Alkyl substituents nomenclature

Common Names The common names of alkynes describe them as derivatives of acetylene. Most alkynes can be named as a molecule of acetylene with one or two alkyl substituents. This nomenclature is like the common nomenclature for ethers, where we name the two alkyl groups bonded to oxygen. 

Readers who are not completely familiar with the nomenclature are again urged to refer to the article by Adams. It has been agreed that the term carborane should be used for clovo or near-c/boron-carbon hydrides in which carbon atoms are in the main skeleton. The alkyl-substituted borons, e.g., ethyldecaborane are not covered by the generic name carboranes. There is still some confusion concerning those carboranes with C-alkyl substituents it has been suggested that the C substituents should be indicated separately, e.g., a carborane with an ethyl and propyl substituent may be named C-ethyl,C -propyl-carborane. 

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. 

Names such as isopropyl, sec-butyl, and tert-butyl are acceptable substituent names in the lUPAC system of nomenclature, but systematic substituent names are preferable. Systematic substituent names are obtained by numbering the alkyl substituent starting at the carbon that is attached to the parent hydrocarbon. This means that the carbon that is attached to the parent hydrocarbon is always the number 1 carbon of the substituent. In a compound such as... 

Conventional chemical nomenclature recognises the longest chain of carbon atoms that is terminally substituted. Alkyl groups also attached to this substituted terminal atom are named as substituents. In practice, the conventional approach treats any alkyl substituent to an otherwise substituted alkyl group as a branch unless it occurs at the opposite terminus of the carbon chain in question. Non-carbon substituents are treated the same way as alkyl substituents. 

A primary amine is a compound containing an NH2 group connected to an alkyl group. lUPAC nomenclature allows two different ways to name primary amines. While either method can be used in most circumstances, the choice most often depends on the complexity of the alkyl group. If the alkyl group is rather simple, then the compound is generally named as an alkyl amine. With this approach, the alkyl substituent is identified followed by the suffix "amine." Below are several examples. 

Substitutive nomenclature of alkyl halides treats the halogen as a halo—(fluoro chloro bromo or lodo ) substituent on an alkane chain The carbon chain is numbered m the direction that gives the substituted carbon the lower number... 

The position of the substituents is given according to IUPAC nomenclature using the prefixes 1-, 3-, and 5-. Formazans unsubstituted in the 1- and 5-positions and 1,5-dialkyl-substituted formazans are unknown. Aryl or heteroaryl groups are the most common 1,5-substituents. The 3- or meso position can be occupied by a variety of substituents (e.g., aryl, heteroaryl, H, OH, SR, halogen, N02, CN, and alkyl). 

For the nomenclature for ethers and alkyl halides the functional group is considered to be a substituent of the main alkane chain. The functional group is numbered and named as a substituent ... 

Deprotonation of a-alkylated acetic acid esters (e.g., the propionic acid ester of Figure 10.13) with LDA at —78°C selectively yields the -enolatcs.Thc quotation marks indicate that this application of the term is based on an extension of the E/Z-nomenclature here, the Cahn-Ingold-Prelog priority of the O I, i1 substituent is considered to be higher than the priority of the OR group. The deprotonation of the ester shown in Figure 10.13 occurs via the strain-free transition state A. The alternative transition state B is destabilized by a 1,3-diaxial interaction. 

There are two ways of naming alkyl halides. The systematic (IUPAC) nomenclature treats an alkyl halide as an alkane with a halo- substituent Fluorine is fluoro-, chlorine is chloro-, bromine is bromo-, and iodine is iodo-. The result is a systematic haloalkane name, as in 1-chlorobutane or 2-bromopropane. Common or trivial names are constructed by naming the alkyl group and then the halide, as in isopropyl bromide. This is the origin of the term alkyl halide. Common names are useful only for simple alkyl halides, such as the following ... 

Following the recommended system of nomenclature (reference 6, Chapter 1), the alkyls having two or more different groups on the silicon are named as derivatives of silane and the term silicon tetra- is reserved for those compounds in which the four substituents are all alike. 

In alkanes or alkyl systems, an infinite number of conformations is possible as a result of rotation about CC single bonds, and each conformation has a certain potential energy. Two conformational extremes, one of low (minimal steric interaction between bond substituents) and one of high (maximal steric interaction) potential energy, have been described for these systems. These are depicted as Newman projections in Fig. 17. A more recent nomenclature system for conformational isomers arising from energy barriers associated with rotation about a CC single bond is shown in Fig. 18. In this case, the most stable conformer is... 

---