Thermodynamics of the ionization of four difluorobenzoic and pentafluorobenzoic acids in water

Precision conductance measurements as a function of concentration and temperature between 0 and 100°C have been made for 2,3-, 2,5-, 3,4-, and 3,5-difluorobenzoic acids and pentafluorobenzoic acid in water. Standard state changes in enthalpy, entropy, and heat capacity as a function of temperature are reported for the ionization of these acids. Comparisons are made with other fluorobenzoic acids that have been reported earlier and with the corresponding methylbenzoic acids. The differences between the ionization of a fluorobenzoic acid and its counterpart methylbenzoic acid is almost entirely a difference in the entropies of ionization with only a small difference in the enthalpies of ionization. Each fluorine substituted in the meta or para position increases the entropy of ionization while substitution in the ortho position decreases the entropy. This is in contrast to the effect of methyl substitution where substitution in any position decreases the entropy of ionization. Walden products for the various anions follow the pattern found for the methylbenzoate anions with a sharp increase from 0 to about 30°C and with ortho substituted anions less mobile than those without ortho substitutents.     

A measurement of the charge asymmetry in the decay η → π+π−γ

An experiment has been performed at the Rutherford Laboratory to look for a possible asymmetry in the decay η → π⁺π^?γ. The asymmetry for 34 680 eta decay is measured to be 0.012 ± 0.006, which is consistent with no C-violation in this decay mode.     

Reaction of vinyl ketoximes with N-bromosuccinimide. Synthesis of isoxazoles and 4-bromoisoxazolines

The reaction of some selected α,β-unsaturated oximes with N-bromosuccinimide gave isoxazoles or 4-bromoisoxazolines in moderate to good yields.