/KCN | Ionic | C-attack | Nitrile | $\ce{R-C≡N}$ |

Similar behavior:

• AgNO₂ (covalent) → Nitroalkane ($\ce{R-NO2}$)
• NaNO₂ (ionic) → Alkyl nitrite ($\ce{R-O-N=O}$)

Memory Aid:

• Ionic salts: Attack through more electronegative atom (C in CN⁻, O in NO₂⁻)
• Covalent salts: Attack through free end (N in both cases)

Nomenclature:

• Nitrile: $\ce{R-CN}$ (e.g., ethanenitrile, $\ce{CH3CN}$)
• Isocyanide: $\ce{R-NC}$ (e.g., methyl isocyanide, $\ce{CH3NC}$)
• Isocyanides have characteristic foul odor