Carbon alkanes and

Straight-chain alkanes are named according to the number of carbon atoms they contain, as shown in Table 3.3. With the exception of the first four compounds—methane, ethane, propane, and butane—whose names have historical roots, the alkanes are named based on Greek numbers. The suffix -one is added to the end of each name to indicate that the molecule identified is an alkane. Thus, pentane is the five-carbon alkane, hexeme is the six-carbon alkane, and so on. We ll soon see that these alkane names form the basis for naming all other organic compounds, so at least the first ten should be memorized. 

ELUmo is a measure of the ability of a compound to accept electrons (i.e., to act as an electrophile or undergo reduction). The above correlations show a decrease in ELUMO as the number of chlorines increases. As ELUM0 decreases, the ability of a compound to behave as an electrophile increases however, properties that increase stability increase LUMO energy and decrease reactivity. For example, between two-carbon alkanes and alkenes, r = -0.5104 and r = -0.9948, respectively. These data agree with Richard and Hunter (1996) in regard to the stability of alkanes over alkenes. 

Write correct molecular formulas for pentadecane, a 15-carbon alkane, and icosane, a 20-carbon alkane. 

Based on visible and IR spectroscopy studies of organic solutes in CO2, Hyatt concluded that CO2 behaves like a hydrocarbon solvent with very low polarizability. Hyatt s study was important in that it demonstrated that CO2 could dissolve (or was miscible with) most low molecular weight organic compounds however, some of his hypotheses do not appear to hold true today. In particular, the notion that CO2 had solvent properties similar to hydrocarbons (as also indicated by Allada) was misleading, but lingered for years. CO2 could not dissolve many of the compounds that would dissolve in low carbon alkanes, and vice versa. In addition, statement 2 was proved incorrect, as discussed later in this section, when CO2 was shown to interact with bases (10). 

Hexane is a six-carbon alkane and has a boiling point of 156°F, a flash point of -7°F, a flammable range of 1.1 to 7.5%, and an ignition temperature of 437°F. The structure and molecular formula for pentane are shown in Figure 5.29. 

All molecules discussed in this chapter will contain only carbon and hydrogen. There are linear chains of carbon atoms, and carbons can branch from the linear chain. The carbon branches are known as alkyl groups. Line notation is used to draw linear alkanes as well as branched alkanes. For example, 4A is identical to 4, 5A is identical to 5, and 6A is identical to 6. Structure 4A is a three-carbon alkane, and 5A is a four-carbon alkane where the carbons are connected in a linear chain. For 6A, there is a five-carbon linear chain, with two one-carbon groups attached to that chain. 

As the number of carbon atoms in an alkane increases, the number of isomers increases dramatically. There are 5 isomers possible for six-carbon alkanes, 9 isomers possible for seven-carbon alkanes, and 75 isomers possible for ten-carbon alkanes. It is possible to draw more than 300,000 isomeric structures for C20H42 and more than... 

X n hydrogen atoms, two fewer hydrogen atoms than noncyclic alkanes, C 2n+2 have. This is because cycloalkanes have no free ends where a carbon atom is attached to three hydrogen atoms. Another example, of a four-carbon alkane and cycloalkane, is shown below. 

Butane is a four-carbon alkane and thus has the formula C4HJQ, which can be represented as CH3CH2CH2CH3. 

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