Enantiomorphs and chirality

Isomeric substances, different compounds having the same formula, may be divided into two main groups  

Diastereomers can have quite different properties, e.g., the cis- and transcompounds maleic and fumaric acids which have different melting points, 130 °C and 270 °C respectively. On the other hand, enantiomers have identical properties with one exception, viz., that of optical activity, the ability to rotate the plane of polarization of plane-polarized light. One form will rotate to the right dextrorotatory) and the other to the left (laevorotatory). The direction and magnitude of rotation are measured with a polarimeter. 

Molecules and substances that exhibit optical activity are generally described as chiral (Greek cheir hand ). Two crystals of the same substance that are 

Dextro- and laevo-forms are now designated in all modern texts as (-h) and (-) respectively. The optically inactive racemate, a true double compound 

L system, was arbitrarily based on the configuration of the enantiomeric glyceraldehyde molecules the (-l-)-isomer was taken to have the structure implied by formula 1 and this arrangement of atoms was called the d configuration. Conversely, formula 2 was designated as representing the l configuration  

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