Gas-phase tautomerism in 1-phenylazonaphthalene-4-ol: verification of the responses of individual tautomers.
Gas-phase tautomerism in 1-phenylazonaphthalene-4-ol (1) was studied by using electron ionization (EI) mass spectrometry on the basis of the fragmentations of the model enol and keto tautomers, where the movable proton is replaced by a methyl group. These fixed tautomers were obtained as an easy separable mixture by simple methylation of the cheap and easily accessible diazene (1). It was found that their EI mass spectral fragmentations are in full congruence with the already published theoretical predictions. The relative energies required for bond cleavage in 1 and its fixed tautomers were estimated by stepwise increasing of the electron energy of the ion source of the mass spectrometer. A simple equation for the approximate estimation of the molar fractions of the individual tautomers was suggested. It was shown that the enol form is dominant in the temperature range of 200-300 degrees C.
Institute of Organic Chemistry with Centre of Phytochemistry, Bulgarian Academy of Sciences, Acad. G.Bonchev str., bl.9, Sofia 1113, Bulgaria. dantonova@orgchm.bas.bg
Daniela
D
Nedeltcheva
Vanya
V
Kurteva
Boriana
B
Damyanova
Simeon
S
Popov