Indicated substituent groups

It must be emphasised that the following substances are merely representative of widely different classes of compounds, and that the test when applied to an unknown compound often provides only a general indication of the probable class to which the compound belongs. Moreoi er, the behaviour of a compound when heated is often determined more by the nature of its substituent groups than by its general character. 

Positive Z values indicate a downfield shift, and an arrow indicates the point of attachment of the substituent group to the double bond. 

When substituent groups are present, they are identified and their positions indicated by numbers in naming the compound. As an example, dimethylcyclohexane has three structures ... 

Newman projection (Section 3.6) A means of indicating stereochemical relationships between substituent groups on neighboring carbons. The carbon-carbon bond is viewed end-on, and the carbons are indicated by a circle. Bonds radiating from the center of Ihe circle are attached to the front carbon, and bonds radiating from the edge of the circle are attached to the rear carbon. 

The parent name is placed last the substituent group, preceded by the number indicating its location on the chain, is placed first. 

Indicate the locations of the substituent groups by the numbers of the carbon atoms to which they attached. 

The many sulphur dyes synthesised via quinonimine intermediates are polymeric products containing numerous disulphide crosslinkages that can be broken by reduction in aqueous sodium sulphide thioether groups survive the reduction process. The smaller thiolate-containing molecules formed are substantive to cellulose. Although the actual structures of such dyes are complex, their essential features can be illustrated in an idealised model (Scheme 6.23), in which X = S, NH or O, and R indicates substituents or annelated rings. 

A location number is necessary to indicate the point of attachment of a particular substituent. We assign these numbers by consecutively numbering the carbons of the base hydrocarbon starting at one end of the hydrocarbon chain. Choose the end so that there will be the lowest sum of location numbers for the substituent groups. Place this location number in front of the substituent name and separate it from the name by a hyphen (i.e., 2-methyl). 

The results obtained in this work indicate that both the structure of the stabilizer and the nature of the surrounding environment are important factors in determining the efficiency of the energy dissipation processes in these derivatives. Molecular structures in which the planar form is favoured and where the intramolecular hydrogen bond is protected from interactions with the medium by the incorpoation of bulky substituent groups, should exhibit highest photostability and impart improved photoprotection to polymer substrates. 

Fig. 5.1 Chemical structures of ginsenosides. Ginsenosides can be separated into protopanaxadi-ols (a) or protopanaxatriols (b), depending on the presence or absence of a substituent group at carbon 6. Individual ginsenosides differ according to their sugar moieties, as indicated by Ri and R2 in the table...

The hydrolysis of substituted phenyl acetates has been studied in the presence of cyclodextrins (Van Etten et al, 1967a, b). No correlation was found between the rate constants for hydrolysis and a for the substituent group. Specificity was directed towards meta-substituents. m-t-Butylphenyl acetate hydrolyses 240 times faster in the presence of 0-01 M cyclohepta-amylose. Comparison of spectral shifts upon inclusion of p-t-butyl and m-t-butylphenol indicated that benzene rings of p-substituted phenols are included within the cavity of cyclodextrins [45], but that the benzene ring of the meta-isomer... 

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