optical isomerism

Question 1

how is a racemate formed from EA of unsymmetrical alkene w HBr

Answer 1

If the alkene is H unsymmetrical, addition of
hydrogen bromide can
lead to isomeric products.

the br- can attack this planar carbocation from both sides leading to a racemate

Question 2

what could determine drug action

Answer 2

Drug action may be determined by the stereochemistry of the drug molecule. Different optical isomers may have very different effects