The determination of free hydroxyl groups in fatty materials

1955 ◽  
Vol 32 (11) ◽  
pp. 675-677
Author(s):  
Edward Handschumaker
Keyword(s):  
Hydroxyl Groups ◽  
Free Hydroxyl

scholarly journals JUSTIFICATION OF THE POSSIBILITY OF USING THERMOMODIFIED VENEER IN AN ENVIRONMENT WITH HIGH HUMIDITY

2021 ◽  
pp. 65-71
Author(s):  
Oleksandra Horbachova
Keyword(s):  
Water Absorption ◽  
Treatment Process ◽  
Uv Light ◽  
Hydroxyl Groups ◽  
Initial Weight ◽  
Water Desorption ◽  
Size Stability ◽  
Free Hydroxyl ◽  
Thermally Modified Wood

Thermally modified wood is widely used in the woodworking industry, as it has increased resistance to environmental factors (humidity, temperature). The effect of high temperature on wood causes a decrease in water adsorption by reducing the available free hydroxyl groups of carbohydrates. The reduction in hygroscopicity contributes to the treated material size stability, as swelling and shrinkage are mainly associated with the phenomena of absorption and water desorption. The study of natural weathering always takes many years. Therefore, to study the resistance of thermodified wood to environmental influences, artificial weathering is used - modeling of external factors (cyclic change of UV light and moisture). The effectiveness of the thermodified veneer use as a material for lining the furniture facades which working in different temperature and humidity conditions was established. The values of moisture and water absorption on the samples of oak veneer, which have previously undergone the heat treatment process, have been determined. It was found that the samples of oak veneer gained the most moisture from the environment in the first two days. The weight of unmodified veneer increased by 0.06 g, similar results showed veneer modified at temperatures of 160 and 190 °C. Thermodified veneer at a temperature of 250 °C for the first two days gained twice less. By the end of the experiment (next 11 days), the samples of ordinary and modified veneer at all temperatures absorbed the same amount of moisture. Untreated veneer and thermodified at temperatures of 160 and 220 °C absorbed 50-66 % of its initial weight, and modified at 250 °C – 20-36 %. Control samples of veneer during the determination of water absorption gained 98 % of the initial weight. Samples modified at 160 °C – 10, 20, 30 min showed the best result – reducing the value to 94 %, 93 % and 91 %. There is a slight improvement in water absorption after exposure to temperature 220 °C for 10, 20, 30 min – 91 %, 91 % and 90 %. Values water absorption at the level of 90 %, 89 % and 86 % were recorded in veneer samples modified at 250 °C.

The synthesis and structure of silica-supported bis(h5-cyclopentadienyl)dichlorotitanium(IV) complexes

1986 ◽  
Vol 51 (7) ◽  
pp. 1430-1438 ◽  
Author(s):  
Alena Reissová ◽  
Zdeněk Bastl ◽  
Martin Čapka
Keyword(s):  
Free Surface ◽  
Hydroxyl Groups ◽  
Titanium Complex ◽  
Surface Hydroxyl ◽  
Surface Hydroxyl Groups ◽  
Free Hydroxyl ◽  
Cyclopentadienyl Anion

The title complexes have been obtained by functionalization of silica with cyclopentadienylsilanes of the type Rx(CH3)3 - xSi(CH2)nC5H5 (x = 1-3, n = 0, 1, 3), trimethylsilylation of free surface hydroxyl groups, transformation of the bonded cyclopentadienyl group to the cyclopentadienyl anion, followed by coordination of (h5-cyclopentadienyl)trichlorotitanium. The effects of single steps of the above immobilization on texture of the support, the number of free hydroxyl groups, the coverage of the surface by cyclopentadienyl groups and the degree of their utilization in anchoring the titanium complex have been investigated. ESCA study has shown that the above anchoring leads to formation of the silica-supported bis(h5-cyclopentadienyl)dichlorotitanium(IV) complex.

