The Effect of Acidity of Al and Fe Silicates with MFI Structure on Benzene and Toluene Alkylation with Isopropyl Alcohol

1996 ◽  
Vol 61 (8) ◽  
pp. 1115-1130 ◽  
Author(s):  
Jiří Čejka ◽  
Naděžda Žilková ◽  
Blanka Wichterlová
Keyword(s):  
Kinetic Study ◽  
Molecular Sieves ◽  
Isopropyl Alcohol ◽  
Acid Sites ◽  
Transport Rate ◽  
Reaction Products ◽  
Oh Groups ◽  
Benzene Alkylation ◽  
Toluene Alkylation ◽  
Low Strength

Kinetic study of toluene and benzene alkylation with isopropyl alcohol on alumo- and ferrisilicates of MFI structure has shown that the alkylation activity does not follow the acidity (both the number and strength of bridging OH groups) of these molecular sieves. The rate of the overall reaction is controlled by the desorption/transport rate of bulky, strongly adsorbed cymenes and cumene. A higher concentration of n-propyltoluenes compared to n-propylbenzene, both undesired reaction products, formed via a bimolecular isomerization of isopropyl aromate with benzene or toluene, was due to the higher reactivity of isopropyltoluene with toluene in comparison with that of cumene with benzene. It is concluded that ferrisilicates of MFI structure possessing low strength acid sites appear to be promising catalysts for achieving both a high isopropyl- and para-selectivity in toluene alkylation to p-cymene.

On the Reaction of 2,5-Dihydroxy-[1,4]-benzoquinone with Diamines – Strain-induced Reactivity Effects

2020 ◽  
Vol 24 ◽  
Author(s):  
Hubert Hettegger ◽  
Andreas Hofinger ◽  
Thomas Rosenau
Keyword(s):  
Nucleophilic Substitution ◽  
Product Structure ◽  
Carbonyl Groups ◽  
Reaction Products ◽  
Double Bonds ◽  
Oh Groups ◽  
Natural Geometry ◽  
Quinoid Structure ◽  
Bond Localization

: The regioselectivity of the reaction of 2,5-dihydroxy-[1,4]-benzoquinone (DHBQ) with diamines could not be explained satisfactorily so far. In general, the reaction products can be derived from the tautomeric ortho-quinoid structure of a hypothetical 4,5-dihydroxy-[1,2]-benzoquinone. However, both aromatic and aliphatic 1,2-diamines form in some cases phenazines, formally by diimine formation on the quinoid carbonyl groups, and in other cases the corresponding 1,2- diamino-[1,2]-benzoquinones, by nucleophilic substitution of the OH groups, the regioselectivity apparently not following any discernible pattern. The reactivity was now explained by an adapted theory of strain-induced bond localization (SIBL). Here, the preservation of the "natural" geometry of the two quinoid C–C double bonds (C3=C4 and C5=C6) as well as the N–N distance of the co-reacting diamine are crucial. A decrease of the annulation angle sum (N–C4–C5 + C4–C5–N) is tolerated well and the 4,5-diamino-ortho-quinones, having relatively short N–N spacings are formed. An increase in the angular sum is energetically unfavorable, so that diamines with a larger N–N distance afford the corresponding ortho-quinone imines. Thus, for the reaction of DHBQ with diamines, exact predictions of the regioselectivity, and the resulting product structure, can be made on the basis of simple computations of bond spacings and product geometries.

Biologically Important Physicochemical Properties of Some Cephalosporins

1992 ◽  
Vol 57 (8) ◽  
pp. 1739-1746
Author(s):  
Katarína Škvareninová ◽  
Štefan Baláž ◽  
Ernest Šturdík ◽  
Miroslav Veverka ◽  
Jana Adamcová ◽  
...  
Keyword(s):  
Physicochemical Properties ◽  
Partition Coefficients ◽  
Dissociation Constants ◽  
Transport Rate ◽  
Hydrolysis Rate ◽  
Antibacterial Effects ◽  
Oh Groups ◽  
Non Linear Equation ◽  
Cell Components ◽  
The Relationship

