See image — Haloalkanes and Haloarenes Chemistry Question

💡 Solution & Explanation

The target molecule is 1-chloropropane (CH3CH2CH2Cl), a primary alkyl chloride. Concept: We need to evaluate each route for its ability to specifically yield 1-chloropropane. Option (a): Propene + HCl in the presence of peroxide. Peroxides cause anti-Markovnikov addition of HCl via a free radical mechanism. Addition of HCl to propene (CH3CH=CH2) under peroxide conditions places Cl at the terminal (less substituted) carbon, giving CH3CH2CH2Cl, i.e., 1-chloropropane. This appears to work. However, the free radical chain mechanism with HCl is known to be very inefficient or essentially non-operative because the propagation steps are energetically unfavorable (the H-Cl bond is too strong for the chlorine radical to abstract H efficiently in the chain, and the overall radical chain for HCl addition is not thermodynamically favorable). In practice, peroxide-catalyzed anti-Markovnikov addition works well for HBr but NOT for HCl. Therefore, option (a) does NOT reliably give 1-chloropropane. Option (b): Propene + Cl2 followed by treatment with aq. KOH. Cl2 adds across the double bond of propene to give 1,2-dichloropropane (CH3CHClCH2Cl). Treatment with aqueous KOH would cause elimination (dehydrohalogenation) to give an alkenyl chloride or further substitution, but it does NOT selectively give 1-chloropropane. Aqueous KOH promotes substitution or elimination, not selective removal of one Cl to give a monochloro compound at C1. This route does not yield 1-chloropropane. Option (c): Propanol-1 + SOCl2/pyridine. Propanol-1 (CH3CH2CH2OH) reacts with thionyl chloride (SOCl2) in the presence of pyridine via an SNi or SN2 mechanism. The hydroxyl group is replaced by Cl with retention or inversion, giving CH3CH2CH2Cl, which is 1-chloropropane directly and cleanly. This is a standard, reliable method for converting a primary alcohol to the corresponding primary alkyl chloride. This route works perfectly. Since option (a) fails (HCl does not undergo peroxide-initiated anti-Markovnikov addition efficiently), option (b) fails (does not give 1-chloropropane), and option (d) requires all to work, only option (c) is correct. Therefore, the correct answer is C.