Title

Aminimides: RconN(CH3)2CH2CH(OH)CH3(R = C6H5and CF3CF2) natural bond orbital and topological analysis of electron density distributions. Part 31

Publication Date

1-1-2020

Document Type

Article

Department

Chemistry

Publication Title

Revue Roumaine de Chimie

Volume

65

Issue

1

DOI

10.33224/rrch.2020.65.1.02

First Page

23

Last Page

38

Abstract

The negative charge in the title ylides is dispersed almost equally among the negative nitrogen, -N⊖, and the oxygen of the C=O group, as it is computationally illustrated at DFT level of theory. As result, the C-N⊖group acquires partial double bond character and, therefore, display (Z)- and (E)- diastereoisomerism of substituents around this bond. Single crystal X-ray measurements for the title aminimides reveal the preference for the (Z)- diastereomer about the CO-N⊖N⊕bond. Computationally, for example, at level B3LYP-D3/6-311+G∗∗of theory, the (E)- diastereomer is at δG298 K= 14.4 kcal/mol higher than the (Z)-aminimide 1 (R=C6H5) and with 19.9 kcal/mol higher than the (Z)- aminimides 2 (R = CF3CF2). The magnitude of the second order energy stabilization .F as a result of negative nitrogen lone pair (NNLP) charge transfer to the acceptor p∗CO is always larger for (Z)- diastereomer than for the (E)- diastereomer. Additionally, the (Z)- configuration of both aminimide 1 (R=C6H5) and aminimide 2 (R=CF2CF3) is locked by several intramolecular hydrogen bonds: OH-N⊖, CH(Me)-O=C, OH-F and HO-HC(Me), all characterized by bond critical properties (BCP) such as electron density ρ(rBCP), laplacian of electron densities ∇2(rBCP) and eigenvalues of the Hessian of the electron density λ1(rBCP), λ2(rBCP), and λ3(rBCP). Natural Bond Orbital (NBO) analysis predicts large charge transfer from the neighboring NNLP into the π∗CO. As a result, the C=O bond is lengthened in comparison with the protonated RCO- NHN. species, whereas the C-N⊖bond is shortened. Bond orders for C=O and CO-N⊖N⊕are close to 1.5. In accordance with the value of bond order, Natural Resonance Theory (NRT) analysis predicts almost equal weights for the O=C-N⊖and the ⊖O-C=N resonance structures.

Share

COinS