formula. which differ in the order of attachment of the individual atoms are called constitutional isomers. An example of the three possible constitutional isomers of pentane (CH) are shown below. 人 Although there are only three constitutional isomers for pentane, for alkanes having larger numbers of carbons, the number of isomers is staggering: for C,he there are over 4 billion possible constitutional isomers In order to be able to communicate chemical information it is essential to have a systematic set of rule defining nomenclature for organic compounds. As mentioned previously, the IUPAC system of nomenclature accomplishes this and the rules for naming linear and branched alkanes are given below The IUPAC name for an alkane is constructed of two parts: 1)a prefix (meth.. eth... prop.. etc )which indicates the number of carbons in the main, or parent, chain of the molecule, and 2) the suffix .. ane to For branched-chain alkanes, the name of the parent hydrocarbon is taken from the longest continuous chain of carbon atom Groups attached to the parent chain are called subs titue nts and are named based on the num ber of carbons in the longest chain of that substituent, and are numbered using the number of the carbon atom on the parent chain to which they are attached. In simple alkanes, substituents are called alkyl groups and are named using the prefix for the number of carbons in their main chan and the suffix.yl. For example, methyl, ethyl, propyl, dodecyl,etc CH3 -CH2 -CH-CH3 CH3 -CH2 -CH-CH2CH If the same substituent occurs more than once in a molecule, the num ber of each carbon of the parentformula, which differ in the order of attachment of the individual atoms, are called constitutional isomers. An example of the three possible constitutional isomers of pentane (C5H1 2) are shown below. Although there are only three constitutional isomers for pentane, for alkanes having larger numbers of carbons, the number of isomers is staggering; for C30H6 2, there are over 4 billion possible constitutional isomers. In order to be able to communicate chemical information, it is essential to have a systematic set of rule defining nomenclature for organic compounds. As mentioned previously, the IUPAC system of nomenclature accomplishes this and the rules for naming linear and branched alkanes are given below: • The IUPAC name for an alkane is constructed of two parts: 1) a prefix (meth... eth... prop..., etc.) which indicates the number of carbons in the main, or parent, chain of the molecule, and 2) the suffix ...ane to indicate that the molecule is an alkane. • For branched-chain alkanes, the name of the parent hydrocarbon is taken from the longest continuous chain of carbon atoms. • Groups attached to the parent chain are called substituents and are named based on the number of carbons in the longest chain of that substituent, and are numbered using the number of the carbon atom on the parent chain to which they are attached. In simple alkanes, substituents are called alkyl groups and are named using the prefix for the number of carbons in their main chain and the suffix ...yl. For example, methyl, ethyl, propyl, dodecyl, etc. • If the same substituent occurs more than once in a molecule, the number of each carbon of the parent