Thiophene and related compounds

Thiophene is the simplest sulfur heterocyclic that can be used as a model compound for desulfurisation. The earliest stage of the HDS process is, the adsorption of thiophene. The INS spectra of adsorbed thiophene [140] were obtained. The challenge is to interpret changes, if any, of the INS spectrum due to adsorption in terms of the interaction of thiophene with the catalyst. The INS spectra of thiophene complexes of known structure were used to aid in the interpretation of the INS spectrum of adsorbed thiophene. Fig. 7.35. 

Thiophene has 2 symmetry and the 21 fundamental vibrations are distributed between four symmetry species as follows iA + iA2+lB + 3B2. All vibrations are active in the Raman spectrum, but those of A2 symmetry are inactive in the infrared spectrum. The INS spectrum of thiophene has been modelled by ab initio and force field calculations [141]. The calculated spectrum and the experimental spectra of pure solid thiophene and thiophene adsorbed by a M0/AI2O3 catalyst are shown in Fig. 7.35. The vibrational modes involving significant hydrogen atom displacements are shovm in Fig.7.36. 

In this chapter we have presented and reviewed the extensive body of work that neutron vibrational spectroscopy applied to catalysis represents. It is one of the largest, most important and influential bodies of neutron work to appear in the literature and much of the original work remains of considerable interest. This is partly because catalyst experiments are difficult to perform and require considerable commitment of neutron time and other resources. 

The re-analysis of old data, so successfully applicable to pure compounds, is unlikely to be as useful in the context of catalytic studies, since the metadata that could establish the nature of the surface to be modelled are unlikely to have survived in sufficient detail. It could well be that a tabula rasa approach is best for future work. 

Mitchell (1994). Acta Phys. Hung., 75, 131-140. Inelastic neutron scattering studies of catalysts. 

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In this review, synthesis, structure, and redox properties of phosphaquinoid compounds are described, keeping the contribution of thienoquinoid structures in mind in the first part. In the second part, synthesis and structure of phosphorus substituted thiophene and related compounds, especially tetraphosphoryl derivatives, are outlined (Scheme 3). 

Mechanics (MM2) Study of Furan, Thiophene, and Related Compounds. 

Pyrrolidinobenzo[b]thiophene and related compounds are conveniently obtained by treating thioindoxyl with the appropriate cyclic secondary amine in the presence of toluene-p-sulfonic acid.391,392... 

The PPP approximation has also been applied in an SCF study of the barrier to internal rotation in 2,2 - and 3,3 -bithienyl. For the latter isomer energy minima were found at about 30° and 150° from the planar form whereas no distinct minima were found for 2,2 -bithienyl. A study of the reactivity of thiophen and related compounds using a HMO delocalized model has been undertaken. Molecular core binding energies have been measured for thiophen and are interpreted in terms of non-empirical calculated energy levels assuming Koopman s theorem. ... 

Sasaki et al. [33] reported equilibrium concentration of minor snUhr-based impurities in the fuel cell fuels in the temperature range 400-1000 C. As sulfur-based impurities in the fuel cell gases, H2S, elementary sulfur, inorganic sulfur compounds, mercaptans alkyl (di-)sulfides, thiophenes, and related compounds have been taken into account. 

Rossi, R., Carpita, A., and A. Lezzi Palladium-Catalyzed Synthesis of Naturally-Occurring Acetylenic Thiophenes and Related Compounds. Tetrahedron 40, 2773 (1984). 

Pyrrole- aud Furan-fused Thiophens and Related Compounds.— During recent years there has been a great interest in the thiophen analogues of indole, the thienopyn oles, especially among Russian workers, and several... 

In addition to useful polymers, thiophene derivatives have a variety of other interesting properties. Novel benzodiazepine analogues such as 46 and related compound 47 continue to... 

Buu-Hoi, No. Ph., Ng. Hoan and D. Lavit Thiophene Derivatives of Potential Biological Interest. Part. I. Thiophene Analogs of Stilbene and Related Compounds. J. chem. Soc. 1950, 21304. 

For perspective, Table V presents the reported relative reactivities of selected thiophene derivatives and related compounds (5, 26, 34). In this table, the dibenzothiophene rate constant has been renormalized to equal... 

Disulfides were shown to be intermediates in the iodine oxidation of 1,3-butadiene-l-thiols and related compounds to form thiophenes (56JOC39). Several simple disulfides were converted to thiophene derivatives under these same conditions (64JOC2372). For example, bis(2-biphenyl) disulfide (13) produced dibenzothiophene (14) in 64% yield when heated with iodine in ethylene glycol for one hour. Treatment of (13) in benzene with aluminum bromide gave (14) in 76% theoretical yield, with an equivalent amount of the thiol, 2-biphenylthiol (62JOC4111). Thus the iodine reagent is more efficient, since it oxidizes the mercaptan, formed by the Friedel-Crafts reaction of disulfide on the adjacent aromatic ring, to disulfide for further reaction, and also serves as a catalyst for the initial reaction. 

With thiophenol in the presence of zinc chloride and hydrochloric acid, thioindoxyl-1,1-dioxide and related compounds give 3-phenyl-thiobenzo[6]thiophene-l, 1-dioxides, which afford the corresponding 2,3-dihydrobenzo[6]thiophene-l,1-dioxide on reduction with zinc and sodium hydroxide.756... 

Cycloaddition of Thiophene-2,3-Quinodimethanes (2,3-Dimethylene-2,3-dihydrothiophenes) and Related Compounds... 

Sulfuration of 1,4-dicarbonyl and related compounds (Paal synthesis) provides one of the most widely used methods for the preparation of thiophenes. P2SS (P4S10), combination of hydrogen sulfide and an acid catalyst, Lawesson s reagent, bis(trialkyltin) sulfides, and hexamethyldisilathiane are the sulfuration reagents used most commonly. 

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