Which of the following does not provide evidence that there are two different mechanisms for nucleophilic substitution?()这道题很有代表性和难度，请认真思考
A. reaction products when CH3I is used as the substrate
B. reaction products when (CH3)3CCH2I is used as substrate
C. the stereochemistry of nucleophilic substitutions
D. the effect of nucleophile concentration on rate
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Assuming no other changes, what is the effect of doubling both the alkyl halide and the nucleophile concentrations in the above reaction?()
A. no change
B. doubles the rate
C. triples the rate
D. quadruples the rate
E. rate is halved
Which of the following statements is generally true for SN1 reactions?()
A. Complete inversion of configuration occurs.
B. These reactions are favored by nonpolar solvents.
C. These reactions are favored by polar solvents.
D. Reaction rates depend only on the concentration of the nucleophile.
E. The mechanism is a one-step back attack.
Which of the following best explains why SN1 reactions involving a neutral reactant are faster in polar solvents?()
A. The substrate is more soluble in polar solvents.
B. The substrate is less soluble in polar solvents.
C. The nucleophile is solvated by polar solvents.
D. Solvation by polar solvents stabilizes the carbocation.
E. Solvation by polar solvents stabilizes the transition state.
Protic and aprotic solvents are very similar as solvents except for their ________.()
A. polarity
B. dielectric constant
C. ability to stabilize anions by hydrogen bonding
D. ability to stabilize cations by hydrogen bonding
E. ability to stabilize cations with unshared pairs of electrons
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