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Keywords = Grunwald-Winstein equations

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13 pages, 1228 KiB  
Article
Rate and Product Studies with 1-Adamantyl Chlorothioformate under Solvolytic Conditions
by Kyoung Ho Park, Mi Hye Seong, Jin Burm Kyong and Dennis N. Kevill
Int. J. Mol. Sci. 2021, 22(14), 7394; https://doi.org/10.3390/ijms22147394 - 9 Jul 2021
Viewed by 2043
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Section Physical Chemistry and Chemical Physics)
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12 pages, 2708 KiB  
Article
The Influence of a Terminal Chlorine Substituent on the Kinetics and the Mechanism of the Solvolyses of n-Alkyl Chloroformates in Hydroxylic Solvents
by Malcolm J. D’Souza, Jeremy Wirick, Osama Mahmoud, Dennis N. Kevill and Jin Burm Kyong
Int. J. Mol. Sci. 2020, 21(12), 4387; https://doi.org/10.3390/ijms21124387 - 19 Jun 2020
Cited by 1 | Viewed by 5063
Abstract
A previous study of the effect of a 2-chloro substituent on the rates and the mechanisms of the solvolysis of ethyl chloroformate is extended to the effect of a 3-chloro substituent on the previously studied solvolysis of propyl chloroformate and to the effect [...] Read more.
A previous study of the effect of a 2-chloro substituent on the rates and the mechanisms of the solvolysis of ethyl chloroformate is extended to the effect of a 3-chloro substituent on the previously studied solvolysis of propyl chloroformate and to the effect of a 4-chloro substituent on the here reported rates of solvolysis of butyl chloroformate. In each comparison, the influence of the chloro substituent is shown to be nicely consistent with the proposal, largely based on the application of the extended Grunwald–Winstein equation, of an addition-elimination mechanism for solvolysis in the solvents of only modest solvent ionizing power, which changes over to an ionization mechanism for solvents of relatively high ionizing power and low nucleophilicity, such as aqueous fluoroalcohols with an appreciable fluoroalcohol content. Full article
(This article belongs to the Special Issue Solution Chemical Kinetics 2.0)
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12 pages, 2411 KiB  
Article
The Effect of the ortho Nitro Group in the Solvolysis of Benzyl and Benzoyl Halides
by Kyoung-Ho Park, Chan Joo Rhu, Jin Burm Kyong and Dennis N. Kevill
Int. J. Mol. Sci. 2019, 20(16), 4026; https://doi.org/10.3390/ijms20164026 - 18 Aug 2019
Cited by 6 | Viewed by 3292
Abstract
A kinetic study was carried out on the solvolysis of o-nitrobenzyl bromide (o-isomer, 1) and p-nitrobenzyl bromide (p-isomer, 3), and o-nitrobenzoyl chloride (o-isomer, 2) in a wide range of solvents under [...] Read more.
A kinetic study was carried out on the solvolysis of o-nitrobenzyl bromide (o-isomer, 1) and p-nitrobenzyl bromide (p-isomer, 3), and o-nitrobenzoyl chloride (o-isomer, 2) in a wide range of solvents under various temperatures. In all of the solvents without aqueous fluoroalcohol, the reactions of 1 were solvolyzed at a similar rate to those observed for 3, and the reaction rates of 2 were about ten times slower than those of the previously studied p-nitrobenzoyl chloride (p-isomer, 4). For solvolysis in aqueous fluoroalcohol, the reactivity of 2 was kinetically more reactive than 4. The l/m values of the extended Grunwald–Winstein (G–W) equation for solvolysis of 1 and 2 in solvents without fluoroalcohol content are all significantly larger than unity while those in all the fluoroalcohol solvents are less than unity. The role of the ortho-nitro group as an intramolecular nucleophilic assistant (internal nucleophile) in the solvolytic reaction of 1 and 2 was discussed. The results are also compared with those reported earlier for o-carbomethoxybenzyl bromide (5) and o-nitrobenzyl p-toluenesulfonate (7). From the product studies and the activation parameters for solvolyses of 1 and 2 in several organic hydroxylic solvents, mechanistic conclusions are drawn. Full article
(This article belongs to the Special Issue Solution Chemical Kinetics 2.0)
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20 pages, 2865 KiB  
Review
Mechanistic Studies of the Solvolyses of Carbamoyl Chlorides and Related Reactions
by Malcolm J. D’Souza and Dennis N. Kevill
Int. J. Mol. Sci. 2016, 17(1), 111; https://doi.org/10.3390/ijms17010111 - 15 Jan 2016
Cited by 14 | Viewed by 6574
Abstract
Carbamoyl chlorides are important intermediates, both in the research laboratory and in industrial scale syntheses. The most studied and used are the disubstituted derivatives, incorporating either aryl or alkyl groups (Ar2NCOCl or R2NCOCl). Sometimes, the groups are tied back [...] Read more.
