Absolute Configuration R,S Sequence Rules

Solved Exercise 5-7 Working with the G ncepts Ee and Optical Purity 

A solution of (-l-)-alanine from a fossil exhibits a value of [a] = -1-4.25. What is its ee and optical purity What is the actual enantiomer composition of the sample, and how is the measured 

We need to look up what the specific rotation of pure (-I- )-alanine is and then use the preceding 

What is the optical rotation of a sample of (-1- )-2-bromobutane that is 75% optically pure What percentages of (-I-) and (-) enantiomers are present in this sample Answer the same questions for samples of 50% and 25% optical purity. 

In Summary Two enantiomers can be distinguished by their optical activity, that is, their interaction with plane-polarized light as measured in a polarimeter. One enantiomer always rotates such light clockwise (dextrorotatory), the other counterclockwise (levorotatory) by the same amount. The specific rotation, [a], is a physical constant possible only for chiral molecules. The interconversion of enantiomers leads to racemization and the disappearance of optical activity. 

---