Intramolecular hydrogen bonding in chemoselective synthesized 2-substituted pyrrole stable phosphorus ylide: GIAO, AIM, and NBO approaches

Kinetic Spectrophotometric Method for the 1,4-Diionic Organophosphorus Formation in the Presence of Meldrum's Acid: Stopped-Flow Approach

The kinetics of the reaction between triphenylphosphine (TPP) and dimethyl acetylenedicarboxylate (DMAD) in the presence of Meldrum’s acid (MA) for the generation of the 1,4-diionic organophosphorus compound has been investigated using the stopped-flow and UV-VIS spectrophotometry techniques. The first step of the reaction between TPP and DMAD for the generation of (I₁) in ethanol was followed by the stopped-flow apparatus. This step was recognized as a fast step. The reaction between the intermediate (I₁) and MA showed first-order kinetics, and it was followed by the UV-VIS spectrophotometry technique. The activation parameters for the slow step of the proposed mechanism were determined using two linearized forms of the Eyring equation. From the temperature, concentration and solvent studies, the activation energy (Ea = 20.16 kJ·mol⁻¹) and the related activation parameters (ΔG^‡ = 71.17 ± 0.015 kJ·mol⁻¹, ΔS^‡ = −185.49 ± 0.026 J·mol⁻¹ and ΔH^‡ =17.72 ± 0.007 kJ·mol⁻¹) were calculated. The experimental data indicated that the reaction was zero-order in MA and second-order overall. The proposed mechanism was confirmed with the observed kinetic data obtained from the UV-VIS and stopped-flow techniques.

Variable temperatures 1H NMR technique on the kinetics and thermodynamic parameters of equilibrium between the Z and E isomers in a stable phosphorus ylide involving an imidazole

Analysis of ¹H NMR spectra of a special ylide involving an imidazole at variable temperatures has been employed to study the kinetics of the interchangeable process in the equilibrium between the two Z- and E-isomers of a stable phosphorus ylide.

Dynamic ¹H NMR studies of hindered internal rotations in the synthesized particular phosphorus ylide: experimental and theoretical approaches

Dynamic (1)H NMR measurements were performed within the synthesized particular phosphorus ylide involving 4-formylphenyl phenylcarbamate. Four rotational process and thereby parameters were targeted for rotation around the CC, C-C, HCNC and OCNC bonds. The Gibbs free activation energy in CDCl3, ΔG(≠)exp, was found to be 64 ± 2, 50 ± 2, 41 ± 2 and 63 ± 2, respectively. These findings were compared with related ab initio and DFT results on simulated situation. Theoretical methods tested, were comparable to the present D (1)H NMR data.