Anthroic acid

The pAT-behaviour of 1-, 2- and 9-anthroic acids in the excited state was studied by Vander Donckt and Porter (1968a). Directly determined p/ (T )-values were found to lie nearer to the p/ (S1)-values calculated using the Forster cycle than to pA (S0). In a study of the fluorescence of 1- and 2-anthroic acids over a wide acidity range (Schulman et al., 1973a), it appeared that the deprotonation reactions did not come to equilibrium in the excited state. For protonation of the carboxyl group only 1-anthroic acid showed an excited state reaction and, as expected, it became more basic in the Si state. Fluorescence lifetime measurements on the prototropic species derived from 1- and 2-anthroic acids help in understanding the failure to reach equilibrium ... 

The Forster cycle calculations on the dissociation of 9-anthroic acid (Vander Donckt and Porter, 1968a) have been criticized (Werner and Hercules, 1969) on the grounds that excited state rotation of the carboxyl group invalidates the equal entropy assumption of the Forster cycle. Pace and Schulman (1972) found that this dissociation equilibrium was not established in the excited-state but obtained a p/ (Sj )-value from fluorescence titrations for protonation of the carboxyl group. As expected its basicity was increased in the Sj state a Apisf-value of 6 units was recorded. 

Membranes exhibit a common stmcture, with lipid molecules arranged in the form of one or more bilayers, or lamellae. Since lipids are generally nonfluo-rescent, lipid-bound fluorophores are an excellent tool to study this environment. These membrane probes are poorly soluble in water, and hence they partition readily into the hydrophobic regions of the membranes. The derivatives of anthroyloxy fatty acids (AF), with the fluorophore 9-anthroic acid esterfied to the 2, 6,9, 12, or 16 position along a fatty acid acyl chain (stearic acid or palmitic acid), are frequently used. The stmcture of an AF probe is shown schematically in Fig. 1... 

Direct introduction of the carboxyl group into an aromatic ring is accomplished with urea hydrochloride, phosgene, oxalyl chloride, or carbon dioxide. Carboxylation of benzene is effected in 15-58% yields by treating with liquid phosgene and aluminum chloride. No catalyst is required in the conversion of dimethylaniline and phosgene to p-dimethyl-aminobenzoic acid (50%). 9-Anthroic acid (67%) is prepared from anthracene by heating to 240° with oxalyl chloride and nitrobenzene. ... 

A mixture of 50 g. (0.3 mole) of pure anthracene, 30 ml. of oxalyl chloride (p. 242), and 150 ml. of dry nitrobenzene is heated under a reflux condenser in a metal bath. The temperature of the bath is raised from 120° to 240° over a period of 5-6 hours, after which the nitrobenzene is removed by steam distillation. The residue is treated with a solution of 40 g. of sodium hydroxide in 700 ml. of water, and the mixture is heated to reflux for 30 minutes. The mixture is filtered, and the cooled filtrate is extracted with petroleum ether (b.p. 30-60°), after which the aqueous solution is heated to boiling and treated with activated carbon. After filtration of the hot solution to remove the carbon, the carbon is washed with 2 N sodium carbonate solution, and the combined filtrate and washings are acidified to give 41.6 g. (67%) of 9-anthroic acid, m.p. 208-212°,... 

We have utilized this approach for the enantiomeric purification of a number of 1-aryl ethanols by condensing them with 9-anthroic acid to the corresponding anthroates followed by irradiation and extraction. ... 

Several chiral substituted a-phenyl-alkyl alcohols, which were partially enantio-merically enriched, were successfully purified by this method after esterification with 9-anthroic acid optical purities higher than 95% were obtained.Fluorescence studies of racemic compounds show a characteristic a-type excimer emission, whereas the chiral enantiomer exhibits a typical y-type monomer emission. Figure 7 shows the spectra of l-(2-chlorophenyl)ethyl 9-anthroate for a crystalline sample of enantiomeric (1) and racemic (2) at 77 K. It has been demonstrated that in the absence of configurational disorder chiral impurities in the range of 1 % can be detected by this method. ... 

Highly reactive aromatics react with the reagent anthracene— 9-anthroic acid bromide (52%). Ketones undergo a-bromocarbonylation in yields of the order of IO-40%.- ... 

Work on the photophysics of carbonyl compounds is much less extensive than in previous years. Solvent affects have been interpreted as involving ir-ir and n-ir transitions in carbonyls and hydrazones. The t-butyl and methyl esters of 9-anthroic acid (and also tetraphenylbutadiene) show a dependence of the emission... 

Direct introduction of the carboxyl group into the aromatic ring has also been accomplished with phosgene and oxalyl chloride. Thus, for example, 9-anthroic acid is prepared in 67% yield from anthracene by heating to 240°C with oxalyl chloride in nitrobenzene [12]. 

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