Page 251 - Mechanism and Theory in Organic Chemistry

6'
1 6-
SO ...c...x

I

SO ...c x-

SOH+C-X
+ /
SO-C + X
H \\

I I
Reaction coordinate Reaction coordinate
(a) (b)

I
Reaction coordinate
(c)
Figure 5.6 Distinct mechanisms. (a) SN2. (b) Ionization to an ion pair with nucleophilic
participation by solvent. (c) Limiting SN 1.

discussed in previous sections. Stereochemistry, effect on rate and product distri-
bution of added salts, influence of structure and of leaving group on kinetics and
products, sensitivity to solvent ionizing power and nucleophilicity, and isotope
effects are all brought to bear. Despite this broad range of available methods, the
ambiguities remain and there is still room for much experimental innovation.

Solvent-Assisted Ionization
Investigations reported by Schleyer and a number of co-workers have contri-
buted significantly to clarification of some of the points in question. A study of