scholarly journals A Simple Method for the Quantification of Free Isocyanates on the Surface of Cellulose Nanocrystals upon Carbamation using Toluene Diisocyanate

Surfaces ◽  
2019 ◽  
Vol 2 (2) ◽  
pp. 444-454 ◽  
Author(s):  
Hatem Abushammala
Keyword(s):  
Elemental Analysis ◽  
Cellulose Nanocrystals ◽  
Toluene Diisocyanate ◽  
Hydroxyl Group ◽  
Simple Method ◽  
Complete Hydrolysis ◽  
Amine Groups ◽  
Ph Increase ◽  
Hydrolysis Of ◽  
Cellulose Surface

In many reports, cellulose and nanocellulose have been carbamated using 2,4-toluene diisocyanate (2,4-TDI) to allow the grafting of molecules or polymers onto their surfaces. Such a process usually involves the reaction of the more reactive isocyanate group of TDI (para-NCO) selectively with a hydroxyl group from the cellulose surface, followed by the reaction of the free isocyanate (ortho-NCO) with a desired molecule. After the first step, it is not possible, using elemental analysis, to determine the amount of ortho-NCO on the cellulosic surface, as an ideal para/ortho selectivity is difficult to obtain. This paper presents a simple method for the quantification of ortho-NCOs on the surface of cellulose nanocrystals upon TDI-based carbamation. It relies on the pH increase upon a complete hydrolysis of ortho-NCOs to amine groups using acidified dimethylsulfoxide. The method was found to be accurate and valid for a degree of substitution of up to 20%.

Crystal structure of minocycline hydrochloride dihydrate form A, C23H28N3O7Cl (H2O)2

2018 ◽  
Vol 34 (1) ◽  
pp. 59-65
Author(s):  
Austin M. Wheatley ◽  
James A. Kaduk ◽  
Amy M. Gindhart ◽  
Thomas N. Blanton
Keyword(s):  
Crystal Structure ◽  
Powder Diffraction ◽  
Density Functional ◽  
Hydroxyl Group ◽  
Water Molecules ◽  
Powder Diffraction File ◽  
X Ray ◽  
Dimethyl Amine ◽  
Minocycline Hydrochloride ◽  
Amine Groups

The crystal structure of minocycline hydrochloride dihydrate has been solved and refined using synchrotron X-ray powder diffraction data, and optimized using density functional techniques. Minocycline hydrochloride dihydrate crystallizes in space groupP212121(#19) witha= 7.40772(1),b= 14.44924(3),c= 22.33329(4) Å,V= 2390.465(12) Å3, andZ= 4. The minocycline cation is a zwitterion: both dimethylamino groups are protonated and one hydroxyl group is ionized. A potential ambiguity in the orientation of the amide group was resolved by considering Rietveld refinement residuals and displacement coefficients, as well as DFT energies. The crystal structure is dominated by hydrogen bonds. Both water molecules and a hydroxyl group act as donors to the chloride anion. Both protonated dimethyl amine groups act as donors to the ionized hydroxyl group. Several intramolecular O–H···O hydrogen groups help determine the conformation of the cation. The powder pattern is included in the Powder Diffraction File™ as entry 00-066-1606.

Synthèse de cétones encombrées via réduction de nitriles tertiaires en présence de métaux alcalins

1978 ◽  
Vol 56 (21) ◽  
pp. 2731-2736 ◽  
Author(s):  
Jean-Paul Mazaleyrat
Keyword(s):  
Radical Anion ◽  
Alkali Metals ◽  
Simple Method ◽  
Hydrolysis Of ◽  
Tertiary Alkyl

The reaction of alkali metals with tertiary alkyl nitriles eventually gives, after protonation, an imine. α-tert-Alkylketones are produced by the hydrolysis of these imines. This reaction, involving radical anion intermediates, is a simple method for the synthesis of highly hindered symmetric ketones.

scholarly journals A simple method for the determination of the cholesterol esterase activity.

