its sn1 that leads to the formation of a racemic mixture...um..explanation-i don't know how to show you a diagram. the verbal explanation is..see- i am taking the example of a carbon atom(the chiral centre) attached to a CH3, C2H5, C3H7 and the other atom it is attached to being a bromine atom. draw the molecule in a way that the bromine atom and c3h7 are in one plane, c2h5 infront of the plane (wedge is used to represent that) and ch3 behind the plane (dotted lines). now sn1 means nucleophilic substitution UNIMOLECULAR reaction. the reaction happens in 2steps, 1st the carbon compound forms a carbon cation as the bromine atom breaks bond with the carbon atom. thats your 1st step. then the 2nd step is when the hydroxide ion reacts with the carbon cation. there are two ways in which OH- could substitute bromine. (please draw and see). so you have two products, one where the OH- ion is attached to the right, the other, OH- ion attached to the left. the two products are such that they are chiral, and are optical isomers. that is, one is the non-super imposable mirror reflection of the other. and both form in equal quantity. and both ofc rotate light in opposite directions(but at the same angle). so we observe no optical activity. (oh please don't forget the other product is a bromide ion, while your writing down the reaction)
i could help much more with a diagram but don't know....um, lemme know if you understood. if not, ill try again :|. good luck
