Investigation of NQR parameters on the tetrazole-azide tautomeric equilibria: a DFT study
Yazarlar (3)
| Makale Türü |
Özgün Makale
(Uluslararası alan indekslerindeki dergilerde yayınlanan tam makale)
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| Dergi Adı | Journal of the Mexican Chemical Society | ||
| Makale Dili | – | Basım Tarihi | 01-2006 |
| Cilt / Sayı / Sayfa | 50 / 4 / 143–148 | DOI | – |
| Makale Linki | https://www.scielo.org.mx/scielo.php?pid=S1870-249X2006000400001&script=sci_abstract&tlng=pt | ||
| UAK Araştırma Alanları |
Fiziksel Kimya
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| Özet |
| A theoretical study was undertaken to reinvestigate whether NQR parameters such as quadrupole coupling constant, asymmetry factor, and NQR frequencies obtained from electric field gradient tensor can provide information to infer about the substituent effect on tautomeric forms of tetrazole-azide equilibria in a gas phase. For this purpose, 14 N-NQR parameters of 5-R-tetrazolo [1, 5-a] pyridines and its corresponding tautomer, on the tetrazole-azide isomerization, were calculated at the B3LYP/6-31++ G** level of theory and compared with each other, where R= H, CH 3, OH, Cl, OCH 3, NO 2. The results reveal that NQR parameters of nitrogen atoms of these compounds are highly sensitive to substituent effects. The influence of these groups on the transition state (TS) was also studied. Moreover, according to some plotted graphs reasonable relationship has been found between the values of the Hammett constant (σ p) of mentioned substituents and their 14 N-NQR parameter data. In general, it is observed that groups which stabilize the azide isomer lower the E act of the isomerization reaction, and conversely, those that favor the tetrazole form, raise the E act, relative to the unsubstituted compound. The TS has a close resemblance to the tetrazole structure. Also, the energy differences between tautomeric forms, the graphs of σ p versus energy values, and the graph of Hammett-constants versus E act as well as the graph of r N3-N4 versus E act have been analyzed. Finally, we have focused on some critical points in the plotted graphs of both E±Q (J) versus v±Q (MHz) and E±Q (J) versus η. |
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