Systematic nomenclature of alkanes

A systematic method for naming alkanes (and other organic compounds) that is simple to use and minimizes memorization was developed by the International Union of Pure and Applied Chemistry and is called the IUPAC nomenclature. To make it easier for the chemists of that time to learn, it incorporated common nomenclature wherever possible. 

Before we look at the steps for naming alkanes, let s see what an IUPAC name looks like. Basically, each alkane is considered a straight-chain carbon backbone on which 

The amount of heat produced by burning (heat of combustion) varies considerably with the type of fuel that is burned. Values for some fuels of interest, in kilocalories (or kilojoules) per gram, are shown in the table that follows. 

The roots for backbones containing one through four carbons come from the common names for these alkanes. You probably recognize most of these already. For backbones of five or more carbons, systematic roots (derived from Greek) are employed. 

Find the longest continuous carbon chain in the compound. The number of carbons in this backbone determines the root (see Table 5.3). If there are two (or more) chains of equal length, choose the one with the greater number of branches. (This results in simpler branching groups that are easier to name.) 

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Both common and systematic names of compounds are used throughout this volume, depending on which the Editor-in-Chief feels is most appropriate. Preparations appear in the alphabetical order of names of the compound or names of the synthetic procedures. The Chemical Abstracts indexing name for each title compound, if it differs from the title name, is given as a subtitle. Because of the major shift to new systematic nomenclature adopted by Chemical Abstracts in 1972, many common names used in the text are immediately followed by the bracketed, new names. Whenever two names are concurrently in use, the carre CChemical Abstracts name is adopted. The prefix n- is deleted from -alkanes and w-alkyls. All reported dimensions are now expressed in S st me International units. 

Combining the names of functional groups with the names of the parent alkanes generates a powerful systematic nomenclature for naming w organic compounds. 

Tire systematic lUPAC nomenclature for carboxylic acids requires the longest carbon chain of the molecule to be identified and the -e of alkane name to be replaced with -oic acid. 

The systematic approach for naming dicarboxylic acids (alkanes with carboxylic acids on either end) is the same as for carboxylic acids, except that the suffix is -dioic acid. Common name Nomenclature of dicarboxylic acids is aided by the acronym OMSGAP (Om s Gap), where each letter stands for the first letter of the first seven names for each dicarboxylic acid, starting from the simplest. 

This method of nomenclature is called systematic nomenclature. It is also called lUPAC nomenclature because it was designed by a commission of the International Union of Pure and Applied Chemistry (abbreviated lUPAC and pronounced eye-you-pack ) at a meeting in Geneva, Switzerland, in 1892. The lUPAC mles have been continually revised by the commission since then. Names such as isobutane and neopentane—nonsystematic names—are called common names and are shown in red in this text. The systematic or lUPAC names are shown in blue. Before we can understand how a systematic name for an alkane is constructed, we must learn how to name alkyl substituents. 

In systematic nomenclature, a carboxylic acid is named by replacing the terminal e of the alkane name with oic acid. For example, the one-carbon alkane is methane, so the one-carbon carboxylic acid is methano/c acid. 

The nomenclature of FA reflects the long history of their smdy and description. Most FA were originally described under trivial names prior to the adoption of the international molecular nomenclature rules in 1892 (Table 3.1). Even after adopting the International Union of Pure and Applied Chemistry (lUPAC) system for nomenclature (lUPAC-IUB, 1977), the habit of assigning trivial names to FA continues. The basis of the systematic nomenclature system is an extension of that accepted for hydrocarbon (alkane/alkene) naming. Hence, the descriptive name is based on the number of carbon atoms contained in the molecule, with the suffix -e replaced with -oic acid. However, in most instances, FA are referred to by their formula notations. As is the case with systematic and trivial names, there exists an lUPAC accepted formula notation nomenclature and several earher versions (Table 3.2). Each system... 

Little needs to be added to the text descriptions for these two topics. The nomenclature rules are straightforward. Again, a small number of common names are still in use and must be learned. However, the systematic nomenclature is logical and easy to master. Note that alkenes, like cyclic alkanes, have two distinct sides, and therefore substituents may be either cis or trans to each other. For alkenes, however, the cis and trans designations should be restricted to molecules with exactly two substituents, one on each of the two doubly bonded carbons. If more substituents are present, the E,Z nomenclature system should always be applied. 

Systematically naming all the various types of organic compounds would probably take another book, lUPAC Nomenclature For Dummies. Here, I just show you the rules for naming simple alkanes (even the naming of alkanes can get complicated, so it s important to use the KISS Rule — Keep It Simple, Silly) ... 

The systematization for the nomenclature of acyclic alkanes (lUPAC) has the following rules ... 

As already intimated above, a more systematic nomenclature (used by Chemical Abstracts, Appendix II) is closely related to what you have already learned about alkane nomenclature in that the longest chain is used as the parent and the final e in the name of the alkane is replaced by amme. Thus, CH3CH2CH2CH2N(CH3)2 is N, A-dimetbylbutanamine, while CH3NH2 is metbanamine, (CH3)2NH is N-metbylmetbanamine, and so on. 

In the lUPAC systematic nomenclature, the final e of the parent alkane is dropped, the suffix oic is added, and the separate word acid is added. Diacids are named similarly, except that the suffix is dioic, and the final e is not dropped. Cyclic acids are named as cycloalkanecarboxylic acids. Tahle 17.1 shows some common mono-and diacids along with some of their physical properties and common names, many of which are stfil used. 

With the isolation and preparation of thousands of new organic compounds it became clear that each organic compound must have an unambiguous name, derived from a set of easily remembered rules. A systematic method of naming compounds was developed by the /ntemational f/nion of Pure and Applied Chemistry. It is referred to as the lUPAC system of nomenclature how it can be used to name alkanes is explained in Sections 4.4 and 4.5. 

In systematic nomenclature, nitriles are named by adding nitrile to the name of the parent alkane. Notice in the following examples that the triple-bonded carbon of the nitrile group is included in the number of carbons in the longest continuous chain. 

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