In the series of cephalosporin derivatives, consisting of eight 7-(R1-CH2-CO-NH)cephalosporanic acids and of seven analogical compounds with 3-acetoxymethyl replaced by 3-CH3, physicochemical properties, which are expected to play a role in their antibacterial effects (the transport rate parameters and partition coefficients in the systems 1-octanol-water and 1-octanol-buffer, dissociation constants of the 4-carboxyl group, reactivity towards L-glutathione imitating the nucleophilic groups of the cell components and hydrolysis rate parameters), were determined. Linear dependences were observed between the partition coefficients and the π-constants of the varying substituents as well as between reactivity towards SH-groups of L-glutathione and OH-groups. The relationship between the transport rate parameters and partition coefficients, both measured in buffered as well as non-buffered system, was described by a common non-linear equation.

Epoxidation of 4-methyloct-4-ene: identification of reaction products and kinetic study

2003 ◽  
Vol 22 (8) ◽  
pp. 889-897 ◽  
Author(s):  
V.D. Ramos ◽  
D. Derouet ◽  
L.L.Y. Visconte
Keyword(s):  
Kinetic Study ◽  
Reaction Products

Nitroxides as reaction intermediates

1982 ◽  
Vol 60 (12) ◽  
pp. 1414-1420 ◽  
Author(s):  
Hans Gunter Aurich
Keyword(s):  
Electron Spin Resonance ◽  
Electron Spin ◽  
Isopropyl Alcohol ◽  
High Reactivity ◽  
Reaction Intermediates ◽  
Reaction Products ◽  
Nitronyl Nitroxide ◽  
Reaction Conditions ◽  
Spin Resonance ◽  
Secondary Reactions

Vinyl nitroxides 4 are obtained by oxidation of the nitrones 3, as was shown by esr studies and by identification of the reaction products. The formation of 4d–f is even observed in oxidation of the hydroxylamines 1d–f, nitroxides 2d–f and nitrones 3d–f being the intermediates. The high reactivity of the vinyl nitroxides 4 at their β-position is illustrated by the reactions of 4a with various compounds affording the nitroxides 7–10, respectively. Compound 4c reacts with its precursor 3c to give 11, 12, or 13, depending on the reaction conditions. From oxidation of 3a, c, and e the dimerization products 5a, c, and e, respectively, could be isolated. Whereas further oxidation of 5d yields 6d, the acyl nitroxides 14a and c are formed in the oxidation of 5a and c, respectively.The formation of quinone 23 in the reaction of 2-methyl-2-nitrosopropane with potassium tert-butoxide in isopropyl alcohol in the presence of oxygen is discussed. The nitroxide 20 has been detected in the reaction mixture. Imines 24 react with nitrosobenzene giving nitroxides 26. These are further oxidized by nitrosobenzene to afford nitrones 27. Whereas 27a and b could be isolated, 27c and d undergo further reaction yielding the diimines 30c and d along with dinitrone 29.The formation and reactions of imino nitroxides 31 and of the nitronyl nitroxide 41 are discussed. Electron spin resonance studies revealed the high reactivity of the imidazolyl-1,3-dioxides 46 and the imidazolyl-1-oxides 50, which easily form radicals 47–49 and 51, respectively, which are derived from secondary reactions.

Delicate Distinction between OH Groups on Proton-Exchanged H-Chabazite and H-SAPO-34 Molecular Sieves

2015 ◽  
Vol 119 (42) ◽  
pp. 24046-24055 ◽  
Author(s):  
Istvan Halasz ◽  
Bjorn Moden ◽  
Anton Petushkov ◽  
Jian-Jie Liang ◽  
Mukesh Agarwal
Keyword(s):  
Molecular Sieves ◽  
Oh Groups

scholarly journals Synthesis of Isopropyl Ferulate Using Silica-Immobilized Lipase in an Organic Medium

2011 ◽  
Vol 2011 ◽  
pp. 1-8 ◽  
Author(s):  
Ashok Kumar ◽  
Shamsher Singh Kanwar
Keyword(s):  
Ferulic Acid ◽  
Molecular Sieves ◽  
Isopropyl Alcohol ◽  
Immobilized Lipase ◽  
Inhibitory Effect ◽  
Organic Medium ◽  
Molar Ratio ◽  
Forward Reaction ◽  
Salt Ions ◽  
The Matrix

