The Heading Parent

A systematic (e.g., CAS) name may have up to four components the heading parent, the substituents, the modifications, and the stereodescriptors. Of these, only the first is always present the others may or may not be. 

The heading parent, e.g., 2-butenoic acid, consists of a molecular skeleton (2-butene) and a suffix (-oic acid) detailing the principal functional group. There can only be one functional group in any one name. (Note elision of the terminal -e in butene.) Where there is no functional group, the heading parent consists only of a molecular skeleton name, e.g., methane, pyridine. 

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This contains two ketone groups which cannot be expressed as a single parent. The heading parent could either be cyclohexanone or 2-propanone but the correct name is 4-(2-oxopropyl)cyclohexanone. In order to arrive at this kind of conclusion, the following rules are applied in sequence until a decision is reached. 

In the Chemical Abstracts Service (CAS) indexing system, phenol is the heading parent and the appropriate names of alkylphenols can thus be derived by using common practices. 

Functional groups are listed in decreasing order of importance in naming. Principal portions of the CAS name are found in the Heading Parent (used as the primary index entry point), secondary portions are part of the Substituent and Name Modification-, exceptions are used as shown For complete details see the latest version of the CAS Index Guide. 

Specific diazonium compounds are found under the heading of the parent compound, e.g., C6H5N2 Cl- under benzene, diazonium chloride . 

The mechanisms by which silenes dimerize, both head-to-tail and head-to-head, have been the subject of intense interest to theoreticians for as long as the dimerization process has been known. Siedl, Grev, and Schaefer167 calculated that the barrier between the parent H2Si=CH2 68 and its head-to-tail dimer 69 was 5.2 kcal mol-1, with the product head-to-tail dimer 69 being 79 kcal mol-1 more stable than reactants. The head-to-head dimer 70 was found to be 19.8 kcal mol-1 less stable than 69. 

The mechanism for accomplishing this is crossover. In one-point crossover (Figure 5.14), two strings chosen at random from the freshly created parent pool are cut at the same randomly chosen position into a head section and a tail section. The heads are then swapped, so that two offspring are created, each having genetic material from both parents. 

Subsystems can interact with each other in many ways. This pattern defines a consistent scheme governing those interactions. For every subsystem, you may choose to uniformly have a distinguished head object that controls the connections between its children s ports and those in other subsystems based on a naming scheme. The head object also mediates all control and asynchronous communication between the subsystem and its parent system and coordinates the activities of its child components (see Figure 12.3). This arrangement gives a consistent structure for every subsystem a head object, a defined role relative to its children, and a consistent protocol regardless of actual subsystem function. 

Polymers formed from two or more monomers such as condensation polymers and copolymers, as well as homopolymers are indexed at each inverted monomer name with the modifying term polymer with followed by the other monomer names in uninverted alphabetical order. The preferential listing for identical heading parents is in the order (1) maximum number of substituents (2) lowest locants for substituents (3) maximum number of occurrences of index heading parent and (4) earliest index position of the index heading. Examples are ... 

While in normal combinatorial peptide libraries (either chemical or phage display) each component has a unique sequence that is different from all others, in the cycloscan libraries all components have the same sequence, but differ in their conformation. This conformational diversity is generated in a dendrimeric hierarchy as shown exemplarily in Scheme 27 for the parent linear heptapeptide A-B-C-D-E-F-G. The diversity of the 1st order sublibrary (this nomenclature was adopted from Furka[468l) is based on the mode of cyclization. Excluding the head-to-tail cyclization there are seven different modes of cyclization that can be used for cycloscan three natural modes of cyclization and four modes of N-backbone cyclization. In addition there are five theoretical modes of C-backbone cyclization (see Scheme 1) which are not included in Scheme 27. 

The natural decay chains have several examples of short-lived a activities that are delayed by a longer-lived parent. In fact, the existence of these activities on Earth is possible by the fact that the head of the chain has a half-life on the order of the age of the Earth. Another more practical example near the end of the 4n chain is 212Pb with a half-life of 10.6 h that decays to 212Bi. The daughter rapidly decays by a or (3 emission. The lead nucleus is also preceded by a shortlived Rn parent, which can produce very thin sources of a particles by emanation. 

All recent ab initio studies on the head-to-tail dimerization reaction for the parent silene H2Si=CH2 predict a very exothermic reaction with a low barrier, despite the fact that the reaction is formally forbidden12. It is believed that the strong polarization of the Si=C double bond leads to a relaxation of the Woodward-Hoffmann rales. A detailed analysis of the symmetry of the head-to-tail silene dimerization reveals, however, that a concerted [2jrs + 2jrs] reaction in the appropriate point group is not forbidden by symmetry (see Figure l)186. 

Some ring-substituted (hydroxy or methoxy) camptothecin derivatives were either isolated in nature or obtained synthetically [253,264-267]. The 9-methoxy- and 10-methoxycamptothecin are less active, but 10-hydroxy-camptothecin is more active than the parent alkaloid against leukaemia P388 [253, 264], Both camptothecin and its 10-hydroxy derivative are being used in mainland China for the treatment of liver carcinoma and tumours of the head... 

I want what men have, I want less domestic obligation. I want my spouse to be the homemaker, the prinicipal carer of our children so I can concentrate on my career. I want to be defined as an individual before a parent, I want nevertheless to be the head of the family. I want my children to carry my name into the future, I want to be the first heir. 

The 2,6-dimethyl derivatives 353a gives the tricyclic ketone 354 resulting from an intramolecular electrocyclic reaction. However, the parent thieno-tropone (51) and its 2- (353b) or 7-methyl derivatives give [4 + 2] dimers (e.g., 355) of the head-to-head type. These dimers are formed by reaction of the 5,6-ene bond of one molecule with the 5,7-diene system of another. The dimerization seems to be the normal photochemical reaction of this group of thienotropones and to be suppressed by a 6-methyl substituent (e.g., in 353a). 

Heptachlor induces tremors, convulsions, paralysis, and hypothermia in rats. Young calves fed with different doses (2.5, 5, or 10 mg/kg/day) of heptachlor formulation for 3 to 15 days showed muscle spasms in the head and neck region, convulsive seizures, elevated body temperatures, and engorged brain blood vessels. The photoisomer of heptachlor (photoheptachlor) and the major metabolite of heptachlor (heptachlor epoxide) are considered more toxic than the parent compound. 

Did he perhaps get this information from I. M. Levitas, the Head of the Society for Jewish Culture in Kyiv, who had made the same claim in an interview with a Kyiv newspaper 85 That would mean that despicable Jewish parents had abandoned more than 25,000 children when they were evacuated by the Soviets. This, however, is disproved by Jewish and Soviet publications,31 54"58 which stressed the evacuation of families in order to sustain morale. 

The first step in choosing the index heading parent is to identify the principal functional group (the term characteristic group is now preferred by lUPAC) ... 

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