Ionisierungs- und Auftrittspotentialmessungen an Dialkylsulfoxiden

1975 ◽  
Vol 30 (3) ◽  
pp. 340-346
Author(s):  
Peter Potzinger ◽  
Heinz-Ulrich Stracke ◽  
Wolfgang Küpper ◽  
Klaus Gollnick
Keyword(s):  
Dissociation Energy ◽  
Heats Of Formation ◽  
Kcal Mole ◽  
Dissociation Energies ◽  
Fragment Ions ◽  
A Value

Ionisation- and appearance potentials of some dialkylsulfoxides and their major fragment ions were determined. In addition to the determination of dissociation energies in the ions and heats of formation of the ions and ionic fragments, a value of 66 kcal/mole for the C-S dissociation energy in neutral dialkyl sulfoxides was obtained.

Photoionisation von Methanol und Formaldehyd / Photoionisation of Methanol and Formaldehyd

1971 ◽  
Vol 26 (12) ◽  
pp. 2047-2057 ◽  
Author(s):  
Peter Warneck
Keyword(s):  
Spectral Region ◽  
Heat Of Formation ◽  
Heats Of Formation ◽  
Kcal Mole ◽  
Yield Curves ◽  
Dissociation Energies ◽  
Fragment Ions

Photoions produced in methanol and formaldehyde by radiation in the spectral region 450 - 1150 Å were analyzed mass spectrometrically and their relative yields were determined as a function of wavelength. First ionisation potentials were determined and the ion yield curves were interpreted in terms of ionisation processes in conjunction with other data. Fragment ions were detected on mass numbers 31, 30, 29, 15, and 14 for methanol, and 29, 2, and 1 for formaldehyde. The associated appearence potentials were determined and were used to calculate heats of formation of the ions CH2OH+ and HCO+, and the radicals CH3, CH2, and HCO. The most important result appears to be the heat of formation found for HCO: ΔHB = 0.43 ± 0.07 eV, corresponding to 9.9 ± 1.6 kcal/mole, as well as the associated dissociation energies for HCO and formaldehyde. Previously existing discrepancies concerning these quantities are thereby clarified

KINETICS OF THE DECOMPOSITIONS OF ETHANE AND PROPANE SENSITIZED BY AZOMETHANE: THE DECOMPOSITION OF THE NORMAL PROPYL RADICAL

1966 ◽  
Vol 44 (24) ◽  
pp. 2927-2940 ◽  
Author(s):  
M. C. Lin ◽  
K. J. Laidler
Keyword(s):  
Activation Energy ◽  
Satisfactory Agreement ◽  
Rate Constant ◽  
Dissociation Energy ◽  
Low Temperatures ◽  
Heats Of Formation ◽  
Kcal Mole ◽  
Energy Diagram ◽  
A Value ◽  
Kinetics Of

The azomethane-sensitized pyrolysis of ethane was studied at low temperatures from 280 to 350 °C. Measurements were made of initial rates of formation of methane, nitrogen, and butane. From the rate of nitrogen production the rate constant for the azomethane decomposition into 2CH3 + N2 was[Formula: see text]A similar study of the propane decomposition, at temperatures from 260 to 300 °C, led to the value[Formula: see text]in satisfactory agreement. The rate of decomposition of the n-propyl radical into CH3 and C2H4 was obtained by comparing the rates of formation of C2H4 and n-C6H14; the rate constant was[Formula: see text]The activation energy of 31.4 kcal/mole, together with that of 8.9 kcal/mole for the reverse reaction obtained by Brinton, leads to a value of 20.3 kcal/mole for the dissociation energy of n-CH3—CH CH2 at 0 °K, and to a value of 22.8 at 25 °C. The corresponding values for the heats of formation 2of the n-propyl radical are 28.4 kcal/mole at 0 °K, and 23.1 kcal/mole at 25 °C. The dissociation energy of n-CH3CH2CH2—H is deduced to be 99.4 kcal/mole at 0 °K and 99.9 kcal/mole at 25 °C. An energy diagram is constructed for the various reactions of n-C3H7 and i-C3H7.

The C—Br bond dissociation energy in halogenated bromomethanes

1951 ◽  
Vol 209 (1096) ◽  
pp. 110-131 ◽  
Keyword(s):  
Bond Dissociation Energy ◽  
Dissociation Energy ◽  
Methyl Bromide ◽  
Frequency Factor ◽  
Unimolecular Dissociation ◽  
Bond Dissociation Energies ◽  
Kcal Mole ◽  
Fast Reaction ◽  
Bond Dissociation ◽  
Dissociation Energies

