Final answer:
An SN2 reaction is a nucleophilic substitution that results in inversion of configuration at the carbon center being attacked. A 'wedge' representing a group on a chiral center will invert to a 'dash' post-reaction, signifying that the group has moved to the opposite side of the carbon atom.
Step-by-step explanation:
An SN2 reaction is a type of nucleophilic substitution where a nucleophile attacks a carbon atom that's attached to a leaving group, leading to a substitution reaction. In an SN2 mechanism, the nucleophile attacks from the side opposite to the leaving group, resulting in an inversion of configuration. This means that if the substrate carbon was initially depicted with a particular group in a 'wedge' position (pointing out of the page), after the reaction, this group would be shown in a 'dash' position (pointing into the page), indicating it has moved to the opposite side of the carbon.
Example of SN2 Inversion:
Consider a chiral carbon center with a bromine atom as a leaving group depicted as a wedge. When a nucleophile, such as a hydroxide ion, approaches from the backside (opposite the bromine), it attacks the carbon, forming a bond and simultaneously expelling the bromine atom. The result is that the molecule, which may have had an 'R' configuration, will now have an 'S' configuration, which is a direct visual representation of SN2 inversion.