An electronic and vibrational study of the cyclopropenyl ion and its fluoroderivatives

Abstract

This article presents the results of ab initio SCF-MO calculations on both the electronic structure and vibrational spectra of the cyclopropenyl cation (CsH:) and its fluoroderivatives, CjH*F+, C,HFi and CsF:. A very simple and unambiguous criterion for choosing the combination of diffuse and polarization functions which, together with the 6-3 11G basis set, best describes the electron distribution in these ions is presented. The electronic structures of the cations are analysed in detail; particular emphasis is given to the analysis of the electronic effects due to successive hydrogen-byfluorine replacements.The results of vibrational normal mode analysis carried out for all hydrogen-deuterium isotopomers of the studied ions are presented and compared with the available experimental data. The theoretical results are used both to review some band assignments previously proposed for the tluorosubstituted molecules and to give a stronger theoretical foundation to the general interpretation of the vibrational spectra of these compounds,

The Remarkably Stabilized Trilithiocyclopropenium Ion, C3Li3+, and Its Relatives

“…Both the cyclopropenyl cation ( 4 ) and the propargyl cation ( 5 ) have been characterized experimentally . The extensively computed energy difference between 4 and the less stable 5 also callibrates the levels used here. , Our best value of 23.3 kcal/mol (Table ) at B3LYP (27.2 kcal/mol at MP4SDTQ/6-31G*) favoring 4 are within the error bounds of the experimental difference of 23 ± 4 kcal/mol based on appearance potential measurements…”

“…The lithiated cyclopropenium ions may also be characterized by vibrational spectroscopy. Experimental frequencies (cm -1 ) are known for the cyclopropenyl cation ( 4 ) [3183, 1626 (a 1 ‘); 1031 (a 2 ‘); 3138, 1290, 927 (e‘); and 990 (e‘‘)], but such IR data are not available for the lithiated derivatives ( 6 , 10 , 3 , and 14 ). Apart from the symmetric (3295.6 cm -1 ) and asymmetric (3245.4 cm -1 ) C−H stretching vibrations of 4 (which are overestimated somewhat compared to experimental values), all of the B3LYP/6-311+G* computed normal modes (Table ) are in excellent aggrement with experiment 34a.…”

“…The first set of geometries examined were based on the structures of the two known C 3 H 3 + isomers, the cyclopropenyl cation ( 4 ) and the propargyl cation, 5 …”

Conformational investigation of α, β‐dehydropeptides. VIII.*N‐Acetyl‐α, β‐dehydroamino acid N'‐methylamides: conformation and electron density perturbation from infrared and theoretical studies

“…For systems containing conjugated double bonds (28) and H-bonds (29), reliable structural results can generally be achieved only if the polarization functions on all atoms are introduced. The ab initio calculations were therefore carried out with the 6 3 1 G** basis set (30).…”

Simulation of reactions of fluoroalkenes by quantum chemistry methods

“…The results of non-empirical calculations for C 3 H 2 F + , C 3 HF 2 , and C 3 F 3 ions are given elsewhere 62 (SCF, Hartree ± Fock, 6-311G).…”