Silica Surface Modification Reactions with Aluminum and Boron Alkyls and (Alkyl)Chlorides: Reactivities and Surface Nanostructures

2008 ◽  
Vol 8 (2) ◽  
pp. 660-666 ◽  
Author(s):  
Jonathan P. Blitz ◽  
Jeannine M. Christensen ◽  
Carol A. Deakyne ◽  
Vladimir M. Gun'ko
Keyword(s):  
Chemical Structure ◽  
Silica Surface ◽  
Molecular Level ◽  
Ring Structure ◽  
Membered Ring ◽  
Silica Surfaces ◽  
Surface Nanostructures ◽  
Reactive Groups ◽  
Aluminum Compounds ◽  
Silica Surface Modification

The functionalization of nanoporous and nanoparticulate silica surfaces requires a molecular level understanding of the chemistry and structures which result from surface reactions. Various types of reactive groups on silica can participate, giving rise to different nanostructures. It is necessary to devise methods to alter the reactive nature of silica surfaces to control the nanoscale chemical structure. Various silica pretreatments are utilized to alter the silica surface prior to reaction with AlEt3, AlEtxCl3−x, BEt3, BCl3, and TiCl4. Reactivities of these surface reactive reagents are compared. Aluminum compounds preferentially react with loss of alkane rather than HCl, in a thermodynamically controlled reaction as determined by ab initio computational methods. Consideration of the structures resulting from reaction of the boron and aluminum compounds above with silica surface diols has been taken into account. Particular attention has been paid to the possibility of forming a cyclic 4-membered ring structure. While this is unlikely to form from reactions with MCl3, such structures may be possible when reacting silicas with MMe3.

AMIDOMYCIN, A NEW ANTIBIOTIC FROM A STREPTOMYCES SPECIES, CHEMICAL STRUCTURE

1957 ◽  
Vol 35 (10) ◽  
pp. 1109-1116 ◽  
Author(s):  
L. C. Vining ◽  
W. A. Taber
Keyword(s):  
Lactic Acid ◽  
Amino Acid ◽  
Alkaline Hydrolysis ◽  
Chemical Structure ◽  
Ring Structure ◽  
Membered Ring ◽  
Optically Active ◽  
Streptomyces Species ◽  
Amide Bonds ◽  
Compound C

Amidomycin, an antibiotic active primarily against yeast, has been isolated from a Streptomyces species. The Compound C10H68O12N4. is neutral, optically active, and shows no unsaturation nor characteristic light absorption maxima. It is composed of 4 moles each of D(−)-valine and D(−)-α-hydroxyisovaleric acid, linked alternately by ester and amide bonds to form a 24-membered ring (I). This structure is assigned from the following observations: on mild alkaline hydrolysis 4 moles of alkali are consumed with formation of a hydroxy acid, C10H19O4N (II). The latter on distillation gave a crystalline lactone, C10H17O3N, considered to be 3,6-diisopropyl-2,5-diketomorpholine (III), which was hydrolyzed to give 1 mole each of D(−)-valine and D(−)-α-hydroxyisovaleric acid.Amidomycin is closely related to valinomycin, an antibiotic isolated from Streptomycesfulvissimus and shown to be a 24-membered ring compound containing D(−)-valine, D(−)-α-hydroxyisovaleric acid, L(+)-valine, and L(−)-lactic acid. It also resembles the enniatins, produced by certain species of Fusarium, but differs from these compounds in the number of units in the ring structure as well as in containing D(−)-valine rather than an N-methyl-L-amino acid.

