2-Methylbutane Isopentane

Another interesting effect seen in alkanes is that increased branching lowers an alkane s boiling point. Thus, pentane has no branches and boils at 36.1 3C, isopentane (2-methylbutane) has one branch and boils at 27.85 °C, and neopentane (2,2-dimethylpropane) has two branches and boils at 9.5 °C. Similarly, octane boils at 125.7 °C, whereas isooctane (2,2,4-trimethylpentane) boils at 99.3 °C. Branched-chain alkanes are lower-boiling because they are more nearly spherical than straight-chain alkanes, have smaller surface areas, and consequently have smaller dispersion forces. 

Make the following molecules with a computational chemistry software pentane, isopentane (2-methylbutane), and neopentane (2,2-dimethylpropane). Note do not forget to do geometry optimization ... 

Predict the ratios of products that result from chlorination of isopentane (2-methylbutane). 

Pentane is a colorless, flammable liquid (the first liquid member of the alkanes) that is lighter than water. It has a pleasant odor that can be detected at 900 ppm, and a moderate odor intensity is observed at 5000 ppm. It occurs as two other isomers, including isopentane [(CH3)2CHCH2CH3] and neopentane [C(CH3)4]. Isopentane (2-methylbutane) apparently has physical and physiological characteristics similar to straight-chain pentane. Neopentane (2,2-dimethylpropane) is similar to butane in physical and physiological characteristics. In air, one part per million of C5 pentane is equivalent to 3 mgm. ... 

Since there are three pentanes, eight possible amyl chlorides, and therefore eight arrangements of the alcohol CsHuOH, the process is not so simple as indicated in the equations above. In the commercial synthesis, normal pentane and isopentane (2-methylbutane) are submitted to chlorination and subsequent hydrolysis. 

More recently, the electrochemical oxidation of lower alkanes in the HF solvent system has been investigated by Devynck and coworkers over the entire pH range. Classical and cyclic voltammetry show that the oxidation process depends largely on the acidity level. Isopentane (2-methylbutane, M2BH), for example, undergoes two-electron oxidation in HFiSbFs and HFiTaFg solutions (equation 18). ... 

Isoprene (2-methylbuta-1,3-diene) is produced mainly by the dehydrogenation of isoamylenes (2-methylbutenes) or isopentane (2-methylbutane), in processes similar to those used in the U.S.A. for butadiene manufacture. 

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