IIT JEE , AIEEE Forum - Chemistry , Organic Chemistry

paddy123

An alcohol, when optically pue, has angle of rotation =(-42.3). On a certain reaction, the same alcohol is obtained as product, but with angle of rotation=(+1.7). What is the optical purity of this alcohol product?

Agni2

Partial racemization

sagarvaze

is it 4.01%

krishna.gopal

Let final mixture contains x percent of present alcohol and 100-x percent of its optical isomer then
-42.3*x+42.3*(100-x)=100*1.7
Solve this to get x.

madhusudan.chavan

It appears that the reaction proceeds with partial racemisation. For the reaction with complete inversion the specific rotation would have remained same with opposite sign. In that case 42.3 is 100%, hence 1.7(observed) = ? ( you can calculate).
In case of racemisation, we expect 50% with same rotation and 50% with opposite rotation, with net result zero.In the present case as the rotation is observed, the other isomer is more than the isomer with same rotation. From this you can calculate %.

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