Neo- prefix

Alternatively, if there are two methyl groups attached to the second carbon atom the neo prefix is added to the parent name. 

Note the usage of the prefixes iso-, neo-, sec-, and tert-, and note when italics are employed. Italicized prefixes are never involved in alphabetization, except among themselves thus 5-ec-butyl would precede isobutyl, isohexyl would precede isopropyl, and 5-ec-butyl would precede rert-butyl. 

Branched-chain alkanes, also known as isoparaffins or isoalkanes, are possible when n > 4. The prefix iso is used when two methyl groups are attached to a terminal carbon atom of an otherwise straight chain and the prefix neo when three methyl groups are attached in that manner. Branched-chain alkanes are sometimes regarded as normal alkanes with attached substituent alkyl groups. An example is... 

It should be noted that italicised hyphenated prefixes which indicate structure, such as cis-. o-, m-, tert-, mixo-, N-. 0-, etc., have been ignored during the alpha-sorting routine used on this index and the group-lists, while the roman character structural prefixes iso and neo, and roman multiplying prefixes such as di, tris, tetra and hexakis, have been included in the indexing procedure. 

Necrosis Death in a particular part of a living tissue example death of a certain area of a leaf. "Neo-" A prefix given to an isomer of another compound. It exists in compounds that were named long ago and is used only when the compound it best known by its common name. 

The chemicals are listed in straight alphabetical order, letter by letter. Compounds consisting of two or more words are compiled as if they were a single word. Prefixes and numerals are disregarded in the alphabetizing. In cases were prefixes are an integral part of the chemical s name they are placed in normal alphabetical order (bis-, cyclo-, di-, iso-, neo-, tetra-, tri-). 

The continuous chain hydrocarbons are known as normal hydrocarbons, and the prefix n- is usually attached to the name. The branched-chain hydrocarbons may have the prefix iso- attached to the name. Usually the prefix iso- is reserved for substances with two methyl groups attached to carbon atoms at the end of an otherwise straight chain. In a straight chain, each carbon atom is connected to no more than two other carbon atoms. The prefix neo- denotes three methyl groups on a carbon atom at the end of a chain. For example, the isomers of pentane are illustrated below. 

The situation with regard to naming alkyl substituents has been muddied considerably by the fact that the IUPAC rules allow use of trivial names for a few alkyl groups. Thus sec-butyl sometimes is used in place of 1-methylpropyl, and rcr/-butyl in place of 1,1-dimethylethyl. These and other examples are included in parentheses in Table 3-2. Further odd-ball but less official customs are the prefix iso, which is reserved for substituents with two methyl groups at the end of an otherwise straight chain (e.g., isopropyl), and the prefix neo,... 

When the structural prefixes cyclo, iso, neo, and spiro are integral parts of chemical names, close them up to the rest of the name (without hyphens) and do not italicize them. 

As we have seen, the prefixes //-, iso-, and neo- are adequate to differentiate the various butanes and pentanes, but beyond this point an impracticable number of prefixes would be required. However, the prefix n- has been retained for any alkane, no matter how large, in which all carbons form a continuous chain with no branching ... 

Prefixes like cyolo, iso, neo, etc., were disregarded in alphabetizing, but this provision was canceled later and from 1927 on one could again look for cyclohexanone under cyclo rather than under hexanone. 

Well known alternatives to this fractional notation are based on the use of a set of eight prefixes alio, cis, dl, epi, muco, myo, neo, and scyllo) for the inositol configurations, and of ten prefixes alio, cis, epi, gala, muco, neo, proto, scyllo, talo, and vibo) for the quercitol configurations. Since these nomenclatures, due mainly to Fletcher, Anderson and Lardy, and... 

The prefixes di, tri, tetra, sec, and tert are ignored in alphabetizing substituent groups, but the prefixes iso, neo, and cycio are not ignored. 

If a chain has more than one substituent, the substituents are cited in alphabetical order, using the same mles for alphabetizing that you learned in Section 2.2. (The prefixes di, tri, sec, and tert are ignored in alphabetizing, but iso, neo, and cyclo are not ignored.) The appropriate number is then assigned to each substituent. 

The stem name carotene brings with it an implication of trans double bond geometry for all bonds. Note that this is opposite to that of polyene FA discussed earlier (see Section 3.2.4). If a cis double bond is present, this is distinguished in the structural name as either cis-" or Z- following the appropriate carbon location. Compounds known to contain a cis double bond but where the location is unknown, or isomers of carotenes with an unlocated cis double bond, are given the prefix neo- and an alphabetical suffix. 

We have just seen that the three C5H12 isomers all incorporate pentane in their names and are differentiated by the prefixes n- iso , and neo. Extending this approach to alkanes beyond C5H12 fails because we run out of descriptive prefixes before all the isomers have unique names. As difficult as it would be to invent different names for the 18 constitutional isomers of CgHjg, for example, it would be even harder to remember which structure corresponded to which name. For this and other reasons, organic chemists have developed systematic ways to name compounds based on their structure. The most widely used approach is called the lUPAC rules lUPAC stands for the International Union of Pure and Applied Chemistry. (See the boxed essay. What s in a Name Organic Nomenclature,)... 

The name pentane derives from the Greek pente, meaning five, indicating that the molecule has five carbon atoms. The other names still use the term pentane, with a prefix iso or neo, trying to convey the fact that these are isomeric molecules. Naming the isomers can become cumbersome when the number of isomers increases. For this reason, chemists have created a standard naming system. ... 

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