The Student Room Group

Optical isomerism

Some students were asked to suggest methods to distinguish between isomers Q and R.
One student suggested testing the optical activity of the products formed when Q and R were reacted separately with HCN.
By considering the optical activity of these products formed from Q and R, explain why this method would not distinguish between Q and R.
(6)
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I know that product R wouldn’t form an optically active compound as it doesn’t have a chiral carbon
On the mark scheme it says product Q Is a racemate Ik a racemate is when there’s an equal amount of optical isomers but I don’t know how we know that product Q is a racemate
(edited 1 year ago)
Reply 1
Original post by zara ijaz
Some students were asked to suggest methods to distinguish between isomers Q and R.
One student suggested testing the optical activity of the products formed when Q and R were reacted separately with HCN.
By considering the optical activity of these products formed from Q and R, explain why this method would not distinguish between Q and R.
(6)
.............................................................................................................

I know that product R wouldn’t form an optically active compound as it doesn’t have a chiral carbon
On the mark scheme it says product Q Is a racemate Ik a racemate is when there’s an equal amount of optical isomers but I don’t know how we know that product Q is a racemate

The two optical isomers both rotate the plane of plane polarised light. One to the left and one to the right. So perhaps by examining this (somehow) as it is equal quantities of both the light may not be rotated at all (as they rotate Diff directions). Not sure though.

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