As we’ve seen in our last topic "Enantiomers", molecules of the general type
are chiral when w, x, y, and z are different. In 1996, the IUPAC recommended that a tetrahedral carbon atom that bears four different atoms or groups be called a chirality center, which is the term that we will use. Several earlier terms, including asymmetric center, asymmetric carbon, chiral center, stereogenic center, and stereocenter, are still widely used.
Noting the presence of one (but not more than one) chirality center is a simple, rapid way to determine if a molecule is chiral. For example, C-2 is a chirality center in 2-butanol; it bears H, OH, CH 3 , and CH3 CH2 as its four different groups. By way of contrast, none of the carbon atoms bear four different groups in the achiral alcohol 2-propanol.
Some other examples are :
