Hexane skeletal structures

S.M. Davis, F. Zaera, and G.A. Somoijai. Surface Structure and Temperature Dependence of n-Hexane Skeletal Rearrangement Reactions Catalyzed over Platinum Single Crystal Surfaces Marked Structure Sensitivity of Aromatization. J. Catal. 85 206 (1984). 

Davis SM, Zaera F, Somorjai GA (1984) Surface structure and temperature dependence of n-hexane skeletal rearrangement reactions catalyzed over platinum single crystal surfaces marked structure sensitivity of aromatization. J Catal 85 206-223... 

Skeletal rearrangement reactions over Pt single crystals have been studied for methyl cyclopentane, 2- and 3-methylpentane350 and for n-hexane.3sl One conclusion351 is that whereas aromatization reactions are very sensitive to surface structure [Pt(l 11)> Pt(100)], isomerization, Cs-cyclization, and hydrogenolysis reactions display little dependence on structure. Temperature and H2 pressure are more important in affecting the selectivity. 

These three chi indexes are not highly intercorrelated. The x index encodes size and branching information. The index encodes even more specific information about skeletal branching, x increases with the increase in skeletal branching in the hexane series the x values increase in the order hexane < 3-methylpentane, < 2-methylpentane, < 2,3-dimethylbutane, < 2,2-dimethyl-butane. The Xpc index is sensitive to specific structural aspects, especially to gem and vicinal substitution patterns. The negative sign on Xpc reflects a... 

C=C—C—C—C—C. Isomerization to a methylpentane would result in localizing the carbonium ion on the tertiary position. This structure can no longer ring close to a cyclopentane but only to a highly strained cyclobutane. Since skeletal isomerization occurs readily at reforming conditions, most of the n-hexane would be converted to isohexane or cracked products rather than to cyclopentane. 

A hexane molecule can be represented in several ways molecular formula, ball-and-stick model, expanded structural formula, condensed structural formula, and skeletal formula. 

A simplified structure called the skeletal formula shows the carbon skeleton in which carbon atoms are represented as the end of each line or as comers. The hydrogen atoms are not shown, but each carbon is understood to have bonds to four atoms. For example, in the skeletal formula of hexane, each line in the zigzag drawing represents a single bond. The carbon atoms on the ends are bonded to three hydrogen atoms. However the carbon atoms in the middle of the carbon chain are each bonded to two carbons and two hydrogen atoms (see Figure 11.2). 

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