In the absence of other reagents, the 17e molybdenum radical, ($-CSHS)MO(CO)~', combines to form the stable dimer, [CpMo(CO)slz. In the presence of TMPD, however, an electron transfer process ensues, in which the normally persistent radical TMPD'+ is produced. Under these conditions, the absorbance of the TMPD'+ radical disappears shortly thereafter. Various kinetic tests have been applied to show that this is the result of a sequence of two electron transfer steps. One is the reaction between CpMo(CO)3' (Mo') and TMPD, and the other is the reaction between Mo' and TMPD+. The net result of the two reactions occurring in sequence is the disproportionation of the molybdenum radical, rather than the combination reaction that occurs in the absence of this redox-active amine. To the contrary, PhNMez shows no such effect, confirming that these observations are correctly attributed to electron transfer and not to ligand-catalyzed disproportionation.That the TMPD-catalyzed sequence really is disproportionation was confirmed by the chemical identification of the products, CpMo(CO)3-and CpMo(C0)3NCCH3+. Since the disproportionation reaction, with K = lo7, is less favored than radical combination, with K = 10l6 L mol-', this is a case where catalysis yields products that are less favored thermodynamically than those that would otherwise form spontaneously. In that sense, then, the light energy has been stored over long periods of time in intermediates that lie at a higher Gibbs energy than the thermodynamic products.
Eight N-substituted maleic acid monoamide derivatives were studied by DSC, TG (DTG) and IR techniques. The thermal studies revealed that the compounds containing a free carboxyl group start to decompose before melting, and the decomposition continues in the melt phase as the temperature is elevated. This was explained by the presence of dimers involving strong intermolecular hydrogen-bonds. This assumption concerning the structure was supported by the results of the IR spectroscopic studies.N-Substituted maleic acid amides prepared from maleic anhydride are important intermediates in the production of biologically active compounds obtained mostly in cyclization reactions. Hence, it is important to know the physical, chemical and thermal behaviour of these compounds. It may be presumed that both in the solid state and in solution (depending on the solvent) hydrogen-bonding may lead to the formation of associates. Eight different N-substituted maleic acid amides were investigated in order to test the above assumption, and to find out what kind of associates are present. Inverse gas chromatography [1], thermal analysis and IR spectrometry were used to study the compounds. The present paper briefly reports the results obtained with the latter two methods.Experimental DSC was used to follow phase transitions, and TG and DTG served to study the decomposition processes. DSC measurements were carried out
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