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1 Polish Journal of Chemistry

1 2005

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The Bonds Analysis of Hexamethylenetetramine

Trzęsowska A., Kruszyński R.

Polish Journal of Chemistry

2005

Vol. 79 / nr 7

1155-1168

Natural Bond Orbital (NBO) method was used for the investigation of the hexamethylenetetramine (hmt). The nature of bonds and electronic properties of the titled compound were analysed by means of quantum mechanical calculations on the structural molecular geometries from neutron diffraction measurements carried out in seven, different temperatures. Calculations were performed using density functional theory method (B3LYP) with 6-31++G(d,p) basis set. The values of total and stabilization energy, orbital populations, vibrational frequencies, dipole moments are discussed. As expected, the total hmt energy value decreases as the temperature decreases. The most profitable energy value was obtained for the lowest hmt measurement temperature, which implies that the significant and favourable reduction of thermal motion took place. The geometric parameters of hmt molecule are similar in all structures, the only normality is the shortening and hence enhancing of C-N bond with the temperature increasing. The NBO analysis of donor-acceptor interactions resulted in decreasing of localized nN, sigma CH orbital occupancy, increasing of CN * occupancy and stabilization energy associated with following delocalizations: nN sigma CN * and sigma CH sigma CN * . The results indicated that there exist very slight interactions between this nitrogen pair and the C-H antibonding orbitals of nearest neighbouring hmt molecule when the sets of hmt molecules are considered.