Phenols, acetates comparison

Bruice and Sturtevant, (1959) and Bruice, (1959) found extremely facile intramolecular nucleophilic attack by neighbouring imidazole in the hydrolysis of p-nitrophenyl 7-(4-imidazoyl)butyrate [19]. The rate constant for imidazole participation (release of p-nitro-phenolate) in this reaction is nearly identical with the rate constant for a-chymotrypsin catalysed release of p-nitrophenolate ion [190 min in equation (11) at pH 7 and 25°] from p-nitrophenyl acetate. Comparison of the rate constant for intramolecular imidazole participation to that for the analogous bimolecular reaction (imidazole attack on p-nitrophenyl acetate) (s" /m s )... 

The / -carboline partial structure was represented in the mass spectra by major ion (93) formed by the favored cleavage r and hydrogen transfer. Further information about this system was supplied by the NMR spectrum of the pentaacetate, which showed phenolic acetate, indolic NH, and four aromatic protons. One of the latter was a singlet at 1.27, attributed to H-6, and spin decoupling of the others indicated that the acetoxy group must be at either C-10 or C-ll. Comparison of the UV spectrum of cordifoline pentaacetate [Amax(loge) 239 (4.66), 271 (4.60), 305 (inf.) (3.82), 338... 

A solution of bismuth trioxide in hot glacial acetic acid provides a specific method for the oxidation of acyloins. " The reaction rate is dependent on the steric accessibility of the ketol system. A 2,3-ketol requires less than one hour for completion but an 11,12-ketol is not yet fully oxidized in thirty hours." The reaction is highly selective as a-keto acids, hydrazines and phenols are not oxidized. In a direct comparison with cupric acetate, this procedure is somewhat superior for the preparation of a 2,3-diketone from a 2-keto-3-hydroxy steroid. ... 

Comparison of an alkalimetric titration curve of an equimolar (1 O 4 M) solution of acetic acid (pK = 4.8) and phenol (pK = 10) with a humic acid that contains 10 4 M carboxylic groups. 

The major conclusion which was reached from the work of Jarret and Saunders was that intramolecularly hydrogen-bonded protons generally give values of (p below the value for a similar proton which is not involved in an intramolecular hydrogen bond. For example, a value of (p of 0.77 was obtained for the hydrogen-bonded site in the maleate ion [12] compared to 0.94 for acetic acid. The value for the phthalate ion [10] was higher, (p = 0.95. The value of (p = 0.95 was obtained for the salicylate ion [22] in comparison to the result for phenol, tp = 1.13. 

Thus, an estimation can be made of the hydrophilicity of the crown ring. The acetal-type crown ring obtained from hexaethyl-ene glycol and a higher aliphatic aldehyde is estimated to be e-quivalent to about four OE units in an alkyl POE monoether, from our study of the cloud point (11). Moroi et al. concluded, from a comparison of the cmc, that a diaza-18-crown-6 is equivalent to 20 OE units in the usual type of nonionic (12). Okahara s group evaluated the effective HLB based on the cloud point, phenol index and phase-inversion-temperature in emulsion of oil/water system and they concluded that 18-crown-6 and monoaza-18-crown-6 rings with dodecyl group are approximately equivalent to 4.0 and 4.5 units, respectively, of OE chains with the same alkyl chain (17). 

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... 

The reactivity of acyl radicals inside and outside the solvent cage has been a matter of discussion. It has been postulated that aryloxy and acyl radicals could disproportionate within the cage to give phenol (or naphthol) and ketene (37) but the results are not conclusive (Scheme 14). On the one hand, photolysis of 1-naphthyl acetate in a solvent without abstractable H-like Freon 113 (1,1,2-trichl-oro-l,2,2-trifluoroethane) yields low amounts of 1-naphthol (< 0.1%) in comparison with the same reaction in acetonitrile (7%) [50]. This reveals that dispropor-... 

Three different sets of experimental aqueous-phase pKa s allow us to judge to what extent solvent effects can be ignored and, where they cannot be ignored, assess the performance of the SMS. 4 model in accounting for solvation. The first involves a diverse set of carboxylic acids and the second a diverse series of alcohols and phenols. Calculated acidities (relative to acetic acid in the case of carboxylic acids and relative to ethanol in the case of alcohols and phenols) have been obtained from the Hartree-Fock 6-311+G model. Previous comparisons with gas-phase acidities suggest that this should be as satisfactory as any other model for this purpose (see, for example. Tables 6-18 and A6-50). 6-3IG geometries have been used in place of 6-311+G geometries in order to save computation time. (See... 

In comparison with the araliphatic alcohols discussed in Section 2.5.2, very few phenol alcohols are used as fragrance and flavor materials. Neither the alcohols corresponding to vanillin, ethylvanillin, and heliotropin nor their esters have special organoleptic properties. Anise alcohol and its acetate are the only products that are used to some extent in perfume and aroma compositions. 

Figure 13. Comparison of UV and MS chromatograms using a 1.0-mm i.d. column packed with a 5-pm diameter Supelcosil C-18. LC-MS interface used aerosol spray deposition on a moving belt. Peaks correspond from left to right to 0.2 pg each of resorcinol, 1,5-dihydroxynaphthol, and 2-methyl-phenol. Conditions 41% acetonitrile and 59% water (v/v) with 0.1% trifluoro-acetic acid at a flow rate of 40 pL/min. A, UV trace at 280 nm, 0.015 AUFS B, MS trace, selected ion chromatogram. (Reproduced from reference 54.

Attempts to confirm the structure of 32 by conversion into the methyl indolizine and comparison with an authentic sample were inconclusive. However, rearrangement of 27 with acetic acid or phenol gave an indolizine triester formulated as 33 which could be converted into 34. This last product had markedly different physical properties from 32 and its decarboxylation product was identical with 3-methylindolizine [Eq. (9)]. 

Excess diazomethane converted thalipine to thalicarpine (94), while partial methylation gave, in addition to 94, thalmelatine (314a) and pennsylvanine (317), identified by IR, NMR, and TLC comparison with authentic samples (132). The CD curve of thalipine shows it to have (S,S) configuration (132). Partial methylation of thalipine was also accomplished indirectly via incomplete acetylation of the phenolic functions, followed by diazomethane treatment, yielding acetates of 314a and 317 hydrolysis of the latter gave 317 (148). 

A careful clinical comparison of the acetate ester of psilocin with the phosphate ester and the free phenol might help resolve this question. The ideal way of resolving this would be to run pharmacokinetic studies on blood levels of these three materials, in parallel with studies of the psychopharmacological responses. I feel that this is not likely to be done in the foreseeable future. 

Another crude model, this time for estimating the strength of tyrosyl-carboxylate interactions, was proposed by Wetlaufer (1956), who showed (1) a qualitatively weak interaction in the miscibility of phenol and aqueous sodium acetate solution, but (2) on the basis of the comparison of the solubility of tyrosine in sodium chloride and sodium acetate solutions, a maximum association constant no greater than 0.10 (assumed binary association) between tyrosine and acetate. By a comparison of salt effects... 

---