The pyrolyses of methyl bromide and of the halogenated bromomethanes, CH 2 CI. Br, CH 2 Br 2 , CHCl 2 .Br, CHBr 3 , CF 3 Br, CCI 3 . Br and CBr 4 , have been investigated by the ‘toluene-carrier' technique. It has been shown that all these decompositions were initiated by the unimolecular process R Br → R + Br. (1) Since all these decompositions were carried out in the presence of an excess of toluene, the bromine atoms produced in process (1) were readily removed by the fast reaction C 6 H 5 .CH 3 + Br → C 6 H 5 . CH 2 • + HBr. Hence, the rate of the unimolecular process (1) has been measured by the rate of formation of HBr. The C—Br bond dissociation energies were assumed to be equal to the activation energies of the relevant unimolecular dissociation processes. These were calculated by using the expression k ═ 2 x 10 13 exp (- D/RT ). The reason for choosing this particular value of 2 x 10 13 sec. -1 for the frequency factor of these reactions is discussed. The values obtained for the C—Br bond dissociation energies in the investigated bromomethanes are: D (C—Br) D (C—Br) compound (kcal./mole) compound (kcal./mole) CH 3 Br (67.5) CHBr 3 55.5 CH 2 CIBr 61.0 CF 3 Br 64.5 CH 2 Br 2 62.5 CCI 3 Br 49.0 CHCl 2 Br 53.5 CBr 4 49.0 The possible factors responsible for the variation of the C—Br bond dissociation energy in these compounds have been pointed out.

Experimental methods for measurement of bond dissociation energies and heats of formation of radicals

1951 ◽  
Vol 207 (1088) ◽  
pp. 5-13 ◽  
Keyword(s):  
Experimental Methods ◽  
Experimental Results ◽  
Heats Of Formation ◽  
Bond Dissociation Energies ◽  
Carrier Gas ◽  
Bond Dissociation ◽  
Dissociation Energies ◽  
Kinetics Of

The paper describes a pyrolytic method of investigating the kinetics of gaseous reactions in which toluene is used as a carrier gas. It is shown that the method is particularly suitable for the determination of bond dissociation energies. The scope of the method is illustrated by various examples. A list of bond dissociation energies obtained is given. The manner in which the experimental results obtained can be cross-checked, is indicated and illustrated by examples. The effects of various constitutional factors on the bond dissociation energies are discussed.

Determination of the heat of formation of trimethylindium and calculation of the mean In—CH3 bond dissociation energy

1968 ◽  
Vol 46 (10) ◽  
pp. 1633-1634 ◽  
Author(s):  
W. D. Clark ◽  
S. J. W. Price
Keyword(s):  
Bond Dissociation Energy ◽  
Dissociation Energy ◽  
Chloroform Solution ◽  
Kinetic Studies ◽  
Heat Of Formation ◽  
Enthalpy Of Reaction ◽  
Kcal Mole ◽  
Bond Dissociation ◽  
The Mean

The enthalpy of reaction of In(CH3)3,c with a chloroform solution of bromine is −162.5 kcal mole−1. With this value ΔHf0298[In(CH3)3,c] = 29.5 kcal mole−1 and ΔHf0298[In(CH3)3,g] = 41.1 kcal mole−1. Combining the latter with ΔHf0298[CH3,g] = 33.2 kcal mole−1 and ΔHf0298[In,g] = 58.2 kcal mole−1 then gives E(In—CH3) = 38.9 kcal mole−1. From previous kinetic studies D[(CH3)2In—CH3] + D[In—CH3] = 87.9 kcal mole−1. Hence D[CH3In—CH3] = 28.8 kcal mole−1.

The C—Br bond dissociation energy in substituted benzyl bromides

1951 ◽  
Vol 209 (1096) ◽  
pp. 97-110 ◽  
Keyword(s):  
Bond Energy ◽  
Benzyl Bromide ◽  
Frequency Factor ◽  
Unimolecular Dissociation ◽  
Bond Dissociation Energies ◽  
Kcal Mole ◽  
Bond Dissociation ◽  
Dissociation Energies ◽  
Rate Determining Step

The ‘toluene-carrier’ technique has been used for the determination of the C—Br bond dissociation energies in the substituted benzyl bromides: p -, m - and o -xylyl bromides; p -, m - and o -chlorobenzyl bromides; p - and m -bromobenzyl bromides; p - and m -nitrobenzyl bromides; and p - and m -nitrilebenzyl bromides. The rate-determining step of the decompositions of all these compounds is represented by the unimolecular dissociation processes ( s ) Ph s . CH 2 . Br → Ph s . CH 2 • + Br, ( s ) where Ph s . CH 2 . Br refers to the substituted benzyl bromide. Assuming that the frequency factor of the decomposition of each benzyl bromide is equal to the frequency factor of reaction ( u ) Ph . CH 2 . Br → Ph . CH 2 • + Br, ( u ) the differences in activation energies between E u and E s were calculated using the relation E u ─ E s = RT In ( k s / k u ); (I) k s and k u denote the unimolecular rate constants of reactions ( s ) and ( u ) respectively. Since E s and E u are equal to the C—Br bond dissociation energies in the substituted benzyl bromides and benzyl bromide itself, equation (I) yields the differences, ∆ D’ s, between D ( Ph . CH 2 —Br) and the values for D ( Ph s . CH 2 —Br). The calculated differences in the C—Br bond dissociation energies are listed below: substituted ∆ D substituted ∆ D benzyl bromides (kcal. /mole) benzyl bromides (kcal. /mole) o -chloro 0·9 m -methyl 0-0 m -chloro 0·1 p -methyl 1·4 p -chloro 0·4 m -nitro 2·1 m -bromo 0·3 p -nitro 1·1 p -bromo 0·3 m -nitrile 1·4 o -methyl 2·0 p -nitrile 0·7 The significance of these findings is discussed, and the effect of substitution on a bond energy is contrasted with the effect of ionic reactions.

