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Which of the following reaction sequences can be used to prepare propane (CH3-CH2-CH3)?

1. CH3CH=CH2 treated with (1) B2H6 then (2) CH3COOH
2. CH3-CH2-CHO treated with NH2-NH2 in KOH/ethylene glycol under heat (Wolff-Kishner)
3. CH3CH2CH2OH treated with Red P / HI at 150 degrees C
4. CH3CH2CH2COONa treated with NaOH/CaO under heat (decarboxylation)

Correct answer: CH3CH2CH2COONa treated with NaOH/CaO under heat (decarboxylation)

Solution

Options A (hydroboration of propene) and B (Wolff-Kishner on propanal) both yield propane; option D (decarboxylation of sodium butanoate) also gives propane. Option C gives 1-iodopropane, not propane. The canonical lab preparation is the decarboxylation route (D), but A and B are also valid. Given single-answer format, D is the expected answer as it is the classic named reaction for alkane preparation.

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