2013 ◽  
Vol 60 (3) ◽  
Author(s):  
Agnieszka Ewa Stępień ◽  
Mykhailo Gonchar
Keyword(s):  
Human Serum ◽  
Esterase Activity ◽  
Cholesterol Oxidase ◽  
Cholesterol Esterase ◽  
Cholesterol Esters ◽  
Simple Method ◽  
Bacterial Enzyme ◽  
Low Costs ◽  
Hydrolysis Of

The proposed method determines the activity of cholesterol esterase (CEH) and takes advantage of its ability to catalyze the hydrolysis of cholesterol esters naturally present in human serum. The assay is based on Allain's method of spectrophotometric determination of cholesterol by means of cholesterol oxidase, peroxidase, but using 3,5-dichloro-dihydroxybenzenesulfonic acid (DHBS) as phenolic chromogen and human serum as a source of substrate for the CEH as a novelty. Furthermore, it is characterized by low costs and high precision. It can be employed to control the activity of CE preparations used for the preparation of enzymatic kits for the determination of cholesterol or for screening of potential bacterial enzyme producers.

scholarly journals Synthesis and Characterizations of Dipeptide Derivative of Gentamicin

2019 ◽  
Vol 28 (2) ◽  
pp. 73-82
Author(s):  
Oun D. Khudair ◽  
Diar A. Fatih
Keyword(s):  
Acid Chloride ◽  
Solution Method ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Free Hydroxyl ◽  
Ester Linkage ◽  
Amine Groups ◽  
Conventional Solution ◽  
Dipeptide Derivative

Abstract       The target derivative are gentamicin linked with L-Val- L-Ala by an ester linkage. These were synthesized by esterification method, which included the reaction of -OH hydroxyl group on (carbon No.5) of gentamicin with the acid chloride of the corresponding dipeptide, The preparation of new derivative of gentamicin involved protected the primary & secondary amine groups of Gentamicin, by Ethylchloroformate (ECF) to give N-carbomethoxy Gentamicin which was used for further chemical synthesis involving the free hydroxyl groups. Then prepared dipeptide (L-Val- L-Ala) by conventional solution method in present DCC & HoBt then reacted with thionyl chloride to prepared acid chloride of dipeptides, then after, linked by ester linkage to N-protection gentamicin in present pyridine as base, finally deportation the amino group of synthesized compound by using TFAA in present anisole. The characterization of the titled compounds were performed utilizing FTIR spectroscopy, CHNS elemental analysis, and by measurements of their physical properties.  

scholarly journals Acidic hydrolysis of astilbin and its application for the preparation of taxifolin from Rhizoma Smilacis Glabrae

2020 ◽  
pp. 174751982094835
Author(s):  
Xiao-Lin Qiu ◽  
Qing-Feng Zhang
Keyword(s):  
Activation Energy ◽  
Kinetic Parameters ◽  
Hydrolysis Reaction ◽  
Simple Method ◽  
Acidic Hydrolysis ◽  
A Value ◽  
Hcl Concentration ◽  
Hydrolysis Of

The acidic hydrolysis of astilbin to produce its aglycone, taxifolin, was investigated in this study. The effects of aq. HCl concentration and temperature on the reaction were studied, and the kinetic parameters were calculated. The results showed that with higher aq. HCl concentration and temperature, the hydrolysis of astilbin became faster. The activation energy of the hydrolysis reaction under 1 mol L−1 aq. HCl was calculated with a value of 148.6 kJ mol−1. The reaction was successfully applied to produce taxifolin from a sample of Rhizoma Smilacis Glabrae. A simple method for the purification of taxifolin from Rhizoma Smilacis Glabrae was developed with purity of 97.5%.

scholarly journals Potential Anti-Acetylcholinesterase Activity of Cassia timorensis DC.

Molecules ◽  
2020 ◽  
Vol 25 (19) ◽  
pp. 4545
Author(s):  
Nurul Amira Nurul Azman ◽  
Maram B. Alhawarri ◽  
Mira Syahfriena Amir Rawa ◽  
Roza Dianita ◽  
Amirah Mohd Gazzali ◽  
...  
Keyword(s):  
Hydrogen Bond ◽  
Acetylcholinesterase Activity ◽  
The Other ◽  
Hydroxyl Group ◽  
Anionic Site ◽  
Methanol Extracts ◽  
Plant Parts ◽  
Ache Inhibitory Activity ◽  
First Time ◽  
Hydrolysis Of

