Question

Draw the curved arrow mechanism for the reaction between (2R,3R)-3,5-dimethylhexan-2-ol and PCl3.

Answer 1

Sn2 mechanism

Step-by-step explanation:

In this case, our nucleophile is the "OH" on (2R,3R)-3,5-dimethylhexan-2-ol. The alcohol group will attack the
`PCl_3` to produce a new bond between O and P with a positive charge in the oxygen. Additionally, when the OH attacks a Br atom leaves the molecule producing a bromide ion.

In the next step, the bromide ion produced will attack the carbon bonded to the OH that now is bonded to
`PCl_2`. An Sn2 reaction takes place and the substitution would be made in only one step. Due to this, we will have an inversion in the stereochemistry and the absolute configuration on carbon 2 will change from "R" to "S" to produce (2S,3R)-2-bromo-3,5-dimethylhexane.

I hope it helps!