This carbon, is attached to four different substituents making it chiral. The presence of a single chiral carbon atom sufficient to render the molecule chiral, and modern terminology refers to such groupings as chiral centers or stereo centers.Īn example is shown in the bromochlorofluoromethane molecule shown in part (a) of the figure below. The lack of a plane of symmetry makes the carbon chiral. A carbon atom that is bonded to four different substituents loses all symmetry, and is often referred to as an asymmetric carbon. When a carbon is bonded to fewer than four different substituents it will have a plane of symmetry making it achiral. Symmetry can be used to explain why a carbon bonded to four different substituents is chiral. If if lacks a plane of symmetry it is chiral. If an object or molecule has a plane of symmetry it is achiral. This idea can be used to predict chirality. However, a similar line down the middle of a hand separates it into two non-mirror image halves. When looking at the flask, a line can be drawn down the middle which separates it into two mirror image halves. A plane of symmetry is a plane or a line through an object which divides the object into two halves that are mirror images of each other. (Try putting your right shoe on your left foot-it just doesn’t work.) An achiral object is one that can be superimposed on its mirror image, as shown by the superimposed flasks in the figure below.Īn an important questions is why is one chiral and the other not? The answer is that the flask has a plane of symmetry and your hand does not. Your left and right hands are nonsuperimposable mirror images. Examples of some familiar chiral objects are your hands. Molecules that are nonsuperimposable mirror images of each other are said to be chiral (pronounced “ky-ral,” from the Greek cheir, meaning “hand”).
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