Organic Ions in the Gas Phase. II. The Tropylium Ion

Abstract

The rate constants were determined from the slopes of the lines and their temperature dependency is shown in Fig. 6.The energies of activation were calculated from the Arrhenius relationship to be 65.6 kcal. mole-' for the decomposition of potassium nitrate and 34.3 kcal. mole-' for the reaction between potassium nitrite and oxygen. The corresponding frequency factors are l O l o J set.-' and 103,58 set.-', respectively.These values are further confirmation of the suggested mechanism involving an initial reaction between nitrite and molecular oxygen, since an activation energy which is approximately equal to the dissociation energy of oxygen would be required if the primary step of the oxidation process involved the dissociation of molecular oxygen.The corresponding activation energies for the deconiposition of sodium nitrate and for the reaction between sodium nitrite and oxygen6 are 44.7 and 20.7 kcal. mole-'. The difference in the energies of activation for the decoiiipositions of sodium and potassium nitrate is apparently larger than could be accounted for by the difference in dissociation energies of the N-0 bond. This however may be attributed to the more extensive polarizing power of the sodium ion. The sodium ion, which induces a relatively greater positive and negative charge in the oxygen molecule a t the surface of the melt could cause oxygen to be more strongly attracted to the nitrite ion and accordingly the steepness of the potential energy profile would be effected. Therefore the height of the barrier is a function of both, the K-0 bond strength and the repulsion between the nitrites and oxygen.Acknowledgment.-The author expresses his gratitude to J. Campisi for carrying out the X-ray analyses and to S. Gordon for reviewing the manuscript.SEWARK 2, SEW JERSEV

Free Radicals by Mass Spectrometry. XLIII. Ionization Potentials and Ionic Heats of Formation for Vinyl, Allyl, and Benzyl Radicals

“…It is of interest in this respect, particularly in view of the well-known isomerization (2,3) to calculate heats of formation for these two ionic species from the current data. Taking IP(cyc10-heptatrienyl) = 6.24 V (26,27), D(C7H7-C7H7) in ditropenyl = 1.85 + 0.05 V (26), and AH,(ditropenyl) = 94.6 kcal/mol (28), one obtains AH,(cyclo-C7H7+) = 212 kcal/mol.…”

Mass spectra of some deuterostyrenes

“…Meyerson and R ylander [2,5,6] using spectra of isotopically labeled molecules and considerations of energetics of ion formation in their study. They suggest that formation of a tropyliu'm.…”

“…This is t he case in deuterium subs tituted butanes [1]1 . In o ther t ypes of deuterated hydrocarbons there is more or less r earrangem ent of hy droge nic atom s in t il e ion~zation process and this is strikingly s hown in a romatIC hydrocarbons [2].…”

Stoßaktivierungs-Massenspektren von C6H6M+ -und C7H7M+ - Fragment-Ionen aus Übergangsmetall-π-Komplexen /Collisional Activation Mass Spectra of C6H6M+ and C7H7M+ Fragment Ions from Transition Metal π-Complexes

“…Seit den klassischen Untersuchungen von Meyerson et al [14] ist eine Fülle an Publikationen zum Strukturproblem gasförmiger C7H7 + -Ionen erschienen. Als besonders aufschlußreich erwiesen sich CA-Messungen an C7H7+-Fragmenten aus sechzig verschiedenen Verbindungen, wobei Tropylium-, Benzyl-, o-, m-und p-Tolyl-sowie NorbornadienylStrukturen in je nach Vorläufer unterschiedlichen Anteilen nachgewiesen wurden [15].…”