Esters, test for

As in the case of hydrocortisone acetate, where hydrocortisone might be expeeted to occur as a result of hydrolysis of the acetate ester, tests for the presenee of known impurities are based on the known manufacturing sequence or on likely degradation pathways. For example, the tests carried out on clotrimazole are based on the last step in its manufacture as shown in Figure 13.8. Unreacted imidazole is an obvious impurity and chlorotritanol would be readily formed from unreacted chlorotrityl bromide by hydrolysis, which would occur when the clotrimazole is extracted from the reaction mixture. 

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