Presence Of Tetrabutylammonium Hydroxide Research Articles

Fine‐Tuning Texture of Highly Acidic HZSM‐5 Zeolite for Efficient Ethanol Dehydration

AbstractAchieving high and stable ethylene yield from (bio)ethanol dehydration over highly active acidic zeolite remains challenging due to undesired side‐reactions. To overcome this issue, the fine‐tuned textural property of the HZSM‐5 catalyst with a hierarchical structure is crucial to overcome diffusion restrictions and limit undesired side‐reactions. Herein, the texture of high acid catalysts obtained via hydrothermal synthesis was simply tuned in the presence of tetrabutylammonium hydroxide as a meso‐ and micropore directing agent and the controlled molar ratio of NaF‐to‐Al2O3. The hierarchically designed HZSM‐5 with the small nanosheet size of 6.5 nm exhibits a high external surface area and mesopores, largely enhancing the catalytic performance of ethanol dehydration up to 95 % ethylene yield as well as preventing the formation of heavy hydrocarbons. To gain insights into the mechanistic points of view, the in situ DRIFTS study revealed that ethylene could form through ethoxy‐mediated mechanism or decomposition of diethyl ether (DEE). The catalyst deactivation caused by polyaromatics obtained from side‐reactions is the reason for low ethanol conversion and high DEE selectivity. Reducing the crystal size of highly acidic zeolite to ultra‐thin nanosheet can shorten the residence time of ethanol, intermediates, and products in porous structures, substantially suppressing the transformation of coke precursors into heavy hydrocarbons to achieve high and stable ethylene yield.

Ditopic Chemodosimeter for Selective Detection of Nerve Agent Tabun Simulant DCNP

AbstractSelective optical detection of highly toxic nerve agents and their mimics like diethyl cyanophosphate (DCNP) is of paramount importance for armed forces and first responders in order to decide the suitable medical countermeasures. The reported optical chemical sensors for DCNP suffered from poor selectivity due to their single point covalent interaction with analyte. To overcome this limitation, we herein, report a novel protocol utilizing a ditopic chemodosimeter which, in presence of tetrabutylammonium hydroxide (TBAOH), underwent dual interaction with reactive subunits of DCNP, viz., electrophilic phosphorus and cyanide, to induce unique changes in its fluorescence as well as colorimetric properties. Other interfering analytes could not trigger the similar optical response in the sensing probe due to the absence of electrophilic phosphorus and cyanide. A truth table was constructed to reveal that only DCNP but not other analytes could induce changes in both fluorescence as well as colorimetric properties of sensing probe. The linearity range of the proposed method was found to be 30–70 μM while chromogenic limit of detection (LOD) was calculated to be 99 nM which are comparable to the reported methods. Thus, use of indigenously available 2‐hydroxy‐1‐naphthaldehyde as sensing probe without requiring further chemical manipulation represented a significant improvement over the literature methods for DCNP sensing.

Unexpected formation of 1,2- and 1,4-bismethoxyl Sc3N@I h-C80 derivatives via regioselective anion addition: an unambiguous structural identification and mechanism study.

An attempt to achieve heterocyclic cycloadducts of Sc3N@Ih-C80via reaction with Ph2C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> O, PhC Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> CPh or PhCN in the presence of tetrabutylammonium hydroxide (TBAOH) stored in CH3OH led to the formation of the unexpected bismethoxyl adducts of Sc3N@Ih-C80 (1 and 2). Further studies reveal that TBAOH in CH3OH can boost the CH3O− addition efficiently, regardless of the presence of other reagents. Single-crystal X-ray diffraction results firmly assign the molecular structures of 1 and 2 as respective 1,4- and 1,2-bismethoxyl adducts, and reveal unusual relationships between the internal Sc3N cluster and the addition modes, in addition to the unusual packing mode in view of the orientation of the methoxyl groups. Electrochemical results demonstrate smaller electrochemical gaps for 1 and 2, relative to that of Sc3N@Ih-C80, confirming their better electroactive properties. Finally, a plausible reaction mechanism involving anion addition and a radical reaction was proposed, presenting new insights into the highly selective reactions between the methoxyl anion and metallofullerenes. 1 and 2 represent the first examples of methoxyl derivatives of metallofullerenes. This work not only presents a novel and facile strategy for the controllable synthesis of alkoxylated metallofullerene derivatives, but also provides new non-cycloadducts for the potential applications of EMFs.

