Branched alkanes, naming

The lUPAC rules name branched alkanes as substituted derivatives of the unbranched alkanes listed in Table 2 2 Consider the CgHi4 isomer represented by the structure... 

So far the only branched alkanes that we ve named have methyl groups attached to the mam chain What about groups other than CH3 What do we call these groups and how do we name alkanes that contain them d... 

By combining the basic principles of lUPAC notation with the names of the various alkyl groups we can develop systematic names for highly branched alkanes We 11 start with the following alkane name it then increase its complexity by successively adding methyl groups at various positions... 

Alkanes are a class of saturated hydrocarbons with the general formula C H2n. -2- They contain no functional groups, are relatively inert, and can be either straight-chain (normal) or branched. Alkanes are named by a series of IUPAC rules of nomenclature. Compounds that have the same chemical formula but different structures are called isomers. More specifically, compounds such as butane and isobutane, which differ in their connections between atoms, are called constitutional isomers. 

This base name will be modified by adding the names of the branches (substituent groups) in front of the base name. Alkane branches are named by taking the name of the alkane that contains the same number of carbon atoms, dropping the — ane ending and adding —yl. Methane becomes methyl, propane becomes propyl, etc. If there is more than one branch, list them alphabetically. 

When naming branched alkanes, be sure to consider the branches when finding the longest carbon chain. The longest chain isn t always the one in which the carbon atoms all lie in a horizontal line. 

S Branched alkanes. Branched-chain alkanes can be considered to be constituted of a principal chain and side-chains. They are named by using a precise set of operations ... 

The following example illustrates the step-by-step construction of the name of the branched alkane shown below. 

Other types of alkanes include closed circles and branched chains, but we discuss the straight-chain alkanes here because they make clecir the basic strategy for naming hydrocarbons. From the standpoint of nciming, the hydrogen atoms in a hydrocarbon are more or less filler atoms. Alkanes names cire based on the largest number of consecutively bonded carbon atoms, so the ncime of a hydrocarbon tells you about that molecule s structure. 

Branched alkanes are named using a four-step process ... 

The following branched alkanes have lUPAC-accepted common names ... 

To name branched alkanes, additional steps to name the branching group and locate it on the root chain are needed. 

The most widely applied isomerization catalysts are platinum-promoted solid acids, namely chlorinated alumina1,2 and mordenite.3 5 The former catalysts require the continuous addition of chlorine-containing compounds, are moisture-sensitive and are poisoned by sulfur impurities.6 They are also highly corrosive and hence, environmentally hazardous. Zeolite catalysts are significantly less active and have to be operated at higher temperatures (500-550 K). As a consequence of thermodynamic limitations only relatively low yields of the target branched alkanes can be achieved under these conditions. 

In branched alkanes, if there is one methyl (—CH3) group on the second carbon, the "iso" prefix is added to the front of the parent name. 

Alkyl groups having more than four carbons and no branches are named as described in Section 4.4A change the -ane ending of the parent alkane to the suffix -yl. Thus the seven-carbon alkyl group CH3CH2CH2CH2CH2CH2CH2— is called heptyl. 

If another shorter alkane is attached to one of the nonterminal carbons, forming a branched alkane, the longest carbon chain forms the basis of the name, and the attached alkane is the prefix as shown in Figure 1.6. Figure 1.7 shows the structural formula of 2-methyl-2,3-dibromopentane in four steps. 

In the structural formula above, all the numbered carbon atoms, with one exception, are bonded only to hydrogen atoms. The one exception is the third carbon atom, which has a —CH3 group attached. This group is known as a methyl group, because it is similar to a methane molecule, but with one less hydrogen atom. Because the methyl group is attached to the third carbon, the complete name for this branched alkane is 3-methylheptane. 

The names of all alkanes end with -ane. Whether or not the carbons are linked together end-to-end in a ring (called cyclic alkanes or cycloalkanes or whether tliey contain side chains and branches, the name of every carbon-hydrogen chain that lacks any double bonds or functional groups will end with the suffix -ane. 

The names of the first ten straight-chain alkanes, shown in Table 18.1, are used as the basis for naming most organic compounds. To name a branched alkane, you must be able to answer three questions about its structure. 

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