Effect of pressure on the rate of solvolysis of t -butyl chloride in ethanol-water mixtures

The pseudo first order rate constants for the solvolysis of benzyl chloride in aqueous t-butyl alcohol (t-BuOH) are reported at 40.00, 50.25, and 60.50 "C at various pressures up to 4084 atm. From these data the first temperature derivatives (AH* and AS*), the first (AV*) and second pressure derivatives, aAV*/aP, and the mixed second derivative, aAVo*/aT, of the rate are evaluated. These activation parameters exhibit extremum behavior in the highly aqueous solvent region. This behavior is discussed in terms of solvent structure variation. The signs of the pressure dependence of AH* and AS* are shown to be consistent with those required by the Maxwell type relationships for classical thermodynamic systems.Les constantes de vitesse du pseudo premier ordre pour la solvolyse du chlorure de benzyle dans I'alcool tertiobutyllique (t-BuOH) sont rapportees a 40.00, 50.25, et 60.50 "C pour differentes pressions supkrieures a 4084 atm. A partir de ces donnees, les dtrivies premieres de la vitesse par rapport a la temperature (AH* et AS*), ses dkrivees premiere (AV*) et seconde par rapport a la pression, a V*/aP, et sa dkrivee seconde aAVo*/aT sont calcultes. Ces parametres d'activation montrent un comportement extrgme dans la region des solvants fortement aqueux. Ce comportement est analyse en fonction de la variation de structure du solvant. On montre que les signes de AH* et AS* dependant de la pression sont compatibles avec ceux requis par les relations du type relations de Maxwell pour des systemes thermodynamiques classiques.

Section: The Volume Of Activationmentioning

confidence: 95%

The Pseudo Thermodynamics of Solvolysis. A Detailed Study of the Pressure and Temperature Dependence of Benzyl Chloride Solvolysis in t-Butyl Alcohol – Water Mixtures

Dickson¹,

Hyne²

1971

“…Without further justification at this point we assume that a quadratic relationship between 111 k and p is sufficient for the purpose of evaluating the error in k due to uncertainty in pressure. Accordingly, differentiation of [7],…”

Section: Determination Ofthe Error Itz Kmentioning

confidence: 99%

“…Various methods have been suggested, including the use of polynomial In k vs. p functions (6), incremental extrapolation (7), and by assuming that the volume of activation has a functional dependence upon pressure approximated by the empirical Tait equation (8,9), which has been found to represent satisfactorily the PVT properties of many real substances.…”

Section: Introductionmentioning

confidence: 99%

The volume of activation for benzyl chloride hydrolysis and its pressure dependence

Lohmüller¹,

Macdonald²,

Mackinnon³

et al. 1978

Various equations which have been proposed to provide the 'best' functional form for the dependence of rate upon pressure for reactions in solution have been tested for the extraction of ΔV≠ and dΔV≠/dp for the hydrolysis of benzyl chloride at 30 °C and at pressures over the range 1 to 6895 bar. One hundred individual rate constants were determined for this reaction at pressure increments of 345 bar and provide a sufficiently large body of data to permit application of statistical methods for testing the various rate–pressure functions with little risk of bias.

“…The plot is clearly non-linear demanding at least a second-order function to describe the dependence of In k uponp. The problem of deriving an analytical expression for this dependence has been discussed at length by various workers (7,8). Golinkin, Laidlaw, and Hyne (7) concluded that the quadratic function provided the best representation of the dependence of In k uponp for benzyl chloride solvolysis in aqueous alcohols.…”

Section: P ( a T M )mentioning

confidence: 99%

“…It should be stressed at this point that the uncertainties listed in Table 2 are those obtained on the basis that eq. [2] represents the correct functional dependence of In k upon p. Since this question is subject to considerable controversy (7,8), the actiial uncertainty in A Vo* is probably greater than that calculated from the least-mean square fit of the ratelpressure data to eq. [2].…”

mentioning

confidence: 99%

The pressure dependence of benzyl chloride solvolysis in aqueous acetone and aqueous dimethylsulfoxide

Macdonald¹,

Hyne²

1970

First-order rate constants for the solvolysis of benzyl chloride in a series of aqueous acetone and aqueous dirnethylsulfoxide (DMSO) mixtures at 50.100 "C and at various pressures in the range 1-4083 atm are reported. Volume of activation, calculated from the ratelpressure data, is found to exhibit extremum behavior with varying solvent composition in both solvent systems. The activation volumes are dissected into their initial state and transition state contributions by determining the "instantaneous" volumes of solution of benzyl chloride in the solvent systems. The contributions of both the initial state and the transition state to the behavior of the activation volume as a function of solvent composition are discussed.