Alicyclic hydrocarbons Synthesis

Nitroalkanes can be formed from the direct nitration of aliphatic and alicyclic hydrocarbons with either nitric acid ° or nitrogen dioxide in the vapour phase at elevated temperature. These reactions have achieved industrial importance but are of no value for the synthesis of nitroalkanes on a laboratory scale, although experiments have been conducted on a small scale in sealed tubes. 

The enthalpy of fomation of two such species has been measured, namely the cyclopropane and cycloheptane derivatives. The difference between the values for these two species, both as solids, is 238.1 kJmol . Is this difference plausible Consider the difference between the enthalpies of formation of the parent cycloalkanes as solids, 194 kJ mol . The ca 44 kJ mol discrepancy between these two differences seems rather large. However, there are idiosyncracies associated with the enthalpies of formation of compounds with three-membered rings and almost nothing is known at all about the thermochemistry of compounds with seven-membered rings. Rather, we merely note that a seemingly well-defined synthesis of cycloheptyl methyl ketone was shown later to result in a mixture of methyl methylcyclohexyl ketones, and superelectrophilic carbonylation of cycloheptane resulted in the same products as methylcyclohexane, namely esters of 1-methylcyclohexanecarboxylic acid. The difference between the enthalpies of formation of the unsubstituted alicyclic hydrocarbons cycloheptane and methylcyclohexane as solids is 33 kJmol . This alternative structural assignment hereby corrects for most of the above 44 kJ mol discrepancy in the enthalpies of formation of the two oximes. More thermochemical measurements are needed, of oximes and cycloheptanes alike. 

Alicyclic Hydrocarbons. Low-resolution GS or GCMS studies have suggested the presence of alicyclics, such as cycloalkanes (Hayes, 1967) or bicyclics with aliphatic side chains (Kvenvolden et al., 1970 Oro et al., 1971). High-resolution GCMS, however, confirmed only cyclopentene (Studier et al., 1972). An earlier study detected a cyclic terpene. A and/or A" menthene, but it may have been a contaminant (Studier et al., 1968). In any event, the Fischer-Tropsch synthesis readily produces alicyclic hydrocarbons (Weitkamp et al., 1953). 

Freund synthesis. Formation of alicyclic hydrocarbons by the action of sodium (Freund) or zinc (Gustavson) on open-chain dihalo compounds 1,3-dichloropropane derived from the chlorination of propane, obtained from natural gas, is cyclized in the Hass process by treating with zinc dust in aqueous alcohol in the presence of sodium iodide as catalyst. 

Low molecular weight products from the alkaline degradation of cellulose have been identified by g.e.-m.s. of their trifluoroacetate derivatives. Both the residual aqueous phase and the floating oily product were examined and found to contain essentially the same products. These included unsaturated, aliphatic and alicyclic hydrocarbons, aldehydes, ketones, alcohols, and furans. The synthesis of molecules with more than six carbon atoms also occurred. 

Dehydrogenation (the conversion of alicyclic or hydroaromatic compounds into their aromatic counterparts by removal of hydrogen and also, in some cases, of other atoms or groups) finds wide application in the determination of structure of natural products of complex hydroaromatic structure. Dehydrogenation is employed also for the synthesis of polycyclic hydrocarbons and their derivatives from the readily accessible synthetic hydroaromatio compounds. A very simple example is the formation of p-methylnaphthalene from a-tetra-lone (which is itself prepared from benzene—see Section IV, 143) ... 

The complexes formed by aliphatic and alicyclic di- and oligoolefins are often much more stable and more easily isolated as crystalline solids than those of the corresponding monoolefins. In many instances, the silver nitrate complex has been employed for isolation of the hydrocarbon from its synthesis mixture and sometimes for determination of the ring conformation (9, 225, 238, 408, 446). 

Concentrated sulphuric acid has been initially used for dimerization and oligomerization of cyclic monoolefins such as cyclohexene and diolefins such as cyclo-pentadiene, and later on for indene-coumarone fractions. Diluted sulphuric acid and benezenesulpho-nic acid have been further employed for the polymerization of more active cycloolefins like norbornene and dicyclopentadiene. In these reactions, monomer conversion, product yield and molecular mass depended largely on the acid concentration and monomer nature as well as on the other reaction parameters. Various compositions of initiators containing sulphuric acid in association with phosphoric acid, boric acid, sulphonic acids or inorganic sulphates of the type M (S04) (M = Al, Cr, Mg, Co, V) have also been reported for the polymerization of unsaturated alicyclic and cyclic fractions and for reactions with heavy aromatic fractions in hydrocarbon resin synthesis [2]. 

Hedin 458) has recently summarized factors that influence the biosynthesis of the boll weevil pheromone complex. Total synthesis was at a maximum during the summer and a minimum during the winter. In this study Hedin 458) did two types of experiments. The first series exposed 10-day-old adult weevils to a saturated atmosphere of a number of terpene hydrocarbons. It was found that only myrcene and limonene produced detectable amounts of oxygenated substances and that males produced more than females. No compounds isolated suggested that the weevils are capable of cyclizing alicyclic terpenes or their pyrophosphates. 

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