No abstract

By using cyclopropyl bromide as precursor, the allyl cation C3H 5+ can be generated at low temperature in an SbF5 matrix and observed by IR spectroscopy; the experimental IR spectrum agrees well with that computed by ab initio methods. Characterization by 13C NMR spectroscopy failed, but the 13C NMR chemical shifts of this and other allyl cations could be predicted accurately for the first time by the GIAO/MP‐2 method.

Thermal dimerization of nitroso compounds in the solid state was investigated by using para-substituted nitrosobenzenes as model compounds. A mechanism that includes the interplay of topochemical reaction trajectories and phase transfer was proposed on the basis of FT-IR spectroscopic kinetics, time-resolved powder diffraction, and low-temperature X-ray structure determination. From shapes of the kinetic curves analyzed on the basis of the Avrami model, it was found that phase transfer could be triggered by a dimerization reaction of para-substituted nitrosobenzene to azodioxide, which, in turn, can be caused by different packing factors such as disorder in the starting nitroso monomer crystals. Since the represented model can be extended to a broad series of compounds, we propose it as a general method for investigations of solid-state reaction mechanisms.

No abstract

This investigation is a case study about the nature of the adiabatic organic solid-state reactions by kinetic measurements of the processes that occur during the dimerization of aromatic nitroso compounds under three different topochemical environments in crystals.

The IR spectrum of the 2-butyl cation, measured at -125 "C i n an SbF5 matrix and calculated ab initioEven though the 2-butyl cation can be observed directly in super acid media, it has been difficult to establish the preferred structure with certainty.The potential energy surface is quite flat, as the degenerate rearrangements which interconvert the three inner Hs [as well as C(2)-C(3) and C(l)-C(4)] could not be slowed on the NMR time scale at -140 "C2a nor even by CPMAS measurements at -190 oC.26 The temperature dependence of both the deuterium and the 13C isotope effects, observed by Saunders and Walker in the NMR,2c could best be fit by assuming that two isomers were present, the more stable having an H-bridged structure (e.g.

Mechanochemical Oxone oxidation of selected para-substituted anilines was used as a rapid and solvent-free route to nitrosobenzenes; besides avoiding bulk solvents and short reaction times, this method exploits high vapour pressures of nitrosobenzenes for the solvent-free separation of the product by sublimation, demonstrating an entirely solventfree route to chemical synthesis and product isolation. † Electronic supplementary information (ESI) available: 1 H and 13 C NMR spectra of products of mechanochemical synthesis before and after sublimation. Example thermogravimetric isothermal curve for p-bromonitrosobenzene demonstrating the ease of sublimation and detailed experimental results. See

The Hel and Hell photoelectron spectra of the title compounds have been recorded and an alysed on the basis of comparison with chlorotrifluoromethane and methyl halides. Spin-orbit splitting could be observed in the ground state of CF3l+ where it amounts to 0.73 eV and is unresolved in CF3Br+. Vibrational fine structure observed in two band systems D and E in CFsBr^, and X and E in CF3l+ is also discussed. P h o to e le c tr o n S p e c tra o f B ro m o -a n d I o d o tr if lu o r o m e th a n e