Reaction of Zn(II) with a BINOL-amino-acid Schiff base: An unusual off-on-off fluorescence response

An amino-acid based Schiff base (S)-2 is prepared from the condensation of (S)-3,3′-diformyl BINOL (BINOL = 1,1′-bi-2-naphthol) with l-valine in the presence of tetrabutylammonium hydroxide in methanol. This compound is found to exhibit off-on-off fluorescence response toward Zn2+. The spectroscopic studies reveal that (S)-2 reacts with 1 equiv Zn2+ to form a dimeric [2+2] complex with greatly enhanced fluorescence. Excess amount of Zn2+ might cause dissociation of this dimeric complex to give significantly reduced fluorescence.

Microwave-assisted green synthesis of 4,5-dihydro-1H-pyrazole-1-carbothioamides in water.

Rapid, efficient, simple and green procedure for the synthesis of 4,5-dihydro-1H-pyrazole-1-carbothioamides via the multicomponent reaction of aryl aldehydes, acetophenones and thiosemicarbazide in water in the presence of tetrabutylammonium hydroxide under microwave irradiation is reported.

Isothermal kinetics of C60 polyhydroxylation in a two-phase system in the presence of tetrabutylammonium hydroxide

The isothermal kinetics of fullerene (C60) polyhydroxylation with sodium hydroxide in the presence of phase-transfer catalyst tetrabutylammonium hydroxide (TBAH) in a two-phase system was investigated. A spectrophotometric method for the determination of the degree of C60 polyhydroxylation was developed. The isothermal kinetic curves of C60 polyhydroxylation were measured in the temperature range from 300 to 328 K. The dependence of effective activation energy on the degree of polyhydroxylation was calculated by using the isoconversional method. The kinetics of polyhydroxylation is mathematically described successfully with the kinetic model of first order chemical reaction. The values of the rate constants, activation energy and pre-exponential factor of polyhydroxylation were calculated. The thermodynamic parameters of activated complex formation for C60 polyhydroxylation [standard enthalpy of activation (∆H*), standard entropy of activation (∆S*) and standard free Gibbs energy of activation (∆G*)] were calculated by using Eyring equation. The effect of stirring speed on the reaction rate constants of polyhydroxylation in the presence of the two types of phase transfer catalysts, TBAH and cetyltrimethylammonium bromide (CTAB) was determined. The reaction mechanism of phase-transfer catalyst and activation of C60 molecule for the reaction of polyhydroxylation was suggested.

Synthesis of 1-substituted 2,6,7-trioxa-4-phospha-1-borabicyclo[2.2.2]octan-1-uide

ABSTRACT1-Substituted 2,6,7-trioxa-4-phospha-1-borabicyclo[2.2.2]octan-1-uides were obtained in 31–71% yields by the reaction of tetrakis(hydroxymethyl)phosphonium sulfate with alkyl- or arylboronic acids in the presence of tetrabutylammonium hydroxide.

Hydrothermal synthesis of lanthanide (hydr)oxide micro/nanorods in presence of tetrabutylammonium hydroxide

Uniform and well-defined lanthanide hydroxide and oxide micro/nanorods Ln(OH)3 (Ln=La, Pr, Sm, Eu, Gd, Er) and Gd(OH)3:Eu3+, Gd2O3:Eu3+ were successfully synthesized through a green and facile hydrothermal method. Tetrabutylammonium hydroxide (TBAH) and lanthanide nitrides were used as the hydrothermal precursors without the addition of any templates/surfactants. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and photoluminescence (PL) spectra. The result demonstrated that lanthanide hydroxide micro/nanorods with 20–80 nm in diameter and 50–450 in length were obtained. The size of the Ln(OH)3 (Ln=La, Pr, Sm, Eu, Gd, Er) rods increased with the increase of the atomic number. The size of the Gd(OH)3:Eu3+ rods decreased with the increase of pH value by modulating the amount of the TBAH solution. The as-formed product via the hydrothermal process, Gd(OH)3:Eu3+, could be transformed to Gd2O3:Eu3+ with the same morphology and a slight shrinking in size after a post annealing process. It is a facial method to synthesize photoluminescent nanomaterial of Gd2O3:Eu3+. The Gd2O3:Eu3+ microrods exhibited strong red emission corresponding to 5D0→7F2 transition (610 nm) of Eu3+ under UV light excitation (257 nm).

