Formulae of groups

We have already mentioned the formulae for groups, such as S04 , without discussing the principles by which such formulae are assembled. These may (or may not) involve some reference to structure. The general approach is to select one or more atom(s) as the central or characteristic atom(s). This is so whether the ion or group is a coordination entity or not. Thus, I in ICl4 , V in V02 and Si and W in [SiW,204o] are all central atoms and are cited first. The subsidiary atoms then follow, in alphabetical order of symbols (this rule is slightly modified for coordination compounds). 

Organic ligands are cited under C, and NO and CO are regarded as neutral. Because square brackets are always of highest seniority (or priority), a hierarchical sequence of enclosing marks is adopted to ensure that this seniority is preserved [ ], [()], [ () ], [ [()] ], [ [()] ], etc. 

For certain species it is not possible to define a central atom. Thus, for chain species, such as thiocyanate, the symbols are cited in the order in which they appear in the chain. 

Addition compounds are represented by the formulae of the individual constituent species, with suitable multipliers that define the appropriate molecular ratios of the constituent species, and separated by centre dots. In general, the first symbols determine the order of citation. 

These suggestions are advisory and should be used where there are no overriding reasons why they should not be. For example, PCI3O is a correct presentation but, because the group P=0 persists in whole families of compounds, the presentation POCI3 may be more useful in certain contexts. There is no objection to this. 

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Silicate Structural Groups Structural Arrangement Formula of Group Number of 0 Ions Shared Average Si 0 Ratio (Unsubstituted) 1 Series Name Idealized Formula with Substitution Involved... 

Type of Functional Group Example Compound Structural Formula of Group ... 

Type of functional group Example eompound Structural formula of group ... 

Bafmer series Frequencies of certain lines in the spectrum of hydrogen are simply related to each other, and can be expressed by a general formula. One group of lines is termed the Balmer series. Other series were later discovered in the spectrum of hydrogen by Lyman, Paschen, Brackett and Pfund. 

As an example, the empirical formula of phenylalanine may be split into a more extended form that shows the presence of a phenyl ring, as well as an amino and a carboxylic acid group (the condensed form in Figure 2-4). 

Epichlorohydnn is the common name of an industrial chemical used as a component in epoxy cement The molecular formula of epichlorohydnn is C3H5CIO Epichlorohydnn has an epoxide functional group it does not have a methyl group Write a structural formula for epichloro hydrin... 

Acridine is a heterocyclic aromatic compound obtained from coal tar that is used in the syn thesis of dyes The molecular formula of acndine is C13H9N and its ring system is analogous to that of anthracene except that one CH group has been replaced by N The two most stable reso nance structures of acridine are equivalent to each other and both contain a pyndine like struc tural unit Wnte a structural formula for acridine... 

Fig. 8. Formula of ceUulose (a) the central part of the molecular chain, and (b) end groups of the molecule denoting the carbon numbering scheme where...

Two methyl groups were omitted from the formula of the... 

The amines are a group of compounds with the general formula R-NHj, and all the common amines are hazardous. As a class the amines pose more than one hazard, being flammable, toxic, and, in some cases, corrosive. The amines are an analogous series of compounds and follow the naming pattern of the alkyl halides and the alcohols that is, the simplest amine is methyl amine, with the molecular formula of CH NHj. Methyl amine is a colorless gas with an ammonia-like odor and an ignition temperature of 806°F. It is a tissue irritant and toxic, and it is used as an intermediate in the manufacture of many chemicals. Ethyl amine is next in the series, followed by propyl amine, isopropyl amine, butyl amine and its isomers, and so on. 

The following are the names and formulas of this group of alkaloids —... 

The formula of hyoscine may now be written as tropylscopine (tropylscopeine by analogy with the tropeines) and the relationship of scopine to oscine, teloidine and tropine, the other principal hydrolytic products of this group, are shown by the following formulae. 

ALKALOIDS OF OTHER PAPAVER SPP. For the following papaveraceous alkaloids neither constitutional formulas nor group relation-... 

The formation of (A) and (C) indicates that cryptopine must have in its structure the grouping I, whilst the production of (B) and (D) shows that the alkaloid must also contain the piperonyl ring in the form of grouping II, and from these the structme of anhydrotetrahydromethyl-cryptopine is represented by formula III ... 

Constitution. Comparison of the empirical formula of the three alkaloids, and the fact that jatrorrhizine and columbamine each stands to palmatine in the relation of a monohydric phenol to its methyl ether, makes it clear that the only difference between jatrorrhizine and columbamine must be in the position of the free hydroxyl group. The method by which this point was settled is described in dealing with the two tetrahydro-derivatives of these alkaloids (p. 291). The constitution of palmatine (XXV R = R = Me) is dealt with under tetrahydropalmatine, but it is still necessary to describe the complete synthesis of this alkaloid via oxypalmatine (XXVII) and tetrahydropalmatine. 

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