Selenium monoxide

The thermodynamic quantities selected for selenium monoxide, SeO(g), stem from the work by Smoes and Drowart [84SMO/DRO]. Earlier work has been reviewed by Mills [74M1E]. The equilibrium reaction  

The main purpose of the work was the determination of the energy of dissociation of SeO(g) by a joint evaluation of the above thermochemical data and spectroscopic information as sketched in Appendix A. The enthalpy and Gibbs functions of SeO(g), SeS(g), Sc2(g), and SO(g) required for the process were calculated by statistical thermodynamic methods in the temperature interval 298.15 to 2000 K. The value adopted from the evaluation by the review is (SeO, g, 0 K) = (424.7 6.0) kJ-moP.  

The standard enthalpy of formation of SeO(g) was calculated from the dissociation energy and the auxiliary data in Appendix A. The selected result is  

The selected standard entropy of the monoxide was calculated from the molecular parameters in [84SMO/DRO] to be  

This value agrees well with the value obtained by Papousek [62PAP], 234.1 J-K -moP, from a statistical-mechanical calculation. The uncertainty is added 

---

Selenium-containing donors, synthesis and manufacture of, 22 212 Selenium dichloride, 22 75t Selenium diethyldithiocarbamate, 22 73t Selenium dioxide, 22 73t, 75t, 88 toxicify of, 22 95 Selenium disulfide, 22 73t Selenium hexafluoride, 22 75t, 87 toxicify of, 22 96 Selenium hypofluorite, 22 75t Selenium iodides, 22 87 Selenium monobromide, 22 75t, 88 Selenium monochloride, 22 75t, 87 in selenium recovery, 22 85 Selenium monoxide, 22 88 Selenium oxidation, selenium recovery via, 22 81-83... 

SMO/DRO] Smoes, S., Drowart, J., Determination of the dissociation energy of selenium monoxide by the mass-spectrometric Knudsen-cell method, J. Chem. Soc. Faraday Trans., 80, (1984), 1171-1180. Cited on pages 118, 119, 562, 563, 564. 

Attempts have been made to develop methods for the production of aromatic isocyanates without the use of phosgene. None of these processes is currently in commercial use. Processes based on the reaction of carbon monoxide with aromatic nitro compounds have been examined extensively (23,27,76). The reductive carbonylation of 2,4-dinitrotoluene [121 -14-2] to toluene 2,4-diaLkylcarbamates is reported to occur in high yield at reaction temperatures of 140—180°C under 6900 kPa (1000 psi) of carbon monoxide. The resultant carbamate product distribution is noted to be a strong function of the alcohol used. Mitsui-Toatsu and Arco have disclosed a two-step reductive carbonylation process based on a cost effective selenium catalyst (22,23). 

Tellurium burns in air with a greenish-blue flame. The combustion product is dioxide, Te02, the most stable oxide of the metal. Tellurium also forms other oxides the monoxide, TeO, the trioxide, TeOs, and the pentoxide, Te205. Monoxide has not yet been obtained in solid form. Like sulfur and selenium, tellurium forms oxyacids. Such oxyacids include orthotelluric acid, HeTeOe and tellurous acid, H2Te03, in which the metal is in +6 and +4 valence states respectively. 

Selenium has now been added to the growing list of transition metals shown capable of catalyzing the reductive A/-heterocyclization of 2-nitrostyrenes to indoles with carbon monoxide <99TL5717>. Utilizing the palladium-phosphine catalyzed methodology, Soderberg achieved the synthesis of several 4-substituted 2-methylindole natural products isolated from TricMoma... 

Analogous oxides are known containing one atom of sulphur replaced by selenium or tellurium. The tellurium compound, tellurium sulphoxide, STeOa, decomposes with production of tellurium monoxide, TeO, when gradually heated in a vacuum to 225° C.8 Attempts to produce sulphur monoxide similarly from sulphur sesquioxide have not been successful. 

Carbon monoxide has no action on selenium oxychloride.2 Water causes decomposition of the liquid into selenium dioxide and hydrogen chloride. Anhydrous ammonia reacts according to the equation. -... 

After combustion of the sample and carriers in an oxygen stream, reducing conditions are achieved by a flow of carbon monoxide over the sample ash. Arsenic, zinc, cadmium, and any remaining selenium and mercury are reduced to elemental form. When the sample is heated to 1150°C in a slow carbon monoxide stream in a quartz tube in a furnace, recovery of all five elements in the liquid nitrogen trap is complete in 30 min. The recovery trap is washed with nitric acid to dissolve all the metals, and the radioactivity of a nitric acid solution of the products is counted with a Ge(Li) detector. 

Ethoxyselenoformic acid, C2HBO.COSeH,3 is prepared by the interaction of magnesium bromohydroselenide and ethyl chloroformate. It soon decomposes, yielding its anhydride, B.pt. 125° to 127° C., a liquid of nauseating odour, carbon monoxide, selenium and alcohol. 

Carbon monoxide serves as the sole carbon and energy source for the carboxydo bacteria under aerobic conditions. Using water as the oxygen donor, carbon monoxide oxidase catalyzes the hydroxylation of carbon monoxide, giving carbon dioxide or bicarbonate for assimilation. Most work has been carried out on the enzyme from Pseudomonas carboxydovorans.,ftJ7>W38 The activity of carbon monoxide oxidase is considerably stimulated upon anaerobic treatment with sulfide and dithionite, or by aerobic treatment with selenite. The binding of selenite to the oxidase specifically activates the CO — methylene blue reaction.1039 The molybdenum cofactor liberated from selenium-activated carbon monoxide oxidase does not contain selenium. Here, then, the... 

The results described in the previous sections have demonstrated the versatility of molybdenum as a reaction centre in biology. The molybdenum cofactor stands at the centre of an important network of cellular functions that are all catalyzed by molybdoenzymes. The similarities and differences in these reactions are of great interest, and relate clearly to the detailed arrangement of terminal sulfur and oxygen atoms. However, the unexpected results found for carbon monoxide oxidase and the requirement for selenium in some cases indicate that other factors are also important. 

Treatment of 3,4-diaminopyridine (350) with carbon monoxide in the presence of selenium in N-methylpyrrolidine gives imidazo[4,5-c]pyridin-2-one (351) (96%) (Equation (28)) <87BCJ1793>. The selenium must be present in a stoichiometric or excess amount, or an acyclic urea formed via an intermolecular condensation of two 3,4-diaminopyridine moieties is the major product. 

---