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Hydroxyl Protons (hydroxyl + proton)

Distribution by Scientific Domains
Chemistry75%

Selected Abstracts

Synthesis of imidazole-containing conjugated polymers bearing phenol unit as side group and excited state intramolecular proton transfer-mediated fluorescence

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 18 2009
Koji Takagi
Abstract Dibromobenzimidazole and dibromoimidazole bearing hydroxyl group-protected phenol unit (1 and 2) were prepared and they showed an intramolecular hydrogen bonding between ether oxygen and amino proton of imidazole. The palladium-catalyzed Suzuki coupling polymerization of 1 and 2 with benzene bis(boronic acid) derivatives gave soluble polymers (3 and 4), where the molecular weights were limited probably due to the coordination ability of imidazole to palladium metal. The phenol hydroxyl groups were subsequently deprotected using BBr3 to obtain 3, and 4,. From the 1H NMR spectra, the complete conversion to the hydroxyl group and the formation of another type of intramolecular hydrogen bonding between hydroxyl proton and imine nitrogen were confirmed. In the UV and PL spectra of 3, and 4,, the excited state intramolecular proton transfer (ESIPT) occurred to shift the emission spectra toward lower energy region compared to 3 and 4. Especially, the PL spectrum of 3, demonstrated large stokes shift (145 nm) in THF solution. The ESIPT-mediated fluorescence was influenced by the addition of methanol and trifluoroacetic acid, which inhibited the formation of intramolecular hydrogen bonding. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4822,4829, 2009 [source]

Experimental and theoretical NMR study of selected oxocarboxylic acid oximes

MAGNETIC RESONANCE IN CHEMISTRY, Issue 1 2004
Kamilla Malek
Abstract 1H and 13C NMR spectra of the oxocarboxylic acid oximes 2-hydroxyiminopropanoic acid (1), 2-(4-methylthiazol-2-yl)-2-(hydroxyimino)acetic acid (2) and 2-cyano-2-(hydroxyimino)acetic acid (3) were measured in DMSO- d6, D2O and acetone- d6 solutions. The data indicate the presence of hydrogen bonding in 1 and 2 and a strong electron-withdrawing effect due to the cyano group in 3. The effect of intra- and intermolecular hydrogen bonding on the hydrogen and carbon chemical shifts in these molecules was studied theoretically. Total energy calculations of the stability of various hydrogen-bonded species, in addition to equilibrium parameters and chemical shifts, were calculated using ab initio methods (RHF, MP2) and density functional theory (B3LYP), implemented in the Gaussian 98 software package. The gauge-including atomic orbital (GIAO) method was used to predict magnetic shielding constants. Chemical shift calculations for the most stable species agree fairly well with the observed data, especially for the hydroxyl protons. Substituents adjacent to the ,-carbon show some influence of the oximic and carboxyl groups on the 13C chemical shifts, as expected for groups with different polar and anisotropic character. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Dichloro[1,1,-(5,9-dithia-2,12-diazoniatrideca-1,12-diene-1,13-diyl)dinaphthalen-2-olato-,2O,O,]dimethyltin(IV) acetonitrile solvate

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 1 2003
Stanley A. Bajue
Reaction of the potentially hexadentate ligand 1,9-bis(2-hydroxy-1-naphthalene­methyl­imino)-3,7-di­thia­nonane with di­methyl­tin chloride gave the title 1:1 adduct, in which the long ligand wraps around the SnCl2Me2 unit and in which the stereochemistry is fully trans. This compound crystallizes from aceto­nitrile as the 1:1 solvate [Sn(CH3)2(C29H30N2­O2S2)Cl2]·­C2H3N. During the reaction, the hydroxyl protons move to the N atoms. Most of the chemically equivalent bond lengths agree to within experimental uncertainty, but the Sn,Cl bond that is inside the ligand pocket is substantially longer than the Sn,Cl bond that points away from the long ligand [2.668,(1) versus 2.528,(1),Å]. The O,Sn,O angle is 166.0,(1)°. Comparison of the Sn,O, C,O and aryl C,C bond lengths with those of related compounds shows that the most important resonance forms for the Schiff base aryl­oxide ligand are double zwitterions, but that the uncharged resonance forms having carbonyl groups also contribute significantly. [source]

3-Hydroxybenzene 1,2,4-Trisphosphate, a Novel Second Messenger Mimic and unusual Substrate for Type-I myo -Inositol 1,4,5-Trisphosphate 5-Phosphatase: Synthesis and Physicochemistry

CHEMBIOCHEM, Issue 11 2006
Stephen J. Mills Dr.
Abstract 3-Hydroxybenzene 1,2,4-trisphosphate 4 is a new myo -inositol 1,4,5-trisphosphate analogue based on the core structure of benzene 1,2,4-trisphosphate 2 with an additional hydroxyl group at position-3, and is the first noninositol based compound to be a substrate for inositol 1,4,5-trisphosphate 5-phosphatase. In physicochemical studies on 2, when three equivalents of protons were added, the 31P NMR spectrum displayed monophasic behaviour in which phosphate-1 and phosphate-2 behaved independently in most of the studied pH range. For compound 4, phosphate-2 and phosphate-4 interacted with the 3-OH group, which does not titrate at physiological pH, displaying complex biphasic behaviour which demonstrated co-operativity between these groups. Phosphate-1 and phosphate-2 strongly interacted with each other and phosphate-4 experienced repulsion because of the interaction of the 3-OH group. Benzene 1,2,4-trisphosphate 2 is resistant to inositol 1,4,5-trisphosphate type I 5-phosphatase catalysed dephosphorylation. However, surprisingly, 3-hydroxybenzene 1,2,4-trisphosphate 4 was dephosphorylated by this 5-phosphatase to give the symmetrical 2,3-dihydroxybenzene 1,4-bisphosphate 16. The extra hydroxyl group is shown to form a hydrogen bond with the vicinal phosphate groups at ,15,°C, and 1H NMR titration of the ring and hydroxyl protons in 4 shows the OH proton to be strongly stabilized as soon as the phosphate groups are deprotonated. The effect of the phenolic 3-OH group in compound 4 confirms a critical role for the 6-OH group of the natural messenger in the dephosphorylation mechanism that persists even in radically modified analogues. [source]