Determination of methacrylic acid in food simulants by pyrolytic butylation-gas chromatography

An on-line pyrolytic butylation approach was proposed to determine methacrylic acid (MA) in food simulants by gas chromatography (GC) without an expensive pyrolyzer. MA in food simulants was converted into butyl methacrylate in the presence of tetrabutylammonium hydroxide (TBAH) without any pretreatment at 330°C in the injection-port, contributing to high GC signal response. The derivatizing conditions for the proposed method were optimized, namely the injection-port temperature, type and amount of the organic alkaline used for derivatization. A series of standard solutions of MA in the range of 1.0–50mg/kg were analyzed with correlation coefficient r≥0.9975. The limits of detection (LODs) were less than 0.15mg/kg for MA in four matrix simulants (distilled water, 3%w/v acetic acid, 10%v/v ethanol, and isooctane). Relative standard deviations (RSDs) for retention time, peak height and peak area were all less than 3.88%. The technique was successfully applied to the analysis of MA migrating from plastic cup samples, with recoveries of added MA in the range of 96.5–123.0%. Direct injection of the simulants into the GC system after migration tests, without any pretreatment step, makes the developed method of great value for rapid screening analysis of samples in bulks.

Practical Radiosynthesis and Preclinical Neuroimaging of [11C]isradipine, a Calcium Channel Antagonist.

In the interest of developing in vivo positron emission tomography (PET) probes for neuroimaging of calcium channels, we have prepared a carbon-11 isotopologue of a dihydropyridine Ca2+-channel antagonist, isradipine. Desmethyl isradipine (4-(benzo[c][1,2,5]oxadiazol-4-yl)-5-(isopropoxycarbonyl)-2,6-dimethyl-1,4-dihydropyridine-3-carboxylic acid) was reacted with [11C]CH3I in the presence of tetrabutylammonium hydroxide in DMF in an HPLC injector loop to produce the radiotracer in a good yield (6 ± 3% uncorrected radiochemical yield) and high specific activity (143 ± 90 GBq·µmol−1 at end-of-synthesis). PET imaging of normal rats revealed rapid brain uptake at baseline (0.37 ± 0.08% ID/cc (percent of injected dose per cubic centimeter) at peak, 15–60 s), which was followed by fast washout. After pretreatment with isradipine (2 mg·kg−1, i.p.), whole brain radioactivity uptake was diminished by 25%–40%. This preliminary study confirms that [11C]isradipine can be synthesized routinely for research studies and is brain penetrating. Further work on Ca2+-channel radiotracer development is planned.

Use of “on line [11C]methylation” in the synthesis of l-[O-11C-methyl]tyrosine, a promising radiotracer for positron emission tomography

A labeled tyrosine analog, viz., l-[O-11C-methyl]tyrosine ([11C]MT), was obtained by a reaction of [11C]-methyl iodide with a tyrosine salt in DMSO in the presence of tetrabutylammonium hydroxide on the Sep-Pak tC18 cartridge surface. The efficiency of the “on line O-[11C]methylation” was 55%.

Contents: Macromol. Rapid Commun. 6/2014

A Mitsunobu reaction of trifluoroacetamide (TFA amide) and alcohols is used in a postpolymerization modification process. The reaction is conducted on polystyrene (PSt) bearing 20 mol% TFA amide groups with 4-methyl benzyl alcohol in the presence of a N,N,N′,N ′-tetramethylazodicarboxamide and tributylphosphine as mediators. The Mitsunobu reaction on polymer proceeds efficiently, as confirmed by the obvious precipitation generation during the reaction and the conversion of TFA amide moiety reached 88.6% confirmed by 19 F NMR measurement, yielding PSt bearing tertiary TFA amide moieties. The obtained polymers featuring tertiary TFA amide moieties are deprotected in the presence of tetrabutylammonium hydroxide as a base to afford corresponding polymers featuring functionalized polyamine scaffolds with 92.5% conversion. In addition, the precise structural assignment is proven by synthesis and analysis of the model monomeric compounds and the respective model polymers.

Preparation of Functional Polyamine Scaffolds via Mitsunobu Post‐Polymerization Modification Reactions

A Mitsunobu reaction of trifluoroacetamide (TFA amide) and alcohols is used in a post‐polymerization modification process. The reaction is conducted on polystyrene (PSt) bearing 20 mol% TFA amide groups with 4‐methyl benzyl alcohol in the presence of a N,N,N′,N′‐tetramethylazodicarboxamide and tributylphosphine as mediators. The Mitsunobu reaction on polymer proceeds efficiently, as confirmed by the obvious precipitation generation during the reaction and the conversion of TFA amide moiety reached 88.6% confirmed by 19F NMR measurement, yielding PSt bearing tertiary TFA amide moieties. The obtained polymers featuring tertiary TFA amide moieties are deprotected in the presence of tetrabutylammonium hydroxide as a base to afford corresponding polymers featuring functionalized polyamine scaffolds with 92.5% conversion. In addition, the precise structural assignment is proven by synthesis and analysis of the model monomeric compounds and the respective model polymers. image

Preparing L‐α‐Glycerophosphocholine in a Phase‐Transfer Catalytic Reaction: Kinetic Study

ABSTRACTThe transesterification of phosphatidylcholine with methanol was successfully carried out using a promising solvent methyl tert‐butyl ether instead of traditional ether, and the reaction was dramatically enhanced in the presence of tetrabutylammonium hydroxide as the phase‐transfer catalyst. Kinetics of the reaction including the effects of the reaction conditions on the conversion of phosphatidylcholine and the apparent rate constant (kapp) were investigated in detail. On the basis of the experimental evidence, the transesterification mechanism was proposed and a kinetic model was developed, and the experimental data were well described by the pseudo–first‐order equation.

