Hydrogenated benzene compounds

The petroleum oil which is found in the Caucasus in the region of the Black Sea and commonly known as Russian petroleum differs from American petroleum in that while the latter contains almost entirely hydrocarbons of the aliphatic series, the former contains hydrocarbons known as naphthenes which are hydrogenated benzene compounds. 

In the petrochemical field, hydrogen is used to hydrogenate benzene to cyclohexane and benzoic acid to cyclohexane carboxylic acid. These compounds are precursors for nylon production (Chapter 10). It is also used to selectively hydrogenate acetylene from C4 olefin mixture. 

Replacement of a hydrogen of benzene by chlorine is termed chlorination. When one or more hydrogens are replaced by an -NO2 (nitro group), it is called nitration. Reaction of benzene with sulfuric acid, a reaction known as sulfonation, leads to a sulfonic acid. Note that in each substitution reaction, a small hydrogen-containing compound is formed. 

The efficient hydrogenation of various benzene compounds in biphasic systems has also been described by similar surfactant-protected irid-ium(O) nanoparticles [47]. The solubility of the nanoparticles was assured by 10 equivalents of water-soluble N,N-dimethyl-N-cetyl-Ar-(2-hydroxyethyl)-ammonium chloride salt. TEM observations show that the particles are monodispersed in size with an average diameter of 1.9 0.7 nm (Fig. 7). 

Hydrogenation of aromatic nitro compounds [8,18,29] and hydrogenation of benzene derivatives [2,9,21] have been generally accepted as model reactions to check the heterogeneous nature of catalyst, because homogeneous species are not believed to be active. But at least two well-studied examples show that molecular catalysts can hydrogenate benzene [36,37]. 

An alternative approach to stabilize nanoparticles is to use polyoxoanions (see Scheme 9.5). Finke and coworkers described polyoxoanion- and ammonium-stabilized rhodium zerovalent nanoclusters for the hydrogenation of classical benzene compounds [95, 108]. This organometallic approach allows reproducible preparation of stable nanoparticles starting from a well-defined complex in terms of composition and structure (see Section 9.3.5). 

The prefix cyclo- appears before the root of the name in ring compounds, except for those involving the benzene ring (Problem 9.9). The benzene compounds form a special category of compounds referred to as aromatic compounds. The opposite of aromatic is aliphatic. Further modifications of the system, such as those when elements other than carbon and hydrogen are involved, will be noted when functional groups are discussed. 

Oxidation of 172 with chromium trioxide in pyridine gave the monoketone 176, whereas oxidation of spiradine F under the same conditions afforded the hydroxylactam 177. Catalytic hydrogenation of compound 176 afforded the a-ketol 178. The latter was treated with sodium methoxide in benzene to give an enolated a-diketone (179), which definitely fixed the position of the hydroxyl group at C-6 in spiradine G. Comparison of an ORD curve of compound 178 with that of 5a-cholestane-6-one established the indicated absolute configuration for these alkaloids. It is worth noting that these alkaloids bear many structural similarities to the earlier mentioned alkaloid ajaconine. 

Radical anions of 2,3-dimethylpyrazine and 2,5-di-/-butyl-3-isopropylpyrazine have been prepared with metallic potassium in 1,2-dimethoxyethane, and their e.s.r. spectra examined (596a). Heats of hydrogenation of compounds containing isolated and conjugated C=N double bonds have been measured, and the empirical delocalization energy for pyrazine has been determined as 22.3 kcal/mol (93.3 kJ/mol) and corresponds to only 62% of the empirical delocalization energy of benzene (597). 

Aldehyde and Ketone Reactions.—(i) The formation of addition prodmts with hydrogen cyanide, H—CN. (2) The formation of oxime compounds with hydroxyl amine, H2—NOH. (3) The formation of hydrazone compounds with a benzene compound known as phenyl hydrazine, H2N—NH—CeHs. 

Oxidation of naphtho[l,8-de]-l,2,3-triazin-l-amine (1) afforded the nitrene 2 which led to 1,8-didehydronaphthalene (3) by loss of two moles of nitrogen.7-254-257 Compound 3 could be trapped by alkenes, acetylenes, hydrogen, benzene or sulfur compounds. 

The catalytic hydrogenation of benzene has been carried out as a model reaction to increase the hydrogenated cyclic compounds from aromatics. Catalyst samples containing nickel on different supports were prepared and tested. It was found that a-Al203 supported nickel showed the best activity for benzene conversion reaction. Nickel metal area, its dispersion and nickel crystal size were determined. The best activity is obtained with 40% nickel concentration (as oxide) and at the optimum nickel crystallite size of 196A° and optimum metal area of 10.8m2/g. 

Other than the binary hydrides 207), which will not be covered in this review, only a few metal-hydrogen-honded compounds of zirconium and hafnium are presently known, the first being the borohydride M(BH4)4. Although its preparation goes back to the work of Hoekstra and Katz 2i0), it is only recently that structural studies have revealed that metal-hydrogen-boron bridges are involved in the structure. The proton NMR spectrum 263, 582) of a benzene solution shows a quartet... 

---