When the (R,R) isomer of the amine shown is treated with an excess of methyl iodide, then silver oxide, then heated, the major product is the Hofman product.

  1. Draw the structure of the major (Hofman) product.
  2. Some Zaitsev product is also formed. It has the (E) configuration. When the same amine is treated with m-CPBA and heated, the Zaitsev product has the (Z) configuration. Use stereochemical drawings of the transition states to explain these observations.

Short Answer

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(a)

(b)

Step by step solution

01

Step-1. Explanation of part (a):

Hofmann elimination occurs via an E2 mechanism requiring anti-coplanar stereochemistry. Hofmann orientation loses a hydrogen from methyl as well as NCH33group to make less substituted double bond. The least stable alkene, that is the alkene with least number of substituents is the hofmann alkene.

Hofmann product

02

Step-2. Explanation of part (b):

Hofmann elimination requires anti-coplanar geometry while cope elimination requires syn-coplanar stereochemistry. Cope elimination takes place in the presence of m-CPBA and heat which forms N-amine oxide and further on heating, highly substituted or Zaitsev alkene forms and Z alkene forms as bond formation and bond-breaking occurs simultaneously and in one orientation, thus rotation of groups do not occur. Hofmann elimination also leads to formation of Zaitsev alkene but it is formed as a minor product.

Formation of products via Hofmann and cope elimination

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Most popular questions from this chapter

(A true story.) A drug user responded to an ad placed by a DEA informant in a drug-culture magazine. He later flew from Colorado to Maryland, where he bought some 1-phenyl-2-propanone (P2P) from the informant. The police waited nearly a month for the suspect to synthesize something, then obtained a search warrant, and searched the residence. They found the unopened bottle of P2P; apparently, the suspect was not a good chemist and was unable to follow the instructions the informant gave him. They also found pipes and bongs with residues of marijuana and cocaine, plus a bottle of methylamine hydrochloride, some muriatic acid (dilute HCL), zinc strips, flasks, and other equipment.

(a) Assume you are consulting for the police. Show what synthesis the suspect was prepared to carry out, to provide probable cause for the charge of attempting to manufacture a controlled substance.

(b) Assume you are a member of the jury. Would you convict the defendant of attempting to manufacture a controlled substance?

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Show how you would accomplish the following synthetic conversions.

(a) benzyl bromide to benzylamine

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A.Hafner and S.Brase, Angewandte Chemie Int. Ed., M.Heinrich et al., Journal of Organic Chemistry, 2012, 77, 1520. 2012, 51, 3713

Predict the products of the following reactions:

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  2. 4-fluoropyridineNaOCH2CH3
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  5. cyclopentanone(2)LiAlH4(1)aniline,H+
  6. 2-bromopentane(2)Ag2O,heat(1)(CH3)3N:

h.

i.

j.

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