Organic Lab Reactions 276

Organic Lab Reactions 276 - with hydrochloric acid, nuclear...

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ACID USED FOR DIAZOTIZATION 271 whereas benzidine is converted to biphenyl in 80% yield, 14 the desmina- tion of 3,3'-dimethoxybenzidine takes place in but 24% yield. 46 Acid Used for Diazotization In most of the recorded deaminations with ethanol, sulfuric acid has been used rather than hydrochloric or nitric acid. As a general practice this appears to be a good choice since, in certain cases, diazotization with hydrochloric acid involves a risk that the deamination product may contain chlorine in place of a bromine atom or a nitro group originally present in the aromatic amine.* In the deamination of polybromoamines, if the bromine atoms are ortho or para to the amino group and if the diazotization is carried out
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Unformatted text preview: with hydrochloric acid, nuclear bromine is exchanged for chlorine. Bromine atoms meta to the diazo group are not affected. 32-46 B N 2 +C1-N 2 +Br-Monobromodiazonium chlorides do not isomerize, but dibromodiazonium chlorides do so readily, even at low temperatures. Thus, in H^6 normal methanol solutions of 2,4-dibromo- and 2,6-dibromobenzenediazonium chlorides, after one hour at 0, 6.2% and 21.4%, respectively, of the * It must be emphasized, however, that a number of satisfactory deaminations have been effected via the diazonium chlorides. 46 Starke, J. prakt. Chem., [2] 59, 221 (1899). "Hantzsch, Ber., 30, 2334 (1897)....
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