Arachidonylethanolamide, an arachidonic acid derivative in porcine brain, was identified in a screen for endogenous ligands for the cannabinoid receptor. The structure of this compound, which has been named "anandamide," was determined by mass spectrometry and nuclear magnetic resonance spectroscopy and was confirmed by synthesis. Anandamide inhibited the specific binding of a radiolabeled cannabinoid probe to synaptosomal membranes in a manner typical of competitive ligands and produced a concentration-dependent inhibition of the electrically evoked twitch response to the mouse vas deferens, a characteristic effect of psychotropic cannabinoids. These properties suggest that anandamide may function as a natural ligand for the cannabinoid receptor.

Many (>170) exceptions to the 'even-electron rule from the literature (unrecognized in most cases) and from the authors' Laboratory are presented and discussed. The large number of violations suggests that although the generalization may be a helpful guide for the explanation of mass spectral behaviour of many organic compounds, the term 'rule' seems to be unjustified.

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tion [a direct measure of its acidity (Figures 1 and 3)] is controlled by regulating the steam supply to the evaporator through a diaphragm-type steam reducing valve. The liquid level in the evaporator is kept constant by regulating the flow from expeller into the evaporator through a diaphragm-type regulating valve made of PTFE, responding to the hydrostatic head. The liberated gases go through a PTFE demister and a tube and shell-type heat exchanger and are collected in a polyethylene storage vessel.The feed preparation vessel of the second stage is made of stainless steel and is equipped with a steam jacket and a stirrer.The U/H2O2 precipitator is made of polyethylene and is equipped with a stirrer and built-in filter candles. Both the filter candles and the filter plate are made of Pall Grade H stainless steel with a porosity of 0.4 µ (98% nominal holdback). The CaF2 precipitator (s/s) is equipped with a stirrer, a steam jacket, and a cooling coil. An underpressure of approximately 20 cm H2O, provided by the liquid jet absorber, is maintained to speed up the expulsion of NHs(g) and H20(g).The CaO feed screw, the rotary drum filter, the liquid jet absorber, and the NH3/H2O rectification unit are commercially available items. Conclusions

The isomeric 3- and 4-dehydrobenzenesulfonic acid anions b and c were prepared by collision induced dissociation (CID) of the [M - H](-) ions of isomeric sulfobenzoic acids obtained by negative electrospray ionization (ESI). The CID spectra (MS(3)) of anions b and c are different from each other, and both are different from that of the isomeric benzenesulfonate anion a, obtained from benzenesulfonic acid. The stability of ions b and c shows that 1,2-proton transfer does not take place in this system under the conditions of the CID experiment. Density functional (DFT) calculations at B3LYP/6-31+G(2d,p) level of theory show that benzenesulfonate anion a is the most stable isomer, and the energies of isomers b and c are higher by more than 65 kcal mol(-1). The calculated energies of the transition states involved in the 1,2-hydrogen migration leading to the interconversion of the isomeric anions are very high (>120 kcal mol(-1)relative to ion a, barrier energies >55 kcal mol(-1)), much higher than those of transition structures leading to fragmentation. This situation does not allow isomerization of ions b and c to a, under the conditions of the CID experiments. The isomeric 2-dehydrobenzenesulfonic acid anion isomerizes to the benzenesulfonate anion a by a facile proton transfer from the SO(3)H group to the adjacent position 2. The results of this work indicate that the gas phase deprotonation of meta- and para-sulfobenzoic acids is a kinetically controlled process.