Heteroatom-containing compounds

Bitumens and heavy oils present a challenge for upgrading, pardy because of their high levels of metals, N, S and 0. There have been niunerous publications related to organometallic compounds in heavy oils and bitumen, and the effects that they have during thermal and catalytie processing. 

Other molecules containing nitrogen and oxygen have a strong inhibition effect on desulphurization reactions.H2S, which is produced during HDS reactions, is also known to act as an inhibitor. 

Because of the current limitations in HDS technology, Whitehurst et al, suggested alternative approaches listed below  

Altering the desulphurization reaction pathways for hindered sulphur compounds by using zeolite-containing catalysts. 

HDS reactions that take place in more than one stage modifying the feed in the first stage, such as isomerization of alkyl groups in hindered alkyldibenzothiophenes, to produce less sterically hindering positions for sulphur removal. 

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Kielbasinski, P. and Mikoiajczyk, M. (2007) Chiral Heteroatom-containing Compounds, in Future Directions in Biocatalysis (ed. T.Matsuda), Elsevier, pp. 159-203. 

The hydrogen donors vary widely from heteroatom-containing compounds such as alcohols, amines, acids and cyclic ethers to hydrocarbons such as alkanes (Table 20.1). The choice of donor is largely dependent on several issues ... 

Other heteroatom-containing compounds exhibit similar chemistry. Primary amines, for example, can be oxidized on irradiated semiconductor suspensions to form Schiff bases which undergo coupling with the starting amine. In fact,... 

Table 15 [8 19 56, 59 93 107 108 109, 110, 111, 112 113, 114] contains NMR data for a vanety of tnfluoromethyl compounds that do not fit into the more common categones already covered Most carbon-attached tnfluoromethyl (CF3-C) 19F-NMR signals fall in the 25 ppm range from -60 to -85 ppm, a notable exception being tnfluoromethylacetylenes, with signals at approximately -50 ppm Tnfluoromethylated compounds in which the CFj is directly bonded to an atom oilier carbon are considered in Table 16 [57 59,95 109,115,116 117 118,119,120 121 122, 123 124, 125 These heteroatom containing compounds are of interest to both organic and inorganic chemists and have been studied by NMR for numerous reasons...

Using soft ionization techniques in the positive ion mode, (M-H)+ is most often observed in the case of saturated compounds and (M + H)+ in the case of unsaturated compounds or heteroatom-containing compounds. However, halogen compounds or compounds containing an sp3 oxygen often prevent the observation of the molecular ion. Thus, for example, it is very difficult to form the molecular ion or the pseudomolecular ion of acetals or orthoesters. 

Although heteroatom-containing compounds are readily oxidized, these cation radicals have not been widely employed for carbon-carbon bond formation, because such cation radicals react with nucleophiles on the heteroatom, where the unpaired electron is localized. For... 

Figure 24 The mechanism of oxidation of heteroatom-containing compounds by P450 enzymes (a) The one-electron oxidation mechanism of heteroatom oxygenation (b) The one-electron and hydrogen atom abstraction mechanisms of heteroatom dealkylation...

The classical silica gel chromatographic method for determination of percent olefins in shale oils was studied and found wanting, mainly because of cross-contamination from high levels of olefins and heteroatom-containing compounds. This paper describes a new hydroboration/oxidation procedure for olefins, and reports its use in hydrocarbon-type analysis of both whole shale oils and distillate fractions. Percent composition values for three whole oils ranged as follows saturates, 13-26 olefins, 16-20 aromatics, 5-14 polar compounds, 41S2. A discussion of IR analysis for relative amounts of specific olefin types such as terminal, internal trans, and methylene structures is included. 

Direct oxidative activation of sp3 C—H bonds adjacent to a heteroatom is an ideal synthetic route to heteroatom-containing derivatives. Recently, our group has developed an efficient method for the alkylation of 1,3-dicarbonyl compounds using Fe2(CO)9 as a catalyst (Equation 11.2) [8]. The scope of this transformation is fairly broad and various heteroatom-containing compounds have been shown as effective alkylation reagents. Kinetic isotopic effect (KIE) experiments have shown that the reaction has a kH/kD value of 5.4 0.1, which supports a rate-determining C—H bond cleavage step for the overall transformation. 

The next important class of heteroatom containing compounds are those that contain nitrogen. The hydrogenation of these compounds proceeds with the formation of ammonia (6.48). 

Friedel-Crafts alkylation and acylation reactions are quite versatile. They form the basis of several named reactions that have been used to synthesize heteroatom-containing compounds such as quinolines, isoquinolines, indoles, and many others. This section will examine several more common transformations that will show the scope and utility of these processes. It will also introduce a modest amount of heterocyclic chemistry into our synthetic discussion. 

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