Numbering prefix substituents

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. 

Selection of the principal chain in unsaturated branched acyclic hydrocarbons. A principal chain must be chosen upon which to base the name of branched unsaturated acyclic hydrocarbons. The general criteria listed in Table 4.10 are applied. Those that are specifically relevant to polyenes and polyynes are criterion (b), which is the maximum number of double and triple bonds considered together criterion (c), which is the maximum length criteria (d), (f) and (g) criterion (h), which is the maximum number of substituents cited as prefixes and criteria (i) and (j). 

When the same number and kinds of substituents are carried by the two aromatic radicals, the IUPAC system simply numbers the substituents in a conventional manner, whereas the Chemical Abstracts system names the compound as an assembly of identical units with the prefix azodi- preceding the name of the unsubstituted parent compound ... 

The prefixes used to designate the number of substituents follow ... 

Structures and the recommended names of compounds belonging to the bomane group of bicyclic terpene hydrocarbons are given in Chart 14. Reasons for coining the name bornane and for the necessity of using the norbomane-type names to systematize the nomenclature of the bicyclo 2.2. [] heptane bicyclics have been presented earlier. Examination of the names in Chart 14 reveals that in the systematic bicyclo 2.2.1 ]heptane names and the recommended norbornane names the prefix numbers for substituents and double bonds and the order of names of substituents are identical. 

If a structure has identical substituents, then the prefixes di-, tri-, tetra-, etc. are used to represent the number of substituents. For example, the structure in figure given below is called 2,2-dimethylpentane and not 2-methyl-2-methylpentane. 

If there is more than one identical substituent the number of substituent is indicated by using prefixes -di, -tri, -tetra and so on. 

The prefix reveals the identity, location, and number of substituents attached to the earbon chain. 

Identify the substituents (e.g. minor functional groups) on the main chain and their number. Two substituents on the same carbon are given the same number. The substituent name and position is the prefix. The names of two or more different substituents should be included in alphabetical order in the prefix (e.g. hydroxy before methyl). 

Name and number all substituents, and add them as prefixes to the "alkanol" name. 

When substituents are alphabetized, ISO- is used as part of the alkyl group name, but the hyphenated prefixes are not. Thus isobutyl is alphabetized with /. but n-butyl, t-butyl, and sec-butyl are alphabetized with b. The number prefixes di-. tri-, tetra-, etc are ignored in alphabetizing. 

No more than one class of suffix designation for substituents is affixed to any stem. All remaining substituents are expressed in prefixes, arranged alphabetic ly. The alphabetical arrangement of prefixes depends only on the root term for the prefix and is independent of the number of substituents of the particular type. For example,/Zworo precedes hydroxy, fluoro precedes dihydroxy, hydroxy precedes methyl, and trihydroxy precedes methyl. 

Select the longest continuous chain of carbon atoms as the parent compound, and consider all alkyl groups attached to it as branch chains or substituents that have replaced hydrogen atoms of the parent hydrocarbon. If two chains of equal length are found, use the chain that has the larger number of substituents attached to it as the parent compound. The alkane s name consists of the parent compound s name prefixed by the names of the alkyl groups attached to it. 

The main chain is numbered in such a way that the first substituent encountered along the chain receives the lowest possible number. Each substituent is then located by its name and by the number of the carbon atom to which it is attached. When two or more identical groups are attached to the main chain, prefixes such... 

When tioo or more substituents are present, list thetn in alphabetical order. When there are two or more of the same substituent, the number of substituents of that type is indicated by a prefix di- (two), tri- (three), tetra- (four), paita-(five), and so forth. Notice how the following example is named ... 

In molecules that contain two or more identical substituents, the prefixes di. tru tetra, penta, and so forth, are used to denote the number of substituents. Numbers are then used to denote their positions. (Note that two substituents may be bonded to the same carbon atom.)... 

Parenthetically, we might note that the prefixes cis- and trans- are ambiguous when naming the diols derived from 1-methylcyclohexene because the ring has three substituents. In such cases, the substituent with the lowest number is taken as the reference substituent, denoted r, and the other substituents are identified as being cis (c) or trans (f) to that reference substituent. When two substituents share the same lowest number, the substituent with... 

In Summary Simple monosubstituted benzenes are named by placing the substituent name before the word benzene. For more highly substituted systems, 1,2-, 1,3-, and 1,4- (or ortho-, meta-, and para-) prefixes indicate the positions of disubstitution. Alternatively, the ring is numbered, and substituents labeled with these numbers are named in alphabetical order. Many simple substituted benzenes have common names. 

Number the chain so that the first substituent gets the lower number. Then name and number all substituents, giving like substituents a prefix (di, tri, etc.). 

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