26. Amines

Explain why the reaction of an alkyl halide with ammonia gives a low yield of primary amine.

Show how you would convert alanine to the following derivatives. Show the structure of the product in each case.

(c) N-benzyloxycarbonyl alanine

(d) tert-butyloxycarbonyl alanine

Within each structure, rank the indicated nitrogens by increasing basicity.

(d)

(e)

In each pair of compounds, select the stronger base, and explain your choice.

(c)

(d)

Guanidine (shown) is about as strong a base as hydroxide ion. Explain why guanidine is a much stronger base than most other amines.

Explain why N,N,2,6-tetramethylaniline (shown) is a much stronger base than N,N-dimethylaniline.

Addition of one equivalent of ammonia to 1-bromoheptane gives a mixture of heptan-1-amine, some dialkylamine, some trialkylamine, and even some tetraalkylammonium bromide.

(a) Give a mechanism to show how this reaction takes place, as far as the dialkylamine. 

(b) How would you modify the procedure to get an acceptable yield of heptan-1-amine?

Rank the amines in each set in order of increasing basicity.

(a)

Rank the amines in each set in order of increasing basicity.

(e)

Which of the amines listed next is resolved into enantiomers? In each case, explain why interconversion of the enantiomers does or does not take place.

(a) cis-2-methylcyclohexanamine 

(b) N-ethyl-N-methylcyclohexanamine 

(c) N-methylaziridine 

(d) ethylmethylanilinium iodide

(e) methylethylpropylisopropylammoniumiodide

The following drugs are synthesized using the methods in this chapter and in previous chapters. Devise a synthesis for each, starting with any compounds containing no more than six carbon atoms.

(c) Dopamine, one of the neurotransmitters in the brain. Parkinson’s disease is thought to result from a dopamine deficiency.

The ribonucleosides that make up ribonucleic acid (RNA) are composed of D-ribose (a sugar) and four heterocyclic “bases.” The general structure of a ribonucleoside is shown here.

The four heterocyclic bases are cytosine, uracil, guanine, and adenine. Cytosine and uracil are called pyrimidine bases because their structures resemble pyrimidine. Guanine and adenine are called purine bases because their structures resemble purine.

b. Predict which nitrogen atoms are basic.

Show how you would use direct alkylation to synthesize the following compounds.

(a) benzyltrimethylammonium iodide 

(b) pentan-1-amine 

(c) benzylamine

Which of the following compounds are capable of being resolved into enantiomers?

(d) 1,2,2-trimethylaziridine

(e)

(f)

Predict the products of the following reactions.

(c)