Hydroxy-, spectra

The 4-Hydroxy-thiazoles are characterized by infrared absorption near 1610 cm (KBr) (3) or 1620 to 16.S0cm (CCI4) (8), indicating a strongly polarized carbonyl group. H-5 resonates near 5.6 ppm in the NMR spectrum like similar protons in other mesoionic compounds (3). Two fragmentations of the molecular ion are observed in the mass spectra. The first involves rupture of the 1,2 and 3,4 bonds with loss of C2R 0S . In the second, the 1,5 and 3,4 bonds are cleaved with elimination of C2R 0. ... 

The NMR spectrum of the 2-hydroxy-1,3-dioxolylium cation (117) (68JA1884) shows a significant ring current. The aromaticity of vinylene carbonate was pointed out by Balaban (59MI40100). 

Pyridin-2-one, 1-hydroxy-fluorescence spectrum, 2, 163 (81XL1515) Pyridin-2-one, 6-methoxy-pK 2, 151 <71JCS(B)289)... 

Lumazine, 6,7-diphenyl-5,6-dihydro-properties, 3, 306 UV spectrum, 3, 279 Lumazine, 6,7-diphenyl-2-thio-glycosidation, 3, 297 reactions, 3, 300 Lumazine, 6,7-diphenyl-4-thio-reactions, 3, 300 Lumazine, 2,4-dithio-methylation, 3, 299 Lumazine, l-/3-D-glucopyranosyl-NMR, 3, 282 Lumazine, 1-hydroxy-structure, 3, 282... 

EtOH) was examined in detail by Mead and Koepfli, who, from its reactions and the resemblance of its absorption spectrum to that of 2-hydroxy-6-methoxy-4-methylquinoline, regard it as Z-2 -hydroxyquinine (2 -hydroxy-6 -methoxy-3-vinylruban-9-ol). According to P. B. Marshall, this metabolite is inactive in chick malaria, but Kelsey efaZ. (1946) find that at a dosage of 40-70 mgm./kilo./day, it exercises about the same degree of suppression as 15 mgm./kilo./day of quinine, and quote E. K. Marshall for the observation that it has about one-twentieth the activity of quinine in the malaria of ducks. 

P-Hydroxy-A-norpregn-3(5)-en-2-one (7) A solution of the hydroxy-methylene steroid (5) (24.8 g) dissolved in 240 ml of acetic acid and 240 ml of ethyl acetate is ozonized at — 10° with one molar equivalent of ozone. The resulting solution is diluted with 240 ml. of water and 60 ml of 30 % hydrogen peroxide and allowed to stand overnight. The solution is diluted with 1.5 liters of water and extracted with 3 x 700 ml portions of ethyl acetate. The combined extracts are washed with water, saturated sodium chloride solution, dried over sodium sulfate and concentrated to dryness under vacuum, leaving 23.4 g of a colorless amorphous residue of crude diacid. This material shows a maximum in the ultraviolet spectrum at 224 mp (s 6,400) indicating a 53 % yield of unsaturated acid (6). It is used without further purification. 

In the absence of oxygen, these thiolene-2-ones are rather stable and have been kept at 0°C for several months. 3-Hydroxythiophene, on the other hand, which has been prepared in low yield from 3-thio-phenemagnesium bromide in the same way as the 2-isomer, or through decarboxylation of 3-hydroxy-2-thiophenecarboxylic acid, "" is very unstable. Its IR spectrum indicates that it also exists as a tautomeric mixture largely in its enolic form. ... 

The UV spectrum of 5-phenyl-3 hydroxythiophene is very similar to that of its methyl ether in alcoholic solution, indicating that it exists largely in the enol form in this solvent. The same coincidence of the wavelength maxima was also obtained for 5-phenyl-2-hydroxy-thiophene and its methyl ether. In chloroform solution, the maxima were shifted toward longer wavelengths, suggesting that the tautomeric equilibrium in this solvent is displaced more toward the keto form. ... 

Ultraviolet spectra have long been used to study systems of this type. In 1889, comparison of the ultraviolet spectrum of 2-hydroxy-quinoline with those of its O- and A -methylated derivatives led... 

Attempts have been made to deduce the structure of the predominant form of a potentially tautomeric compound from the shifts which occur in the ultraviolet spectrum of the compound in question on passing from neutral to basic or acidic solutions. The fact that no bathochromic shifts were observed for 2- and 4-hydroxy quinoline and 1-hydroxyisoquinoline under these conditions was taken as evidence that they existed in the oxo form [similar work on substituted quinol-4-ones led to no definite conclusions ]. A knowledge of the dissociation constants is essential to studies of this type, and the conclusions can, in any case, be only very tentative. A further dif-... 

