Correlation of Ultraviolet Absorption and Chemical Constitution in Various Pyrimidines and Purines

Heyroth, Francis F.; Loofbourow, John R.

doi:10.1021/ja01323a024

Cited by 49 publications

(16 citation statements)

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“…The absorption spectra of purines and pyrimidines have received considerable attention. 3 8,12,15,16 Comparing our results with those of these workers we concluded that: (1) compound R was probably a pyrimidine rather than a purine; (2) the compound (if a pyrimidine) was substituted in the 2, 6; 4, 6; or 2, 4, 6 positions, to account for the selective absorption with Xmax. 265 mu; (3) there was no amino group present since we did not obtain a precipitate with phosphotungstic acid; (4) the compound appears to be relatively symmetrical about the 2, 5 positions; otherwise there should be a large shift in absorption maximum at an alkaline pH; (5) if no amino group is present, a hydroxy or keto group capable of enolization must be present to account for acetylation; (6) the compound may be derived from a weakly acidic substance which has been eluted from the alumina column as an ammonium salt.…”

supporting

confidence: 70%

The Identification of Pyrimidines in the Fluorescing Fractions of the Teeth of the Sperm Whale (Physeter Macrocephalus)

Hartles

Leaver

1955

J Dent Res

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E HAVE earlier reported on the fluorescence of human teeth when irra-W diated with ultraviolet light.6 During the course of this work we were fortunate enough to obtain a few teeth of the sperm whale (Physeter macrocephalus). These teeth are characterized by a complete absence of enamel and consist of a central core of dentin surrounded by a thick layer of cementum. The incisal tip of the tooth consists of exposed dentin. Each tooth was about 5 or 6 inches in length and weighed between 400 and 650 Grams. In view of the relatively large amount of material available, it was decided to investigate the fluorescing fractions of these teeth. EXPERIMENTALThe methods of exciting and examining fluorescence were the same as those described earlier.6 The cementum and dentin were separated by cleavage, and any small portions of either tissue which remained were removed with the aid of a grinding wheel.Whale Cementum.-The cementum was dull white in color and fluoresced strongly with a blue color. Its specific gravity was about 1.9; the nitrogen content averaged 3 per cent (w/w).Extraction of lipids: The cementum was broken into small pieces in a percussion mortar and dried at 1000 C. A sample (15.393 Gm.) was extracted with ether in a continuous extractor for 6 hours; this yielded 0.031 Gm. of lipid material (0.20 per cent w/w) having a weak blue fluorescence both in solution and in the solid state. This lipid fraction was saponified with 60 per cent (w/v) NaOH. The nonsaponifiable matter, when dissolved in light petroleum, fluoresced weakly blue and gave a faintly positive Liebermann-Burchard reaction, indicating the presence of a sterol. Adsorption chromatography on activated alumina resolved 2 fractions. Ultraviolet absorption spectra of these fractions did not reveal any selective absorption. The saponifiable matter was acidified with H2SO4 and the acidic materials extracted with ether. A faintly positive molybdate test for phosphate suggested the presence of phospholipid. Adsorption chromatography on alumina yielded only one fluorescing fraction; its ultraviolet absorption spectrum showed a small inflexion in the region of 240 to 270 miu. The quantity of fluorescing materials present in these fractions was very small and their study was not pursued.

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supporting

confidence: 70%

The Identification of Pyrimidines in the Fluorescing Fractions of the Teeth of the Sperm Whale (Physeter Macrocephalus)

Hartles

Leaver

1955

J Dent Res

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“…6 4 . 1 (11), and 2.3-3.2 (111). All three are progressively displaced to higher wave-lengths as n increases, but the displacements are larger in the linear than in the angular isomers and thus fall in with the general rule that hmag.…”

Section: Compoundmentioning

confidence: 99%

“…Other materials of carbohydrate nature may also serve as sources of furans, but it is only recently that a thorough investigation has been made into the optimum conditions for the preparation of 5-hydroxymethylfurfuraldehyde from sucrose. have obtained a 54% yield by the use of 0.25% aqueous oxalic acid a t 130" under pressure, the yield being based on the fructose portion of the molecule, since the glucose portion takes no part in the reaction.4 This is probably due to the fact that fructose has a much greater tendency than glucose to react in the furanose form (I), which by successive dehydrations can readily pass into 5-hydroxymethylfurfuraldehyde (11). They have also shown that glucose (111) will undergo the reaction, provided it is pretreated with dilute alkali to facilitate the formartion of the 1 : 2-enediol (IV), which by loss of water can give (V), a postulated intermediate in the above scheme.…”

Section: Furansmentioning

confidence: 99%

Organic chemistry

Baxter¹,

Braude²,

Lythgoe³

et al. 1945

Annu. Rep. Prog. Chem.

