Oxidation of secondary alcohols by sodium N-chlorobenzenesulphonamide in aqueous solution. A kinetic study

1991 ◽  
Vol 56 (8) ◽  
pp. 1671-1679 ◽  
Author(s):  
Chirchingi K. Mythily ◽  
Dandinasivara S. Mahadevappa ◽  
Kanchugarakoppal S. Rangappa
Keyword(s):  
Isotope Effects ◽  
Activation Parameters ◽  
Secondary Alcohols ◽  
Energy Relation ◽  
Linear Free Energy ◽  
Rate Limiting Step ◽  
Different Temperatures ◽  
Entropy Of Activation ◽  
Free Energy Relation ◽  
Solvent Isotope

The kinetics of oxidation of five secondary alcohols by sodium N-chlorobenzenesulphonamide (chloramine-B) has been studied in acid medium at 40°C. The reaction is first order with respect to the oxidant and alcohol and fractional order in [H+]. The influence of added halide ions and of reaction product and the effects of varying ionic strength and dielectric constant of the medium have also been studied. The solvent isotope effects k’(H2O)/k’(D2O) were determined. The rates were studied at four different temperatures and the activation parameters were evaluated. Attempts have been made to arrive at a linear free energy relation through the Taft treatment. An isokinetic relation is observed with β = 248 K, indicating the entropy of activation as the rate controlling factor. Protonated chloramine-T (monochloramine-T) has been postulated as the reactive oxidizing species, the main product of oxidation being the corresponding ketone. A mechanism involving the interaction of protonated haloamine species and the alcohol in a rate limiting step has been proposed.

The hydration of 1-aryl-3,3,3-trifluoropropynes and some other phenylacetylenes in sulfuric acid. An excess acidity analysis

1990 ◽  
Vol 68 (10) ◽  
pp. 1876-1881 ◽  
Author(s):  
Robin A. Cox ◽  
Ewart Grant ◽  
Todd Whitaker ◽  
Thomas T. Tidwell
Keyword(s):  
Sulfuric Acid ◽  
Isotope Effects ◽  
Activation Parameters ◽  
Linear Free Energy Relationship ◽  
Hydration Kinetics ◽  
Hydration Mechanism ◽  
Linear Free Energy ◽  
Vinyl Cation ◽  
Solvent Isotope ◽  
Kinetics Of

The excess acidity method has been used to analyse the hydration kinetics of the phenylacetylenes Y-C6H4-C≡C-Z in aqueous sulfuric acid mixtures; Z = CF3 (1), H (2), COC6H4-X (3), and CO2H (4). All substrates gave acetophenone-type products consistent with the normal hydration mechanism involving rate-determining vinyl cation formation. Standard-state log k0 intercepts, and m≠m* slopes, were both used in linear free energy relationship plots against the substituent σ+ values. Solvent isotope effects and activation parameters were obtained in some cases. The deactivating Z substituents in 1, 3, and 4 all cause reaction to be some 100 times slower than that of the parent phenylacetylene 2. Compounds 2,3, and 4 all have ρ+ values of about −3.8, but 1 is more substituent sensitive, with a ρ+ of −5.3. A σ+ value of 0.38 is calculated for the CF3C≡C substituent. The ρ+ values were found to be acidity independent for 1 and 2, and probably for 3, but not for 4. Proton transfer at the transition state was found to be most advanced for the fastest reaction, that of 2, contrary to intuition. Keywords: alkyne hydration, excess acidity, phenylacetylenes, vinyl cations, deactivated carbocations.

scholarly journals Rate and Product Studies with 1-Adamantyl Chlorothioformate under Solvolytic Conditions

2021 ◽  
Vol 22 (14) ◽  
pp. 7394
Author(s):  
Kyoung Ho Park ◽  
Mi Hye Seong ◽  
Jin Burm Kyong ◽  
Dennis N. Kevill
Keyword(s):  
Rate Constants ◽  
Isotope Effects ◽  
Ion Pairs ◽  
Carbonyl Sulfide ◽  
Activation Parameters ◽  
Chloride Ions ◽  
Reaction Channels ◽  
Decomposition Pathway ◽  
Solvent Isotope ◽  
Solvent Isotope Effects