Structure determination of the 1/1 α/β mixed lactose by X-ray powder diffraction

2005 ◽  
Vol 61 (4) ◽  
pp. 455-463 ◽  
Author(s):  
Jacques Lefebvre ◽  
Jean-François Willart ◽  
Vincent Caron ◽  
Ronan Lefort ◽  
Frédéric Affouard ◽  
...  
Keyword(s):  
Powder Diffraction ◽  
Size Effects ◽  
Room Temperature ◽  
Real Space ◽  
Hydroxyl Groups ◽  
Soft Constraints ◽  
Rietveld Refinements ◽  
X Ray ◽  
Mixed Compound

The mixed form of α/β lactose was obtained by heating amorphous α-lactose at 443 K. NMR spectroscopy determined the stoichiometry of this mixed compound to be 1/1. The X-ray powder diffraction pattern was recorded at room temperature with a sensitive curved detector (CPS 120). The structure was solved by real-space methods (simulated annealing) followed by Rietveld refinements with soft constraints on bond lengths and bond angles. The H atoms of the hydroxyl groups were localized by minimization of the crystalline energy. The cell of 1/1 α/β lactose is triclinic with the space group P1 and contains two molecules (one molecule of each anomer). The crystalline cohesion is achieved by networks of O—H...O hydrogen bonds. The width of the Bragg peaks is interpreted through a microstructural approach in terms of isotropic strain effects and anisotropic size effects.

Substitutional and solvation effects on conformational equilibria. Effects on the interaction between opposing axial oxygen atoms

1969 ◽  
Vol 47 (23) ◽  
pp. 4441-4446 ◽  
Author(s):  
R. U. Lemieux ◽  
A. A. Pavia
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Hydrogen Bonding ◽  
Magnetic Resonance ◽  
Hydroxyl Groups ◽  
Evidence Based ◽  
Electrostatic Repulsion ◽  
Hydrogen Bridge ◽  
Conformational Equilibria ◽  
Free Hydroxyl ◽  
Oxygen Atoms

Evidence based both on nuclear magnetic resonance and rotation data primarily obtained from methyl 3-deoxy-β-L-erythro-pentopyranoside and a number of its derivatives is interpreted to show that the electrostatic repulsion between the oxygen atoms at the 2 and 4 positions is substantially less when these oxygens are linked to acyl groups than when in the form of either methyl ethers or as hydroxyl groups hydrogen bonded to solvent. Also, experimental evidence is presented which requires the hydrogen bridge between two axially disposed hydroxyl groups to be substantially strengthened by hydrogen bonding of the free hydroxyl by solvent.

Light-Mediated Cross-Coupling of Anomeric Trifluoroborates

2021 ◽  
Author(s):  
Eric Miller ◽  
Maciej Walczak
Keyword(s):  
Cross Coupling ◽  
Hydroxyl Groups ◽  
Anomeric Effect ◽  
Computational Studies ◽  
Carbohydrate Chemistry ◽  
New Class ◽  
Free Hydroxyl ◽  
Anomeric Carbon ◽  
Stereoselective Reactions

Stereoselective reactions at the anomeric carbon constitute the cornerstone of preparative carbohydrate chemistry. Here, we report the synthesis of axial C1 trifluoroborates and stereoselective C-arylation and etherification reactions under photoredox conditions. These reactions are characterized by high anomeric selectivities for 2-deoxysugars and broad substrate scope (24 examples), including disaccharides and trifluoroborates with free hydroxyl groups. Computational studies show that high axial selectivities for these reactions originate from a combination of kinetic anomeric effect of the intermediate C1 radical and stereoelectronic stabilization of Ni(III) through the metallo-anomeric effect. Taken together, this new class of carbohydrate reagents adds the palette of anomeric nucleophile reagents suitable for efficient installation C-C and Cheteroatom bonds.

Structure determination of the stable anhydrous phase of α-lactose from X-ray powder diffraction

2005 ◽  
Vol 61 (2) ◽  
pp. 185-191 ◽  
Author(s):  
Cyril Platteau ◽  
Jacques Lefebvre ◽  
Frederic Affouard ◽  
Jean-François Willart ◽  
Patrick Derollez ◽  
...  
Keyword(s):  
Powder Diffraction ◽  
Room Temperature ◽  
Structural Model ◽  
Hydroxyl Groups ◽  
Rietveld Refinements ◽  
X Ray ◽  
Hydrogen Bond Networks ◽  
Monte Carlo Simulated Annealing ◽  
Annealing Method

The stable anhydrous form of α-lactose has been obtained by the dehydration of α-lactose monohydrate in methanol. An X-ray powder diffraction pattern was recorded at room temperature with a laboratory diffractometer equipped with an INEL curved sensitive detector CPS120. The starting structural model of this form was found by a Monte-Carlo simulated annealing method. The structure was obtained through Rietveld refinements and the minimization of crystalline energy for the localization of the H atoms of the hydroxyl groups. Soft restraints were applied to bond lengths and angles. Networks of O—H...O hydrogen bonds account for the crystalline cohesion. A comparison is made between the hydrogen-bond networks of this form and those of the monohydrate and hygroscopic anhydrous forms of α-lactose.

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