Diazotization titration, also known as nitrate titration, is a type of titration used in the pharmaceutical analysis that involves the conversion of primary aromatic amines into specific diazonium compounds. Peter Griffin first discovered the reaction mechanism for diazotization titration in 1853.
As per the reaction the primary aromatic group reacts with sodium nitrite (NaNO2) and a diazonium compound or diazonium salt will be formed. To prevent azo coupling, the diazotization reaction is carried out in acidic conditions (HCl solution).
Basic conditions required for diazotization titrations:
The following are some basic requirements that must be met for the diazotization titration to proceed:
The temperature of the reaction:
An ideal temperature is required for all reactions to take place. This ideal temperature can be increased or decreased to significantly slow (Rate) or stop the process. Similarly, diazonium compounds are unstable at high temperatures and decompose easily.
This may cause adverse reactions and give the wrong result. Therefore, to avoid this problem, titration needs to be performed at low temperatures (0 to 5°C). Most amines form relatively stable diazo compounds at temperatures between 10–150 °C.
Rate of titration:
The rate of reaction differs depending on the compounds. The rate of reaction of amino compounds with HONO will also vary. Depending on their rate of conversion, we can classify them as either fast diazotisable or slow diazotized.
Compounds with sulpha groups, nitrous oxide groups, and carboxylic groups are known as slow diazotisable compounds. Fast diazotisable compounds are those that solely include amino groups, or -CH3 or hydroxyl groups.
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