Problem Set #10

Answers

January 16, 1998

1. Propose a mechanism for the following reaction -

Answer:

2. Show how you would convert (R)-2-butanol to (S)-2-butanethiol?

Answer:

The conversion involves a change in configuration at C-2 of the butanol. In other words a bimolecular nucleophilic displacement (S_N2) is needed.

SH- would be an effective nucleophile. This can be prepared by bubbling H₂S into sodium hydroxide solution in water/ethanol.

BUT one cannot do a direct displacement of an OH group of an alcohol. This means that we must make the alcohol into a better leaving group. To do this we could react the 2-butanol with p-toluenesulphonyl chloride in pyridine as a solvent, isolate the tosylate ester, and then treat with SH- in water ethanol..........

3. Give the structural formula of an alkene and show the reagents needed to make the following alcohols.

A) 2-Butanol

B) 1-Hexanol

C) 2-Methyl-1-heptanol

Answer:

4. Triethanolamine (TEA) is used in industry to remove acid components from gas streams. It also finds extensive use as a buffer in biological systems. "TEA" is made from ammonia and ethylene oxide as shown below. Show how this synthesis occurs and propose a mechanism for one of the steps.

Answer:

5. Show you would effect the following reaction.

Answer:

6. Try question 12.43 in Ege.

23jan98; jp