Carbamoyl chlorides are important intermediates, both in the research laboratory and in industrial scale syntheses. The most studied and used are the disubstituted derivatives, incorporating either aryl or alkyl groups (Ar2NCOCl or R2NCOCl). Sometimes, the groups are tied back to give a ring and piperidino- and morpholino-derivatives are commonly encountered. Some studies have been made with two different groups attached. Solvolyses tend to occur at the carbonyl carbon, with replacement of the chloride ion. Studies of both rate and products are reviewed and the solvolysis reactions are usually SN1, although addition of an amine leads to a superimposable bimolecular component. Many of the studies under solvolytic conditions include the application of the extended Grunwald–Winstein equation. The monosubstituted derivatives (ArNHCOCl or RNHCOCl) are less studied. They are readily prepared by the addition of HCl to an isocyanate. In acetonitrile, they decompose to set up and reach equilibrium with the isocyanate (ArNCO or RNCO) and HCl. Considering that the structurally related formyl chloride (HOCOCl) is highly unstable (with formation of HCl + CO2), the unsubstituted carbamoyl chloride (H2NCOCl) is remarkably stable. Recommended synthetic procedures require it to survive reaction temperatures in the 300–400 °C range. There has been very little study of its reactions. Full article
(This article belongs to the Special Issue Solution Chemical Kinetics)
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23 pages, 761 KiB  
Review
Influence of Sulfur for Oxygen Substitution in the Solvolytic Reactions of Chloroformate Esters and Related Compounds
by Malcolm J. D'Souza and Dennis N. Kevill
Int. J. Mol. Sci. 2014, 15(10), 18310-18332; https://doi.org/10.3390/ijms151018310 - 10 Oct 2014
Cited by 7 | Viewed by 9519
Abstract
The replacement of oxygen within a chloroformate ester (ROCOCl) by sulfur can lead to a chlorothioformate (RSCOCl), a chlorothionoformate (ROCSCl), or a chlorodithioformate (RSCSCl). Phenyl chloroformate (PhOCOCl) reacts over the full range of solvents usually included in Grunwald-Winstein equation studies of solvolysis by [...] Read more.
The replacement of oxygen within a chloroformate ester (ROCOCl) by sulfur can lead to a chlorothioformate (RSCOCl), a chlorothionoformate (ROCSCl), or a chlorodithioformate (RSCSCl). Phenyl chloroformate (PhOCOCl) reacts over the full range of solvents usually included in Grunwald-Winstein equation studies of solvolysis by an addition-elimination (A-E) pathway. At the other extreme, phenyl chlorodithioformate (PhSCSCl) reacts across the range by an ionization pathway. The phenyl chlorothioformate (PhSCOCl) and phenyl chlorothionoformate (PhOCSCl) react at remarkably similar rates in a given solvent and there is a dichotomy of behavior with the A-E pathway favored in solvents such as ethanol-water and the ionization mechanism favored in aqueous solvents rich in fluoroalcohol. Alkyl esters behave similarly but with increased tendency to ionization as the alkyl group goes from 1° to 2° to 3°. N,N-Disubstituted carbamoyl halides favor the ionization pathway as do also the considerably faster reacting thiocarbamoyl chlorides. The tendency towards ionization increases as, within the three contributing structures of the resonance hybrid for the formed cation, the atoms carrying positive charge (other than the central carbon) change from oxygen to sulfur to nitrogen, consistent with the relative stabilities of species with positive charge on these atoms. Full article
(This article belongs to the Special Issue Chemical Bond and Bonding 2015)
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16 pages, 291 KiB  
Article
Kinetic Studies that Evaluate the Solvolytic Mechanisms of Allyl and Vinyl Chloroformate Esters
by Malcolm J. D'Souza, Aaron F. Givens, Peter A. Lorchak, Abigail E. Greenwood, Stacey L. Gottschall, Shannon E. Carter and Dennis N. Kevill
Int. J. Mol. Sci. 2013, 14(4), 7286-7301; https://doi.org/10.3390/ijms14047286 - 2 Apr 2013
Cited by 2 | Viewed by 7621
Abstract
At 25.0 °C the specific rates of solvolysis for allyl and vinyl chloroformates have been determined in a wide mix of pure and aqueous organic mixtures. In all the solvents studied, vinyl chloroformate was found to react significantly faster than allyl chloroformate. Multiple [...] Read more.