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“…Experimental investigations of the electronic structure of organic molecules started very early, by performing absorption measurements. The ultraviolet absorption spectra of eighteen pyridines and purines [4], fourteen ethylenic hydrocarbon molecules [5], and 1,3 cyclohexadiene [6] have been measured already in 30s. Later Platt and Klevens presented the spectra of several alkylbenzenes [7], some ethylenes and acetylenes [8], and seventeen polycyclic aromatic hydrocarbons composed of fused benzene rings [9] (e.g.…”

Section: Introductionmentioning

confidence: 99%

Empirical LCAO parameters forπmolecular orbitals in planar organic molecules

2009

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We present a parametrization within a simplified LCAO model (a type of Hückel model) for the description of π molecular orbitals in organic molecules containing π-bonds between carbon, nitrogen, or oxygen atoms with sp 2 hybridization, which we show to be quite accurate in predicting the energy of the highest occupied π orbital and the first π-π* transition energy for a large set of organic compounds. We provide four empirical parameter values for the diagonal matrix elements of the LCAO description, corresponding to atoms of carbon, nitrogen with one z p electron, nitrogen with two z p electrons, and oxygen. The bond-length dependent formula (proportional to 1/d 2 ) of Harrison is used for the non-diagonal matrix elements between neighboring atoms. The predictions of our calculations have been tested against available experimental results in more than sixty organic molecules, including benzene and its derivatives, polyacenes, aromatic hydrocarbons of various geometries, polyenes, ketones, aldehydes, azabenzenes, nucleic acid bases and others. The comparison is rather successful, taking into account the small number of parameters and the simplicity of the LCAO method, involving only z p atomic orbitals, which leads even to analytical calculations in some cases.Keywords: linear combination of atomic orbitals, Hückel model, empirical parameters, πmolecular structure, highest occupied π orbitals, π-π* transition the assignment of electronic transitions (e.g. singlet-singlet or singlet-triplet transitions, Rydberg transitions, π-π* transitions etc.), and the calculation of the oscillator strength of the transitions. Apart from basic knowledge and the numerous applications of planar organic molecules containing atoms with sp 2 hybridization, the π molecular electronic structure of such compounds is involved in several biological functions. For example, we mention chlorophyll in photosynthesis, the retinal molecule involved in vision or in photondriven ion pumps like bacteriorhodopsin [1], and many molecules with photobiological functions such as vitamin A, vitamin D precursors, carotene etc., containing polyene chromophores [2]. Also new organic semiconductors based in pentacene and other hydrocarbon molecules have attached an enormous interest regarding their use in molecular electronics [3]. Experimental investigations of the electronic structure of organic molecules started very early, by performing absorption measurements. The ultraviolet absorption spectra of eighteen pyridines and purines [4], fourteen ethylenic hydrocarbon molecules [5], and 1,3 cyclohexadiene [6] have been measured already in 30s. Later Platt and Klevens presented the spectra of several alkylbenzenes [7], some ethylenes and acetylenes [8], and seventeen polycyclic aromatic hydrocarbons composed of fused benzene rings [9] (e.g. phenanthrene and chrysene). At the same period spectra were taken from naphthalene and biphenyl derivatives [10], m-and o-disubstituted benzene derivatives [11], and mono-substituded and p-disubstituted benzene derivativ...

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Correlation of Ultraviolet Absorption and Chemical Constitution in Various Pyrimidines and Purines

Cited by 49 publications

References 0 publications

The Identification of Pyrimidines in the Fluorescing Fractions of the Teeth of the Sperm Whale (Physeter Macrocephalus)

The Identification of Pyrimidines in the Fluorescing Fractions of the Teeth of the Sperm Whale (Physeter Macrocephalus)

Organic chemistry

Empirical LCAO parameters forπmolecular orbitals in planar organic molecules

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