An optical pure alkyl chloride has a rotation of [alpha]d of +12.3 while the coresponding alcohol has [alpha]d +10.8. in a reaction of this alkyl chloride with NaOH the resulting alcohol shown alpha d = -8.4
a) how much of the substituion proceeded by the Sn1 mechanism and how much by the Sn2 mechanism?
b) what optical purity would be expected if the reaction was carried out in half the amount of solvent (all concentrations doubled)?