Understanding the microcrystal tests of three related phenethylamines: theortho-metallated (±)-amphetamine formed with gold(III) chloride, and the tetrachloridoaurate(III) salts of (+)-methamphetamine and (±)-ephedrine

2013 ◽  
Vol 69 (4) ◽  
pp. 388-393 ◽  
Author(s):  
Matthew R. Wood ◽  
Roger A. Lalancette
Keyword(s):  
Drug Use ◽  
Illicit Drug ◽  
Illicit Drug Use ◽  
Ring Structure ◽  
Membered Ring ◽  
Asymmetric Unit ◽  
Organic Components ◽  
Bidentate Complex

Theortho-metallation product of the reaction of (±)-amphetamine with gold(III) chloride, [D,L-2-(2-aminopropyl)phenyl-κ2N,C1]dichloridogold(III), [Au(C9H12N)Cl2], and the two salts resulting from crystallization of (+)-methamphetamine with gold(III) chloride, D-methyl(1-phenylpropan-2-yl)azanium tetrachloridoaurate(III), (C10H16N)[AuCl4], and of (±)-ephedrine with gold(III) chloride, D,L-(1-hydroxy-1-phenylpropan-2-yl)(methyl)azanium tetrachloridoaurate(III), (C10H16NO)[AuCl4], have different structures. The first makes a bidentate complex directly with a dichloridogold(III) group, forming a six-membered ring structure; the second and third each form a salt with [AuCl4]−(each has two formula units in the asymmetric unit). The organic components are all members of the same class of stimulants that are prevalent in illicit drug use. These structures are important contributions to the understanding of the microcrystal tests for these drugs that have been employed for well over 100 years.

Determination of the Orientation of Silanes on Silica Surfaces by Fourier Transform Infrared Photoacoustic Spectroscopy

1986 ◽  
Vol 40 (4) ◽  
pp. 513-519 ◽  
Author(s):  
Marek W. Urban ◽  
Jack L. Koenig
Keyword(s):  
Fourier Transform ◽  
Photoacoustic Spectroscopy ◽  
Surface Coverage ◽  
Silica Surface ◽  
Fourier Transform Infrared ◽  
Coupling Agents ◽  
Surface Hydroxyl ◽  
Silica Surfaces ◽  
Quantitative Surface Analysis ◽  
Infrared Photoacoustic Spectroscopy

Fourier transform infrared photoacoustic spectroscopy has been used for quantitative surface analysis of silica treated with trifunctional coupling agents such as γ-Methacryloxypropyltriethoxysilane (γ-MPS), γ-Glycidoxypropyltrimethoxysilane (γ-GPS), and γ-Aminopropyltri-ethoxysilane (γ-APS). The calibration curves are obtained for several characteristic bands of the coupling agents. Using a highly polarizable gas in the photoacoustic cell and comparing the spectra with a nonpolarizable coupling gas, it is possible to evaluate orientation of the coupling agents on the silica surface. The type of orientation is a function of the extent of surface coverage. At low surface coverage, coupling agents tend to take a perpendicular orientation with respect to the surface, and increasing surface coverage leads to parallel orientation. Increasing the coupling agent concentration also causes orientational changes of the species which form chemical bonds with the silica surface (hydroxyl, water, and carbonyl groups).

Synthese eines Doppel-Carbodiphosphorans und seiner Vorstufen / Synthesis of a Double-Carbodiphosphorane and its Precursors

1982 ◽  
Vol 37 (6) ◽  
pp. 677-679 ◽  
Author(s):  
Hubert Schmidbaur ◽  
Thomas Costa
Keyword(s):  
Phosphonium Salt ◽  
Ring Structure ◽  
Membered Ring ◽  
Phosphonium Bromide ◽  
High Yields

Abstract The reaction of 1,4-dibromobutane with bis(diphenylphospliino)methane (1) yields two products, one of which is identified as butane-1,4-bis[diphenyl(diphenylphosphinomethyl)-phosphonium bromide] (3 a). Transylidation of this bis-phosphonium salt using two equiv-alents of (CH3)3P = CH2 affords the bis-ylide [CH2CH2P(C6H5)2 = CH-P(C6H5)2]2 (4) in high yields. This conversion can be reversed on treatment of 4 with etheral HCl (to give 3b). Methylation of 4 with CH3I occurs at phosphorus, however, and produces the bis-semiylide salt (5), [CH2CH2P(C6H5)2CHP(C6H5)2CH3]22⊕ 2I⊖. Transylidation of 5 (again with (CH3)3P = CH2) leads to the bis-carbodiphosphorane (6), [CH2CH2P(C6H5)2 = C = P(C6H5)2CH3]2. All compounds were characterized by elemental and detailed NMR analyses. The second product of the above quaternisation reaction is a cyclic bis-phosphonium salt (2) with a seven-membered ring structure.

