Alkanes systematic nomenclature

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. 

In older, less systematic nomenclature, the root counted all the carbons. As an example, butane meant C4H10, with the suffix (word ending) ane indicating an alkane. However, there is more than one structure with... 

The systematic nomenclature for alkenes is quite similar to that for alkanes. 

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

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. 

Methylethyl is the systematic name for this group isopropyl is a common name. Systematic nomenclature for alkyl groups is similar to that for branched-chain alkanes, with the provision that numbering always begins at the point where the group is attached to the main chain. There are four C4 groups. 

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. 

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. 

Like other compounds, alcohols may have both systematic and common names. Systematic nomenclature treats alcohols as derivatives of alkanes. The ending -e of the alkane is replaced by -ol. Thus, an alkane is converted into an alkanol. For example, the simplest alcohol is derived from methane methanol. Ethanol stans from ethane, propanol from propane, and so on. In more complicated, branched systans, the name of the alcohol is based on the longest chain containing the OH substituent— not necessarily the longest chain in the molecule. 

A single alkane may have several different names a name may be a common nfflne, or it may be a systematic name developed by a well-defined set of rules. The most widely used system is lUPAC nomenclature. Table 2.6 summarizes the rules for alkanes and cycloalkanes. Table 2.7 gives the r-ules for naming alkyl groups. 

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