77852-83-6Relevant academic research and scientific papers
INTERMOLECULAR PROTON TRANSFERS IN THE SOLID STATE. CONVERSION OF THE HYDROXYAZO INTO THE QUINONE HYDRAZONE TAUTOMER OF 2-AMINO-3-HYDROXY-6-PHENYLAZOPYRIDINE. X-RAY CRYSTAL STRUCTURES OF THE TWO FORMS.
Desiraju, Gautam R.
, p. 1025 - 1030 (1983)
The thermal transformation of the low (1a) to the high temperature (1b) form of 2-amino-3-hydroxy-6-phenylazopyridine has been studied by differential scanning calorimetry and variable temperature i.r. spectroscopy.Form (1a) is converted into (1b) through two intermediate phases and the i.r. spectra show changes in the >C=C1/c and the structure has been refined to R 0.048 for 607 non-zero reflections.The bond lengths in (1a and b) are in accord with a hydroxazo and a quinone hydrazone structure, respectively.The hydrogen bonding in each form can only be explained if (1a) is the azo and (1b) the hydrazone tautomer.In the crystal stucture of (1a), the hydroxy-group is close to an azo-group of an adjacent molecule and the solid state tautomerization can be accounted for by an intermolecular co-operative shift of protons across the various hydrogen bonds in structure (1a).
