U-Butane

Figure 7.13 reprinted with permission from Jorgensen W L, R C Binning Jr and B Bigot. Structures md Properties of Organic Liquids u-Butane and 1,2-Dichloroethane and Their Conformational Equilibria. The Journal of the American Chemical Society 103 4393-4399. 1981 American Chemical Society. 

To conclude this computer project, we shall lirst search the potential surface for rotation of u-butane about its 23 C C bond, for which we think we know the answei, then seai ch the potential sutface foi I-butene, foi which we do not. In I -butene, the double bond establishes a rigid plane but the methyl group can take up several d i ffe ren t positions re I at i ve to i t by rotation ab ou t th e 2 - 3 s i n g I e bo n d,... 

Dahloff, G., Pfennig, A., Hammer, H., and van Oorschot, M. Vapor-liquid equilibria in quaternary mixtures of dimethyl ether + u-butane + ethanol + water, 7 Chem. Eng. Data, 45(5) 887-892, 2000. 

The computed kinetic limit of superheat of /i-butane, for example, is 378.3 K and the experimentally measured3 value is 376.9 K. With ordinary liquids, the kinetic limit of superheat approaches the critical temperature (7k S/7 crit = 0.89). However, under ordinary conditions, when the liquid is in contact with solid surfaces, it boils far below the kinetic limit of superheat. Thus, the boiling point of u-butane, for example, is 272.5 K. Similarly, the theoretical kinetic superheat of water is 300°C, while the ordinary boiling point of water is 100°C. 

The reaction steps proposed for the transformation of u-butane to maleic anhydride [4] are shown in Table 1. However, none of the intermediates shown in Table 1 was detected under typical reaction conditions for kinetic reasons. 

The letter n (for normal), as in u-butane, denotes an unbranched chain of C atoms. The prefix iso-(i-) indicates a CH3 branch on the second C from the end e.g., isopentane is... 

Butane and all larger alkanes exhibit stmctural isomerism. Structural isomerism occurs when two molecules have the same atoms but different bonds. That is, the molecules have the same formulas but different arrangements of the atoms. For example, butane can exist as a straight-chain molecule (normal butane, or u-butane) or with a branched-chain stmcture (called isobutane), as shown in Figure 20.4. Because of their different stmctures, these structural isomers have different properties. 

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