Olle Mårtensson

Valence electron density and structure of sydnones

Abstract The valence electron density of 3-methylsydnone is calculated in the ieh approach and presented in the form of contour diagrams of pertinent sections of the molecule. The chemical properties and the formula symbolism of sydnones is discussed on this basis.

Wave function constructed from complex hybrids

Abstract The influence on the total wave function of an atomic basis consisting of complex hybrids is considered. The complex character of the wave function in the MO-LCAO scheme as well as in the VB method is derived, and its consequences with respect to time reversal symmetry are discussed.

On the mechanism of mutagenic action of hydroxylamine

The mutagenic action of hydroxylamine is discussed from quantum chemical point of view. The discussions are based on SCF-LCAO-MO calculations in the semi-empirical approach by Pariser, Parr and Pople on cytosine and its reaction products with hydroxylamine (Residues II, III and IV in Fig. 1). The nitrogen atoms of the amino group of Residue II and the hydroxylamino group of Residue III are shown to have lower electron densities than that of the amino group of cytosine itself. This means that the proton is more easily released from the nitrogen atom of Residue II or Residue III toward the oxygen atom of guanine making another mode of hydrogen bond formation, and this is expected to lead to the replication errors. Just the same considerations are also made from the comparison of the total energies of cytosine, Residues II and III, and of their tautomers. The calculated excitation energies of cytosine and of its reaction products with hydroxylamine agree well with the observed values and chemical reactivities of cytosine, Residues II and III, 5-methylcytosine, 5-hydroxymethylcytosine, etc., are explained well by their π-electron densities.

Molecular properties and odour. Effects of substituents on pyridine and pyridine odour

Abstract It is investigated how the odour of pyridine changes when substituents of different kinds are inserted on the pyridine ring. The relation between the space filling and electronic properties of molecules and odour is studied. Far infrared spectra have been recorded for pyridines in order to test a hypothetical correlation between odour and vibrational energies.

Valence electron density and structure of the ammonia-boron trifluoride complex

Abstract The valence electron density of the NH 3 -BF 3 complex has been calculated in the iterative extended Huckel approach, and the results are presented in the form of contour diagrams of the charge distribution of the complex as well as its constituent molecules. In this approach the complex is formed under a transfer of 0.76 electrons from ammonia to boron trifluoride. This is commented on particularly on the basis of contour diagrams of the density difference between the complex and constituent molecules. The corresponding charge transfer obtained by the CNDO/2 method is 0.43 electrons.

Valence charge distribution in pyrrole and furan

Abstract The valence charge distribution of pyrrole and furan, calculated in the charge iterative, extended Huckel approach, is presented in the form of contour diagrams of pertinent sections of the molecules. The diagrams are commented on.

On the electronic structure and odours of esters of the isothiocyanic acid

The electronic structure of the esters of the isothiocyanic acid is calculated in an iterative extended Huckel method. Contour diagrams of the valence electron density are given. The odour character of these molecules is discussed in terms of the electronic structure obtained and the theories of smell put forward by Amoore and Wright respectively.