( +)-Tartaric acid as a specific rotation of Calculate the specific rotation of a mixture of 68% ( +)-tartaric acid and 32% ( -)-tartaric acid.
Solution:
Here we have to calculate the specific rotation of the mixture (+)(-)tartaric acid
Given :
Specific rotation of mixture of (+)(-)tartaric acid is = +12.0o
32% of the mixture i.e (-) tartaric acid will cancel the optical rotation of the 32% of the mixture that is (+)tartaric acid
Thus the amount of excess +tartaric acid left = d-l
---------100% = 68-32/68+32 = 36% d+l
The specific rotation of will therefore be only 36% of the rotation of pure (+)tartaric acid
(+12.0o)36% = +4.3o
Thus the specific rotation of the mixture is +4.3o