Fragmentations and reactions of the organophosphate insecticide Diazinon and its oxygen analog Diazoxon studied by electrospray ionization ion trap mass spectrometry

The fragmentations and reactions of Diazinon and related compounds have been studied by electrospray ionization ion trap mass spectrometry. Several novel fragmentation and rearrangements have been observed, including an intramolecular thiono-thiolo rearrangement. The stability, in the gas-phase, of the protomers of 2-isopropyl-4-methyl-6-pyrimidinol has been demonstrated. The complexity of the gas phase ion processes observed suggest that, at present, caution should be exercised in using this approach for the analysis of environmental and other samples until our understanding of these processes increases considerably.     

Ring size effects. III. Carbonium ion stability as a factor in the course of the pinacol rearrangement

The formation of the initial carbonium ion in the pinacol rearrangement will be the major factor in determining product composition when the reaction is carried out at 0°C with concentrated sulfuric acid.     

Studies Directed Towards a Practical Synthesis of Brevicomins (II)1 : A Novel Synthesis of 1, 5-Dimethyl-8-Oxobicyclo [3.2.1]octane-6-one

The recent interest in pheromones,² as means of controlling insect pests, has prompted us to examine syntheses which could be both simple and practical. We recently reported a three-step synthesis of brevicomin (3), the aggregating pheromone of the pine bark beetle, Dendroctonus brevicomis.³     

A Synthesis of 7,7-Dimethyl-6,8-Dioxabicyclo[3.2.1]Octane a Constituent of the Hop,Humulus Lupulus

A synthesis of 7,7-dimethyl-6,8-dioxabicyclo-[3.2.1]octane, a component of hop oil, is described. The appproach focuses on 2-acetyl-3,4-dihydro-2H-pyran and 2-(carboxymethy)-3,4-dihydro-2H-pyran as intermediates.     

The intercalation of ethidium bromide in the chromonic lyotropic phases of drugs and nucleic acids

Chromonic liquid crystalline phases are formed by a variety of drug and dye/water systems. In contrast to conventional lyotropic phases (where micelle formation underlies the mesogenic properties), in chromonic systems the molecules stack in columns. The different chromonic phases are different arrangements of these columns. We have examined the solution of ethidium bromide (EB) in the well-documented chromonic Intal/water system. EB is a widely used nucleic acid stain which changes colour when intercalated into DNA and which becomes fluorescent.

We have charted the changes in the temperature/composition phase diagram of the Intal/water system caused by adding EB. Although there are changes in the position of the phase boundaries, the overall pattern remains qualitatively the same—implying that the host phase is accepting EB as a similar chromonic molecule. The intercalation of EB molecules in the chromonic host phase results in optical effects—a metachromic colour change and fluorescence, similar to those occurring when the dye stains DNA.

These observations strengthen our belief that the central stack of bases in DNA can be regarded as being chromonic in nature.