Hexane constitutional isomers

Constitutional isomerism becomes more complex as the size of the hydrocarbon molecule is increased. For example, there are three constitutional isomers of pentane, C5H12. The number of constimtional isomers increases quite rapidly with an increasing number of carbon atoms. Thus, there are five constimtional isomers of hexane, CeH, nine isomers of heptane, C7H16, 75 isomers of decane, C10H22, and 366,319 isomers of eicosane, C20H42. You can begin to understand why it is possible to make so many different molecules based on carbon. 

There are five constitutional isomers with molecular formula CgH. We are now able to name three of them (hexane, isohexane, and neohexane), but we cannot name the other two without defining names for new stmctural units. (For now, ignore the names written in blue.)... 

Problem 11.6. How many isomeric hexanes exist, i.e., how many constitutional isomers exist for the molecular formula C5H14 Show one structural formula for each isomer. Do not show more than one structural formula for each isomer. 

Acetaldehyde and propionaldehyde made up at least 90% of the C-C oxygenates for all experiments. The Cg oxygenates include 2,5-dimethyltetrahydrofuran, 2,4-dimethyltetrahydro-furan, 2,2,4-trimethyloxepane (not shown), and small amounts of other species (not shown) such as 3-ethoxy-l-butene and hexanal. The major product was 2,5-dimethyltetrahydrofuran, optimized at 21% selectivity for CgH,4/02 2.5, after which it did not change substantially. Its 2,4-constitutional isomer showed a similar trend but was minor in comparison (maximum -4% selectivity). Selectivity to Cg oxygenated hydrocarbons exceeded 30% for CgHj4/02 = 2.25 to... 

Following are structural formulas for the cis isomers of 1,2-, 1,3-, and 1,4-dimethylcyclo-hexane and three sets of C-NMR spectral data. Assign each constitutional isomer its correct spectral data. 

The number of constitutional isomers rapidly increases with the number of carbons in the series. For example, there are three constitutional isomers with the molecular formula C5H12 (pentanes see Figure 24.5), five of (hexanes), and 75 of... 

Recall that constitutional isomers are compounds that have the same molecular formula but differ in their constitution (cormectivity of atoms). We must draw aU of the constitutional isomers with molecular formula CeHi4, so we are looking for all of the different ways of coimecting six carbon atoms. We begin with a linear chain (parent = hexane) ... 

To draw all of the constitutional isomers of C7H, we will follow the same methodical approach that we used in Problem 4.3. We start with a hnear chain of seven carbon atoms (heptane). Then, we draw aU possible substituted hexanes with molecular formula C7H16. There are only two possibUities - the methyl group can be placed at either C2 or C3. Then, we move on to the pentanes, and finally any possible butanes. This methodical analysis gives the following constitutional isomers ... 

Stereoisomers are isomers that have the same constitution but differ in the arrangement of atoms in space. Cis- and fran -l,3-dimethylcyclo-hexane are stereoisomers. The cis isomer is more stable than the trans. 

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