TY - JOUR
T1 - Infrared, Raman and temperature-dependent NMR spectra, vibrational assignments, normal coordinate analysis, and DFT calculations of benzoxazoline-2-thione
AU - Mohamed, Tarek A.
AU - Mustafa, Ahmed M.
AU - Zoghaib, Wajdi M.
AU - Afifi, Mahmoud S.
AU - Farag, Rabei S.
AU - Badr, Yehia
PY - 2010/3/18
Y1 - 2010/3/18
N2 - The tautomerism of benzoxazoline-2-thione (BOT; thio-keto) and 2-mercaptobenzoxazole (MBO; thio-enol) has been thoroughly investigated by means of Raman (3600-100 cm-1), infrared (4000-200 cm-1), 1H and 13C NMR spectra and X-ray powder diffraction (XRD). In addition, temperature-dependent 1H NMR spectra from -90 to +90 °C were acquired. To complement experimental results with theoretical predictions, we performed Density Functional Theory (DFT) calculations utilizing B3LYP, B3PW91 and SVWN methods at 6-31G(d) basis set. Both computational and spectral results were in favor of thio-keto BOT structure with no evidence for the existence of thio-enol (MBO) tautomer which firmly eliminates the possibility of an existing equilibrium between keto and enol forms. Moreover the dimerization percentage of thio-keto benzoxazoline-2-thione (BOT) and benzothiazoline-2-thione (BTT) were found to be 11.9% and 2.5%, respectively which favors strong hydrogen bonding interactions in BOT. Aided by normal coordinate analysis, force constants in internal coordinates and potential energy distributions (PEDs), a complete vibrational assignment for all fundamentals was obtained. The results are compared with the sulfur analogue, benzothiazoline-2-thione (BTT) whenever appropriate.
AB - The tautomerism of benzoxazoline-2-thione (BOT; thio-keto) and 2-mercaptobenzoxazole (MBO; thio-enol) has been thoroughly investigated by means of Raman (3600-100 cm-1), infrared (4000-200 cm-1), 1H and 13C NMR spectra and X-ray powder diffraction (XRD). In addition, temperature-dependent 1H NMR spectra from -90 to +90 °C were acquired. To complement experimental results with theoretical predictions, we performed Density Functional Theory (DFT) calculations utilizing B3LYP, B3PW91 and SVWN methods at 6-31G(d) basis set. Both computational and spectral results were in favor of thio-keto BOT structure with no evidence for the existence of thio-enol (MBO) tautomer which firmly eliminates the possibility of an existing equilibrium between keto and enol forms. Moreover the dimerization percentage of thio-keto benzoxazoline-2-thione (BOT) and benzothiazoline-2-thione (BTT) were found to be 11.9% and 2.5%, respectively which favors strong hydrogen bonding interactions in BOT. Aided by normal coordinate analysis, force constants in internal coordinates and potential energy distributions (PEDs), a complete vibrational assignment for all fundamentals was obtained. The results are compared with the sulfur analogue, benzothiazoline-2-thione (BTT) whenever appropriate.
KW - Benzoxazoline-2-thione
KW - DFT calculations
KW - Force constants
KW - Infrared
KW - Raman
KW - Temperature-dependent H NMR
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U2 - 10.1016/j.vibspec.2009.12.001
DO - 10.1016/j.vibspec.2009.12.001
M3 - Article
AN - SCOPUS:76849102734
SN - 0924-2031
VL - 52
SP - 128
EP - 136
JO - Vibrational Spectroscopy
JF - Vibrational Spectroscopy
IS - 2
ER -