What is a dextrorotatory compound?
A dextrorotatory compound is a compound that rotates the plane of polarized light clockwise as it approaches the observer (to the right if you are steering a car).
The prefix dextro comes from the Latin word dexter. It means "to the right".
A dextrorotatory compound is often, but not always, prefixed "(+)-" or "D-".
If a compound is dextrorotatory, its mirror image counterpart is levorotatory. That is, it rotates the plane of polarized light counterclockwise (to the left).
It is entirely possible that an L- labeled compound is dextrorotatory, however, so L- does not necessarily mean levorotatory. For example, many L-amino acids are dextrorotatory (Fundamentals of Biochemistry, Voet, Voet, and Pratt).
Two examples of dextrorotatory compounds are D-(+)-glyceraldehyde