What is a dextrorotatory compound?

A dextrorotatory compound, also known as a dextro compound or (+)-compound, refers to a specific type of compound that exhibits a positive rotation of plane-polarized light. The term "dextrorotatory" is derived from Latin roots, where "dextro" means right and "rotatory" refers to rotation.

When light passes through a solution of a dextrorotatory compound, the plane of polarization of the light is rotated in a clockwise direction when viewed from the observer's side. This rotation is typically measured using a polarimeter, and the observed rotation is denoted by a specific angle of rotation, such as +α degrees.

Dextrorotatory compounds are optically active, meaning they can rotate the plane of polarized light due to their molecular structure or asymmetric arrangement of atoms or groups around a chiral center. Chiral compounds have mirror-image forms called enantiomers, and dextrorotatory compounds are specific enantiomers that rotate light in a clockwise direction.

In contrast, levorotatory compounds (or (-)-compounds) are the mirror-image enantiomers that rotate plane-polarized light counterclockwise. The designation of a compound as dextrorotatory or levorotatory depends on the direction of rotation, and it is indicated by a plus or minus sign, respectively, before the numerical value of the observed rotation.