Illustrated Glossary of Organic Chemistry

Front side attack: In an ionic substitution reaction, approach of the nucleophile to the same face of the molecule as the existing (in SN2) or former (in SN1) carbon-leaving group bond. Causes retention of configuration at the carbon suffering substitution.

Front side attack on a tetrahedral carbon atom in the SN2 reaction mechanism.

Front side attack on a carbocation in the SN1 reaction mechanism.