# The reaction which forms a pair of diastereomers

The reactions among the following which results in the formation of a pair of diastereomers are:

I am aware of the fact that $$\ce{HBr}$$ gives anti addition product and $$\ce{BH3}$$ forms syn addition product. In part (a) since the back side is less sterically hindered ( due to presence of only $$\ce{H}$$ ) $$\ce{BR-}$$ preferentially attacks from the back side.Similar is the case with (b).c) proceeds with a free radical mechanism.d) however occurs via anti-markinicoff addition so that $$\ce{OH}$$ adds to the primary carbon.Since there are two possible ways in which the $$\ce{OH}$$ group may add( either from the back side or the front side)my idea is that it may result in a pair of diastereomers. However I am not quite sure about it. Thanks.

• Consider that, in order to form diastereoisomers here, you need to form a new chiral center. So which of these reactions will generate a new chiral center in the product? – MarcoB Jan 4 '17 at 8:48
• @MarcoB that implies that the correct answer should be b). – Pink Jan 4 '17 at 8:53
• @aniline To quote the Lion King: ‘Look harder!’ – Jan Jan 4 '17 at 23:29