Seventeen methanol extracts from different plant parts of five different Cassia species, including C. timorensis, C. grandis, C. fistula, C. spectabilis, and C. alata were screened against acetylcholinesterase (AChE). C. timorensis extracts were found to exhibit the highest inhibition towards AChE whereby the leaf, stem, and flower methanol extracts showed 94–97% inhibition. As far as we are aware, C. timorensis is one of the least explored Cassia spp. for bioactivity. Further fractionation led to the identification of six compounds, isolated for the first time from C. timorensis: 3-methoxyquercetin (1), benzenepropanoic acid (2), 9,12,15-octadecatrienoic acid (3), β-sitosterol (4), stigmasterol (5), and 1-octadecanol (6). Compound 1 showed moderate inhibition towards AChE (IC50: 83.71 μM), while the other compounds exhibited poor to slightly moderate AChE inhibitory activity. Molecular docking revealed that the methoxy substitution of 1 formed a hydrogen bond with TYR121 at the peripheral anionic site (PAS) and the hydroxyl group at C5 formed a covalent hydrogen bond with ASP72. Additionally, the OH group at the C3′ position formed an interaction with the protein at the acyl pocket (PHE288). This possibly explains the activity of 1 in blocking the entry of acetylcholine (ACh, the neurotransmitter), thus impeding the hydrolysis of ACh.

Darstellung von o-Phenylen-bis(dibromphosphan) — Reaktionsprodukte von o-Phenylen-bis(dichlorphosphan) / Synthesis of o-Phenylene-bis(dibromophosphane) — Reaction Products of o-Phenylene-bis(dichlorophosphane)

1984 ◽  
Vol 39 (12) ◽  
pp. 1706-1710 ◽  
Author(s):  
H.-J. Wörz ◽  
E. Quien ◽  
H. P. Latscha
Keyword(s):  
Hydrogen Peroxide ◽  
Hydrogen Bromide ◽  
Equimolar Amount ◽  
Reaction Products ◽  
Large Excess ◽  
Cyclic Anhydride ◽  
Complete Hydrolysis ◽  
Hydrolysis Of

o-Phenylene-bis(dibromophosphane) (1) is prepared by reaction of P ,P,P′,P′-tetrakis(dim ethylamino)-o-phenylenediphosphane with hydrogen bromide in ether. The reaction of o-phenylene- bis(dichlorophosphane) (2) with CH3OH in ether yields o-phenylene-bis(phosphonousacid- dimethylester) (3). The Michaelis-Arbuzov conversion of 3, either by heat or by catalytic amounts of CH3I in toluene, yields ophenylene-bis(methylphosphinic-acid-methylester) (4). The reduction of 2 must be carried out with a large excess of LiAlH4 (1:4) in ether to give o-phenylenediphosphane (5). The cyclic anhydride (6) of P.P′-dichloro-o-phenylenediphosphonous acid is formed when 2 is hydrolyzed in ether with an equimolar amount of water. Complete hydrolysis of 2 with an excess of water gives o-phenylenediphosphonous acid (7). With hydrogen peroxide o-phenylenediphosphonic acid (8) can be isolated.

scholarly journals Allylamine PECVD Modification of PDMS as Simple Method to Obtain Conductive Flexible Polypyrrole Thin Films

Polymers ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 2108
Author(s):  
Robert Texidó ◽  
Salvador Borrós
Keyword(s):  
Thin Films ◽  
Step Method ◽  
Great Stability ◽  
Simple Method ◽  
Pdms Surface ◽  
Polymeric Chains ◽  
Plasma Grafting ◽  
One Step ◽  
Different Shapes ◽  
Amine Groups

In this paper, we report a one-step method to obtain conductive polypyrrole thin films on flexible substrates. To do this, substrates were modified through allylamine plasma grafting to create a high amount of reactive amine groups on PDMS surface. These groups are used during polypyrrole particle synthesis as anchoring points to immobilize the polymeric chains on the substrate during polymerization. Surface morphology of polypyrrole thin films are modified, tailoring the polyelectrolyte used in the polypyrrole synthesis obtaining different shapes of nanoparticles that conform to the film. Depending on the polyelectrolyte molecular weight, the shape of polypyrrole particles go from globular (500 nm diameter) to a more constructed and elongated shape. The films obtained with this methodology reflected great stability under simple bending as well as good conductivity values (between 2.2 ± 0.7 S/m to 5.6 ± 0.2 S/cm).

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