One of the following diastereomeric chlorides undergoes racemisation on heating whilst the other is returned unchanged. Explain.
From the reaction conditions I can see that there must be an elimination of HCl, presumably E2 with the base being the amine group on another molecule. Then addition back to the double bond.
However, I have a couple of questions. Firstly, wouldn't HCl add back onto the alkene the other way around so as to form the more stable tertiary heteroatom stabilised carbocation which would then be attacked by chloride making racemisation and being "returned unchanged" impossible.
Secondly, why would one isomer undergo racemisation and the other remain the same?