Which one of the following is likely to give a precipitate with AgNO3 solution?

Step 1: Understand the $\ce{AgNO3}$ test

Silver nitrate test detects reactive alkyl halides:

$\ce{R-X + AgNO3 ->[alcohol] AgX v + R-ONO2}$

Reactivity depends on:

• Ease of ionization (for $S_N1$)
• Accessibility (for $S_N2$)

Step 2: Analyze each option

(a) Vinyl chloride ($\ce{CH2=CHCl}$):

• Vinyl halide (Cl on sp² carbon)
• C-Cl has partial double bond character
• Does not undergo $S_N$ reactions
• No precipitate ✗

(b) Chloroform ($\ce{CHCl3}$):

• Three Cl on same carbon
• Very stable, unreactive
• No precipitate ✗

(c) tert-Butyl chloride ($\ce{(CH3)3CCl}$):

• Tertiary halide
• Forms very stable 3° carbocation
• Highly reactive in $S_N1$
• Forms precipitate readily ✓✓✓

(d) Carbon tetrachloride ($\ce{CCl4}$):

• Four Cl atoms
• No H atoms, cannot eliminate
• Very stable, unreactive
• No precipitate ✗

Answer: (c) tert-Butyl chloride

Key Points:

Reactivity toward $\ce{AgNO3}$:

| Type | Example | Reactivity | Reason | |------|---------|------------|--------| | 3° alkyl | $\ce{(CH3)3CCl}$ | High | Stable carbocation | | Benzylic | $\ce{C6H5CH2Cl}$ | High | Resonance | | Allylic | $\ce{CH2=CHCH2Cl}$ | High | Resonance | | 2° alkyl | $\ce{(CH3)2CHCl}$ | Moderate | Less stable carbocation | | 1° alkyl | $\ce{CH3CH2Cl}$ | Low | Unstable carbocation | | Vinyl | $\ce{CH2=CHCl}$ | None | sp² carbon | | Aryl | $\ce{C6H5Cl}$ | None | sp² carbon | | Geminal poly | $\ce{CHCl3, CCl4}$ | None | Very stable |

Why vinyl/aryl halides don't react:

• C-X bond has partial double bond character (resonance)
• sp² carbocation extremely unstable
• Require extreme conditions for substitution