The ionization potentials of ethyl, isopropyl, and propargyl radicals have been measured by electron impact on radicals produced by thermal decomposition of appropriate compounds. The values are:ethyl 8.78±0.05 ev., isopropyl 7.90±0.05 ev., and propargyl 8.25±0.08 ev. From the appearance potentials of these ions in various compounds, the following values of bond dissociation energies were obtained:[Formula: see text][Formula: see text] assuming no kinetic energy of the products.
The vertical ionization potentials of the β- and γ-methyl substituted allyl radicals as measured by electron impact are 8.03 ± 0.05 v. and 7.71 ± 0.05 v, respectively. From appearance potential data the following bond dissociation energies can be derived, assuming the dissociation processes to be free from complications:[Formula: see text]With assumptions about the structure of the ions produced by electron impact from the corresponding butenes the dissociation energies of the C4H7—H bonds in these latter compounds can be estimated, and the heats of formation of the corresponding radicals derived, namely:[Formula: see text]From data on the allyl halides we evaluate the heat of formation of the allyl radical to be:[Formula: see text]
'The mercury photosensitized (Hg3P1) decolnpositio~l of olefins has been examined using a reactor coupled directly t o a mass spectrometer. The primary split of ethylene has been shown to he predominantly molecular, and that of propylene mainly into an ally1 radical ancl a hydrogen atom. With 1-butene the split is predominantly a t a C-C boncl giving ally1 arid n~ethyl radicals, alLhough a rupture of a C-H boncl occurs as well. \Vith 2-butene and isobutene a C-H bond is brolten. I t is concluded that the ally1 and methallyl radicals produced have large cross sections for reaction with excited mercury atoms.
The fast Lewis acid-base reaction between copper(I1) bis(diethy1dithiocarbamate) and pyridine Cu(DDC), + pyridine + C~(DDC)~.pyridine has been studied from 280 to 320 OK in benzene. The method employed is the analysis of electron paramagnetic resonance line positions and line widths using the solutions of the modified Bloch equations in the fast exchange limit. Arrhenius plots, over the temperature range employed, gave values for the thermodynamic data of the process.La reaction rapide acide de Lewis acid-base entre le bis(diethy1dithiocarbamate) de cuivre(I1) et la pyridine Cu(DDC), + pyridine C~(DDC)~.pyridine a kt6 ttudik dans le benzkne entre 280 et 320 OK. La mtthode utilisee est l'analyse par resonance paramagnetique electronique des positions de raies et des largeurs de raies en utilisant les solutions des equations modifiees de Bloch dans la limite d'un tchange rapide. Les courbes d'Arrhenius, sur I'echelle de temperature utilisee, donnent les valeurs qui se rapportent aux donnbes thermodynamiques du processus.
A mass spectrometer equipped for continuous sampling and capable of producing 60 spectra per second has been used to follow the oxidation of acetaldehyde at temperatures in the region of 250 °C. In normal slow oxidation peracetic acid was formed and then decomposed into carbon dioxide, methanol, and water. Under flame conditions peracetic acid built up in an autocatalytic manner during the induction period and vanished suddenly at the onset of the flame. Possible reaction mechanisms are discussed. Temperature surges during cool and hot flames are estimated.
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