Aromatic rings Aromaticity

Fragmentation Fragmentation occurs on both sides of the carbonyl group. For example, in acetophenone, the major ions occur at masses 77, 105, and 120 (see Figure 20.3). Ions at m/z 39, 50, and 51 also suggest the presence of an aromatic ring. Aromatic compounds, such as quinone, tetralone, and anthraquinone, readily lose CO. 

Aromatic C with side chain hydroxylation and N-substituted aromatic C C=C-OH c=o R-(C=0)-R C=N, C-N Carbonyl C in aromatic ring Aromatic C attached to amide group Phenol C Aryl ethers and ketones Carbonyl C Pyrimidine C Is—Jt 286.0-287,4h,i k-°- -UA,-v... 

The nonaromatic eight-membered rings absorb little in accessible regions of the ultraviolet (UV) spectrum. Table 1 represents stmctures and data on reported spectra of triheterocines, whose absorptions are due to fused aromatic rings, aromatic substituents, or carbonyl groups. 

Hydroxylation of aromatic rings. Aromatic rings are frequently oxidized into phenols followed by conjugation and excretion. The mechanism of the reaction is discussed later, and we shall first consider an example of phenol formation. In the hydroxylation of chlorobenzene, all three isomers are produced, i.e. ortho-, meta- and para-dnloro-phenol, but in different amounts (Fig. 31.13). As a rule, hydroxylation occurs on the less hindered site, usually the para position. Electronic factors are also operative. This is seen in the hydroxylation of many drugs, two of which are shown in Fig. 31.14. 

Pendant Aromatic Rings Aromatic (conjugated unsaturated rings such as fliose of benzene, C H ) rings attached to the main chain of a polymer molecule. 

Keywords All-metal aromatic rings Aromaticity/antiaromaticity DFT - Rings of metal atoms... 

A second eccentricity is that atom labels are drawn smaller when in rings. Additionally, whereas it is customary to omit the C atom label for carbon atoms, DEPICT provides them everywhere except in aromatic rings. Aromatic atoms, in turn, are written in lowercase, betraying a kinship to SMILES notation. These peculiarities detract somewhat from the diagram s aesthetic appearance however, they probably reflect the defaults used to visualize SMILES. Reportedly, the defaults can be replaced by adjustable parameters within the Daylight Toolkit. 

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