Isomers of butane

Compare your isomers of butane and pentane with the isomers of other... 

The propellant mixture present in the can was also detected in the headspace GC/MS analysis. These peaks eluted very early in the chromatogram and were not well separated. The propellant was a mixture primarily of propane and the isomers of butane and pentane. 

In contrast, the constitutional isomers of butane have different physical properties. Thus, n-butaneboils at-0.5°C but Mobutane boils at-12 C. Although the composition of the two butanes is the same, their three-dimensional geometries are quite different as a result of different patterns of chemical bonding. Note, for example, that one of the carbon atoms of wobutane makes bonds to three other carbon atoms. No carbon atom in n-butane does. Thus, the chemistry of the two butanes differs in many ways, but not as a consequence of handedness. They are simply examples of different ways to put together the same set of structural elements. Think about a Lego set. 

The molecular formulas just shown for 10 alkane hydrocarbon molecules represent the proportions of carbon to hydrogen in each molecule. These formulas do not reveal much about their structures, but rather indicate the proportions of each element in their molecules. Each molecule may have several different structures while still having the same formula. Molecules with different structures but the same formulas are called isomers. For example, n-butane is formed in a straight chain, but in an isomer of butane, the CH branches off in the middle of the straight chain. Another example is ethane, whose isomeric structure can be depicted as H,C H,C-CH,. The name for the normal structure sometimes uses n in front of the name. 

Figure 6-4 Both molecules are the same isomer of butane.

Figure 1. Illustrates the structural formulas for isomers of butane and pentane.

Propane has the formula C3H8 and butane C4H8. There are two isomers of butane, / -butane and isobutane (2-methylpropane). Propane and the butane isomers are gases at room temperature and atmospheric pressure like methane and ethane, all three are asphyxiants. A high concentration of propane affects the central nervous system. There are essentially no known systemic toxicological effects of the two butane isomers behavior similar to that of propane might be expected. 

Explain why there is no cis- nor trans- isomer for the open chain isomer of butane, CH3CH2CH2CH3, but for 2-butene, CH3CH=CHCH3, there is a cis- and a trans- isomer. 

These two structural formulas are isomers of butane. Although it may seem that there are other possibilities, the next two structural formulas are really not different from the two shown above. The structure shown below is the same as the first one shown above. The carbon atoms are still in a line, but the line bends, which is permissible. 

These two compounds are isomers because they are different compounds with different properties, yet they have the same molecular formula. They are constitutional isomers because their atoms are connected differently. The first compound (n-butane for normal butane) has its carbon atoms in a straight chain four carbons long. The second compound ( isobutane for an isomer of butane ) has a branched structure with a longest chain of three carbon atoms and a methyl side chain. 

If all alkanes had unbranched (straight-chain) structures, their nomenclature would be simple. Most alkanes have structural isomers, however, and we need a way of naming all the different isomers. For example, there are two isomers of formula C4H10. The unbranched isomer is simply called butane (or n-butane, meaning normal butane), and the branched isomer is called isobutane, meaning an isomer of butane. ... 

For example, the isomer of butan-2-ol that rotates the plane of polarized light clockwise is named ( + )-butan-2-ol or tZ-butan-2-ol. Its enantiomer, ( —)-butan-2-ol or Z-butan-2-ol, rotates the plane counterclockwise by exactly the same amount. 

Nomenclature. The question arises as to how the various isomers of a hydrocarbon can be named and distinguished. When the number of poffiible isomers is small this offers no problem. The two isomers of butane are named normal butane and isobutane. The three isomers of pentane are known as normal pentane, isopentane, and neopentane. 

Infrared absorption peaks [Table], 234 Inhibitors, 39 Initiation, 34 Intermediates, 31, 41 Inorganic esters, 262, 272, 276 Inversion, 124, 139 Ion-dipole attraction, 23 Ionic bonds, 6 Isobutyl group, 146 Isolated bonds, 146 Isomerism, 2 alkyl halides, 118 cis-trans, 88 geometric, 88 optical, 70 Isomerization, 202 Isomers of butane, 50 of heptane, 66 of 2-hexene, 11 of pentane, 50 Isoniazide, 457 Isoprene rule, 181 Isopropyl group, 54 Isoquinoline, 458 Isotope effect, 130 lUPAC, 56... 

Zemski KA, Justes DR, Bell RC, Castleman AW Jr (2001) Reactions of niobium and tantalum oxide cluster cations and anions with n-butane. J Phys Chem A 105 4410 Bell RC, Castleman AW Jr (2002) Reactions of vanadium oxide cluster ions with 1, 3-butadiene and isomers of butane. J Phys Chem A 106 9893... 

In the example given above, there were eight possible arrangements of the constituent atoms that corresponded to the same molecular formula. Each one of these possible arrangements is called an isomer. Isomers may be divided into two fundamental classes. The first type consists of those isomers which differ in the exact number of each type of bond that connects the atoms in the various molecules. These are called structural isomers, because the structure is different in each one. In the above example, the ethers and the alcohols are structural isomers of each other. In the second type, the isomers all have exactly the same connectivity, i.e. the manner and order in which the atoms are connected to each other are the same, but differ only in the precise position that each group occupies relative to all the others in the molecule. These are called stereoisomers. In the above example, the two isomers of butan-2-ol are stereoisomers. 

In order to proof the applicability of the mentioned approaches and to study the incorporation of different gases in the hydrate lattices depending on their properties (solubility, dimension, etc.) we performed investigations on gas hydrates which have been synthesized from gas mixtures as a free gas phase and water. The gas mixtures contain besides methane the isomers of butane (n-butane iso-butane) and pentane (iso-pentane, 2,2-dimethylpropane), respectively. The exact compositions of the gas mixtures are given in table 1. The experiments and results are described in detail in the diploma thesis of M. Luzi. ... 

Isomers are two molecules with the same molecular formula but different physical arrangements. Constitutional isomers have their atoms arranged in a different order. A constitutional isomer of butane has a main chain that is forked at the end and one carbon shorter in its main chain than butane. 

Problem 4.1 (a) Use the superscripts 1, 2,3, and so on to indicate the different kinds of equivalent H atoms in propane, CH3CH2CH3. (b) Replace one of each kind of H by a CH3 group, (c) How many isomers of butane, C4H10, exist ... 

For the first three compounds, there is only one possible arrangement of the atoms. However, for C4H10 there are two possible arrangements. How do we know which is correct The problem is solved by using the structural formula, which shows each atom and bond in a molecule. The following are the structural formulas for methane, ethane, propane, and the two isomers of butane ... 

Conformational isomers of butane. The hydrogen atoms are much more crowded in the conformation depicted in (b) compared with the conformation shown in (a). The form shown in (a) is energetically favored. 

This same situation is also reflected in the investigations by Dickinson and Dalziel 315,323) on a number of secondary alcohols. They found that the yeast enzyme is completely inactive toward those secondary alcohols where both alkyl groups are larger than methyl and active with only one isomer of butan-2-ol and octan-2-ol. This is in contrast to LADH which is active toward all substrates mentioned. 

Hydrocarbon structures may be altered so that their physical characteristics make them more economically valuable. One such alteration is called branching, or isomers. An isomer is a hydrocarbon that has the same molecular formula, i.e., the same number of hydrogen atoms and carbons, but a different structural form. The molecular formula for butane is C4H10 the molecular formula for the isomer of butane would be t-C4Hio (Figure 4.9). The formula stays the same, but the structure... 

---