NATURAL SCIENCES

Journal of fundamental
and
applied researches

The quantum chemical ab initio calculation of geometricaland electronic parameters of the anions of 2-methyl-5-nitromethyl-2h-tetrazole

2013. ¹2, pp. 181-187

Tyrkov Alexey G.  - D.Sc. (Chemistry), Professor, Head of Chair, Astrakhan Statå University, 1Schaumyn Sq., Astrakhan, 414000, Russian Federation, tyrkov@rambler.ru

Abdelrakhim Makhommed Akhmed  - post-granduate student, Astrakhan Statå University, 1Schaumyn Sq., Astrakhan, 414000, Russian Federation, sbn86chem@yandex.ru

Konstantin P. Pashchenko - Ph.D. (Chemistry), Assiciate Professor, Astrakhan Statå University, 1Schaumyn Sq., Astrakhan, 414000, Russian Federation, estnauki2009@rambler.ru

Ildar R. Akmaev - student, Astrakhan Statå University, 1Schaumyn Sq., Astrakhan, 414000, Russian Federation, estnauki2009@rambler.ru

To find the correlation between the calculated characteristics of nitromethyltetrazolyl anions and experimental data of their reactivity with ?-nitrocarbocations carried out by ab initio quantum-chemical calculation of molecular geometry and electron density distribution in the 2-methyl-5-dinitromethyl-2H-tetrazole, 2-methyl-2H-tetrazol-5-yl nitroacetate and 2-nitro-2-(2-methyl-2H-tetrazol-5-yl) acetonitrile anions. Calculations of the ions carried out by the method of RHF, in the basis 6-31G (d), geometry optimization was performed on a gradient criterion 10-5 (in atomic units of energy). It is shown that the anions are not planar, the differences concern geometry of dinitromethyl and ethylnitroacetate groups. Anions geometry was used to calculate their electronic characteristics. Calculations showed that, despite the different nature of the substituents in the 5-position of the heterocycle, the general nature of delocalization of the negative charge in the anions doesn’t significantly change. The largest negative charge is localized on the oxygen atoms of nitro groups, the carbon atoms of the nitromethyl group are much more "soft" nucleophilic centers. However, the presence of bulky tetrazole ring, probably, creates enough shielding for the C-center and makes it impossible to process C-alkylation. The carried out quantum-chemical calculation allows to explain features of nucleophilic reactivity of the competing reaction centers of anions with ?-nitrocarbocations.

Key words: ambident anions,2-methyl-5-dinitromethyl-2H-tetrazole,ethyl 2-methyl-2H-tetrazole-5-yl nitroacetate,2-nitro-2-(2-methyl-2H-tetrazol-5-yl) acetonitrile,RHF method,O-,C-alkylation,?-nitrocarbocations