At 25.0 °C the specific rates of solvolysis for allyl and vinyl chloroformates have been determined in a wide mix of pure and aqueous organic mixtures. In all the solvents studied, vinyl chloroformate was found to react significantly faster than allyl chloroformate. Multiple correlation analyses of these rates are completed using the extended (two-term) Grunwald-Winstein equation with incorporation of literature values for solvent nucleophilicity (NT) and solvent ionizing power (YCl). Both substrates were found to solvolyze by similar dual bimolecular carbonyl-addition and unimolecular ionization channels, each heavily dependent upon the solvents nucleophilicity and ionizing ability. Full article
(This article belongs to the Section Physical Chemistry, Theoretical and Computational Chemistry)
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18 pages, 459 KiB  
Article
Use of Linear Free Energy Relationships (LFERs) to Elucidate the Mechanisms of Reaction of a γ-Methyl-β-alkynyl and an ortho-Substituted Aryl Chloroformate Ester
by Malcolm J. D’Souza, Jaci A. Knapp, Gabriel A. Fernandez-Bueno and Dennis N. Kevill
Int. J. Mol. Sci. 2012, 13(1), 665-682; https://doi.org/10.3390/ijms13010665 - 10 Jan 2012
Cited by 11 | Viewed by 9311
Abstract
The specific rates of solvolysis of 2-butyn-1-yl-chloroformate (1) and 2-methoxyphenyl chloroformate (2) are studied at 25.0 °C in a series of binary aqueous-organic mixtures. The rates of reaction obtained are then analyzed using the extended Grunwald-Winstein (G-W) equation and [...] Read more.
The specific rates of solvolysis of 2-butyn-1-yl-chloroformate (1) and 2-methoxyphenyl chloroformate (2) are studied at 25.0 °C in a series of binary aqueous-organic mixtures. The rates of reaction obtained are then analyzed using the extended Grunwald-Winstein (G-W) equation and the results are compared to previously published G-W analyses for phenyl chloroformate (3), propargyl chloroformate (4), p-methoxyphenyl choroformate (5), and p-nitrophenyl chloroformate (6). For 1, the results indicate that dual side-by-side addition-elimination and ionization pathways are occurring in some highly ionizing solvents due to the presence of the electron-donating γ-methyl group. For 2, the analyses indicate that the dominant mechanism is a bimolecular one where the formation of a tetrahedral intermediate is rate-determining. Full article
(This article belongs to the Special Issue Correlation Analysis Applied to Solvolysis Reactions)
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12 pages, 153 KiB  
Article
Correlation of the Rates of Solvolysis of i-Butyl Fluoroformate and a Consideration of Leaving-Group Effects
by Yelin Lee, Kyoung-Ho Park, Mi Hye Seong, Jin Burm Kyong and Dennis N. Kevill
Int. J. Mol. Sci. 2011, 12(11), 7806-7817; https://doi.org/10.3390/ijms12117806 - 10 Nov 2011
Cited by 5 | Viewed by 6862
Abstract
The specific rates of solvolysis of isobutyl fluoroformate (1) have been measured at 40.0 °C in 22 pure and binary solvents. These results correlated well with the extended Grunwald-Winstein (G-W) equation, which incorporated the NT solvent nucleophilicity scale and the [...] Read more.