In 1951, Witkop et al. interpreted the infrared spectra of quinol-2-and -4-ones to favor the oxo formulation. Since then, many investigators, especially Mason, have reported that potential a- and y-hydroxy compounds show infrared absorption bands in the vN—H (3500-3360 cm ) and vC—O (1780-1550 cm ) regions of the spectrum and, hence, exist predominantly in the oxo form references to this work appear in Table I. A study of the bands which occur in the NH-stretching region of the infrared spectra of a series of substituted pyrid-2-ones and quinol-2-ones also supported an oxo formulation for these compounds. Detailed band assignments have been published for pyrid-2- and -4-one. Mason has reported that solutions of j8-hydroxy compounds in chloroform or carbon tetrachloride show... 

Many of the properties oj -hydroxypyridines are typical of phenols. It was long assumed that they existed exclusively in the hydroxy form, and early physical measurements seemed to confirm this. For example, the ultraviolet spectrum of a methanolic solution of 3-hydroxypyridine is very similar to that of the 3-methoxy analog, and the value of the dipole moment of 3-hydroxypyridine obtained in dioxane indicates little, if any, zwitterion formation. However, it has now become clear that the hydroxy form is greatly predominant only in solvents of low dielectric constant. Comparison of the pK values of 3-hydroxypyridine with those of the alternative methylated forms indicated that the two tautomeric forms are of comparable stability in aqueous solution (Table II), and this was confirmed using ultraviolet spectroscopy. The ratios calculated from the ultraviolet spectral data are in good agreement with those de-... 

Shugar and FoxS " reported that 4-ethoxypyrimidin-2-one exists in the 0X0 form 102 since its ultraviolet spectrum is different from that of 103. They further claimed that the isomeric compound, 2-ethoxy-4-hydroxypyrimidine, existed in the hydroxy form (104) however, reexamination of the ultraviolet spectral data suggests that this unlikely conclusion may be incorrect, and the infrared spectrum of 104 does, indeed, show a carbonyl absorption band. 2-Methylthiopyrim-idin-4-one has been reported to exist in the hydroxy form, but this to appears unlikely. 

Trihydroxypteridine exists predominantly in the dioxo-mono-hydroxy form 191(R = H), its ultraviolet spectrum closely resembling those of both the 1- and the 3-methyl derivatives and that of l,3-dimethyl-7-methoxypteridine-2,4-dione (191, R = Me). These spectra are quite different from those of 8-methyl- (192, R = H) and l,3,8-trimethyl-pteridine-2,4,7-trione (192, R = Me), which are similar to each other and to those of other 8-substituted pteridine-2,4,7-triones. However, the ultraviolet spectrum of 2,4,7-trihydroxypteri-dine does, indeed, show that a small proportion of the trioxo form is present at equilibrium. A somewhat larger proportion of the 6-methyl derivative exists in the trioxo form, although structure 193 predominates. The trioxo form (194) of 2,4,7 trihydroxy-l,3,6-trimethyl-pteridine is the most important tautomer, but the corresponding 6-carboxylic acid exists entirely in the monohydroxy-dioxo form 195. 

Pfleiderer has suggested that the 7-hydroxy group exists as such in these compounds because this form is stabilized by mesomerism of type 191 (R — H). The tautomerism of 7-hydroxypteridine-2,4-dione in the excited electronic state has been studied on the basis of its fluorescence spectrum. 

Attempts to prepare 6-hydroxybenzofuroxan by demethylation of 5-methoxybenzofuroxan, by pyrolysis of 4-azido-3-nitrophenol, and by hypochlorite oxidation of 4-amino-3-nitrophenoD failed. This rather unstable compound was finally prepared by hydrolysis of 5-acetoxybenzofuroxan its tautomeric possibilities are numerous, but from the similarity of its ultraviolet spectrum to that of 5-methoxybenzofuroxan it was considered to be largely in the hydroxy form. It is a fairly strong acid, of pK 6.76 (cf. 5-hydroxybenzo-furazan, pK 7.28). 7-Hydroxy-4,6-dinitrobenzofuroxan has been reported as arising from oxidation and nitration of dinitrosoresorcinol monooxime (tetraoxocyclohexene trioxime). ... 

