Photoelectron spectroscopy and quantum chemical analysis of some N-nitrosamines

Abstract

carbonyl compounds by H atom donors may be of the same order.The chemistry of the triplet state of sym-triazine has been studied34 and was found to be similar to that of the diazabenzenes examined in this work.Abstract: Photoelectron (PES) and electronic absorption spectra of a series of N-nitrosamines have been obtained and compared with the results of C N D 0 / 2 and C N D O / S calculations; all observable PES and electronic absorption bands have been assigned. The highest occupied molecular orbital is a A orbital, and the subjacent occupied orbital is an n orbital localized on the nitroso oxygen. Bond orders, charge densities, and dipole moments determined by the calculations are presented and discussed. The calculated A charge densities indicate that the amino nitrogen is electron deficient; however, the calculated total charge densities indicate that amino nitrogen is slightly electron rich. Barriers to syn-anti isomerization of dimethylnitrosamine by means of both rotation around the N-N bond and inversion at the nitroso nitrogen have been calculated by means of the C N D O / 2 method. The inversional barrier is four times greater than the rotational barrier. The calculated rotational barrier, 18.2 kcal/mol, has the same magnitude as that of the experimentally determined barrier, 23 kcal/mol. Conformational analyses of methylphenylnitrosamine and of diisopropylnitrosamine have been made by means of the C N D O / 2 method and have been compared with the analyses of previous investigations.

Interactions of Organic Nitroso Compounds with Metals

“…Nauman and co-workers obtained photoelectron and electronic absorption spectral data for a series of nitrosamines . The charge densities of the NNO moieties obtained from their theoretical calculations (CNDO/2 and CNDO/S) revealed an electronegative O-atom, an electropositive nitroso N-atom, and a slightly electronegative amine N-atom; they also proposed an involvement and redistribution of the molecules' σ electrons.…”

“…The charge densities of the NNO moieties obtained from their theoretical calculations (CNDO/2 and CNDO/S) revealed an electronegative O-atom, an electropositive nitroso N-atom, and a slightly electronegative amine N-atom; they also proposed an involvement and redistribution of the molecules' σ electrons. Thus, they suggested that the dipolar resonance form in eq 43 should be classified as the limiting case for the π-electron system; they calculated that the HOMO of R 2 NNO is the nitroso π-orbital, with the second HOMO being an n orbital localized mostly on the O-atom. ,343b Wang and co-workers measured the HeI photoelectron spectra of the nitrosamines R 2 NNO (R = Me, Et, n -Pr), performed ab initio SCF MO calculations (631*G basis sets), and suggested that the HOMO of R 2 NNO is π in nature and largely localized in the NO group , The infrared spectra of aliphatic nitrosamines display bands in the 1425−1460 and 1030−1150 cm -1 ranges due to υ NO and υ NN , respectively .…”

Ab initio calculations of the electronic structures of Dimethylnitrosamine (DMN) and its Metabolite Hydroxydimethylnitrosamine (HDMN): A possible intermediate in carcinogenesis by DMN

“…The total charges on the atoms for conformation S are given in Table 111, following the usual Mulliken population analysis [57], together with the computed dipole moment p. The alternation of charge found for many polar molecules [44] is observed from 0 3 to N1 but the present calculations predict the carbon atoms to be negative, in contrast to the semiempirical results [32].…”

“…There have been several studies of the photo-electron spectra, both x-ray PES [31,34] and uv PES [32,33] which have established the first few ionization potentials, but there has been disagreement as to the nature and symmetry of the highest occupied orbitals [31,33].…”

Electron spectroscopy: x-ray and electron excitation

“…The composite structure of these bands has been analyzed using deconvolution techniques. The partial p and d densities of states in Cul have been determined (271). ESCA has been used to investigate the valence bands of the silver halides; assignments of the photoemission peaks are made using a point charge electrostatic model (272).…”