Hydrocarbon structural isomers

Polya s Theorem clearly showed the way to the general enumeration of all acyclic hydrocarbons, irrespective of how many double or triple bonds they might have but it was to be 35 years before this enumeration was carried out. In two papers [ReaR72,76] I obtained the solution to this general problem in both the structural isomer and stereoisomer cases, as generating functions in three variables. Of these variables, x marks the number of carbon atoms, y the number of double bonds, and z the number of triple bonds. The de- rivation of these generating functions was Polya theory all the way — a succession of applications of Polya s Theorem with occasional use of Otter s result. The derivation was really rather tedious, but the generating functions, once obtained, can be used to compute the... 

AlsB77 Alspach, B., Aronoff, S. Enumeration of structural isomers in alicyclic hydrocarbons and porphyrins. Canad. J. Chem. 55 (1977) 2773-2777. 

A branched hydrocarbon C4H10 reacts with chlorine in the presence of light to give two branched structural isomers with the formula C4H9C1. Write the structural formulas of (a) the hydrocarbon (b) the isomeric products. 

There is little variation in the shape of the isotherms for a series of meso structural isomers (C-15 3,3 -C-15 12,12 ) upon moving the carbonyl group up the hydrocarbon chain. There is an expansion of the film, as would be expected if the head groups were allowed to drift apart at large areas (> 240 A2) per molecule. A comparison of the IT//1 isotherms for the series of structural isomers shows that the meso-diastereomers become more expanded at low surface pressures as the carbonyl group is moved up the hydrocarbon chain. 

Intramolecular Friedel-Crafts reactions can sometimes compete with organosil-icon hydride reductions of benzylic-type alcohols to cause formation of undesired products. An example is the attempted reduction of alcohol 26 to the corresponding hydrocarbon. When 26 is treated with triethylsilane in trifluoroacetic acid at room temperature for 15 hours, a mixture of the two fluorene isomers 27 and 28 is obtained in a combined yield of 45%. None of the hydrocarbon structurally related to the substrate alcohol 26 is obtained.171 Whether this problem could be circumvented by running the reduction at a lower temperature or with a different acid remains subject to experimentation. 

Compounds that have the same molecular formulas, but different structural formulas, are isomers. When dealing with hydrocarbons, this amounts to a different arrangement of the carbon atoms. Isomers such as these are structural isomers. 

Draw all the structural isomers for hydrocarbons having the molecular formula C4H10. 

The possibility of having branched-chain hydrocarbons that are structural isomers of the continuous-chain hydrocarbons begins with butane (n = 4). The HJPAC rules for the systematic naming of these hydrocarbons follow. 

Among the paraffin hydrocarbons (C H2W+2, where n is a whole number), what is the empirical formula of the compound of lowest molar mass which could demonstrate optical activity in at least one of its structural isomers ... 

Hosoya, H., Topological index. A newly proposed quantity characterizing the topological nature of structural isomers of saturated hydrocarbons, Bui Chem. Soc. Jpn., 44, 2332-2339, 1971. 

Its structure is different from the structure of a straight-chain alkane. Like many hydrocarbons, this isomer of CeHi4 has a branch-like structure. Alkanes such as 2-methylpentane are called branched-chain alkanes. (The branch is sometimes called a side-chain.)... 

As in isomers of other hydrocarbons, the physical and chemical properties of the structural isomers of aromatic hydrocarbons differ. The physical properties of the three positional isomers of dimethylbenzene (xylene) are given in Table 1. 

This resemblance is highly significant if one considers that 10,359 structural isomers exist for saturated hydrocarbons with 16 C atoms (Lederberg, 1972). Apparently the meteoritic hydrocarbons were made by FTT reactions, or some other process of the same extraordinary selectivity. The Miller-Urey reaction, incidentally, shows no such selectivity. Gas chromatograms of hydrocarbons made by electric discharges in methane show no structure whatsoever in the region around Cjg (Ponnamperuma et al., 1969). Apparently all 10 possible isomers are made in comparable yield, as expected for random recombination of free radicals. 

Capillary electrophoresis has been used for the analysis of chiral pollutants, e.g., pesticides, polynuclear-aromatic hydrocarbons, amines, carbonyl compounds, surfactants, dyes, and other toxic compounds. Moreover, CE has also been utilized to separate the structural isomers of various... 

Hosoya, H. (1971 Topological Index. A Newly Proposed Quantity Characterizing the Topological Nature of Structural Isomers of Saturated Hydrocarbons. Bull.Chem.Soc.Jap., 44, 2332-2339. 

As the number of carbons in a hydrocarbon increases, the number of possible structural isomers increases. For example, nine alkanes having the molecular formula C7H16 exist. C nH, has 316 319 structural isomers. 

Structural isomers differ in the order in which atoms are bonded to each other. A straight-chain hydrocarbon and a branched-chain hydrocarbon with the same molecular formula are structural isomers. 

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