Conformational Analysis of N-Alkyl-N-[2-(diphenylphosphoryl)ethyl]amides of Diphenylphosphorylacetic Acid: Dipole Moments, IR Spectroscopy, DFT Study

Abstract

Experimental and theoretical conformational analysis of N-methyl-N-[2-(diphenylphosphoryl)ethyl]diphenylphosphorylacetamide, N-butyl-N-[2-(diphenylphosphoryl)ethyl]diphenylphosphorylacetamide, and N-octyl-N-[2-(diphenylphosphoryl)ethyl]diphenylphosphorylacetamide was carried out by the methods of dipole moments, IR spectroscopy, and Density Functional Theory (DFT) B3PW91/6-311++G(df,p) calculations. In solution, these N,N-dialkyl substituted bisphosphorylated acetamides exist as a conformational equilibrium of several forms divided into two groups—with Z- or E-configuration of the carbonyl group and alkyl substituent, and syn or anti arrangement of the phosphoryl-containing fragments relative to the amide plane. The substituents at the phosphorus atoms have eclipsed cis- or staggered gauche-orientation relative to the P=O groups, and cis orientation of the substituents is due to the presence of intramolecular H-contacts P=O...H−Cphenyl or p,π conjugation between the phosphoryl group and the phenyl ring. Preferred conformers of acetamides molecules are additionally stabilized by various intramolecular hydrogen contacts with the participation of oxygen atoms of the P=O or C=O groups and hydrogen atoms of the methylene and ethylene bridges, alkyl substituents, and phenyl rings. However, steric factors, such as a flat amide fragment, the bulky phenyl groups, and the configuration of alkyl bridges, make a significant contribution to the realization of preferred conformers.

Construction of Highly Dispersed Cu–P/Cl Active Sites Using Methyldiphenyloxophosphine for Efficient Acetylene Hydrochlorination

“…As shown in Figure , several characteristic absorption peaks could be clearly distinguished in the spectrum of the MDPO sample, among which the peaks located at 1590 and 1485 cm –1 belong to the skeletal vibrations, including the C–C stretching vibration in the benzene rings, the peaks located at 1440 and 997 cm –1 are associated with the characteristic vibration of the benzene ring directly attached to P, the peak located at 1173 cm –1 can be attributed to the stretching vibration of the PO structure in MDPO, and the peak at 1125 cm –1 can belong to the in-plane bending vibration of the benzene rings. In addition, the characteristic peaks of the stretching vibration of P–C are located in the range of 650–750 cm –1 , and the characteristic peaks of the C–H out-of-plane bending vibration of aromatic compounds appear at 900–675 cm –1 . ,, At first glance, the spectrum of the CuCl 2 -MDPO sample appears similar to that of MDPO. Notably, the PO stretching vibration and the in-plane bending vibration of the benzene rings are red-shifted by 18 and 29 cm –1 in CuCl 2 -MDPO due to electron aggregation and electron feeding, further demonstrating the generation of a local active domain as a result of the coordination between the MDPO ligand and CuCl 2 precursors, as was verified by the appearance of peaks attributable to P–O/P–O–Cu and P–Cu species in the P 2p XPS spectrum of the 15% Cu 8 MDPO 1 /AC catalyst (Figure ).…”

“…In addition, the characteristic peaks of the stretching vibration of P−C are located in the range of 650−750 cm −1 , and the characteristic peaks of the C−H out-of-plane bending vibration of aromatic compounds appear at 900−675 cm −1 . 33,45,46 At first glance, the spectrum of the CuCl 2 -MDPO sample appears similar to that of MDPO. Notably, the P�O stretching vibration and the inplane bending vibration of the benzene rings are red-shifted by 18 and 29 cm −1 in CuCl 2 -MDPO due to electron aggregation and electron feeding, further demonstrating the generation of a local active domain as a result of the coordination between the MDPO ligand and CuCl 2 precursors, as was verified by the appearance of peaks attributable to P−O/P−O−Cu and P−Cu species in the P 2p XPS spectrum of the 15% Cu 8 MDPO 1 /AC catalyst (Figure 4).…”