13049-38-2Relevant academic research and scientific papers
Equilibria of isomeric transformations of alkylbiphenyls
Roshchupkina, I. Yu.,Nesterova, T. N.,Rozhnov, A. M.
, p. 299 - 306 (1987)
Equilibria of mutual transformations of mono-, di-, and tri-alkylbiphenyls (ABP) were investigated in the liquid phase at 308 to 423 K.On the basis of experimental equilibrium constants, values of ΔrHm0/(kJ * mol-1) and ΔrSm0/(J * K-1 * mol-1) were calculated.Below are given correspondingly: reaction, compound and values for Et-BP (I), i-Pr-BP (II), and t-Bu-BP (III): 4-ABP = 3-ABP, I, 0.23, 5.76; II, (0.45+/-0.4), (5.72+/-1.13); III, (0.48+/-0.53), (4.83+/-0.53); 2-ABP = 4-ABP, I, -3,3, -5.76; II, -12.6, -5.76; III, -15.4, -5.76; 3,5-di-ABP = 3,3'-di-ABP, I, -0.1, 5.76; II, (0+/-0.60), (5.98+/-1.65); III, (-1.34+/-0.67), (4.48+/-1.87); 3,3'-di-ABP = 3,4'-di-ABP, I, -0.37, 0; II, (-0.64+/-1.6), (-0.48+/-4.6); III, (-0.90+/-0.39), (0+/-1.08); 4,4'-di-ABP = 4,3'-di-ABP, I, 0.24, 11.53; II, (0.47+/-0.06), (11.88+/-0.15); III, (0.35+/-2.2), (11.37+/-6.23).The joint processing of the above results gave the values of ΔrHm0/(kJ * mol-1) and ΔrSm0/(J * K-1 * mol-1) for meta-to-para-transformations of ABP: I, 0.33, 0; II, (0.59+/-0.76), (0.31+/-2.12); III, (0.71+/-1.34), (-0.37+/-3.78).
Hydrodesulfurization of alkyldibenzothiophenes: Evidence of highly unreactive aromatic sulfur compounds
Macaud,Milenkovic,Schulz,Lemaire,Vrinat
, p. 255 - 263 (2000)
Crude oil usually contains ~ 1 wt % of sulfur and SOx (a major air pollutant) is emitted, during combustion of fuels. Deep HDS is hindered mainly by the alkyldibenzothiophenes. 4,6-Dimethyldibenzothiophene (4,6-DMDBT) is always present in hydrotreated gas oils, even after hard HDS conditions. The synthesis of 4,6-DMDBT is used as a model to improve the reactivity of HDS catalysts. Various dialkylbenzothiophenes containing methyl, ethyl, diisobutyl, and diisopropyl substituents in the fourth and sixth positions were synthesized and their reactivities compared over an NiMo/Al2O3 industrial catalyst. In a batch reactor at 573 K and at a total pressure of 5 MPa, studies were conducted. Kinetic studies and competitive reactions showed that adsorption on the surface of the catalyst was not the rate-determining step for their transformation. HDS was proposed to proceed via a network of parallel reactions after partial hydrogenation of one aromatic ring of the sulfur compound. Variations in the reactivities of the different dibenzothiophene derivatives agreed well to the steric hindrance generated by the alkyl groups near the sulfur atom. 4,6-Diisopropyldibenzothiophene showed very low reactivity, and the steric effect led to the disappearance of desulfurization under the reaction conditions.
PALLADIUM(II)-CATALYZED OXIDATIVE COUPLING OF ARENES BY THALLIUM(III)
Yatsimirsky, Anatoly K.,Deiko, Sergei A.,Ryabov, Alexander D.
, p. 2381 - 2392 (2007/10/02)
Oxidation of benzenes with electron-donating and moderate electron-withdrawing substituents by thallium(III) trifluoroacetate in the presence of catalytic amounts of palladium(II) acetate affords biaryls in good yields.The GLC study of the isomer distribution has shown that 4,4'-biaryls are the major products.Thus, the 4,4'-biaryls can be easily isolated either by recrystallization or column chromatography.The competitive experiments and kinetic study using arenes and arylthallium derivatives as starting materials as well as quenching experiments have demonstrated the first step of the reaction to be fast thallation of arene to form arylthallium intermediate ArTl(OOCCF3)2.The latter undergoes the rate-determining transmetallation step reacting with monomeric complex Pd(OAc)2, which is formed upon depolymerization of trimer Pd3(OAc)6.Subsequent fast decomposition of arylpalladium species gives the final reaction products.The thallation of arene and substitution of TlIII for PdII in ArTl(OOCCF3)2 are characterized by the slopes of Hammet plots of -5.6 (?+) and -3.0 (?), respectively.