A study was carried out on the solvolysis of 1-adamantyl chlorothioformate (1-AdSCOCl, 1) in hydroxylic solvents. The rate constants of the solvolysis of 1 were well correlated using the Grunwald–Winstein equation in all of the 20 solvents (R = 0.985). The solvolyses of 1 were analyzed as the following two competing reactions: the solvolysis ionization pathway through the intermediate (1-AdSCO)+ (carboxylium ion) stabilized by the loss of chloride ions due to nucleophilic solvation and the solvolysis–decomposition pathway through the intermediate 1-Ad+Cl− ion pairs (carbocation) with the loss of carbonyl sulfide. In addition, the rate constants (kexp) for the solvolysis of 1 were separated into k1-Ad+Cl− and k1-AdSCO+Cl− through a product study and applied to the Grunwald–Winstein equation to obtain the sensitivity (m-value) to change in solvent ionizing power. For binary hydroxylic solvents, the selectivities (S) for the formation of solvolysis products were very similar to those of the 1-adamantyl derivatives discussed previously. The kinetic solvent isotope effects (KSIEs), salt effects and activation parameters for the solvolyses of 1 were also determined. These observations are compared with those previously reported for the solvolyses of 1-adamantyl chloroformate (1-AdOCOCl, 2). The reasons for change in reaction channels are discussed in terms of the gas-phase stabilities of acylium ions calculated using Gaussian 03.

scholarly journals Poly(N-isopropylacrylamide-co-methacrylic acid) microgel stabilized copper nanoparticles for catalytic reduction of nitrobenzene

2015 ◽  
Vol 33 (3) ◽  
pp. 627-634 ◽  
Author(s):  
Zahoor H. Farooqi ◽  
Zonarah Butt ◽  
Robina Begum ◽  
Shanza Rhauf Khan ◽  
Ahsan Sharif ◽  
...  
Keyword(s):  
Copper Nanoparticles ◽  
Methacrylic Acid ◽  
Catalytic Reduction ◽  
Aqueous Media ◽  
Activation Parameters ◽  
Reducing Agent ◽  
Different Temperatures ◽  
Entropy Of Activation ◽  
Micro Reactors

Abstract Poly(N-isopropylacrylamide-co-methacrylic acid) microgels [p(NIPAM-co-MAAc)] were synthesized by precipitation polymerization of N-isopropylacrylamide and methacrylic acid in aqueous medium. These microgels were characterized by dynamic light scattering and Fourier transform infrared spectroscopy. These microgels were used as micro-reactors for in situ synthesis of copper nanoparticles using sodium borohydride (NaBH4) as reducing agent. The hybrid microgels were used as catalysts for the reduction of nitrobenzene in aqueous media. The reaction was performed with different concentrations of cat­alyst and reducing agent. A linear relationship was found between apparent rate constant (kapp) and amount of catalyst. When the amount of catalyst was increased from 0.13 to 0.76 mg/mL then kapp was increased from 0.03 to 0.14 min-1. Activation parameters were also determined by performing reaction at two different temperatures. The catalytic process has been discussed in terms of energy of activation, enthalpy of activation and entropy of activation. The synthesized particles were found to be stable even after 14 weeks and showed catalytic activity for the reduction of nitrobenzene.