The specific rates of solvolysis of isobutyl fluoroformate (1) have been measured at 40.0 °C in 22 pure and binary solvents. These results correlated well with the extended Grunwald-Winstein (G-W) equation, which incorporated the NT solvent nucleophilicity scale and the YCl solvent ionizing power scale. The sensitivities (l and m-values) to changes in solvent nucleophilicity and solvent ionizing power, and the kF/kCl values are very similar to those observed previously for solvolyses of n-octyl fluoroformate, consistent with the additional step of an addition-elimination pathway being rate-determining. The solvent deuterium isotope effect value (kMeOH/kMeOD) for methanolysis of 1 was determined, and for solvolyses in ethanol, methanol, 80% ethanol, and 70% TFE, the values of the enthalpy and the entropy of activation for the solvolysis of 1 were also determined. The results are compared with those reported earlier for isobutyl chloroformate (2) and other alkyl haloformate esters and mechanistic conclusions are drawn. Full article
(This article belongs to the Special Issue Correlation Analysis Applied to Solvolysis Reactions)
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14 pages, 377 KiB  
Article
Correlation of the Rates of Solvolysis of Neopentyl Chloroformate—A Recommended Protecting Agent
by Malcolm J. D’Souza, Shannon E. Carter and Dennis N. Kevill
Int. J. Mol. Sci. 2011, 12(2), 1161-1174; https://doi.org/10.3390/ijms12021161 - 15 Feb 2011
Cited by 13 | Viewed by 9259
Abstract
The specific rates of solvolysis of neopentyl chloroformate (1) have been determined in 21 pure and binary solvents at 45.0 °C. In most solvents the values are essentially identical to those for ethyl and n-propyl chloroformates. However, in aqueous-1,1,1,3,3,3-hexafluoro-2-propanol mixtures [...] Read more.
The specific rates of solvolysis of neopentyl chloroformate (1) have been determined in 21 pure and binary solvents at 45.0 °C. In most solvents the values are essentially identical to those for ethyl and n-propyl chloroformates. However, in aqueous-1,1,1,3,3,3-hexafluoro-2-propanol mixtures (HFIP) rich in fluoroalcohol, 1 solvolyses appreciably faster than the other two substrates. Linear free energy relationship (LFER) comparison of the specific rates of solvolysis of 1 with those for phenyl chloroformate and those for n-propyl chloroformate are helpful in the mechanistic considerations, as is also the treatment in terms of the Extended Grunwald-Winstein equation. It is proposed that the faster reaction for 1 in HFIP rich solvents is due to the influence of a 1,2-methyl shift, leading to a tertiary alkyl cation, outweighing the only weak nucleophilic solvation of the cation possible in these low nucleophilicity solvents. Full article
(This article belongs to the Special Issue Correlation Analysis Applied to Solvolysis Reactions)
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15 pages, 223 KiB  
Article
Analysis of the Nucleophilic Solvation Effects in Isopropyl Chlorothioformate Solvolysis
by Malcolm J. D’Souza, Brian P. Mahon and Dennis N. Kevill
Int. J. Mol. Sci. 2010, 11(7), 2597-2611; https://doi.org/10.3390/ijms11072597 - 29 Jun 2010
Cited by 12 | Viewed by 11803
Abstract
Correlation of the solvent effects through application of the extended Grunwald-Winstein equation to the solvolysis of isopropyl chlorothioformate results in a sensitivity value of 0.38 towards changes in solvent nucleophilicity (l) and a sensitivity value of 0.72 towards changes in solvent [...] Read more.
Correlation of the solvent effects through application of the extended Grunwald-Winstein equation to the solvolysis of isopropyl chlorothioformate results in a sensitivity value of 0.38 towards changes in solvent nucleophilicity (l) and a sensitivity value of 0.72 towards changes in solvent ionizing power (m). This tangible l value coupled with the negative entropies of activation observed indicates a favorable predisposition towards a modest rear-side nucleophilic solvation of a developing carbocation. Only in 100% ethanol was the bimolecular pathway dominant. These observations are very different from those obtained for the solvolysis of isopropyl chloroformate, where dual reaction channels were proposed, with the addition-elimination reaction favored in the more nucleophilic solvents and a unimolecular fragmentation-ionization mechanism favored in the highly ionizing solvents. Full article
(This article belongs to the Section Physical Chemistry, Theoretical and Computational Chemistry)
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14 pages, 252 KiB  
Article
Use of Empirical Correlations to Determine Solvent Effects in the Solvolysis of S-Methyl Chlorothioformate
by Malcolm J. D’Souza, Stefan M. Hailey and Dennis N. Kevill
Int. J. Mol. Sci. 2010, 11(5), 2253-2266; https://doi.org/10.3390/ijms11052253 - 25 May 2010
Cited by 11 | Viewed by 11031
Abstract
The specific rates of solvolysis of S-methyl chlorothioformate (MeSCOCl) are analyzed in 20 solvents of widely varying nucleophilicity and ionizing power at 25.0 °C using the extended Grunwald-Winstein Equation. A stepwise SN1 (DN + AN) mechanism is [...] Read more.
