Names of Straight-Chain Alkanes

For branching compounds, the parent structure is the longest continuous chain present in the compound. Consider the compound to have been derived from this structure by replacement of hydrogen by various alkyl groups. Arabic number prefixes indicate the carbon to which the alkyl group is attached. Start numbering at whichever end of the parent structure that results in the lowest-numbered locants. The arabic prefixes are listed in numerical sequence, separated from each other by commas and from the remainder of the name by a hyphen. 

If the same alkyl group occurs more than once as a side chain, this is indicated by the prefixes di-, tri-, tetra-, etc. Side chains are cited in alphabetical order (before insertion of any multiplying prefix). The name of a complex radical (side chain) is considered to begin with the first letter of its complete name. Where names of complex radicals are composed of identical words, priority for citation is given to that radical which contains the lowest-numbered locant at the first cited point of difference in the radical. If two or more side chains are in equivalent positions, the one to be assigned the lowest-numbered locant is that cited first in the name. The complete expression for the side chain may be enclosed in parentheses for clarity or the carbon atoms in side chains may be indicated by primed locants. 

These trivial names may be used for the unsubstituted hydrocarbons only  

Univalent radicals derived from saturated unbranched alkanes by removal of hydrogen from a terminal carbon atom are named by adding -yl in place of -ane to the stem name. Thus the alkane ethane becomes the radical ethyl. These exceptions are permitted for unsubstituted radicals only  

Isopropyl (CH3)2CH— Isobutyl (CH3)2CHCH2— sec-Butyl CH3CH2CH(CH3)— teri-Butyl (CH3)3C— 

---

The names of straight-chain alkanes are given in Table 18.1 they all end in -ane. Name a hydrocarbon side chain as a substituent by changing the ending -ane to -yl (as in the last two columns in Table 18.1). 

Table 3.3 Names of Straight-Chain Alkanes Number of carbons (/ ) Name...

To name a straight-chain alkane, simply match the appropriate chemical prefix with the suffix -ane. The prefixes, which relate to the number of Ccirbons in the continuous chain, are listed in Table 64. 

Table 2-5 Names and Physical Properties of Straight-Chain Alkanes, C H2,+2 ...

Number of carbon atoms Molecular formula of straight-chain alkane Name of alkane Stem used in naming... 

Straight-chain alkanes are named according to the number of carbon atoms they contain, as shown in Table 3.3. With the exception of the first four compounds—methane, ethane, propane, and butane—whose names have historical roots, the alkanes are named based on Greek numbers. The suffix -one is added to the end of each name to indicate that the molecule identified is an alkane. Thus, pentane is the five-carbon alkane, hexeme is the six-carbon alkane, and so on. We ll soon see that these alkane names form the basis for naming all other organic compounds, so at least the first ten should be memorized. 

As the name hydrocarbon suggests, these partners may be hydrogen or carbon. The simplest of the alkanes, called continuous or straight-chain alkanes, consist of one straight chain of carbon atoms linked with single bonds. Hydrogen atoms fill all the remaining bonds. 

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. 

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 ... 

To names simple alkanes the longest carbon chain is selected. The names of the simplest straight chain alkanes are shown in the following figure ... 

IUPAC Names of Dicarboxylic Acids Aliphatic dicarboxylic acids are named simply by adding the suffix -dioic acid to the name of the parent alkane. For straight-chain dicarboxylic acids, the parent alkane name is determined by using the longest continuous chain that contains both carboxyl groups. The chain is numbered beginning with the carboxyl carbon atom that is closer to the substituents, and these numbers are used to give the positions of the substituents. 

Recall that carbon can bond to form long, continuous, chain-like structures. Alkanes that bond in this way are called straight-chain alkanes. (They are also called unbranched alkanes.) Straight-chain alkanes are the simplest alkanes. Table 13.2 lists the names of the first ten straight-chain alkanes. 

The naming rules for straight-chain alkanes can, with a few additions, help you recognize and name other organic compounds. You now know that the name of a straight-chain alkane is composed of a root (such as meth-) plus a suffix (-ane). Earlier in the chapter, you saw the isomers of C6Hi4. Figure 13.13 shows one of them, called 2-methylpentane. 

Straight-chain alkanes are named according to the number of carbons in their chain. 

Straight chain alkanes take n- in the front of name, which means "normal" and shows the alkane is unbranched. 

For example, the names of all alkanes end with the suffix -ane. The simplest alkane is methane, CH4, the main component of natural gas. Table 3 lists the names and formulas for the first 10 straight-chain alkanes. For alkanes that consist of five or more carbon atoms, the prefix comes from a Latin word that indicates the number of carbon atoms in the chain. 

Each alkane-based substituent group branching from the parent chain is named for the straight-chain alkane having the same number of carbon atoms as the substituent. The ending -ane is replaced with the letters -yl, as shown in the following diagram. 

Count the number of carbon atoms in the longest continuous chain. Use the name of the straight-chain alkane with that number of carbons as the name of the parent chain of the structure. 

---