The amide proton is quite acidic and will be removed

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Unformatted text preview: ile than the alcohol. The cyclisation occurs because, in the intermediate for the second substitution, there are two alcohols as potential leaving groups. Either can leave but when the ring opens again, the alcohol is still part of the molecule and will re- cyclise, but if the ethoxide leaves it is lost into solution and does not come back. Solutions for Chapter 10 – Nucleophilic Substitution at the Carbonyl Group O O HO EtO HN OEt H2N OEt ±H OH OH HN OEt O O HN O ■ The use of the ‘double- headed’ arrow shorthand is explained on p. 217 of the textbook. The second reaction is more straightforward. The amide proton is quite acidic and will be removed by the base making a better nucleophile. Notice that in these suggested solutions we are using the shorthand of the double- headed arrow on the carbonyl group. O B H N Cl O base O N R O O R O O N O PROBLEM 5 In making esters of the naturally occurring amino acids (general structure below) it is important to keep them as their hydrochloride salts. What would happen to these compounds if they were neutralised? NH2 R CO2H NH3 EtOH HCl R CO2Et Purpose of the problem Exploration of a simple reaction that can go seriously wrong if we do not think about what we are doing. Suggested solution The amino acids do not usually react...
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This document was uploaded on 02/10/2014.

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