(a) When n-heptane burns in a gasoline engine, the combustion process takes place too quic...

(a) When n-heptane burns in a gasoline engine, the combustion process takes place too quickly. The explosive detonation makes a noise called knocking. When 2,2,4-trimethylpentane (isooctane) is burned, combustion takes place in a slower, more controlled manner. Combustion is a free-radical chain reaction, and its rate depends on the reactivity of the free-radical intermediates. Explain why isooctane has less tendency to knock than does n-heptane.

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(b) Alkoxy radicals (R—O·) are generally more stable than alkyl (R·) radicals. Write an equation showing an alkyl free radical (from burning gasoline) abstracting a hydrogen atom from tert-butylalcohol, (CH3)3COH. Explain why tert-butyl alcohol works as an antiknock additive for gasoline.