Which of the following is a secondary alkyl halide?

• A. $C_2{H}_5\mathrm{Cl}$ (ethyl chloride)
• B. ${\mathrm{CH}}_3{\mathrm{CH}}_2\mathrm{Cl}$ (1-chloropropane)
• C. ${\mathrm{CH}}_3{\mathrm{CCl}}_3$ (chloroform)
• D. ${\mathrm{CH}}_3\mathrm{CHCl}{\mathrm{CH}}_3$ (2-chloropropane)

Answer: (D)

Verified step by step guidance

1. Understand the classification of alkyl halides based on the carbon atom bonded to the halogen: a primary (1°) alkyl halide has the halogen attached to a carbon bonded to only one other carbon, a secondary (2°) alkyl halide has the halogen attached to a carbon bonded to two other carbons, and a tertiary (3°) alkyl halide has the halogen attached to a carbon bonded to three other carbons.
2. Analyze each compound by identifying the carbon atom bonded to the halogen and counting how many carbons are attached to that carbon.
3. For ethyl chloride (\(C_2H_5Cl\)), the chlorine is attached to a carbon bonded to only one other carbon, so it is a primary alkyl halide.
4. For 1-chloropropane (\(CH_3CH_2CH_2Cl\)), the chlorine is attached to the end carbon, which is bonded to only one other carbon, making it a primary alkyl halide.
5. For 2-chloropropane (\(CH_3CHClCH_3\)), the chlorine is attached to the middle carbon, which is bonded to two other carbons, classifying it as a secondary alkyl halide.