Kinetics and Mechanism of Oxidation of Aliphatic Secondary Alcohols by Benzimidazolium Fluorochromate in Dimethyl Sulphoxide Solvent

2021 ◽  
Vol 37 (3) ◽  
pp. 626-633
Author(s):  
Bhawana Arora ◽  
Jitendra Ojha ◽  
Pallavi Mishra
Keyword(s):  
Activation Parameters ◽  
Sigmatropic Rearrangement ◽  
Dimethyl Sulphoxide ◽  
Secondary Alcohols ◽  
Hydrogen Ions ◽  
Reaction Conditions ◽  
First Order Kinetics ◽  
Aqueous Solvent ◽  
Ester Formation ◽  
Different Temperatures

Oxidation of secondary alcohols is an important part of synthetic organic chemistry. Various studies are carried out at different reaction conditions to determine the best mechanistic pathways. In our study, oxidation of different secondary alcohols was done by using Benzimidazolium Fluorochromate in Dimethyl Sulphoxide, which is a non-aqueous solvent. Oxidation resulted in the formation of ketonic compounds. The reaction showed first order kinetics both in BIFC and in the alcohols. Hydrogen ions were used to catalyze the reaction. We selected four different temperatures to carry out our study. The correlation within the activation parameters like enthalpies and entropies was in accordance with the Exnerʼs criterion. The deuterated benzhydrol (PhCDOHPh) oxidation exhibited an important primary kinetic isotopic effect (kH / kD = 5.76) at 298 K. The solvent effect was studied using the multiparametric equations of Taft and Swain. There was no effect of addition of acrylonitrile on the oxidation rate. The mechanism involved sigmatropic rearrangement with the transfer of hydrogen ion taking place from alcohol to the oxidant via a cyclic chromate ester formation.

D2O−H2O solvent isotope effects on the enthalpies of bicaret hydration and dilution of its aqueous solutions at different temperatures

2014 ◽  
Vol 590 ◽  
pp. 145-150 ◽  
Author(s):  
Evgeniy V. Ivanov ◽  
Dmitriy V. Batov ◽  
Galina A. Gazieva ◽  
Angelina N. Kravchenko ◽  
Vladimir K. Abrosimov
Keyword(s):  
Aqueous Solutions ◽  
Isotope Effects ◽  
Different Temperatures ◽  
Solvent Isotope ◽  
Solvent Isotope Effects

scholarly journals Reconciling Imbalanced Transition State Effects with Nonadiabatic CPET Reactions

2021 ◽  
Author(s):  
Joseph Schneider ◽  
McKenna Goetz ◽  
John Anderson
Keyword(s):  
Transition State ◽  
Potential Energy Surfaces ◽  
Variable Temperature ◽  
Reaction Rates ◽  
State Theory ◽  
Energy Relation ◽  
Linear Free Energy ◽  
Proton Potential ◽  
Classical Models ◽  
Free Energy Relation

Recently there have been several experimental demonstrations of how concerted proton electron transfer (CPET) reaction rates are affected by off-main-diagonal energies, namely the stepwise thermodynamic parameters ΔG°PT and ΔG°ET. Semi-classical structure-activity relationships have been invoked to rationalize these asynchronous linear free energy relation-ships despite the widely acknowledged importance of quantum effects such as nonadiabaticity and tunneling in CPET reactions. Here we report variable temperature kinetic isotope effect data for the asynchronous reactivity of a terminal Co-oxo complex with C–H bonds and find evidence of substantial quantum tunneling which is inconsistent with semi-classical models even when including tunneling corrections. This indicates substantial nonadiabatic tunneling in the CPET reactivity of this Co-oxo complex and further motivates the need for a quantum mechanical justification for the in-fluence of ΔG°PT and ΔG°ET on reactivity. To reconcile this dichotomy, we include ΔG°PT and ΔG°ET in nonadiabatic models of CPET by having them influence the anharmonicity and depth of the proton potential energy surfaces, which we approximate as Morse potentials. With this model we independently reproduce the dominant trend with ΔG°PT + ΔG°ET as well as the subtle effect of ΔG°PT − ΔG°ET (or η) in a nonadiabatic framework. The primary route through which these off-diagonal energies influence rates is through vibronic coupling. Our results reconcile predictions from semiclassical transition state theory with models that treat proton transfer quantum mechanically in CPET reactivity and suggest that similar treatments may be possible for other nonadiabatic processes.

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