Is 2-bromobutane chiral?
For a molecule to be chiral it must have non-superimposable mirror images.  Here is a drawing of the two mirror images for 2-bromobutane.



The chiral carbon atom is denoted by an asterisk.  In the case of 2-bromobutane there are 4 different substituents attached to it. The molecule is chiral, you can't pick up one of the mirror images and superimpose it on the other.

Note to think about:


4 different substituents may make an atom chiral, but the molecule as a whole may still be achiral


For example meso compounds



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some molecules without 4 different substituents attached to an atom may still be chiral .


For example, compounds with axial chirality such as chiral allenes (1,3-dimethylallene), chiral biphenyls, chiral helicenes, etc.



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