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Unformatted text preview: 1 CHM 201- Organic Chemistry I Exam 3 Key. Answers on last page. 1. An S N 2 reaction proceeds in the direction that allows the stronger base to displace the weaker base. For the equilibrium shown below, which side predominates at equilibrium? CH 3 CH 2 Cl + Br- CH 3 CH 2 Br + Cl- a. product (right) side b. reactant (left) side c. neither 2. For each of the following pairs of S N 2 reactions, indicate which reaction occurs faster. Comparison I: (CH 3 ) 2 CHCH 2 CH 2 Br + OH- or CH 3 CH 2 CHBr + OH- | CH 3 Comparison II: CH 3 CH 2 Cl + CH 3 O- or CH 3 CH 2 Cl + CH 3 S- (in ethanol) a. I: left reaction II: left reaction b. I: right reaction II: left reaction c. I: left reaction II: right reaction d. I: right reaction II: right reaction 3. The following represents: a) the rate-determining step of an S N 2 reaction b) the rate-determining step of an S N 1 reaction c) a fast step of an S N 1 reaction d) the transition state of the rate-determining step of an E1 reaction e) the intermediate in an E2 reaction 4. Under a certain set of experimental conditions, the reaction of pure (R)-2-bromobutane with water molecules proceeds exclusively by an S N 1 reaction, with no trace of an S N 2 reaction. Under these conditions, the reaction produces a mixture of 55% (S)-2-butanol and 45% (R)-2-butanol. The best explanation for this is: a) the solvent can stabilize the intermediate carbocation b) the entering nucleophile can attack the planar carbocation from either face with equal probability c) the leaving group can shield one face of the carbocation from attack by the nucleophile d) all S N 1 reactions of chiral reagents produce racemic products...
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