The HN- and N-methylimines of formaldehyde, acetaldehyde and acetone: electronic structure and inversion barriers of nitrogen atom

Authors

  • Natalia V. Kutsik-Savchenko Ukrainian State Chemical Technology University, Gagarin Ave., 8, Dnepropetrovsk, 49000, Ukraine
  • Oleg S. Lebed Ukrainian State Chemical Technology University, Gagarin Ave., 8, Dnepropetrovsk, 49000, Ukraine
  • Aleksander V. Prosyanik Ukrainian State Chemical Technology University, Gagarin Ave., 8, Dnepropetrovsk, 49000, Ukraine

DOI:

https://doi.org/10.15421/081504

Keywords:

imines, inversion, electron density, intramolecular interactions

Abstract

The transmission of electronic effects and factors which affect the inversion barriers of atom N (ΔEi¹) in unsubstituted (I) and N-methyl derivatives (II) of formaldehyde (a), acetaldehyde (b), and acetone (c) have been investigated using the DFT method within the NBO. It was defined that the negative charge on the N atom (qN) decreases with N-methylation. The energy of lone pare, qN and ΔEi¹ values (imines Ia, E-Ib; Z-Ib, Ic; IIa E-IIb; Z-IIb, IIc) increases and the negative charge on C= atom decreases with C-methylation. The reduction of qN values in N-methylimines is caused by the major influence of more electronegativity of C atom and minor influence of two-electronic interactions. The relative increase of qN values with increase of degree of C-methylation is caused by hyperconjugation of the methyl groups with the antibonding orbitals of C=N bond but not +I-effects of C-substituents. C-methylation increases the inversion barriers owing to the interactions of the orbitals of iminyl atom C and does not affect their changes due to the interactions involving orbitals of =C–R2 bonds. It denies the supposed dominant influence of nN®s*C–R interactions on ΔEi¹ values. In general, electronegativity of N-substituents and steric strain has the dominant influence on the inversion barriers but not the intramolecular interactions.

Author Biographies

Natalia V. Kutsik-Savchenko, Ukrainian State Chemical Technology University, Gagarin Ave., 8, Dnepropetrovsk, 49000

junior researcher at the Research Laboratory of biologically active compounds,    tel. +3(8093)-89-14-786

Oleg S. Lebed, Ukrainian State Chemical Technology University, Gagarin Ave., 8, Dnepropetrovsk, 49000

Assistant of the Department of Organic Chemistry, candidate of Chemical Sciences

Aleksander V. Prosyanik, Ukrainian State Chemical Technology University, Gagarin Ave., 8, Dnepropetrovsk, 49000

Сhief of the Department of Organic Chemistry, professor, doctor of Chemical Sciences

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Published

2015-10-07

Issue

Vol. 23 No. 1 (2015): Bulletin of Dnipropetrovsk University. Series Chemistry

Section

Organic Chemistry

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Copyright (c) 2015 Oles Honchar Dnipropetrovsk National University

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