Benzoid chromophore

The spectrum of ketoprofen is shown in Figure 4.9. In this case the simple benzoid chromophore has been extended by four double bonds and thus the symmetry of the benzene ring has been altered. In addition, the strong absorbance band present in benzene at 204 nm has undergone a bathochromic shift giving a X max for ketoprofen at 262 nm having an /I (1%, 1 cm) value of 647. 

Other drugs which have an extended benzoid chromophore include cyproheptadine, dimethindine, protriptyline, zimeldine. 

Benzoid Chromophobe. The spectrum of the aromatic parent, benzene (Figure 2), displays considerable fine structure, a property which is not shared to the same extent with many of its derivatives. The three-bonded spectrum (248, 254, and 260 /x) of benzene will be considered as one chromophore. Benzene absorbs at 184 fi (Om 60,000), 203.5 fi (Om 7400), and 254 fi (Om 204) in hexane (4). These maxima are considered as the 7T 7T bands of the benzene chromophore. Increasing alkyl substitution causes a bathochromic shift of the 254-/i band, an eflFect which reaches its maximum at tetrasubstitution. New intense bands appear in the spectrum of benzoid compounds upon introduction of a substituent... 

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