e).
Steric Effecs
These effects are exemplified by the rate of SN2 reaction on various substrates (Figure 5). Chloromethane readily undergoes this type of reaction owing to the limited steric hindrance surrounding the cartoon that bears the chlorine. 2-Chloro-2-methylpropane has too much steric hindrance at this cartoon, thereby preventing any SN2 reaction (and favoring other modes of reaction, such as elimination). Biochemical example: the enzyme “lock and key” (or “hand in glove”) analogy, where molecules of a certain shape fit into similarly shaped openings (Figure 6). Polar bonds are also important in these cases.