The pyrolysis of benzoyl bromide and the determination of the relevant bond dissociation energies

1952 ◽  
Vol 214 (1117) ◽  
pp. 273-280 ◽  
Keyword(s):  
Least Square Method ◽  
Heat Of Formation ◽  
Least Square ◽  
Bond Dissociation Energies ◽  
Kcal Mole ◽  
Bond Dissociation ◽  
Rapid Decomposition ◽  
Dissociation Energies ◽  
Rate Determining Step

Pyrolysis of benzoyl bromide in the presence of excess of toluene has been investigated. It has been shown that the rate-determining step is the unimolecular dissociation C 6 H 5 . CO. Br → C 6 H 5 . CO + Br, followed by the rapid decomposition of benzoyl radicals C 6 H 5 . CO → C 6 H 5 ⋅ + CO. Bromine atoms and phenyl radicals seem to be removed from the system by the reactions C 6 H 5 . CH 3 + Br → C 6 H 5 . CH 2 ⋅ + HBr and C 6 H 5 . CH 3 + Ph ⋅→ C 6 H 5 . CH 2 ⋅ + C 6 H 6 . The activation energy of the rate-determining dissociation process has been estimated using the least square method at 57⋅0 kcal/mole and has been identified with D (C 6 H 5 ⋅ CO-Br). Thus, having D (C 6 H 5 ⋅ CO-Br) = 57⋅0 kcal/mole, the heat of formation of benzoyl radicals has been calculated at ∆ H f (C 6 H 5 . CO) = 15⋅6 kcal/mole, and consequently the values for various bond dissociation energies of the type D (C 6 H 5 . CO- X ) have been derived.

Notizen: Massenspektrometrische Bestimmung der Dissoziationsenergie von Gold-Monoborid

1969 ◽  
Vol 24 (2) ◽  
pp. 293 ◽  
Author(s):  
Karl A. Gingerich
Keyword(s):  
Dissociation Energy ◽  
Mass Spectrometric ◽  
Kcal Mole ◽  
A Value ◽  
Mass Spectrometric Evidence

Mass-spectrometric evidence for the existence of the molecule AuB is presented. The enthalpy of the reaction Au2 (g) + B (g) = AuB (g) + Au (g) was determined as: ΔH0° = - 33.2 kcal/mole. Combined with the known dissociation energy of Au2 , a value of D0° (AuB) =85.2 ±5.0 kcal/mole is obtained for the dissociation energy of gold monoboride.

THE DETERMINATION OF THE SATURATION VAPOR PRESSURE OF SOLID HYDROXYLAMINE USING A PISTON PRESSURE GAUGE

1965 ◽  
Vol 43 (8) ◽  
pp. 2157-2161 ◽  
Author(s):  
R. A. Back ◽  
J. Betts
Keyword(s):  
Vapor Pressure ◽  
Dissociation Energy ◽  
Pressure Gauge ◽  
Saturation Vapor Pressure ◽  
Vapor Density ◽  
Kcal Mole ◽  
Density Measurements ◽  
Glass Cylinder ◽  
Saturation Vapor

The saturation vapor pressure of solid hydroxylamine has been determined at temperatures from −12 to 7° C and found to fit the equation[Formula: see text]From this have been calculated several thermochemical quantities, including a heat of sublimation of 15.34 kcal/mole, and a dissociation energy of 61.3 kcal/mole for the NH2—OH bond. Vapor density measurements showed that hydroxylamine vapor consisted of single molecules of NH2OH at 0.27 Torr and 25 °C.A novel pressure gauge used in the measurements is described. Pressures were determined with an accuracy of ±0.001 Torr by measuring the force acting on a piston, moving freely in a glass cylinder, suspended on the arm of a torsion balance.

The ultra-violet absorption spectra of some gaseous alkali-metal halides and the dissociation energy of fluorine

1953 ◽  
Vol 219 (1136) ◽  
pp. 120-140 ◽  
Keyword(s):  
Alkali Metal ◽  
Absorption Spectra ◽  
Dissociation Energy ◽  
Ultra Violet ◽  
Metal Halides ◽  
Dissociation Energies ◽  
A Value ◽  
Upper Limits ◽  
Alkali Metal Halides

Measurements of the fluctuation bands in the ultra-violet absorption spectra of NaF, KF, RbF, RbCl, RbBr, Rbl, CsF, CsCl, CsBr and Csl are reported, and upper limits for the dissociation energies of the twelve K, Rb and Cs halides are deduced. Thermochemical information about these molecules is considered, and a value for the dissociation energy of fluorine, D F 2 = 37.6 ± 3.5 kcal or 157.3 ± 14.6 kJ (298° K), is derived.

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