[References]Alkyl halides undergo nucleophilic substitution and elimination reactions. When the kinetics of the reaction are measured, if the rate of the reaction is found to bedependent only upon the concentration of the alkyl halide the reaction is first order. The substitution reaction is thus termed SN1, and the elimination reaction istermed E1. These reactions are unimolecular and occur in two steps. The first step is rate-limiting and involves the loss of the leaving group to form a carbocation.In the second, fast, step the nucleophile adds to the carbocation in the SN1 reaction or elimination occurs to give an alkene in the E1 reaction. Because thecarbocation is planar, the nucleophile can add to either face and therefore racemization is usually observed although solvent effects can influence this somewhat. E1elimination follows Zaitsev's rule and typically yields the most substituted alkene as the major product.Conditions which favor the SN1/E1 pathway include the use of a weak nucleophile and a polar protic solvent. The same reaction conditions apply for both SN1 andE1, therefore these reactions will compete. It is usually difficult to predict which pathway, substitution or elimination, will predominate and so a mixture of productsis frequently observed.In contrast to the E1 reaction which involves a carbocation intermediate, the E1cB reaction takes place through a carbanion intermediate. Base-induced abstractionof a proton in a slow, rate-limiting step gives an anion which then expels the leaving group from the adjacent carbon. The reaction is particularly suited to theelimination of substrates which contain poor leaving groups two carbons removed from a carbonyl group. The poor leaving group disfavors the alternative E1 and E2reactions, and the carbonyl group helps to stabilize the anion via resonance.Draw curved arrows to show the movement of electrons in this step of the mechanism.Arrow-pushing Instructions20OHH₂OонH3CPrevious Next>F11OHHXICH3H3CCengage Learning Cengage Technical SupportCH3+F9

Here we are required to draw the arrow to show the mechanism for the reaction The given reaction…

of a proton in a slow, rate-limiting step gives an anion which then expels the leaving group from the adjacent carbon. The reaction is particularly suited to the elimination of substrates which contain poor leaving groups two carbons removed from a carbonyl group. The poor leaving group disfavors the alternative E1 and E2 reactions, and the carbonyl group helps to stabilize the anion via resonance. Draw curved arrows to show the movement of electrons in this step of the mechanism. Arrow-pushing Instructions 20 OH H₂O :OH H3C Previous Next> OH H CH3 H3C CH3 +

of a proton in a slow, rate-limiting step gives an anion which then expels the leaving group from the adjacent carbon. The reaction is particularly suited to the elimination of substrates which contain poor leaving groups two carbons removed from a carbonyl group. The poor leaving group disfavors the alternative E1 and E2 reactions, and the carbonyl group helps to stabilize the anion via resonance. Draw curved arrows to show the movement of electrons in this step of the mechanism. Arrow-pushing Instructions 20 OH H₂O :OH H3C Previous Next> OH H CH3 H3C CH3 +

Organic Chemistry

8th Edition

ISBN:9781305580350

Author:William H. Brown, Brent L. Iverson, Eric Anslyn, Christopher S. Foote

Publisher:William H. Brown, Brent L. Iverson, Eric Anslyn, Christopher S. Foote

Chapter8: Haloalkanes, Halogenation, And Radical Reactions

Section: Chapter Questions

Problem 8.21P

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Alkyl halides undergo nucleophilic substitution and elimination reactions. When the kinetics of the reaction are measured, if the rate of the reaction is found to be dependent only upon the concentration of the alkyl halide the reaction is first order. The substitution reaction is thus termed SN1, and the elimination reaction is termed E1. These reactions are unimolecular and occur in two steps. The first step is rate-limiting and involves the loss of the leaving group to form a carbocation. In the second, fast, step the nucleophile adds to the carbocation in the SN1 reaction or elimination occurs to give an alkene in the E1 reaction. Because the carbocation is planar, the nucleophile can add to either face and therefore racemization is usually observed although solvent effects can influence this somewhat. E1 elimination follows Zaitsev’s rule and typically yields the most substituted alkene as the major product. Conditions which favor the SN1/E1 pathway include the use of a weak…
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