Determination of Detrapping and Trapping Rate Constants for Hydrogen Based on Experimental Thermal Desorption Spectra

A method for constructing curves is proposed that are linear in a wide region and from whose slopes it is possible to determine the rate constant, if a parameter, θ, is calculated numerically from a rapidly converging recurrent formula or from its explicit form. The values of rate constants and parameter θ thus simply found are compared with those found by an optimization algorithm on a computer; the deviations do not exceed ±10%.

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Determination of the Accurate Values of the Rate Constant and Thermodynamic Parameters for the Rotation About the C(sp2)-C(aryl) Bond; Adamantan-1-yl 3-Bromo-2,4,6-trimethylphenyl Ketone

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19980955 ◽

1998 ◽

Vol 63 (7) ◽

pp. 955-966

Author(s):

Eva Přibylová ◽

Miroslav Holík

Keyword(s):

Thermodynamic Parameters ◽

Shape Analysis ◽

Rate Constants ◽

Line Shape ◽

Microsoft Excel ◽

Hindered Rotation ◽

H Nmr ◽

Line Shape Analysis ◽

Coalescence Temperature

Four programs for the 1H NMR line shape analysis: two commercial - Winkubo (Bruker) and DNMR5 (QCPE 165) and two written in our laboratory - Newton (in Microsoft Excel) and Simtex (in Matlab) have been tested in order to get highly accurate rate constants of the hindered rotation about a single bond. For this purpose four testing criteria were used, two of them were also developed by us. As supplementary determinations the rate constants obtained for the coalescence temperature and for the thermal racemization of chromatographically separated enantiomers were used which fitted well the temperature dependence of the rate constants determined by the line shape analysis. As a test compound adamantan-1-yl 3-bromo-2,4,6-trimethylphenyl ketone was prepared and studied. It was shown that supermodified simplex method used in our algorithm (Simtex), though time consuming, gives the most accurate values of the rate constants and consequently the calculated thermodynamic parameters Ea, ∆H≠, and ∆S≠ lay in relatively narrow confidence intervals.

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Determination of the Nucleophilicity of Tricarbonyliron Coordinated Cyclohepta-1,3,5-triene

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19991770 ◽

1999 ◽

Vol 64 (11) ◽

pp. 1770-1779 ◽

Cited By ~ 6

Author(s):

Herbert Mayr ◽

Karl-Heinz Müller

Keyword(s):

Gibbs Energy ◽

Ambient Temperature ◽

Rate Constants ◽

Second Order ◽

Order Rate ◽

Electrophilic Additions ◽

Kinetics Of

The kinetics of the electrophilic additions of four diarylcarbenium ions (4a-4d) to tricarbonyl(η4-cyclohepta-1,3,5-triene)iron (1) have been studied photometrically. The second-order rate constants match the linear Gibbs energy relationship log k20 °C = s(E + N) and yield the nucleophilicity parameter N(1) = 3.69. It is concluded that electrophiles with E ≥ -9 will react with complex 1 at ambient temperature.

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