[big]

Which molecule reacts most rapidly with water?
A) CH₃CH₂CH₂Cl
B) CH₃CHClCH₃
C) (CH₃)₂CHCH₂Cl
D) (CH₃)₃CCl

[Fluorine]

They all contain the same halogen substitute, chlorine, so let's focus on the next atom - carbon. Does it change reactivity if the halogen is placed on a primary, secondary, or tertiary carbon? In which way?

A) 1-Chloropropane = primary
B) 2-Chloropropane = secondary
C) 1-Chloro-3-methylpropane = primary
D) tert-Butylchloride = tertiary