The coalescence temperature in I d would be expected to be reasonably close to that determined for the mnoimlne 4 (84.5 'C).(1 1) The dipole-dipole repulsion was calculated using the equations cited by J. M. Lehn and G. Ourisson, Bull. SOC. Chlm. Fr., 1113 (1963. Coplanar geometry and standard bond lengths and angles were used. The resulting value of 17 MI mol-' would correspond to <1% change in the isomer distribution at 35 'C. The lone-pair moment is not directly included in this estimation. However, even if this moment Is assumed to be ca. 1.0 D, the dipole repulsion would still only exert a minimal effect on the EZratio. A referee has suggested that 13C assignments for the ring methyls may be the reverse due to a deshielding 6 effect, cf., H. Pearson, Chem. Commun., 912 (1975).(18) 0.1-Substituted 4-methoxy-5,5-dimethyl-2-imidazolidinethiones have been prepared by reaction of N-l-(2-chloro-2-methylpropy1idene)amines with potassium thiocyanate in methanol under reflux. The 1-substituted 4-methoxy-5,5-dimethyl-2-imidazolidinethiones were conveniently converted into the corresponding 1-substituted 5,5-dimethyl-2-imidazolidinethiones by lithium aluminum hydride treatment in ethereal medium. The structure elucidation was based on NMR, IR, and mass spectrometry next to x-ray crystallographic analysis. The formation of the heterocyclic five-membered rings was explained by a mechanism involving an aziridine intermediate, which underwent competitive opening. N-1 -(2-Chloro-2-methylpropylidene)amines (11, easily obtained from isobutyraldimines and N-chlorosuccinimide, are a new class of simple bifunctional compounds which have been used recently as synthetic blocks in organic ~ynthesis.3,~ An entry into the heterocyclic chemistry is presented here.

Phosphorus-31 nuclear magnetic resonance (NMR) spectra were recorded from freshly excised and resting anterior byssus rectractor muscles of the mussel Mytilus edulis.The absolute concentrations of phosphometabolites measured by NMR compare well with the values obtained by a biochemical method. Quantitative measurements were achieved in several minutes by applying to the obscrved NMR signals a correction taking the saturation effects into account.The time evolution of the phosphometabolite concentrations reveals that the hydrolysis of phosphoarginine is a first-order reaction producing inorganic phosphate, whilst the adenosine triphosphate level remains constant for more than 10 h.The phosphoarginine hydrolysis rate varies as a function of the season and reaches a maximum during the reproduction period of the mussel. This increase in phosphoarginine consumption could be bound up with the higher excitability of the muscles during spring. The activation energy of the phosphoarginine hydrolysis reaction also depends on the season and the difference between the value determined in winter and that measured in spring is explained by a modification of the mode of action or of the proportions of the enzymes involved in the muscular metabolism.Quantitative measurements of phosphometabolite concentrations of tissues in vivo are important for understanding the metabolic processes. 31P NMR is known as a good nondestructive and non-invasive method for this kind of study [l, 21. Different types of muscles have been examined using 31P NMR but only a small number of studies on invertebrate muscles have been performed up to now [3,4].Lamellibranches can avoid dessication by keeping their valves closed due to the tonic contraction of the smooth part of the adductor muscle. In this case the oxygen level rapidly decreases and the tissues are in non-aerobic conditions. The anterior byssus retractor muscle of the mussel Mytilus edulis is a smooth muscle that shows this tonic property even when isolated from the animal and separated from all nervous connections; the muscle keeps its functional properties when immersed in sea water in aerobic as well as anaerobic conditions. By following the time course of the oxygen consumption of the muscle in aerobic conditions, it has been shown that, in resting conditions, the metabolism is high (72 nmol g-' min-') when compared to other muscles in the same conditions [5]. In absence of oxygen, the resting metabolism seems to be so low that the biochemical methods are inadequate to measure the concentration variations of the chemical substances directly involved.Correspondence to A. Schanck, BHtiment Lavoisier, CPMC/CRIS, Place Louis Pasteur, 1, B-2348 Louvain-la-Neuve, BelgiumAbbreviations and Symbols. P-Arg, phosphoarginine; T,, nuclear spin-lattice relaxation time; IP-Argr integrated intensity of the phosphoarginine NMR peak; Ip,. integrated intensity of the Pi NMR peak; kp-Argr phosphoarginine hydrolysis rate constant; Tp, pulse interval; Q temperature coefficient.The aim of the present work...

Etude cin6tique compl6mentaire de la &action provoqu6e par les particules alpha Hz 3. Dz = 2 H D , par W. MUND et M. VAN MEERSCHE (Louvain)

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