Pentane, structural isomers

The products are called 1,4-octasubstituted or 1,4,8,11,15,18,22,25-octasubstituted phthalocyanines. In this case only one structural isomer is possible. 3,6-Diheptylphthalonitrile when refluxed in pentan-1 -ol in the presence of nickel(II) acetate and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) for 48 hours yields the nickel phthalocyanine 16. 

Molecules such as w-pentane, mo-pentane, and eo-pentane, which have the same molecular formula but different structures, are known as structural isomers. Structural isomers have different physical and chemical properties. For example, -pentane has a boiling point of 36°C, wo-pentanes boiling point is 30°C, and < o-pentanc s is 10°C. 

Was this your answer The structural isomer with the greatest amount of branching in the carbon framework will likely have the highest octane rating, making neo-pentane the clear winner. Just for the record, the ratings are... 

How many structural isomers can be identified for pentane, C5Hx2 ... 

We can draw no other structure for an alkane having the molecular formula C5H12. Thus pentane has three structural isomers, in which the numbers of carbon and hydrogen atoms remain unchanged despite the differences in structure. 

The structural isomers of pentane, C5H12, have quite different boiling points (see Example 24.1). Explain the observed variation in boiling point, in terms of structure. 

Draw all the structural isomers for CgHig that have the following root name (longest carbon chain). Name the structural isomers, a. hexane b. pentane... 

Isooctane is 2,2,4-trimethylpentane. Draw structural formulas for and name a branched heptane, hexane, pentane, and butane that are structural isomers of isooctane. 

Practice Exercise Draw all the possible structural isomers for pentane, C5H12. 

Effect of molecular shape. For a pair of nonpolar substances with the same molar mass, stronger attractions occur for a molecular shape that has more area over which the electrons can be distorted. For example, the two five-carbon alkanes, n-pentane and neopentane (2,2-dimethylpropane) are structural isomers— same molecular formula (C5H12) but different properties. n-Pentane is more cylindrical and neopentane more spherical (Figure 12.15). Thus, two -pentane molecules make more contact than do two neopentane molecules, so dispersion forces act at more points, and n-pentane has a higher boiling point. 

Recall from Section 3.2 that two or more compounds with the same molecnlar formula but different properties are called isomers. Those with different arrangements of bonded atoms are constitutional (or structural) isomers alkanes with the same number of C atoms but different skeletons are examples. The smallest alkane to exhibit constitutional isomerism has fonr C atoms two different compounds have the formula C4H10 (Table 15.3). The unbranched one is butane (common name, n-butane n- stands for normal, or having a straight chain), and the other is 2-methylpropane (common name, wobntane). Similarly, three compounds have the formula C5H12. The unbranched isomer is pentane (common name, n-pentane) the one with a methyl group at C-2 of a four-C chain is 2-methylbntane (common name, isopentane). The third isomer has two methyl branches on C-2 of a three-C chain, so its name is 2,2-dimethylpropane (common name, neopentane). 

Butane and isobutane are structural isomers, molecules with the same molecular formula but different structures. Because of their different structures, they have different properties—indeed they are different compounds. Isomerism is ubiquitous in organic chemistry. Butane has 2 structural isomers. Pentane (C5H12) has 3, hexane (CgHi4) has 5, and decane (C10H22) has 75 ... 

Photochemical chlorination of pentane gave a mixture of three isomenc monochlorides The pnncipal monochlonde constituted 46% of the total and the remaining 54% was approximately a 1 1 mixture of the other two isomers Write structural formulas for the three monochlonde iso mers and specify which one was formed in greatest amount (Recall that a secondary hydrogen is abstracted three times faster by a chlonne atom than a pnmary hydrogen)... 

With the five-carbon alkane, pentane, there are three ways to draw the structural formula of this compound with five carbon atoms and twelve hydrogen atoms. The isomers of normal pentane are isopentane and neopentane. The structural formulas of these compounds are illustrated in Table 2, while typical properties are given in Table 1. 

Table 2. Illustrates the Structural Formulas for Isomers of Pentane.

The chain and branched chain saturated hydrocarbons make up a family called the alkanes. Some saturated hydrocarbons with five carbon atoms are shown in Figure 18-11. The first example, containing no branches, is called normal-pentane or, briefly, n-pentane. The second example has a single branch at the end of the chain. Such a structural type is commonly identified by the prefix iso- . Hence this isomer is called /50-pentane. The third example in Figure 18-11 also contains five carbon atoms but it contains the distinctive feature of a cyclic carbon structure. Such a compound is identified by the prefix cyclo in its name—in the case shown, cyclopentane. 

Methane, CH4, has one carbon atom. The next two members of the alkane family are ethane, C2H6, and propane, C3H8. Molecules of these compounds contain chains of two carbon atoms and three carbon atoms, respectively. Alkanes with more than three carbon atoms have more than one isomer. There are two structural formulas for butane, C4H10, and three structural formulas for pentane, C5H12. 

Write structural formulas for the three isomers of pentane. 

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