Mechanisms for this type of reaction are discerned by the parameter m in the Grunwald–Winstein equation. It’s not alkylation, but the presence of sulfur in mustard gas increases the rate of one of these reactions in a classic example of anchimeric (“an-kye-MER-ic”) assistance. Carbocation (“carbo-CAT-eye-on”) intermediates act as Lewis acids in one of these reactions. (10[1])In one type of this reaction, inversion of configuration occurs (10[1])due to a “backside attack.” (10[3])A pentavalent (-5[1])transition state occurs in one type of this reaction whose name indicates that it is bimolecular. High temperatures or bulky bases cause eliminations to be favored over these reactions. For 10 points, the nucleophilic SN1 and SN2 mechanisms exemplify what type of reaction, in which one group of a compound is exchanged for another? (10[1])■END■ (10[1]0[1])