Syn diazotates

The syn-diazotate very rapidly undergoes transformation when warmed or in the presence of excess of alkali to the anti-diazotate which is much more stable and can be isolated in a solid form suitable for storage. 

According to this theory the labile normal diazotates are regarded as the syn- (= cis-) compounds, the stable wo-diazotates as the anti-(= trans-) compounds. 

Whilst the conversion of the simple phenyl-syw-diazotate into its isomeride requires strong alkali, the syn-iotms of other diazotates are so labile that, almost instantaneously after formation from the diazonium salts, they change into the anti-iorm and hence can never be obtained in solution. An important example of this change is described under (/), namely, p-nitrophenyldiazotate, which, on coupling with j8-naphthol, yields the much-used dye para-red . 

In this connexion the spatial isomerism of the oximes must also be mentioned. A theory for this type of isomerism had already been suggested by Werner and Hantzsch and is similar to that already discussed in the case of the diazotates. According to this theory, those oximes in which the C-atom bearing the isonitroso-group is also united to two different radicles exist in a syn- and an anti-form ... 

SYNS ANTI-RUST DIAZOTIZING SALTS DUSITAN SODNY (CZECH) ERINITRIT FILMERINE NATRIUM NITRIT (GERMAN) NCI-C02084 NITRITE de SODIUM (FRENCH) NITROUS ACID, SODIUM SALT... 

AtoxyaUumes The reaction of alkane diazotates (probably syn) with triethyl-oxoaium fluoroborate in CHjQz suspensions gives azoxyalkanes in 50-60% yield ... 

The syn form being the more unstable represents the unstable diazotate, while the anti form is the iso-diazotate, the stable compound. 

A diazonium chloride will react with silver hydroxide to give, in the first place, a diazonium hydroxide but this readily undergoes isomeric change, forming derivatives of the weakly acidic diazoic acid. The acid itself cannot be isolated but the alkali diazotate exists in two forms, namely the syn- and the anti-isomers. 

---