The specific rates of solvolysis of S-methyl chlorothioformate (MeSCOCl) are analyzed in 20 solvents of widely varying nucleophilicity and ionizing power at 25.0 °C using the extended Grunwald-Winstein Equation. A stepwise SN1 (DN + AN) mechanism is proposed in the more ionizing solvents including six aqueous fluoroalcohols. In these solvents, a large sensitivity value of 0.79 towards changes in solvent nucleophilicity (l) is indicative of profound rearside nucleophilic solvation of the developing carbocation. In twelve of the more nucleophilic pure alchohols and aqueous solutions, the sensitivities obtained for solvent nucleophilicity (l) and solvent ionizing power (m) are similar to those found in acyl chlorides where an association-dissociation (AN + DN) mechanism is believed to be operative. Full article
(This article belongs to the Section Physical Chemistry, Theoretical and Computational Chemistry)
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13 pages, 196 KiB  
Article
Corrrelation of the Specific Rates of Solvolysis of Ethyl Fluoroformate Using the Extended Grunwald-Winstein Equation
by Mi Hye Seong, Jin Burm Kyong, Young Hoon Lee and Dennis N. Kevill
Int. J. Mol. Sci. 2009, 10(3), 929-941; https://doi.org/10.3390/ijms10030929 - 2 Mar 2009
Cited by 6 | Viewed by 12659
Abstract
The specific rates of solvolysis of ethyl fluoroformate have been measured at 24.2 °C in 21 pure and binary solvents. These give a satisfactory correlation over the full range of solvents when the extended Grunwald-Winstein equation is applied. The sensitivities to changes in [...] Read more.
The specific rates of solvolysis of ethyl fluoroformate have been measured at 24.2 °C in 21 pure and binary solvents. These give a satisfactory correlation over the full range of solvents when the extended Grunwald-Winstein equation is applied. The sensitivities to changes in the NT solvent nucleophilicity scale and the YCl solvent ionizing power scale, and the kF/kCl values are very similar to those for solvolyses of n-octyl fluoroformate, consistent with the addition step of an addition-elimination pathway being rate-determining. For methanolysis, a solvent deuterium isotope effect of 3.10 is compatible with the incorporation of general-base catalysis into the substitution process. For five representative solvents, studies were made at several temperatures and activation parameters determined. The results are also compared with those reported earlier for ethyl chloroformate and mechanistic conclusions are drawn. Full article
(This article belongs to the Special Issue Grunwald-Winstein Equations – 60 Years & Counting)
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18 pages, 212 KiB  
Article
Grunwald-Winstein Analysis - Isopropyl Chloroformate Solvolysis Revisited
by Malcolm J. D’Souza, Darneisha N. Reed, Kevin J. Erdman, Jin Burm Kyong and Dennis N. Kevill
Int. J. Mol. Sci. 2009, 10(3), 862-879; https://doi.org/10.3390/ijms10030862 - 2 Mar 2009
Cited by 22 | Viewed by 16032
Abstract
Specific rates of solvolysis at 25 °C for isopropyl chloroformate (1) in 24 solvents of widely varying nucleophilicity and ionizing power, plus literature values for studies in water and formic acid, are reported. Previously published solvolytic rate constants at 40.0 °C are supplemented [...] Read more.
