Correlation of the Rates of Solvolysis of t-Butyl Fluoroformate Using the Extended Grunwald-Winstein Equation

Lee, Yong-Woo; Seong, Mi Hye; Kyong, Jin Burm; Kevill, Dennis N.

doi:10.5012/bkcs.2010.31.11.3366

Cited by 11 publications

(14 citation statements)

References 23 publications

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“…Fluoroformates have been appreciably studied [1,9] and they can be used where the chloroformate ester is insufficiently stable for subsequent use in derivatization or other synthetic procedures. In particular, simple tert -alkyl chloroformates are of very low stability [1,10,11] but the 1-adamantyl and tert -butyl fluoroformates [12] are of considerably increased stability and they have found uses in both synthetic [13,14] and mechanistic studies [15,16]. …”

Section: Introductionmentioning

confidence: 99%

Influence of Sulfur for Oxygen Substitution in the Solvolytic Reactions of Chloroformate Esters and Related Compounds

D’Souza

Kevill

2014

IJMS

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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.

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Section: Introductionmentioning

confidence: 99%

Influence of Sulfur for Oxygen Substitution in the Solvolytic Reactions of Chloroformate Esters and Related Compounds

D’Souza

Kevill

2014

IJMS

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“…Solvolyses of t -butyl fluoroformate ( 8, Figure 1) [21] were found to proceed entirely by an ionization pathway (Equation 4), which included the loss of carbon dioxide to give the relatively stable t -butyl cation. Solvolyses of tertiary 1-adamantyl fluoroformate ( 9, Figure 1) [22] led to two types of mechanisms, i.e.…”

Section: Introductionmentioning

confidence: 99%

Correlation of the Rates of Solvolysis of i-Butyl Fluoroformate and a Consideration of Leaving-Group Effects

Lee

Park

Seong

et al. 2011

IJMS

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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.

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“…The rate ratios for ethyl-, 2,9 n-propyl-, 3,10 i-butyl-, 25,26 and 1-adamantylmethyl haloformates (1 and 2) in 100% MeOH, 100% EtOH, and 80% EtOH are close to unity, suggesting that electronic and/ or steric influences due to a branching β-alkyl group adjacent to an oxygen atom in the alkyl haloformates can be neglected. The specific solvolysis rates of i-propyl 5,11 and tbutyl haloformates 12 in 70% TFE were somewhat higher than the specific rates for solvolyses of ethyl, 2,9 n-propyl, 3,10 i-butyl, 25,26 n-octyl, 4 and 1-adamantylmethyl haloformates. Higher rate ratios were found in 70% TFE relative to 100% MeOH, 100% EtOH, and 80% EtOH (k i-PrOCOCl /k EtOCOCl ≒38 and k t-BuOCOF /k EtOCOF ≒10 at 40.0 o C).…”

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confidence: 73%

“…mechanisms (Scheme 1(a)), with the formation of a tetrahedral intermediate as the rate-determining step. Solvolyses of t-butyl fluoroformate 12 were found to proceed entirely by an ionization pathway (Scheme 1(c)) that included the loss of carbon dioxide to give the relatively stable t-butyl cation as an intermediate. Solvolyses of tertiary 1-adamantyl fluoroformate 13 led to two types of mechanisms, a bimolecular pathway (Scheme 1(a)) and an ionization pathway (Scheme 1(c)).…”

mentioning

confidence: 99%

“…In methanol, the k MeOH /k MeOD ratio was in the range of 2.00 to 3.98 for solvolyses of alkyl and aryl haloformates, which have been reported to proceed through a bimolecular mechanism. [1][2][3][4][8][9][10][11]30,31 The k ROH /k ROD values for i-propyl chloroformate and t-butyl fluoroformate in the range of an ionization mechanism were 1.25 5 in pure water (S=H) and 1.26 12 in methanol (S=Me), respectively. Activation Parameters.…”

mentioning

confidence: 99%

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Rate and Product Studies of 1-Adamantylmethyl Haloformates Under Solvolytic Conditions

Park¹,

Lee²,

Lee³

et al. 2012

Bulletin of the Korean Chemical Society

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Reactions of 1-adamantylmethyl chloroformate (1-AdCH 2 OCOCl, 1) and 1-adamantylmethyl fluoroformate (1-AdCH 2 OCOF, 2) in hydroxylic solvents have been studied. Application of the extended Grunwald-Winstein (G-W) equation to solvolyses of 1 in a variety of pure and binary solvents indicates an addition-elimination pathway in the majority of the solvents except an ionization pathway in the solvents of relatively low nucleophilcity and high ionizing power. The solvolyses of 2 show an addition-elimination pathway in all of the mixed solvents. The leaving group effects (k F /k Cl ), the kinetic solvent isotope effects (KSIEs, k MeOH /k MeOD ), and the enthalpy and entropy of activation for the solvolyses of 1 and 2 were also calculated. The selectivity values (S) for each solvent composition are reported and discussed. These observations are compared with those previously reported for other alkyl haloformate esters.

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Correlation of the Rates of Solvolysis of t-Butyl Fluoroformate Using the Extended Grunwald-Winstein Equation

Cited by 11 publications

References 23 publications

Influence of Sulfur for Oxygen Substitution in the Solvolytic Reactions of Chloroformate Esters and Related Compounds

Influence of Sulfur for Oxygen Substitution in the Solvolytic Reactions of Chloroformate Esters and Related Compounds

Correlation of the Rates of Solvolysis of i-Butyl Fluoroformate and a Consideration of Leaving-Group Effects

Rate and Product Studies of 1-Adamantylmethyl Haloformates Under Solvolytic Conditions

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