Does R S configuration determine the compound is dextrotatory(=R) and leavorotatory(=S)

Question

Well i read in my book that rs configuration can tell us about the optical rotation of a compound (optically active)  but elsewhere it was written that it can't be predicted based upon rs configuration 

Answer 1

Levorotatory and dextrorotatory are physical phenomena they have no direct correlation to R and S designation! R and S are merely the naming tools and they have no relation to the physical properties exhibited by the molecule. 

This is a very common misconception and you will be tested on it on the test.

The only thing that you can say is that if the R isomer has a certain rotation, the S isomer will have the same value with the opposite sign. However, you cannot assign which one is which without having any experimental data.