Give the product of the following displacement reactions :
(a) `(R )-CH_3CHBrCH_2CH_3 + MeO^(Ө)`
(b) `(S)-CH_3CHBrCH_2 CH_3 + MeO^(Ө)`
(c) rac, cis-Iodo ethyl cyclohexane `+ overset (Ө)O H`
(d) .

Explanation

These `SN^2` reaction invert configuration.
(a) `(S)-CH_3CH(OMe)CH_2CH_3`
(b) `(R)-CH_3CH(OMe)CH_2CH_3`
(c)

The priority order changes. In `(A)`, the highest priority is `Br` and in `(B)`, the highest priority is `COOEt`. So the absolute configuration is same.