Seniority chains

If the characteristic group occurs both in a chain and in a cyclic system, the parent is that portion in which the principal group occurs in largest number. If the numbers are the same, that portion is chosen which is considered to be the most important or is the senior ring system. 

When side chains of two or more different kinds are attached to a cyclic component, only the senior side chain is named by the conjunctive method. The remaining side chains are named as prefixes. Likewise, when there is a choice of cyclic component, the senior is chosen. Benzene derivatives may be named by the conjunctive method only when two or more identical side chains are present. Trivial names for oxo carboxylic acids may be used for the acyclic component. If the cyclic and acyclic components are joined by a double bond, the locants of this bond are placed as superscripts to a Greek capital delta that is inserted between the two names. The locant for the cyclic component precedes that for the acyclic component, e.g., indene-A - -acetic acid. 

Most of the authors of individual chapters are senior scientists and/or industry based quality assurance specialists who have participated in the EU-funded Integrated Project (IP) QualityLowInputFood. The project aims are improving the quality and safety and reduction of cost in the organic and low input food supply chains . Several chapters in handbook report preliminary results from the IP and/or associated/linked projects supported by national governments and/or industry (see IP website www.qlif.org for further details). 

The basic order of seniority of subunits is heterocyclic rings and ring systems > heteroatom chains > carbocyclic rings and ring systems > acyclic carbon chains... 

The order of decreasing seniority for chains of heteroatoms of the same kind that have equal length is ... 

When two identical subunits of the highest seniority (A) are present in a CRU in the main chain (backbone), the shorter path between the identical subunits is to be followed. The starting point is chosen in such a way that the shorter path to the subunit of second highest seniority (B) is followed. If the paths are equal, the paths to subunits of third highest seniority (C) are considered in the sense of Rule 14. 

O is senior to N of the two two-carbon chains the one with the larger number of substituents is senior Rules 4,10c)... 

D. Unsaturation is senior to saturation. The more the unsaturation, the greater the seniority, with all other items being equal. Thus, 1,4-phenylene is senior to 2,5-cyclohexadiene-l,4-diyl, which is senior to 2-cyclohexene-1,4-diyl, which in turn is senior to cyclohexane-1,4-diyl. For linear chains-CH=CH—CH=CfU is senior to-CH=CH—CH2-CH2-which is in turn senior to the totally saturated chain segment. 

The seniority of different types of subunits is heterocyclic rings > heteroatoms or acyclic subunits containing heteroatoms > carbocyclic rings > acyclic subunits containing only carbon. The presence of various types of atoms, groups of atoms, or rings that are not part of the main polymer chain but are substituents on the CRU do not affect this order of seniority. 

To obtain a unique name, a single preferred CRU must be selected. Therefore, rules have been developed that specify both seniority among subunits, that is, the point at which to begin writing the CRU, and also the direction in which to move along the chain to reach the end of the CRU. 

For an acyclic chain containing a heteroatom, oxygen is senior to sulfur, sulfur to nitrogen, nitrogen to phosphorus, phosphorus to silicon, silicon to germanium, etc. 

For chains containing carbon, seniority is determined first by length, then by the number of substituents, then by the locants and, finally, by the alphabetical order of substituents. 

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