Hydroxy-8-hydroxyethyl-6,7-dimethyl-2-pteridinone has been shown to have the same absorption spectrum in alkaline solution as its 1,7-dihydro derivative, namely peaks at 231, 283, and 316 mp. This... 

For reasons discussed in Section VI, a survey of the purine series (29) is being made in this Department, but so far no example (including 2-hydroxy- and 8-trifluoromethyl-2-hydroxy-purine) of covalent hydration has come to light. An examination of ionization constants disclosed no apparent anomalies, although the interpretation is made more difficult by the ease of anion formation in the 9-position, which often competes with that from other anionic substituents. The only abnormal spectrum seems to be that of the anion of 2-mercaptopurine which is being further examined. 

Hydroxy-8-azapurine was shown by rapid-reaction techniques (see Section II, E) to be anhydrous in the anion and hydrated in the neutral species. The hydration reaction has a half-time of about 0.5 second, which is too rapid for exact measurements with existing apparatus. The cation of 2-amino-8-azapurine was shown to have an anomalous value and ultraviolet spectrum, although its 6-methyl derivative is quite normal. Hydration in this case proved to be too fast to register in the rapid-reaction apparatus. 

The infrared spectrum of 2-hydroxythiophene was originally interpreted as showing both vOH and vC=0 peaks indicating that it exists as a mixture of the hydroxy form 39 (R — H) and at least one of the 0X0 forms, 40 and/or 41. The ultraviolet spectrum of 2-hydroxythiophene is different from that of the corresponding methyl ether (39, R = Me) suggesting the presence of the chromophore contained in structure 40. The facts that this compound gives a positive... 

The infrared spectrum of 3-hydroxythiophene has been interpreted by Ford and Mackay- to show that it exists as a mixture of both the hydroxy (44) and the oxo forms (45). 5-Phenyl-3-hydroxythiophene apparently behaves similarly to the 2-hydroxy isomer, the ultraviolet... 

The chemical reactions of this compound were recently reconsidered, and both structures 64 and 65 were rejected in favor of the zwit-terion formulation 66, which is supported by the presence of a band at S.lfx (3226 cm ) in the infrared spectrum and is merely an alternative canonical form of 64. On the other hand, the ultraviolet spectrum of 4-hydroxypyrrole-2-carboxylic acid (67) resembles that of its ethyl ether, possibly indicating that the 2-acid exists in the hydroxy form. -... 

Both the infrared and ultraviolet spectra of pyrrolidine-2,3,5-triones (75) have been interpreted to support their existence as hydroxy-maleimides (76), and the occurrence of a strong OH stretching band in the infrared spectrum of 4-phenylpyrrolidine-2,3,5-trione has been taken as evidence that it too exists in a hydroxy form, probably 76 (R CeHg). However, the trioxo formulation is suggested by t/j the infrared spectra of jV-substituted pyrrolidine-2,3,5-triones, although an equilibrium apparently occurs depending upon the substituents and conditions. The zwitterion formulation 77 has been advanced for 4-aminopyrrolidine-2,3,5-trione. For chemical evidence... 

An initial study of the infrared spectrum of oxindole purported to show the presence both of the hydroxy (78) and of the oxo forms (79), and, indeed, chemical evidence led to the same conclusion. On the basis of later infrared work, however, oxindole and its derivatives were considered to exist more or less completely in the oxo form, and this conclusion is supported by ultraviolet spectroscopic data, i.e., by comparison of the spectrum of the parent compound with those of its methyl derivatives. " The infrared spectrum of... 

Quinoxalin-2-ones are in tautomeric equilibrium with 2-hydroxy-quinoxalines, but physical measurements indicate that both in solution and in the solid state they exist as cyclic amides rather than as hydroxy compounds. Thus quinoxalin-2-one and its A -methyl derivative show practically identical ultraviolet absorption and are bases of similar strength. In contrast, the ultraviolet spectra of quinoxalin-2-one and its 0-methyl derivative (2-methoxyquinoxaIine) are dissimilar. The methoxy compound is also a significantly stronger base (Table II). Similar relationships also exist between the ultraviolet absorption and ionization properties of 3-methylquinoxalin-2-one and its N- and 0-methyl derivatives. The infrared spectrum of 3- (p-methoxy-benzyl)quinoxalin-2-one (77) in methylene chloride shows bands at 3375 and 1565 cm" which are absent in the spectrum of the deuterated... 

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