Pentane molecular formula

Three isomeric alkanes have the molecular formula C5H12 The unbranched isomer is as we have seen n pentane The isomer with a single methyl branch is called isopen tane The third isomer has a three carbon chain with two methyl branches It is called neopentane... 

There are three isomeric pentanes, ie, saturated aHphatic hydrocarbons of molecular formula C H 2- They are commonly called / -pentane [109-66-0] isopentane [78-78-4] (2-methylbutane), and neopentane [463-82-1] (2,2-dimethylpropane). 

The next six alkanes are named pentane, hexane, heptane, octane, nonane, and decane. Their molecular formulas are CjHij, C5H14, CjHjg, C Hjg and... 

Note that whereas n-, neo-, and isopentanes have the same molecular formula, C5H12, and are therefore isomers, cyclopentane has the formula C5H10, and so is not an isomer of the open-chained pentanes. 

You can refer to the same molecule in a number of different ways. For example, you can refer to pentane by its name (ahem. .. pentane)] by its molecular formula, CjHj2 or by the complete structure in Figure 6-2. Clearly, these names include different levels of structural detail. A condensed structural formula is another naming method, one that straddles the divide between a molecular formula and a complete structure. For pentane, the condensed structural formula is CH3CH2CH2CH2CH3. This kind of formula assumes that you understand how straight-chain alkanes are put together. Here s the lowdown ... 

Continuing in the alkane series (also called the paraffin series because the first solid hydrocarbon in the series is paraffin, or candle wax), the next compound is pentane. This name is derived from the Greek word penta, for five. As its name implies, it has five carbon atoms, and its molecular formula is C,H12. From pentane on, the Greek prefix for the numbers five, six, seven, eight, nine, ten, and so on are used to name the alkanes, the Greek prefix corresponding to the number of carbon atoms in the molecule. The first four members of the alkane series do not use the Greek... 

Hydrocarbons also differ from one another in the way the carbon atoms connect to each other. Figure 12.1 shows the three hydrocarbons n-pentane, wo-pentane, and neo-pentane. These hydrocarbons all have the same molecular formula, CSH]2, but are structurally different from one another. The carbon framework of n-pentane is a chain of five carbon atoms. In zro-pentane, the carbon chain branches, so that the framework is a/o r-carbon chain branched at the second carbon. In neo-pentane, a central carbon atom is bonded to four surrounding carbon atoms. 

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. 

The strength of the London interaction also depends on the shapes of the molecules. Both pentane (8) and 2,2-dimethylpropane (9), for instance, have the molecular formula C5H12, so they each have the same number of electrons. 

Structural (or constitutional) isomers are compounds with the same molecular formulas but different structural formulas (that is, different arrangements of the atoms in the molecule). Isomerism is especially important in organic chemistry because of the capacity of carbon atoms to be arranged in so many different ways continuous chains, branched chains, and rings. Structural formulas can be written so that every bond is shown, or in various abbreviated forms. For example, the formula for n-pentane (n stands for normal) can be written as ... 

Given a line formula, such as -— (pentane), write the complete structure and clearly show the arrangement of atoms in the molecule. Tell how many hydrogens are attached to each carbon, what the molecular formula is, and what the functional groups are. 

The next six alkanes are named pentane, hexane, heptane, octane, nonane, and decane. Their molecular formulas are C5HI2, C6H14, C7H16, CaHJg, CjH, and C10H22. The alkanes do not stop at the ten-carbon chain however. Since these first ten represent flammable gases and liquids and most of the derivatives of these... 

In the previous section, we mentioned that different molecules, isomers, can have the same molecular formula but have a different structure. We saw that butane, C4H10, has two isomers—butane (also known as n-butane) and 2-methylpropane. As molecules get longer, more and more isomers become possible. In the first sample, we will consider the number of isomers of pentane. 

Constitutional isomers may differ in ways other than the branching of their carbon chain. They may differ in the position of a double bond or other group or by having a ring or some other feature. Notice how the following constitutional isomers all differ by the ways in which atoms are bonded to other atoms. (Check the number of hydrogens bonded to each carbon.) These compounds are not isomers of the pentanes just shown, however, because these have a different molecular formula (C5H10). 

Although we have derived the CnH2n+2 formula using the unbranched n-alkanes, it applies to branched alkanes as well. Any isomer of one of these n-alkanes has the same molecular formula. Just as butane and pentane follow the C H2 +2 rule, their branched isomers isobutane, isopentane, and neopentane also follow the rule. 

So, how does one go about naming all these organic molecules To address that, let s look at the organic molecule pentane. Its molecular formula is and Figure 7.18... 

Pentane has three ismners whose structural formulas are shown here. Again each of these isomers has the molecular formula CbHi2. 

Problem 9.17 Compare the molecular formulas of (a) //-hexane and c>do-hexare (b) //-pentane and c>cIopentane (c) 1-hexene and cydohexene (d) dodecane, n-hex>lcyclohexane, and c>cIohcx>lcydohcxanc. (c) In general, how can you deduce the number of rmgs in a compound from its molecular formula and degree of unsaturation ... 

All three have five carbon atoms and 12 hydrogen atoms, so they have the molecular formula C5H12. However, as you can see, these models represent three different arrangements of atoms, pentane, 2-methylbutane, and 2,2-dimethylpropane. These three compounds are isomers. Isomers are two or more compounds that have the same molecular formula but different molecular structures. Note that cyclopentane and pentane are not isomers because cyclopentane s molecular formula is C5H10. 

Despite their identical molecular formulas, isomers have different properties. The boiling and melting points of 2-methylpropane and butane are different, as are their densities and solubilities in water. In addition, their chemical reactivity is different. Figure 18.3 shows some property differences in the isomers of pentane. 

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. 

There are three alkanes with molecular formula C5H12. Pentane is the straight-chain alkane. Isopentane, as its name indicates, has an iso stmctural unit and five carbon atoms. The third isomer is called neopentane. The structural unit with a carbon surrounded by four other carbons is called neo. ... 

Methylbutane has the same molecular formula as pentane, so it, too, has a molecular ion with m/z = 72 (Figure 13.3). Its mass spectmm is similar to that of pentane, with one notable exception The peak at m/z = 57 (M — 15) is much more intense. 

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. 

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