Abstract
The Raman (3600-100 cm-1), infrared (4000-400 cm-1), far-infrared (400-200 cm-1), 1H and 13C NMR spectra of solid benzothiazoline-2-thione (BTT) are recorded. Additionally, the 1H NMR spectra were obtained at a temperature range from -90 to +90 °C. In addition, 2-mercaptobenzothiazole (MBT) can either be cis (S-H is eclipsing C{double bond, long}N bond) and/or trans (S-H is eclipsing C{double bond, long}S bond). Therefore, we carried out geometry and frequency calculations for thio-keto and thio-enol conformations using Density Functional Theory (DFT) methods of B3LYP, B3PW91 and SVWN utilizing 6-31 G(d) basis set. Theoretical predictions are consistent with vibrational measurements, which are in favor of the thio-keto (thione) tautomer at ambient temperature (25 °C). From the variable temperature 1H NMR spectra, it is evident that the thione BTT is the only existing tautomer at ambient (25 °C), low- (down to -90 °C) and high- (up to +90 °C) temperatures. Therefore, the thio-keto (BTT) and thio-enol (MBT) equilibrium is unquestionably excluded. B3LYP and B3PW91 calculations are in agreement with vibrational spectra as well as X-ray structural parameters of BTT rather than SVWN at 6-31 G(d) basis set. In addition, we calculated the S-H barriers to internal rotation for cis/trans chalcogen analogues of MBT utilizing B3LYP/MP2 potential surface scans with the 6-31 G(d) basis set. The cis/trans S-H barriers were 4.15/3.61, 3.39/2.90 and 3.71/3.36 kcal/mol for 2-mecaptobenzoxazole (MBO), 2-mercaptobezothiazole (MBT) and 2-mercaptobenzoselenazole (MBSe) analogues, respectively.
| Original language | English |
|---|---|
| Pages (from-to) | 27-36 |
| Number of pages | 10 |
| Journal | Journal of Molecular Structure: THEOCHEM |
| Volume | 868 |
| Issue number | 1-3 |
| DOIs | |
| Publication status | Published - Nov 15 2008 |
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Keywords
- H and C NMR
- Barriers to internal rotation
- Benzothiazoline-2-thione
- DFT calculations
- Infrared
- Raman
- Thio-keto and thio-enol tautomerism
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Biochemistry
- Condensed Matter Physics
Cite this
Reinvestigation of benzothiazoline-2-thione and 2-mercaptobenzothiazole tautomers : Conformational stability, barriers to internal rotation and DFT calculations. / Mohamed, Tarek A.; Mustafa, Ahmed M.; Zoghaib, Wajdi M.; Afifi, Mahmoud S.; Farag, Rabei S.; Badr, Yehia.
In: Journal of Molecular Structure: THEOCHEM, Vol. 868, No. 1-3, 15.11.2008, p. 27-36.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Reinvestigation of benzothiazoline-2-thione and 2-mercaptobenzothiazole tautomers
T2 - Conformational stability, barriers to internal rotation and DFT calculations
AU - Mohamed, Tarek A.
AU - Mustafa, Ahmed M.
AU - Zoghaib, Wajdi M.
AU - Afifi, Mahmoud S.
AU - Farag, Rabei S.
AU - Badr, Yehia
PY - 2008/11/15
Y1 - 2008/11/15
N2 - The Raman (3600-100 cm-1), infrared (4000-400 cm-1), far-infrared (400-200 cm-1), 1H and 13C NMR spectra of solid benzothiazoline-2-thione (BTT) are recorded. Additionally, the 1H NMR spectra were obtained at a temperature range from -90 to +90 °C. In addition, 2-mercaptobenzothiazole (MBT) can either be cis (S-H is eclipsing C{double bond, long}N bond) and/or trans (S-H is eclipsing C{double bond, long}S bond). Therefore, we carried out geometry and frequency calculations for thio-keto and thio-enol conformations using Density Functional Theory (DFT) methods of B3LYP, B3PW91 and SVWN utilizing 6-31 G(d) basis set. Theoretical predictions are consistent with vibrational measurements, which are in favor of the thio-keto (thione) tautomer at ambient temperature (25 °C). From the variable temperature 1H NMR spectra, it is evident that the thione BTT is the only existing tautomer at ambient (25 °C), low- (down to -90 °C) and high- (up to +90 °C) temperatures. Therefore, the thio-keto (BTT) and thio-enol (MBT) equilibrium is unquestionably excluded. B3LYP and B3PW91 calculations are in agreement with vibrational spectra as well as X-ray structural parameters of BTT rather than SVWN at 6-31 G(d) basis set. In addition, we calculated the S-H barriers to internal rotation for cis/trans chalcogen analogues of MBT utilizing B3LYP/MP2 potential surface scans with the 6-31 G(d) basis set. The cis/trans S-H barriers were 4.15/3.61, 3.39/2.90 and 3.71/3.36 kcal/mol for 2-mecaptobenzoxazole (MBO), 2-mercaptobezothiazole (MBT) and 2-mercaptobenzoselenazole (MBSe) analogues, respectively.
AB - The Raman (3600-100 cm-1), infrared (4000-400 cm-1), far-infrared (400-200 cm-1), 1H and 13C NMR spectra of solid benzothiazoline-2-thione (BTT) are recorded. Additionally, the 1H NMR spectra were obtained at a temperature range from -90 to +90 °C. In addition, 2-mercaptobenzothiazole (MBT) can either be cis (S-H is eclipsing C{double bond, long}N bond) and/or trans (S-H is eclipsing C{double bond, long}S bond). Therefore, we carried out geometry and frequency calculations for thio-keto and thio-enol conformations using Density Functional Theory (DFT) methods of B3LYP, B3PW91 and SVWN utilizing 6-31 G(d) basis set. Theoretical predictions are consistent with vibrational measurements, which are in favor of the thio-keto (thione) tautomer at ambient temperature (25 °C). From the variable temperature 1H NMR spectra, it is evident that the thione BTT is the only existing tautomer at ambient (25 °C), low- (down to -90 °C) and high- (up to +90 °C) temperatures. Therefore, the thio-keto (BTT) and thio-enol (MBT) equilibrium is unquestionably excluded. B3LYP and B3PW91 calculations are in agreement with vibrational spectra as well as X-ray structural parameters of BTT rather than SVWN at 6-31 G(d) basis set. In addition, we calculated the S-H barriers to internal rotation for cis/trans chalcogen analogues of MBT utilizing B3LYP/MP2 potential surface scans with the 6-31 G(d) basis set. The cis/trans S-H barriers were 4.15/3.61, 3.39/2.90 and 3.71/3.36 kcal/mol for 2-mecaptobenzoxazole (MBO), 2-mercaptobezothiazole (MBT) and 2-mercaptobenzoselenazole (MBSe) analogues, respectively.
KW - H and C NMR
KW - Barriers to internal rotation
KW - Benzothiazoline-2-thione
KW - DFT calculations
KW - Infrared
KW - Raman
KW - Thio-keto and thio-enol tautomerism
UR - http://www.scopus.com/inward/record.url?scp=53249132627&partnerID=8YFLogxK
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U2 - 10.1016/j.theochem.2008.07.037
DO - 10.1016/j.theochem.2008.07.037
M3 - Article
VL - 868
SP - 27
EP - 36
JO - Computational and Theoretical Chemistry
JF - Computational and Theoretical Chemistry
SN - 2210-271X
IS - 1-3
ER -