9. The following reaction, which proceeds via the SN1/E1 mechanisms, gives three alkene products (A, B, C) as well as an ether (D). (a) Show how each product arises mechanistically. (b) For the alkenes, determine the major product and justify your answer. (c) What clues in the reaction as shown suggest that this reaction does not go by the SN2/E2 mechanism route? (CH3)2CH-CH-CH3 CH3OH 1 Bl CH3OH ⑧· (CH3)2 CH-CH=CH2 heat H ⑥③ (CH3)2 C = C = CH3 © СнЗ-С-Снаснз сна (CH 3 ) 2 C H G H CH 3 оснз

9. The following reaction, which proceeds via the SN1/E1 mechanisms, gives three alkene products (A, B, C) as well as an ether (D). (a) Show how each product arises mechanistically. (b) For the alkenes, determine the major product and justify your answer. (c) What clues in the reaction as shown suggest that this reaction does not go by the SN2/E2 mechanism route? (CH3)2CH-CH-CH3 CH3OH 1 Bl CH3OH ⑧· (CH3)2 CH-CH=CH2 heat H ⑥③ (CH3)2 C = C = CH3 © СнЗ-С-Снаснз сна (CH 3 ) 2 C H G H CH 3 оснз

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

Chapter6: Reactions Of Alkenes

Section: Chapter Questions

Problem 6.27P: Reaction of this bicycloalkene with bromine in carbon tetrachloride gives a trans dibromide. In both...

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(a) Give a mechanism for this reaction, showing how the two products arise as aconsequence of the resonance-stabilized intermediate.(b) The bromination of cyclohexene using NBS gives only one major product, as shown onthe previous page. Explain why there is no second product from an allylic shift.
(b) Consider the reaction of 1-bromobutane with a large excess of ammonia (NH3). Draw the reactants, the transition state, andthe products. Note that the initial product is the salt of an amine (RNH3+ Br - ), which is deprotonated by the excess ammonia to give the amine.
(ii) The elimination reaction between 2-bromobutane and NaOCH2CH3 gives two organic products. Draw a mechanism for the reaction which produces the major organic elimination product and provide a rationale as to why that is the major product.
1. The conversion between alcohols, ethers, and epoxides is an important process in organic synthesis. (a) Draw a mechanism for the classic epoxidation of an alkene using MCPBA. (b) Show how this epoxidation can be converted to alcohols/ethers using both acidic and basic conditions. Be sure to highlight the difference between regio- and stereochemistry with the different reactions. (c) Name the end products and be sure to include all necessary stereochemistry. MCPBA CH3OH +H O + Diastereomer SN 1 CH₂ONa SN 2 ↓ OH OCH3 um OCH 3
For the following sets of substitution reactions that occur via an SN2 mechanism, draw the main organic substitution product (i.e., not the leaving group, for each reaction draw the product, though the products may be equivalent) and indicate which reaction occurs at the faster rate. (a) H3C CH₂O H3C E H3C Br (b) Br CH3O H3C + H3C-Br CH3O- H3C-Br
a) Describe the general steps in the mechanism for an SN1 reaction and an SN2 reaction. b) Discuss in detail the similarities and differences between these two mechanisms.
(a) Provide a detailed mechanism for the reaction shown below. Br2/H20 HO. Br
Bromination can occur in a 1,4 fashion across conjugated double bonds, as shown here for cyclohexa-1,3-diene. One mechanism that has been proposed involves a five-membered ring, bromonium ion intermediate, as shown below. (a) According to this mechanism, what should the stereochemistry be for the products-namely, all cis, all trans, or a mixture of both? (b) Observations from experiment show that both cis and trans products are formed. Does this support or discredit the proposed mechanism shown here? Br Br2 Cyclohexa-1,3-diene Br :Br: Br: Br:
Dichloromethane (CH,Cl,) can be treated with butyllithium, CH3CH,CH,CH,-Li (Bu-Li), to make a carbene in situ, analogous to the way a carbene is generated from trichloromethane (CHCI3) using HO¯. (a) Show the mechanism for the generation of a carbene from CH2CI2. (b) Why is butyllithium used instead of HO-? (c) The reaction shown here leads to a mixture of four products. Draw all four products. CH,Cl, ? Bu-Li Draw the mechanism for this reaction
Reaction of this bicycloalkene with bromine in carbon tetrachloride gives a trans dibromide. In both (a) and (b), the bromine atoms are trans to each other. However, only one of these products is formed. Which trans dibromide is formed? How do you account for the fact that it is formed to the exclusion of the other trans dibromide?
Which reaction in each of the following pairs would you expect to be faster? (i) 2. Write both reactions using bond-line presentation and, using arrows providing a mechanistic explanation of the course of the reaction, draw either a transition state or an intermediate product of the reaction; (ii) Shortly (one sentence) explain your reasoning why one of the two reactions will be faster. (a) The Sn2 displacement by ethoxide anion (EtO") on 5-iodo-2,2-dimethylpentane or on 4-iodo-2,2- dimethylpentane.
Which alkyl halide in each of the following pairs will react faster in an SN2 reaction with OH? Explain your answer briefly. (a) Bromobenzene or benzyl bromide, C6H5CH2B. (b) CH3C1 or (CH3)3CCI (c) CH3CH=CHBr or H2C=CHCH2BR