Arrange the alkyl halides in order of reactivity in an S_N1 reaction from most to least reactive:
2-chloropentane, 3-bromo-3-methylpentane, 3-iodo-3-methylpentane, 3-chloro-3-methylpentane 

• A. 2-chloropentane > 3-chloro-3-methylpentane > 3-bromo-3-methylpentane > 3-iodo-3-methylpentane
• B. 3-chloro-3-methylpentane > 3-iodo-3-methylpentane > 3-bromo-3-methylpentane > 2-chloropentane
• C. 3-iodo-3-methylpentane > 3-bromo-3-methylpentane > 3-chloro-3-methylpentane > 2-chloropentane
• D. 2-chloropentane > 3-bromo-3-methylpentane > 3-iodo-3-methylpentane > 3-chloro-3-methylpentane 

Answer: (C)