Here are the essential concepts you must grasp in order to answer the question correctly.
Sₙ1 and E1 Mechanisms
Sₙ1 (nucleophilic substitution unimolecular) and E1 (elimination unimolecular) are reaction mechanisms that involve the formation of a carbocation intermediate. In Sₙ1 reactions, a nucleophile attacks the carbocation, while in E1 reactions, a base abstracts a proton, leading to the formation of a double bond. Both mechanisms are favored by tertiary haloalkanes due to their ability to stabilize the carbocation.
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Drawing the E1 Mechanism.
Carbocation Stability
The stability of carbocations is crucial in determining the rate of Sₙ1 and E1 reactions. Tertiary carbocations are more stable than secondary or primary ones due to hyperconjugation and inductive effects from surrounding alkyl groups. The more stable the carbocation, the faster the reaction will proceed, making tertiary haloalkanes more reactive in these mechanisms.
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Determining Carbocation Stability
Leaving Group Ability
The ability of a leaving group to depart from the substrate is a key factor in Sₙ1 and E1 reactions. Good leaving groups, such as iodide or bromide, can stabilize the transition state and facilitate the formation of the carbocation. The better the leaving group, the faster the reaction will occur, as it can more readily dissociate from the haloalkane.
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How to use the factors affecting acidity to predict leaving group ability.