Prefixes, carbon chain length

Numbered peaks refer to the carbon chain length of (no prefix) dicarboxylic acids, (T prefix) tricarboxylic acids and (0 prefix) oxirane acids. X identifies 1,2-epoxy-1,1,2,3-propanetetracarboxylic acid. 

It is important to learn the prefixes for the carbon chain lengths. We will use them in the nomenclature for all organic molecules. 

Carbon Chain Length and Prefixes Used in the i.U.P.A.C. Nomenciature System... 

A shorthand nomenclature is in common usage for fatty acids. They are written as two numbers separated by a colon. The number before the colon indicates the carbon chain length, and the figure after corresponds to the number of double bonds. Additional figures in parentheses show the position of double bonds, and the letters c, t, a, and e, show whether the bond is c/5-olefinic, rra 5-olefinic, acetylenic, or ethylenic. The position of the double bonds is numbered fi om the carboxyl group, but where it is more meaningful to number from the methyl end it is prefixed by o>. These abbreviations... 

The structure of the normal butane molecule, /1-C4H10, is shown in the adjacent drawing. (The prefixed letter n in the formula is the abbreviation for normal.) The bond lengths and bond angles have the same values as in ethane. The zigzag chain of carbon atoms and the positions of the hydrogen atoms correspond to the stable (staggered) orientation about each of the four carbon-carbon bonds. The n-butane molecule thus presents us with no surprises. 

First, we need to define the names of branches (see graphic, next page). Chemists use the same prefixes to indicate the length of the branch, but now the suffix is -yl instead of -ane. So methane (CH4), when it s a branch off of a chain of carbon atoms, becomes methyl (-CH3), ethane (CH3CH3) becomes ethyl (-CH2CH3), and so on. 

Select the longest continuous chain of carbon atoms as the parent compound, and consider all alkyl groups attached to it as branch chains or substituents that have replaced hydrogen atoms of the parent hydrocarbon. If two chains of equal length are found, use the chain that has the larger number of substituents attached to it as the parent compound. The alkane s name consists of the parent compound s name prefixed by the names of the alkyl groups attached to it. 

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