Reaction of (r) - 2-chloro-4-methylhexane with excess nai in acetone gives racemic 2-iodo-4-methylhexane. what is the explanation that best describes this transformation?

I believe this question has the following five choices to choose from:

>an SN2 reaction has occurred with inversion of configuration

>racemization followed by an S N 2 attack

>an SN1 reaction has taken over resulting in inversion of configuration

>an SN1 reaction has occurred due to carbocation formation

>an SN1 reaction followed by an S N 2 "backside" attack

The correct answer is:

an SN1 reaction has occurred due to carbocation formation