Chem2O6 - 1997/98

Problem Set #10 Answers January 16, 1998

1. Propose a mechanism for the following reaction -


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


The conversion involves a change in configuration at C-2 of the butanol. In other words a bimolecular nucleophilic displacement (SN2) 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


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.


5. Show you would effect the following reaction.


6. Try question 12.43 in Ege.

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23jan98; jp