The structure of the pyrimidines and purines. VIII. The crystal structure of alloxan C4H4N2O5

Singh, Charanpreet

doi:10.1107/s0365110x65004334

Cited by 27 publications

(10 citation statements)

References 1 publication

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“…The C(5)-O(5) hydroxyl bond length (1.40/~) is a little shorter than the hydroxyl bond lengths commonly found in acyclic sugar alcohols (1.43 A; Jeffrey & Kim, 1970), but is the same as those observed in 5,5-dihydroxybarbituric acid (Singh, 1965) and its trihydrate (Mootz & Jeffrey, 1965).…”

Section: Ii) Bond Lengths and Anglesmentioning

confidence: 71%

“…in Table 5. Ring conformations 5-ETHYLBARBITURIC ACID AND 5-HYDROXY-5-ETHYLBARBITURIC ACID 5,5-dihydroxybarbituric acid (Singh, 1965) and its trihydrate (Mootz & Jeffrey, 1965), phenobarbital in the 1:2 crystal complex with 8-bromo-9-ethyladenine (Kim & Rich, 1969), 1-methylphenobarbital (Bideau, Marly & Housty, 1969) and 5-methyl-5-phenylbarbituric acid (Bravic, Housty & Bideau, 1969). However, this is not always the case.…”

Section: Discussion (I) Molecular Conformationsmentioning

confidence: 99%

“…4) is that one of the imine groups N(1) H(1) is hydrogen bonded to the 0(5) hydroxyl oxygen atom. In barbiturate crystal structures, including 5,5-dihydroxybarbituric acid (Singh, 1965) and its trihydrate (Mootz & Jeffrey, 1965), it is usual to find both imine groups in the molecule hydrogen bonded to carbonyl oxygen atoms. The O(5)--H(5) hydroxyl group in HEBA thus is both a hydrogen bonding donor and acceptor.…”

Section: -Ethylbarbituric Acid and 5-hydroxy-5-ethylbarbituric Acidmentioning

confidence: 99%

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The crystal structures of monoclinic 5-ethylbarbituric acid and 5-hydroxy-5-ethylbarbituric acid

Gatehouse¹,

Craven²

1971

Acta Crystallogr Sect B

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The crystal data for the two forms of 5-ethylbarbituric acid (EBA) are (I) monoclinic (m.p. 194--196°), a= 11.151, b =6.838, c= 9.536 A, fl= 92°21 ', space groupP2)/c with four, molecules per cell; (II)triclinic (m.p. 142-145 ), a=6.018, b= 5.344, c= 12.121/~, ~=93 38, fl= 105 42, ),=94 19, space group P1 or PT with two molecules per cell. The crystal structure of (I) is reported together with that of the oxidation product 5-hydroxy-5-ethylbarbituric acid (HEBA) which is monoclinic (m.p. 207-209°), a= 10.088, b = 6.298, c = 11-914 A, fl= 99 36", space group P2t/n with four molecules per cell. The X-ray diffraction data (Cu K~ radiation) were obtained using an automatic four-circle diffractometer. All hydrogen atoms were found in difference Fourier syntheses. Full-matrix least-squares refinement gave R values of 0-06 and 0.05 respectively. The rings in both EBA and HEBA have a 'flap' conformation with C(5) displaced from an otherwise nearly flat ring. In EBA the ethyl group is equatorial, while in HEBA it is axial. All NH and OH hydrogen bond donor groups form hydrogen bonds. The acidic hydrogen atom H(5) in EBA is not hydrogen bonded. The non-hydrogen-bonded carbonyl oxygen atom 0(6) makes close approaches (2.93 and 3.04/~) to carbonyl carbon atoms C(4) and C(6) of an adjacent molecule.

