Aminotetrazoles tautomerism

As was concluded (97MI84), many other factors that may affect the position of the amino-imino tautomerism of aminotetrazoles remain to be elucidated. 

The most probable tautomeric equilibrium of 5-aminotetrazole and its N-substituted derivatives is represented by Scheme 3. The character of the annular tautomerism of 5-aminotetrazole is similar to that described in Section 6.07.4.4.1 in the gas phase the 277-form is preferable, whereas taking into account solvation the polar 177-tautomer 135 becomes more feasible in solution <2006RJ01585>. 

Experimental studies as well as data on amino-imino tautomerism are in agreement with the suggested mechanism of decomposition of the tetrazole ring. It has been shown that secondary reactions significantly increase the number of products of thermal decomposition of aminotetrazoles <2002THE233, 2003MI181>. 

The possibility of an aminotetrazole-iminotetrazoline tautomerism in the solid state has proved problematic (77AHC(2i)323). IR spectra of some substituted 5-aminotetrazoles seem to possess an exocyclic imino absorption and laser-Raman spectra of two forms of hydrated... 

Whether an amino-imino tautomerism of the type 42 43 occurs for 5-aminotetrazoles, which do not allow for intramolecular stabilizations... 

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