Iranian Journal of Chemistry and Chemical Engineering
Volume:15 Issue: 1, May-Jun 1996

Treatment of 10-bromoanthralin (1) with several thiophenols (2) gave the corresponding 10-arylthioanthralins (3) in high yields. Oxidation of thioanthralins (3a-c) and (3k-m) using an excess ofm-chloroperbenzoic acid gave the corresponding sulfones (4a-c) and (4k-m) in good yields. Oxidation of thioanthralins (3d-f) gave a mixture ofthe corresponding sulfones (4d-f) and anthralin -10, 10س-dehydrodimer (5). Oxidation of thioanthralins (3g-j) afforded only anthralin-10, 10س-dehydrodimer (5) with no evidence of sulfone.

Catalytic amount of Ce(IV) as ceric triethylammoniumnitrate (CTEAN) in dichloromethane or acetone can bring about anefficient tetrahydropyranylation of different types of alcohols to afford thecorresponding tetrahydropyranyl ethers in high yields. Deprotection oftetrahydropyranyl ethers can also be achieved efficiently in the presence ofthis catalyst in methanol.

Abstract: Oxidation of ethylene to ethylene oxide over silver catalystand selenium modified catalyst has been studied by continuous flow andpulse techniques over the temperature range of 230-280ـC. The results arediscussed in terms of reaction mechanisms proposed by others, rejectingmechanisms which involve peroxide formation. It has been shown that notonly selectivity towards ethylene oxide production increases considerably byintroduction of 0. 01 atom percent of selenium into silver, but the reactivityincreases also. Above 270ـC selectivity drops almost to the level ofunmodified catalyst because selenium atoms diffuse into the groovesbetween silver crystals on the surface of catalyst. It has also been shownthat intermolecular conversion of ethylene oxide to acetaldehydedecreases.

A method is described by which it is possible to determinethe high barriers to ring inversion and hindered rotation by neatracemization of optically active compounds when the racemization iscaused by ring inversion or hindered rotation. The method is based onpreparation of sufficiently pure enantiomers, mainly by chromatographyon swollen microcrystalline triacetylcellulose (TAC). By this technique thebarrier to ring inversion in dibenzo [a, c] dinaphtho [2, 3-e; 2, 3-g] cyclooctatetraene, a tetrabenzocyclooctatetraene analogue, was determinedto be 67. 2×0. 8 kcal/mol, a record as the highest conformational barrierever reported. The barrier to hindered rotation in 2, 2إ- dimethyl binaphthylwas determined by this method to be 49. 5×0. 5 kcal/mol.

The activation of carbon monoxide by oxygen on Mg(100)surface has been investigated by X-ray photoelectron spectroscopy (XPS).Carbon monoxide is only weakly adsorbed (dispersion-type forces) on amagnesium surface. The XPS result has shown that the dissociation ofcarbon monoxide leading to the formation of a metastable surfacecarbonate species occurs through the participation of an oxygen surfaceO-(s). A stepwise mechanism involving a weakly adsorbed CO moleculepresent at very low surface coverage (<0.1) undergoing surface diffusionand interaction with the transient oxygen adatoms is suggested. TheFrenkel equation has been used to estimate the mean residence time ofCO molecule on the surface, and the residence time of a molecule on aspecific surface site has also been estimated.

The complexation reactions between Tl+ and Pb2+ ions andcrown ethers 12-crown-4 (12C4), 15-crown-5 (15C5), benzo-15-crown-5 (B15C5), 18-crown-6 (18C6), dicyclohexyl-18-crown-6 (DC18C6) andaza-18-crown-6 (A18C6) were studied in 90% acetonitrile and 90%ethanol solutions at 25ـC, using an a. c. polarographic technique. Thestoichiometry and stability of the complexes were determined bymonitoring the shift in peak potential of the polarographic waves of metalions against the crown concentration. The stability of the resulting 1:1complexes of Tl+ and Pb2+ ions, in both solvent systems used, was foundto vary in the order A18C6>DC18C6>18C6>15C5>B15C5>12C4. In90% ethanol, Pb2+ ion complexes with all crown ethers used were morestable than the corresponding Tl+ complexes. The influence of substituentsin the polyether ring and of the nature of solvent and metal ions on thestability of a number of complexes is discussed.

Deprotection of phosphate, phosphite, and sulfite esters bysilica chloride is described. Silica chloride is a mild, selective, and effectivereagent for cleavage of benzyl and t- butyl esters of the above compounds.

Analytical solutions and type curves for the constant rateradial flow of fluid in both conventional and naturally fractured reservoirsincluding the effect of wellbore phase redistribution are presented. Anautomated procedure for non-linear least square minimization using theanalytical solutions and their derivatives with respect to the unknownparameters developed to analyze the pressure build up data affected byphase redistribution. Field examples and analysis are also presented.