Stereochemistry Problems.

Assign (R) or (S) configuration to the indicated stereogenic centre (yellow ball) in the following molecules.
Question 1
Draw all the stereoisomers of the following compounds. Indicate the relationship between the stereoisomers you have drawn
(i.e. enantiomers/diastereomers) and assign (R) or (S) configuration to all stereogenic centres.


2a
2a