Organic Lab Reactions 277

Organic Lab Reactions 277 - 272 THE AROMATIC PRIMARY AMINO...

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272 THE AROMATIC PRIMARY AMINO GROUP ionic halogen is bromide ion. In ethanol, loss of nuclear bromine is con- siderably faster. The diazonium chloride obtained from symmetrical tribromoaniline exchanges with great rapidity. After two hours at +5°, a 3^8 normal ethanol solution contains only 4.2% of ionic chlorine, the remainder having displaced nuclear bromine atoms. In general, the interchange takes place more rapidly as the number of bromine atoms in the ring increases. The presence of water cuts down the speed of the halogen exchange. Tribromobenzenediazonium chloride in 90% ethyl alcohol isomerizes at a rate less than one-twentieth that in absolute ethanol; in pure water, the reaction becomes exceedingly slow. On the other hand, raising the temperature causes a striking increase in the rate of isomerization; and since alcohol deaminations almost in- variably involve reflux conditions, or temperatures close to the boiling point of the alcohol, the diazonium chloride of a polybromoamine should
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