Irreproduabilities in the measurements of isotopic abundance in "N labelled glyeine have been related to the complex nature of chemical processes occurring during the evaporation of glyeine prior to ionization.

Association Reaction / Thermodynamic of Association / UV Study / Solvent Effects / Hydrogen Bonding / Schiff BaseThe study includes two complementary topics. Firstly, the influence of various concentrations of phenols on the UV absorption spectrum of benzil mono benzylidene aniline (BMBA) in different solvents. Experiments show a bathochromic shift in the UV spectrum of BMBA obtained after addition of phenol. When phenol is replaced by 2,4-dimethylphenol, rather similar results are observed. The results are interpreted interms of hydrogen bond formation between BMBA and phenol. Secondly, it is decided to confirm the hydrogen-bond formation stated above by thermodynamic method. Accordingly, the effect of temperature on the equilibrium constant value of the interaction between BMBA and phenol is considered. Evaluated thermodynamic parameters ∆G, ∆H, and ∆S support the interaction stated above by either mono hydrogen-bond of any type O−H · · · N, O−H · · · O or by double hydrogen bonding stated later depending on the pK a of the phenol used.

When small samples of 2and some 3-substituted benzaldoximes are evaporated into the ion source of a mass spectrometer, the records of molecular-ion current with time show two maxima. These maxima have been shown to be due to the syn and anti isomers of the benzaldoximes, which have different heats of sublimation. These differences may represent the heats of polymerisation of the monomers, assuming that the non-planar anti isomers exist in the monomeric form. A mass spectrometric method of identifying the isomers and estimating their heats of sublimation has been developed.

No abstract

The isomerization of benzophenone oxime to benzanilide, previously observed to take place in the ion source of a mass spectrometer and attributed to a Beckmann type rearrangement of the benzophenone oxime molecule ion, has been shown to occur by a thermal mechanism prior to ionization. Mass spectrometric evidence is supplemented by infrared spectrophotometric examination of solid samples and shows that in the solid state, at room temperature, benzophenone oxime has a lifetime of about 600 h.