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Section: Ii) Bond Lengths and Anglesmentioning

confidence: 71%

Section: Discussion (I) Molecular Conformationsmentioning

confidence: 99%

Section: -Ethylbarbituric Acid and 5-hydroxy-5-ethylbarbituric Acidmentioning

confidence: 99%

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The crystal structures of monoclinic 5-ethylbarbituric acid and 5-hydroxy-5-ethylbarbituric acid

Gatehouse¹,

Craven²

1971

Acta Crystallogr Sect B

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“…Singh, 1965;Bolton, 1963;Craven, Vizzini & Rodrigues, 1969;Craven & Vizzini, 1969) have revealed a variety of intermolecular hydrogen-bonding schemes, and it has been shown, for example, in barbital (5,5-diethylbarbituric acid) Vizzini & Rodrigues, 1969;Craven & Vizzini, 1971) phenobarbitone suggested this compound as a subject for detailed study in the expectation that a wide variety of hydrogen-bonding schemes would be encountered.…”

Section: Introductionmentioning

confidence: 99%

Polymorphism of phenobarbitone: the crystal structure of 5-ethyl-5-phenylbarbituric acid monohydrate

Williams¹

1973

Acta Crystallogr Sect B

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“…The confusion for alloxan monohydrate arises based on whether it exists as the planar tetraketone with a coordinated water 2 (2,4,5,6-pyrimidinetetrone hydrate), or instead as the hydrated addition C5 gem-diol product 3 (5,5-dihydroxypyrimidine-2,4,6-trione, commonly known as 5,5-dihydroxybarbituric acid), as shown in Figure 1. Historically, most work has indicated that the gem-diol 3 is the structure in the solid crystalline phase based on X-ray diffraction, 13 IR/Raman, 14 as well as single-crystal X-ray diffraction experiments. 15 In addition, crystallographic studies have concluded that the dihydrate and tetrahydrate forms of alloxan both take on the base gem-diol structure with the appropriate number of additional coordinated water molecules.…”

Section: Introductionmentioning

confidence: 99%

Structure and Reactivity of Alloxan Monohydrate in the Liquid Phase

et al. 2021

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Alloxan is an important toxic glucose analogue used to induce diabetes in lab test animals. Once regarded as a "problem structure," the condensed-phase structure of anhydrous alloxan has largely been settled, but literature inconsistencies remain for the structure of the typically employed reagent alloxan monohydrate. Due to the criticality of structure−function relationships, we have used 1 H/ 13 C{ 1 H} NMR, IR spectroscopy, as well as quantum mechanical (QM) calculations to probe the liquid-phase structure and reactivity of alloxan monohydrate. In protic solvents (D 2 O and acetic acid-d 4 ), hydration at the C5 carbonyl of alloxan monohydrate occurs quantitatively to form the C5 gem-diol (5,5′-dihydroxybarbituric acid). In the aprotic solvent dimethyl sulfoxide (DMSO)-d 6 , there exists a mixture of the C5 gem-diol and planar tetraketo form of alloxan monohydrate. QM calculations explain the solvent-dependent hydration reactivity, where a solvent-assisted H-atom transfer mechanism lowers the activation energy of water addition at the C5 carbonyl by ∼16 or 27 kcal/ mol in water or acetic acid, respectively, compared to the unassisted hydration reaction. Prompt recrystallization of alloxan monohydrate from boiling water does not alter the structure of the reagent. These findings probe the exact structure of alloxan monohydrate to guide future research efforts in biological sciences and in organic synthesis.

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The structure of the pyrimidines and purines. VIII. The crystal structure of alloxan C4H4N2O5

Cited by 27 publications

References 1 publication

The crystal structures of monoclinic 5-ethylbarbituric acid and 5-hydroxy-5-ethylbarbituric acid

The crystal structures of monoclinic 5-ethylbarbituric acid and 5-hydroxy-5-ethylbarbituric acid

Polymorphism of phenobarbitone: the crystal structure of 5-ethyl-5-phenylbarbituric acid monohydrate

Structure and Reactivity of Alloxan Monohydrate in the Liquid Phase

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