A Note on the Conversion of w-Tribromoquinaldine to w-Dibromoquinaldine and the Production of Quinaldic Aldehyde

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Abstract
W-Dibromoquinaldine cannot be prepared by selective bromination of quinaldine, the only product isolated being the w-tribromo derivative, but the former may be prepared by reduction from the latter. Hammick1 reduced tribromoquinaldine by means of stannous chloride in acetone solution, obtaining a yield of 60 per cent. of theory. In order to separate the product from tin compounds, steam distillation was employed. As dibromoquinaldine is only slightly volatile in steam the purification process is tedious. The reduction may however be performed by refluxing w-tribromoquinaldine with a 20 per cent. v/v solution of sulphuric acid in alcohol and pouring the mixture into water. The product separates almost pure in excellent yield, and a single crystallisation from alcohol is all that is necessary. The identity of the product was confirmed by its conversion, by means of alcoholic silver nitrate, to quinaldic aldehyde by the method of Hammick2.
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