Naming Substituents

The lowest-numbered locant for substituents named as prefixes, hydro prefixes, -ene, and -yne, all considered together in one series in ascending numerical order... 

The lowest locant for that substituent named as prefix which is cited first in the name... 

Quaternary ammonium compounds are usually named as the substituted ammonium salt. The anion is Hsted last (3). Substituent names can be either common (stearyl) or lUPAC (octadecyl). If the long chain in the compound is from a natural mixture, the chain is named after that mixture, eg, taHowalkyL Prefixes such as di- and tri- are used if an alkyl group is repeated. Complex compounds usually have the substituents Hsted in alphabetical order. Some common quaternary ammonium compounds and their appHcations in patent Hterature are Hsted in Table 1. 

Cyclic acetals formed by the reaction of saccharides or saccharide derivatives with aldehydes or ketones are named in accordance with 2-Carb-24.1, bivalent substituent names (formed by general organic nomenclature principles) being used as prefixes. In indicating more than one cyclic acetal grouping of the same kind, the appropriate pairs of locants are separated typographically when the exact placement of the acetal groups is known. 

A location number is necessary to indicate the point of attachment of a particular substituent. We assign these numbers by consecutively numbering the carbons of the base hydrocarbon starting at one end of the hydrocarbon chain. Choose the end so that there will be the lowest sum of location numbers for the substituent groups. Place this location number in front of the substituent name and separate it from the name by a hyphen (i.e., 2-methyl). 

The types and position of substituents at the silicon atom are denoted at the beginning of the name. If all the substituents are the same, their position is not necessary to be shown. In this case, the substituent name is preceded by a prefix per- or the total number of substituents is indicated for example, permethyl- , hexaethyl- , octaethyl- , etc. 

The 4e -a, MO 16 of 1 can interact both with a n- and a er-donor substituent. Hence, a-donor substituents have the same effects as 7i-donor substituents, namely a lengthening of vicinal and a shortening of the distal CC bond of 1. 

The foregoing examples illustrate that naming compounds from structures or deducing structures from names requires knowledge of both the parent names and the substituent names of the important types of functional and nonfunctional groups. This information is summarized in the following sections and Table 7-1. 

Class Formula Principal name (suffix)3 Substituent name (prefix)... 

The substituent name for the OH group is hydroxy and should be used whenever the OH group is not the parent function (see Table 7-1). Notice how the precedence rules apply — hydroxy below carboxylic acid and hydroxy below ketone ... 

The substituent name for the RO— function is alkoxy, and it is correct to name R—O—R compounds as alkoxy derivatives of hydrocarbons ... 

Exercise 22-2 How many isomeric products could each of the dimethylbenzenes give on introduction of a third substituent Name each isomer, using chlorine as the third substituent. 

An amide name is based on the name of the carboxylic acid of the same number of carbon atoms, but the -oic ending is changed to amide. Amides with alkyl groups on the nitrogen are substituted amides and are named the same as N-substituted amides, except the parent name is preceded by the name of the alkyl substituent and a capital N precedes the substituent name. 

Of interest also is the synthesis of aminomethylsilanes that have been designed to bear a labile substituent namely [2-(4,5-dihydrofury 1)] at the silicon atom. They are the source of a series of diversely substituted aminomethylsilanes as, for example, Me2HSi-substituted aminomethylsilanes, not readily available in pure form by other means.272... 

RNA modification database at http //medlib.med.utah.edu/RNAmods furnishes information concerning naturally modified nucleosides in RNA (Limbach et al., 1994). After clicking Search, select individual files (pick corresponding radios under categories base type, RNA source, and phylogenetic occurrence) to be accessed, and output options (common name, structures, and/or mass values). Enter partial name (i.e., substituent name such as methyl, thio, etc.) and choose the parent base(s) from which modified nucleosides are derived (Figure 5.8). Click Search button. The tabulated search results based on selected files are returned according to the requested output options. 

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