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

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.

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Kinetic solvent isotope effects [k(H2O)/k(D2O)] for benzyl nitrate, 4-chlorobutan-l-ol and piperidylsulphamoyl chloride. The significance of activation parameters to the mechanism of the reaction

Journal of the Chemical Society Faraday Transactions 1 Physical Chemistry in Condensed Phases ◽

10.1039/f19848002287 ◽

1984 ◽

Vol 80 (8) ◽

pp. 2287 ◽

Cited By ~ 3

Author(s):

Michael J. Blandamer ◽

John Burgess ◽

Ross E. Robertson ◽

Kalavelil M. Koshy ◽

Edward C. F. Ko ◽

...

Keyword(s):

Isotope Effects ◽

Activation Parameters ◽

Solvent Isotope ◽

Solvent Isotope Effects ◽

Mechanism Of The Reaction

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Isotope effects and activation parameters for the proton transfer reaction from 1-(4-nitrophenyl)-1-nitroethane to free anions and ion pairs of cesium n-propoxide in n-propanol solvent

Canadian Journal of Chemistry ◽

10.1139/v86-171 ◽

1986 ◽

Vol 64 (6) ◽

pp. 1021-1025 ◽

Cited By ~ 4

Author(s):

Arnold Jarczewski ◽

Grzegorz Schroeder ◽

Przemyslaw Pruszynski ◽

Kenneth T. Leffek

Keyword(s):

Proton Transfer ◽

Rate Constants ◽

Isotope Effects ◽

Ion Pairs ◽

Activation Parameters ◽

Solvation Shell ◽

Ion Pair ◽

Initial State ◽

Free Ion ◽

Deuteron Transfer

Rate constants for the proton and deuteron transfer from 1-(4-nitrophenyl)-1-nitroethane to cesium n-propoxide in n-propanol have been measured under pseudo-first-order conditions with an excess of base for four temperatures between 5 and 35 °C. Using literature values of the fraction of cesium n-propoxide ion pairs that are dissociated into free ions, separate second-order rate constants for the proton and deuteron transfer to the ion pair and to the free ion have been calculated. The cesium n-propoxide ion pair is about 2.8 times more reactive than the free n-propoxide ion. The primary kinetic isotope effects for the two reactions are the same (kH/kD = 6.1–6.3 at 25 °C) within experimental error. The enthalpy of activation is smaller for the ion-pair reaction and the entropy of activation more negative than for the free-ion reaction. For proton transfer, ΔH±ion pair = 8.3 ± 0.2 kcal mol−1, ΔH±ion = 9.6 ± 1.0 kcal mol−1, ΔS±ion pair = −12.3 ± 0.6 cal mol−1 deg−1, ΔS±ion = −10.1 ± 3.4 cal mol−1 deg−1. The greater reactivity of the ion pair relative to the free ion is interpreted in terms of the weaker solvation shell of the ion pair in the initial state.

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Rate and Product Studies in the Solvolyses of Two Arenesulfonic Anhydrides

Journal of Chemical Research ◽

10.3184/030823407x218084 ◽

2007 ◽

Vol 2007 (6) ◽

pp. 365-369 ◽

Cited By ~ 5

Author(s):

Dennis N. Kevill ◽

Zoon Ha Ryu

Keyword(s):

Binary Mixtures ◽

Isotope Effects ◽

Activation Parameters ◽

Product Selectivity ◽

Displacement Reactions ◽

Solvent Isotope ◽

Solvent Isotope Effects

The specific rates of solvolysis of benzenesulfonic anhydride (1) and p-toluenesulfonic anhydride (2) have been measured conductometrically at −10°C in 34 solvents for 1 and 33 solvents for 2. Studies at higher temperatures have allowed extrapolated values in additional solvents to be calculated. All of the values, for 35 solvents for 1 and for 37 solvents for 2, have been used in an extended Grunwald–Winstein equation treatment using NT and YOTs values. Activation parameters in several solvents and kinetic solvent isotope effects (MeOH/MeOD) have been determined for both substrates. Product selectivity values ( S) have been determined for binary mixtures of water with ethanol, methanol, or 2, 2, 2-trifluoroethanol. The results from the kinetic and product studies are compared to those previously reported for methanesulfonic anhydride (3). An SN2 mechanism is proposed for the solvolytic displacement reactions of the three substrates in all of the solvents used in the investigation.

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Correlation of rates of uncatalyzed and hydroxide-ion catalyzed ketene hydration. A mechanistic application and solvent isotope effects on the uncatalyzed reaction

Canadian Journal of Chemistry ◽

10.1139/v00-032 ◽

2000 ◽

Vol 78 (4) ◽

pp. 508-515

Author(s):

John Andraos ◽

A Jerry Kresge

Keyword(s):

Carbon Atom ◽

Rate Constants ◽

Isotope Effects ◽

Nucleophilic Attack ◽

Carbonyl Carbon Atom ◽

Basic Solution ◽

Carbonyl Carbon ◽

Hydroxide Ion ◽

Solvent Isotope ◽

Solvent Isotope Effects

Rates of hydration of a number of ketenes were measured in neutral and basic solution using flash photolytic techniques, and rate constants for their uncatalyzed, kuc, and hydroxide-ion catalyzed, kHO, reactions were determined. These results, plus additional data from the literature, were found to provide the remarkably good correlation log kuc = -3.21 + 1.14 log kHO, which spans 10 orders of magnitude in reactivity and includes 31 ketenes. This good correlation implies that uncatalyzed and hydroxide-ion catalyzed ketene hydraton occur by similar reaction mechanisms, which for the hydroxide-ion catalyzed process is known to involve nucleophilic attack on the carbonyl carbon atom of the ketene. Rate constants for phenylhydroxyketene, on the other hand, do not fit this correlation, which suggests that the mechanistic assignment upon which these rate constants are based may not be correct. Solvent isotope effects on these uncatalyzed ketene hydrations are weak; most are less than kH/kD = 2. It is argued that these isotope effects are largely, if not entirely, secondary in nature and that they are consistent with both a reaction mechanism in which nucleophlic attack of a single water molecule on the ketene carbonyl carbon atom produces a zwitterionic intermediate and also a mechanism that avoids this intermediate by passing through a cyclic transition state involving several water molecules.Key words: ketene hydration, rate correlation, nucleophilic attack, solvent isotope effects, phenylhydroxyketene.

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