scholarly journals Clean chlorination of silica surfaces by a single-site substitution approach

2018 ◽  
Vol 47 (12) ◽  
pp. 4301-4306 ◽  
Author(s):  
Niladri Maity ◽  
Samir Barman ◽  
Edy Abou-Hamad ◽  
Valerio D'Elia ◽  
Jean-Marie Basset
Keyword(s):  
Silica Surface ◽  
Single Site ◽  
Silanol Groups ◽  
Silica Surfaces ◽  
Selective Chlorination ◽  
Hydrogen Bonded

Unveiling a clean, selective chlorination method for the quantitative substitution of well-defined non-hydrogen bonded silanol groups of the silica surface.

A method for introducing organic functional groups on silica surfaces using a functionalized vinylsilane containing polymer

2015 ◽  
Vol 6 (4) ◽  
pp. 555-560 ◽  
Author(s):  
Jung-Woo Park ◽  
Dong-Su Kim ◽  
Min-Seok Kim ◽  
Ji-Hwan Choi ◽  
Chul-Ho Jun
Keyword(s):  
Functional Groups ◽  
Silica Surface ◽  
New Method ◽  
Silica Surfaces ◽  
Organic Functional Groups

A new method for introducing robustly bound organic functional groups on the silica surface using a vinylsilane-containing polymer is developed.

Models for biomedical interfaces: a computational study of quinone-functionalized amorphous silica surface features

2017 ◽  
Vol 19 (11) ◽  
pp. 7793-7806 ◽  
Author(s):  
Marta Corno ◽  
Massimo Delle Piane ◽  
Patrick Choquet ◽  
Piero Ugliengo
Keyword(s):  
Amorphous Silica ◽  
Silica Surface ◽  
Computational Study ◽  
Antimicrobial Properties ◽  
Surface Features ◽  
Silica Surfaces

The structural and IR features of amorphous silica surfaces, functionalized by ortho-benzoquinone groups, were computed to obtain a deeper knowledge of multifunctional coatings with antimicrobial properties.

PYRANOSE–FURANOSE AND ANOMERIC EQUILIBRIA: INFLUENCE OF SOLVENT AND OF PARTIAL METHYLATION

1966 ◽  
Vol 44 (17) ◽  
pp. 2039-2049 ◽  
Author(s):  
W. Mackie ◽  
A. S. Perlin
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Dimethyl Sulfoxide ◽  
Ring Structure ◽  
Tautomeric Equilibrium ◽  
Membered Ring ◽  
Partial Methylation ◽  
Hydroxyl Proton ◽  
Methyl Derivatives ◽  
Influence Of Solvent

Sugars possessing the arabino (2,3,4-trans,cis) configuration exist as furanoses to a greater extent in dimethyl sulfoxide than in water. Their 2,3-di-O-methyl derivatives show an even stronger preference for a five membered ring structure in both solvents. This is most marked for 2,3-di-O-methyl-D-arabinose and 2,3-di-O-methyl-D-altrose, which are 65% and 80% furanose, respectively, in dimethyl sulfoxide. Compounds in the xylo (2,3,4-trans,trans) or lyxo (2,3,4-cis,trans) series show little tendency to be furanoses in either solvent. However, α-pyranoses in the lyxo series are relatively more stable in dimethyl sulfoxide than in water, whereas the anomeric composition for members of the xylo series is the same in both solvents. Some of these variations in the equilibria are attributed to the preferential stabilization of pyranose forms in water. D-Lyxose and D-ribose show nuclear magnetic resonance spectral differences in the two solvents that appear to be due to conformational, as well as tautomeric, equilibrium changes.An equatorial anomeric hydroxyl proton of a given pair in dimethyl sulfoxide shows a larger spacing (6.5–8.0 c.p.s.) than an axial anomeric hydroxyl proton (4–5 c.p.s.). The signal for the latter proton occurs at higher field than an equatorial OH-1, except when OH-2 is axial.

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