Phenolic function, bathochromic shift

In UV spectra of secobisbenzylisoquinoline alkaloids possessing a phenolic hydroxy group para to the aldehyde function, a marked bathochromic shift is observed upon addition of base. In IR spectra absorption of the lactam group appears at 1645-1640 cm-1, that of the aldehyde function in the range between 1720 and 1680 cm-1, and that of the ester group at 1710 cm-1. 

We conclude our short discussion of relationships between chemical structure and light absorbance by considering some cases in which an acid or base function forms part of a chromophore. Important examples of compounds exhibiting such chro-mophores are phenols and anilines. As is evident from the spectra shown in Fig. 15.5, deprotonation of a phenolic group results in a substantial bathochromic shift... 

The natural product was synthesized together with its 8-hydroxy isomer (160) via the cyclization of 4-methyl-2-(3-hydroxyphenyl) nicotinic acid (90). A11 four ring C monohydroxylated onychines have been prepared by a different, unambiguous route and their mass, UV, and H-NMR spectra discussed in detail, showing that the base- and aluminum chloride-induced bathochromic shifts are useful criteria for the location of phenol functions on the benzene ring of aza-fluorenones (97). 

Lauraceae), was assigned the structure 26 based on spectroscopic evidence (38). The oxygenation pattern of the aromatic rings and the presence of a C-2 phenolic function were determined by its UV spectrum, coupled with base-induced bathochromic shifts. The location of the hydroxy function at C-4, its stereochemical disposition, and the stereochemistry of 6a-H were determined with the help of and 13C NMR data and comparison with those of known compounds. The 3H and 13C NMR assignments for srilankine (26) are depicted in Fig. 1. 

Oxosarcocapnidine (22) shows a bathochromic shift on addition of acid or base. The latter shift indicates the presence of a phenolic group (77). The H-NMR spectrum reveals two methoxy groups (3.98 and 3.95 ppm) and three aromatic AB spin systems, corresponding to a 7,4, 5 -substituted skeleton, which is confirmed by 0-methylation to oxosarcocapnine (24). The position of the phenolic function at C-5 has been established by chemical correlation with sarcocapnidine (13). Fremy s salt oxidation of the 5 -0-methoxymethyl derivative of 13, followed by aeid deprotection, gives 22 in 58% yield. 

This oxidation has been utilized in the determination of the location of the phenolic function in ( + )-tiliacorine, which had been formulated as either 11 or 12. Permanganate in acetone oxidation of its (9-acetyl derivative, followed by ester hydrolysis, yielded secotiliacorine aldehydo lactam, 212, 282, and 310 sh (4.10, 3.44, and 2.94). This product showed a strong bathochromic shift in base, 230, 292, and 340 nm (4.00, 3.27, and 3.21), indicative of a... 

The chromophore of phenylephrine is not extended but its structure includes a phenolic hydroxyl group. The phenolic group functions as an auxochrome under both acidic and alkaline conditions. Under acidic conditions it has two lone pairs of electrons, which can interact with the benzene ring and under basic conditions it has three. Figure 4.11 shows the bathochromic and hyperchromic shift in the spectrum of phenylephrine, which occurs when 0.1 M NaOH is used as a solvent instead of 0.1 M HCl. Under acidic conditions the X max is at 273 and has an A (1 %, 1 cm) value of 110 and under alkaline conditions the X max is a 292 nm and has an A (1%, 1 cm) value of 182. 

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