Question

Is ( R )-lactic acid dextrorotatory or levorotatory?

Answer 1

(R)-lactic acid is D(-)-lactic acid, therefore levorotatory.

Answer 2

We cannot make an interpretation about optically activeness by looking R configuration or S configuration.

Explanation:

For example one of compoud have R configuration can be levorotory or dextrorotary we cannot make decision about polarized light. It is also true for S configuration.

If you want to know which direction or amount of spesific rotation in polarized light, you must put your sample to polarimeter.