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DFT computations have been performed to study the mechanism of the reactions of sulfides with hypochlorous acid and N ‐chlorosulfonamides. Sulfides can attack HOCl both at chlorine and oxygen atoms. The attack at chlorine results in the formation of chlorosulfonium cation (R 2 SCl ⁺ ) and OH ⁻ intermediates, which transform to sulfoxide product. Th...
DFT computations have been performed in acetone and water solvents in order to investigate the mechanism of hydrolysis of acid chlorides. Acetyl chloride and chloroacetyl chloride hydrolyze via concerted, one-step SN2 mechanism, with the attack of water at the sp2 hybridized carbon atom of the CO group, and the transition state (TS) has distorted t...
Complex formation reactions of phenylboronic, phenylphosphonic, phenylarsonic and 4-aminophenyl arsonic acids with β-cyclodextrin (cycloheptaamylose, β-CD) and some simple carbohydrates (mannitol, sorbitol, glucose) have been studied using spectrophotometric, potentiometric methods and solubility measurements, supplemented with HPLC and IR analyses...
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DFT computations have been performed at different levels of theory to identify the mechanism for the oxidation of sulfides and sulfoxides with periodates. The periodate ion (IO4–), periodic acid (HIO4) and their hydrated derivatives all oxidize sulfides to sulfoxides in one-step oxygen-transfer reactions and the relative reactivities are HIO4 >> H5...
DFT computations have been performed on nucleophilic substitutions of phenacyl bromides with pyridines to investigate the mechanism of the reaction. In contrast with earlier suppositions, tetrahedral intermediate is not formed by the addition of pyridine on the CO group of phenacyl bromide, because the total energy of the reacting species increases...
DFT computations were performed on the SN1 and SN2 solvolyses of substituted cumyl chlorides and benzyl chlorides in ethanol and water, by increasing stepwise the CCl distance and by optimization. The total energy increases with the increase in the ClC distance in SN1 reactions, while free energy of activation pass through maximum. To validate the...
DFT computations on the mechanisms of nucleophilic substitutions on benzyl bromides were performed and the calculated activation parameters were compared with experimentally acquired data. In vacuo, the presence of electron-withdrawing (e-w) groups on the benzyl bromides accelerated the reactions and the calculated ΔG‡/ΔH‡/ΔS‡ vs. σ plots were line...
Different characteristics of cleavage kinetics of resin-bound amino alcohols and their peptide derivatives were observed in acid containing protic and aprotic solvent mixtures. The hydrolysis reactions are hindered by steric crowding around the cleaving C--O bond and accelerated by the special solvation effect of CF(3)CH(2)OH on the peptide chain a...
The activation parameters and optimized structures of the reactants and transition states in the S(N)2 reactions of substituted pyridines and N,N-dimethylanilines with methyl iodide were computed at the DFT level in different solvents. The measured and calculated deltaG/deltaH/deltaS versus sigma plots proved to be linear, and their slopes, the del...
(S)-(+)- and (R)-(−)-enantiomers of naphthyl-phenyl-bis(acyloxy)spiro-λ4-sulfane 2 were prepared from the precursors (R)-(−)- and (S)-(+)-naphthyl phenyl sulfoxide dicarboxylic acid 2a with acetic anhydride. The hydrolysis of spiro-λ4-sulfane (R)-(−)-2 in acidic and basic solutions gave as major products sulfoxide (S)-(+)-2a and (R)-(−)-2a, respect...
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Aryl (methylaminocarbonylaryl) sulfides were converted by t-BuOCl to diaryl(acylamino)(chloro)-λ4-sulfanes or the corresponding diaryl(acylamino)sulfonium chlorides depending on the substituent of the S-aryl group. 1H NMR data showed that chloro-λ4-sulfanes exist only in CDCl3 and DMSO-d6 solvents, whereas in CD3OD complete ionic dissociation takes...
Kinetics for the hydrolysis of diarylbis(acylamino)spiro-λ4-sulfanes 3a–e and 9 and precursor acylaminosulfonium salts 5a–e and 8 both leading to sulfoxides 6a–e and 10, respectively, have been studied under pseudo-first-order conditions in dioxane–water mixtures. Medium, substituent (ρ+ –0.44) and solvent isotope effects (kH2O/kD2O ≈2) indicate th...
Kinetics of the hydrolysis of diaryl(acylamino)(acyloxy)spiro-λ4-sulfanes (2a–e, 3–5) leading to sulfoxides have been studied under pseudo-first-order conditions in dioxane–water mixtures or aqueous buffer solutions. A sulfonium-carboxylate-type dipolar structure of the starting spiro-λ4-sulfanes is supported by IR spectroscopic data. Solvent polar...
The conversion of alkylthiolanes and alkylthianes by tert-butyl hypochlorite in methanol yields an equilibrium mixture of cis- and trans-methoxysulfonium chlorides. The corresponding methoxysulfonium tetrafluoroborates prepared from sulfoxides by O-alkylation show equilibration and methoxy exchange in methanol containing chloride ions. The rate con...
Kinetics of the hydrolysis of diaryldiacyloxyspirosulfuranes leading to sulfoxides have been studied under pseudo-first-order conditions in dioxane–water mixtures. It has been found that high solvent polarities and ionic strengths increase the reaction rate. The reaction is also promoted by electron-donating substituents (ρ–0.52). Strong acids have...
Using a set of sulphides o- and p-XC6H4SMe, the electronic effect, steric hindrance, and anchimeric assistance for electrophilic Cl+ addition by TsNHCl and O-transfer by NalO4 were investigated by a kinetic method. The steric effect and anchimeric assistance of the ortho-substituents were evaluated by comparing the reactivity of ortho- and para-sub...
In the reactions of sulphides (RQS) with chlaramine-T (TsNClNa) sulphilimines (RQSNTs) and sulphoxides (RQSO) are known to be produced from a chlorosulphonium-sulphon-amidate ion-pair intermediate (RQSC1, TsNH) in fast competitive SN reactions of different steric controll. The stereomechanism was investigated in reactions of sulphides (RQ*S) with a...