Immobilization of lipases has proved to be a useful technique for improving an enzyme's activity in organic solvents. In the present study, the performance of a silica-immobilized lipase was evaluated for the synthesis of isopropyl ferulate in DMSO. The biocatalyst was cross-linked onto the matrix with 1% glutaraldehyde. The effects of various parameters, molar ratio of ferulic acid to isopropyl alcohol (25 mM : 100 mM), concentration of biocatalyst (2.5–20 mg/mL), molecular sieves (25–250 mg/mL), and various salt ions, were studied consecutively as a function of percent esterification. Immobilized lipase at 25 mg/mL showed maximum esterification (~84%) of ferulic acid and isopropanol at a molar ratio of 25 mM : 100 mM, respectively, in DMSO at 45°C in 3 h under shaking (150 rpm). To overcome the inhibitory effect of water (a byproduct) if any, in the reaction mixture, molecular sieves (3 Å × 1.5 mm; 100 mg/mL) were added to the reaction mixture to promote the forward reaction. Salt ions like Ca2+, Cd2+, and Fe2+ enhanced the activity of immobilized biocatalyst while a few ions like Co2+, Zn2+, Mg2+, Mn2+, Al3+, and Na+ had mild inhibitory effect. Approximately, one third of total decrease in the esterification efficacy was observed after the 5th repetitive cycle of esterification.

Oligomerization of pent-1-ene over zeolite catalysts

2019 ◽  
Vol 19 (4) ◽  
pp. 307-315
Author(s):  
N. G. Grigoryeva ◽  
D. V. Serebrennikov ◽  
S. V. Bubennov ◽  
B. I. Kutepov
Keyword(s):  
Catalytic Properties ◽  
Acid Sites ◽  
Zeolite Catalysts ◽  
Main Reaction ◽  
Reaction Products ◽  
High Concentration ◽  
Reaction Conditions ◽  
One Dimensional ◽  
Fuel Components ◽  
Channel Systems

Oligomerization of pent-1-ene is an effective process for synthesis of high-quality environmentally friendly fuel components. Catalytic properties of H-zeolites FAU, OFF, MOR, ВЕА, MTW and MFI were studied for synthesis of pentene oligomers in an autoclave at 110–200 °C. The wide-pore structure of H-Y and H-Beta (18) zeolites and the high concentration of acid sites were established to cause the high oligomerization activity to obtain 97–100 % yields of oligomers. Oligomers obtained over these catalysts comprised, depending on the reaction conditions, 30–73 % dimers, 25–50 % trimers and 2–14 % oligomers with more than three monomer units (n > 3). Fine-pore zeolites (H-ZSM-5) and zeolites with one-dimensional channel systems (H-OFF, H-MOR, H-ZSM-12) were less active to oligomerization of pent-1-ene, decenes being the main reaction products.

A Novel Iron Silicate Mesoporous Material Synthesis and Its Characterization

2018 ◽  
Vol 24 (8) ◽  
pp. 5532-5536
Author(s):  
M. A Mary Thangam ◽  
Chellapandian Kannan
Keyword(s):  
Mesoporous Materials ◽  
Molecular Sieves ◽  
Mesoporous Material ◽  
Synthesis Method ◽  
Acid Sites ◽  
Mesoporous Molecular Sieves ◽  
Isomorphous Substitution ◽  
Main Role ◽  
Material Synthesis ◽  
Ft Ir

The mesoporous materials have variety of applications in several field particularly it has a main role in Catalysis, Petrochemical industries and Adsorption. Normally the porous material has well ordered 3Dimensional structure, huge surface area, high thermal stability and active acid sites. The properties of these materials can be varied because it is mostly depends on its template, synthesis method and isomorphous substitution of metal ions. There are two major mesoporous materials which are aluminosilicate and aluminophosphate. In this present investigation AlCl3 and FeCl3 are used in equal amount for the synthesis of mesoporous material. The synthesized material is characterized by FT-IR, XRD, TGA, BET, EDAX and TPD. Morphological images were studied by SEM. These characterization techniques confirm the formation of mesoporous molecular sieves.

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