Thiophene dibenzo

Figure 1 Plot of weathering ratio (C3-dibenzo thiophenes C3-ehrysenes) versus souree ratio (C3-dibenzothio-phenes C3-phenanthrenes) for fresh and degraded oil samples from three different erude oil spills (Reprinted with permission from Environ. Sci. Technol, 30, 2332. 1996 Ameriean Chemieal Soeiety)...

As vinylbenzofurans allow a large variety of substituted dibenzofurans to be synthesized, 2- and 3-vinylbenzo[b]thiophenes allow an easy entry, by Diels Alder reaction with the appropriate dienophiles, to substituted dibenzo-thiophenes which are not easily accessible by other methods. Vinylbenzo-[bjthiophenes are less reactive than the corresponding vinylbenzo[b]furans. Some cycloaddition reactions of 2-vinylbenzo[b]thiophene (82) with various dienophiles are reported [83] in Scheme 2.34. 

Metallation of dibenzothiophene 5-oxide with three equivalents of butyllithium followed by carbonation gave a mixture of 4-dibenzo-thiophene carboxylic acid (36 /o) and dibenzothiophene (10%). The reduction or even elimination of sulfoxide groups in the presence of... 

Aromatic amines Benzo anthracenes Benzo fluoranthracenes Benzo pyrenes Benzoic acids Carbazoles Chrysenes Dibenzo thiophenes Fluorenes Imidazoles Indoles Naphthalenes... 

For the kinetics and mechanisms of the gas-phase reactions of other 2- to 4-ring PAHs with OH radicals, N03 radicals, and 03, see, e.g., phenanthrene, Kwok et al. (1994a), and indan, indene, fluorene, and 9,10-dihy-droanthracene, Kwok et al. (1997) for dibenzo-thiophene, a volatile S-PAC that is ubiquitous in polluted ambient air environments and forms mutagenic photooxidation products, see Kwok et al. (1999) see also Kwok et al. (1994b) for a review of gas-phase NO-, radical reactions with aromatics. 

Pathway III of Fig. 26 has been demonstrated for thiophene and benzo-thiophene with Ir complexes (4) and for all thiophenes, including dibenzo-thiophene, with Rh complexes (94, 95). These oxidative additions appear to be influenced by substituents present on the carbon atoms adjacent to the sulfur atom. Insertion between sulfur and the unsubstituted carbon is highly preferred. For 2-methylthiophene the exclusive product is the 1-5 bond insertion product, whereas for 3-methylthiophene, no preference for insertion was observed (1-2 and 1-5 bond insertion products were equal). In competitive studies, thiophene was found to be about twice as reactive as 2,5-dimethylthiophene. This behavior is similar to that observed for relative reaction rates of substituted thiophenes observed with conventional HDS catalysts. Thus steric limitations can occur, even with monomeric, homogeneous catalysts. 

From the preceding discussion, it can be seen that the mathematical description of the chemical transformations involved in product formation can be extremely difficult. However, knowledge of the response of HDS reaction rates to different kinds of feed components and byproducts is extremely important for designing new processes that will allow refineries to meet the stringent standards of the future. The following text attempts to summarize the observations reported in the literature on the effects of inhibitors on the hydrodesulfurization rates of alkyl-substituted dibenzo-thiophenes. It is quite possible that many reports have been overlooked, and the present authors apologize for any oversights that may have occurred in this review. 

Allyl- and benzyl-thiophenes may be cyclized by a direct Bradsher reaction, using dichloromethyl methyl ether or related dichloroalkyl methyl ethers and tin(IV) chloride catalysis to give the corresponding benzo- or dibenzo-thiophenes in 55-60% yield (73JCS(P1)1099). Thus substituted thiophenes having a benzyl group at either the 2- or 3-position, e.g. (349), when treated with a 1,1-dichloroalkyl methyl ether and tin(IV)... 

Dibenzothiophene, 1,2,3,4-tetrahydro-4-keto-synthesis, 4, 905 Dibenzo thiophenes alkylation, 4, 724 Birch reduction, 4, 775 13C NMR, 4, 11 5,5-dioxides... 

Figure 10. Simplification of the proposed pathways from dibenzothiophene co-metabolism by pure cultures of aerobic bacteria. (I) dibenzo-thiophene-sulfoxide, (II) 1,2-dihydroxydibenzothiophene, (III) 3-hydroxy-2-formylbenzothiophene.

OPCW GC/MS TEST MIXTURE containing in dichloromethane 10 rg/mL of n-Alkanes Cs-C24 even numbers Trimethylphosphate 2,6-Dimethylphenol 5-Chloro-2-methylaniline Tri-n-butylphosphate Dibenzo thiophene Malathion Methylstearate... 

Feed model feed with pyrene and dibenzo-thiophene. 

Of the three possible substrates, thiophene, benzo[ ]thiophene, and dibenzo[, thiophene, benzo[ ]thiophene is the most easily hydrogenated to the dihydro derivative this is ascribable to the more pronounced olefinic character of the C(2)-C(3) double bond in benzo[, ]thiophene as compared to that in thiophene. There is no example in the literature of the hydrogenation of dibenzothiophene either to the tetrahydro or the hexahydro stage. The hydrogenation of benzol ]thiophene is catalyzed by transition metals such as Ru, Os, Rh, and Ir. An excellent overview of homogeneous catalytic hydrogenation of thiophenic substrates has been presented recently <2004JOM (689)4277>. 

Thiophene is obtained in 6% yield by passing butadiene into molten sulfur at 320-420°. The reaction is general and affords somewhat higher yields (31 40%) of methylated thiophenes from homologs of butadiene. The free-radical nature of the reaction has been discussed. Dibenzo-thiophene is conveniently prepared by heating biphenyl and melted sulfur with aluminum chloride at 120°. The yield is 47%... 

A mixture of 500 g. (3.25 moles) of biphenyl and 208 g. (6.5 gram atoms) of sulfur is heated to 115-120°, and 25 g. (0.19 mole) of anhydrous aluminum chloride is added over a period of 75 minutes. The temperature is held at 115-120° for another 2 hours, followed by a gradual increase to 240° over a period of 5 hours. The cool residue is extracted with three 500-ml. portions of hot water and then with eight 1-1. portions of ethanol. Evaporation and cooling of the ethanolic solution after a charcoal treatment gives a 65-70% yield of dibenzo-thiophene melting at 98°. Material melting at 99° is obtained by distillation, b.p. 152-154°/3 mm., and recrystallization from ethanol. 

The types of sulfur compounds present in the petroleum fraction also change with the boiling range. Organic sulfides, disulfides, mercaptans, and thiophenes are found in the lighter boiling fractions. Different derivatives of thiophenes, e.g., benzothiophenes, dibenzo-thiophenes, are predominant in the heavier fractions. 

Table 1 Transformation rates for the conversion of substituted dibenzo-thiophenes on a NiMo/A Os catalyst...

TABLE 2.4. Known Ti complexes of the benzo- and dibenzo-thiophenes. 

---