Tertiary alkyl halides favor SN1 with carbocation intermediate

Steps:

• Classify each alkyl halide by carbon type: primary (1°), secondary (2°), or tertiary (3°).
• Recall warm dilute NaOH(aq) promotes nucleophilic substitution; 1° halides use SN2 (no carbocation), while 3° halides use SN1 (carbocation intermediate).
• Examine structures: A, B, C are 1°; D is 3° at the Br-bearing carbon.
• Conclude D is most likely for positively charged (carbocation) intermediate due to 3° stability.

Why D is correct:

• 2-Bromo-2-methylbutane is tertiary, favoring SN1 where Br leaves to form stable (CH3)2C(+)-CH2CH3 carbocation.

Why the others are wrong:

• A: 1-Bromopropane is primary, undergoes SN2 with backside attack, no carbocation.
• B: 1-Bromo-2-methylpropane is primary, undergoes SN2, no carbocation.
• C: 1-Bromo-3-methylbutane is primary, undergoes SN2, no carbocation.

Final answer: D