Specific rates of solvolysis at 25 °C for isopropyl chloroformate (1) in 24 solvents of widely varying nucleophilicity and ionizing power, plus literature values for studies in water and formic acid, are reported. Previously published solvolytic rate constants at 40.0 °C are supplemented with two additional values in the highly ionizing fluoroalcohols. These rates are now are analyzed using the one and two-term Grunwald-Winstein Equations. In the more ionizing solvents including ten fluoroalcohols negligible sensitivities towards changes in solvent nucleophilicity (l) and very low sensitivities towards changes in solvent ionizing power (m) values are obtained, evocative to those previously observed for 1-adamantyl and 2-adamantyl chloroformates 2 and 3. These observations are rationalized in terms of a dominant solvolysis-decomposition with loss of the CO2 molecule. In nine of the more nucleophilic pure alchohols and aqueous solutions an association-dissociation mechanism is believed to be operative. Deficiencies in the acid production indicate 2-33% isopropyl chloride formation, with the higher values in less nucleophilic solvents. Full article
(This article belongs to the Section Physical Chemistry, Theoretical and Computational Chemistry)
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19 pages, 358 KiB  
Article
Correlation of the Rates of Solvolysis of Two Arenesulfonyl Chlorides and of trans-β-Styrenesulfonyl Chloride — Precursors in the Development of New Pharmaceuticals
by Zoon Ha Ryu, Sang Wok Lee, Malcolm J. D’Souza, Lamia Yaakoubd, Samantha E. Feld and Dennis N. Kevill
Int. J. Mol. Sci. 2008, 9(12), 2639-2657; https://doi.org/10.3390/ijms9122639 - 17 Dec 2008
Cited by 12 | Viewed by 13219
Abstract
Additional specific rates of solvolysis have been determined, mainly in fluoroalcohol containing solvents, for benzenesulfonyl chloride (1) and p-nitrobenzenesulfonyl chloride (2). For trans-β-styrenesulfonyl chloride (3), a study has been carried out in 43 pure and binary solvents, covering a wide range of [...] Read more.
Additional specific rates of solvolysis have been determined, mainly in fluoroalcohol containing solvents, for benzenesulfonyl chloride (1) and p-nitrobenzenesulfonyl chloride (2). For trans-β-styrenesulfonyl chloride (3), a study has been carried out in 43 pure and binary solvents, covering a wide range of hyroxylic solvent systems. For the specific rates of solvolyses of each of the three substrates, a good correlation was obtained over the full range of solvents when the extended Grunwald-Winstein equation was applied. The sensitivities to changes in solvent nucleophilicity and solvent ionizing power are similar to values determined earlier and an SN2 process is proposed. For 3, kinetic solvent isotope effects of 1.46 for kH2O/kD2O and 1.76 for kMeOH/kMeOD were determined. These are also compared to literature values for other sulfonyl chlorides. Full article
(This article belongs to the Special Issue Grunwald-Winstein Equations – 60 Years & Counting)
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12 pages, 233 KiB  
Article
Extended Grunwald-Winstein Analysis - LFER Used to Gauge Solvent Effects in p-Nitrophenyl Chloroformate Solvolysis
by Malcolm J. D’Souza, Kevin E. Shuman, Shannon E. Carter and Dennis N. Kevill
Int. J. Mol. Sci. 2008, 9(11), 2231-2242; https://doi.org/10.3390/ijms9112231 - 13 Nov 2008
Cited by 16 | Viewed by 15140
Abstract
Specific rates of solvolysis at 25oC for p-nitrophenyl chloroformate (1) are analyzed using the extended (two-term) Grunwald-Winstein equation. For 39 solvents, the sensitivities (l = 1.68±0.06 and m = 0.46±0.04) towards changes in solvent nucleophilicity (l) and [...] Read more.
Specific rates of solvolysis at 25oC for p-nitrophenyl chloroformate (1) are analyzed using the extended (two-term) Grunwald-Winstein equation. For 39 solvents, the sensitivities (l = 1.68±0.06 and m = 0.46±0.04) towards changes in solvent nucleophilicity (l) and solvent ionizing power (m) obtained, are similar to those previously observed for phenyl chloroformate (2) and p-methoxyphenyl chloroformate (3). The observations incorporating new kinetic data in several fluoroalcohol-containing mixtures, are rationalized in terms of the reaction being sensitive to substituent effects and the mechanism of reaction involving the addition (association) step of an additionelimination (association-dissociation) pathway being rate-determining. The l/m ratios obtained for 1, 2, and 3, are also compared to the previously published l/m ratios for benzyl chloroformate (4) and p-nitrobenzyl chloroformate (5). Full article
(This article belongs to the Special Issue Grunwald-Winstein Equations – 60 Years & Counting)
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