Zinc blende versus wurtzite ZnS nanoparticles: control of the phase and optical properties by tetrabutylammonium hydroxide.

The influence of tetrabutylammonium hydroxide on the phase composition (cubic zinc blende versus hexagonal wurtzite) of ZnS nanoparticles was studied. The ZnS nanoparticles were prepared by a microwave-assisted solvothermal method, and the phase structure and optical properties along with the growth process of ZnS nanoparticles were studied. We report XRD, FE-SEM, EDXS, UV-vis and PL measurements, and first-principles calculations based on TDDFT methods in order to investigate the structural and electronic properties and the growth mechanism of ZnS nanostructures. The effects as well as the merits of microwave heating on the process and characteristics of the obtained ZnS nanostructures and their performance are reported.

ChemInform Abstract: A Cascade Reaction of Pyrrole‐2‐carbaldehyde Substituted Morita—Baylis—Hillman Adducts in the Presence of Tetrabutylammonium Hydroxide or Acetate to Construct Aza‐Heterocycles.

AbstractA phase‐transfer catalyst promoted intramolecular transformation of pyrrole‐2‐carbaldehyde substituted Morita—Baylis—Hillman adducts as an efficient way to construct pyrrolo[1,2‐a]azepin‐7(6H)‐one skeletons in moderate to good yields is presented.

폴리(이미드-아라미드-설폰)의 합성과 그들의 열적성질

이미드/아라미드/설폰기가 교대로 도입된 poly(imide-aramid-sulfone)s을 divinyl sulfone(DVS)과 <TEX>$N^1,N^4$</TEX>-bis(4-(vinylsulfonyl)phenyl)terephthalamide (2)를 pyromellitic diimide와 반응하여 높은 수율로 제조하였다. 또한 고분자를 닮은 3가지 모델 화합물인 N-[2-(p-aminophnenylsulfonyl)ethyl]phthalimide (3), 2,2'-(2,2'-sulfonylbis(ethane-2,1-diyl))diisoindoline-1,3-dione (4), 및 N,N-bis(4-(2-(1,3-dioxoisoindolin-2-yl)ethylsulfonyl)phenyl)terephthalamide (5)을p-aminophenyl vinyl sulfone, DVS, 2와 phthalimide와 반응하여 얻었다. 축합 중합은 phthalimide 기와 DVS의 마이클 첨가 반응에 의하여 균일 용액으로 진행되며 tetrabutylammonium hydroxide (TBAH)가 촉매로 작용하여 poly(imide-aramid-sulfone)s 6-12의 분자량이 큰 중합체를 얻을 수 있었다. DVS/2의 구성비는 1/0, 3/1, 2/1, 1/1, 1/2, 1/3, 및 0/1이다. 얻어진 고분자들은 극성 용매인 N,N-dimethylformamide, dimethylsulfoxide, N-methylpyrrolidinone 및 tetrahydrofuran에 잘 용해하였다. 그 밖에 분자량, 점도 그리고 열적 성질을 평가하였다. A series of poly(imide-aramid-sulfone)s with alternatingly introduced imide/aramid groups were prepared by reacting divinyl sulfone (DVS) and <TEX>$N^1,N^4$</TEX>-bis(4-(vinylsulfonyl)phenyl)terephthalamide (2) with pyromellitic diimide. Three model compounds, N-[2-(p-aminophnenylsulfonyl)ethyl]phthalimide (3), 2,2'-(2,2'-sulfonylbis(ethane-2,1-diyl))diisoindoline-1,3-dione (4), and N,N-bis(4-(2-(1,3-dioxoisoindolin-2-yl)ethylsulfonyl)phenyl)terephthalamide (5), resembling polymers were prepared with good yields by reacting p-aminophenyl vinyl sulfone, DVS, and 2 with phthalimide. Condensation polymerization was carried out by Michael-type addition reaction of the difunctional phthalimide group with the DVS group in the presence of tetrabutylammonium hydroxide (TBAH), resulting in poly(imide-aramid-sulfone)s 6-12 with moderate molecular weights and good yields. They were highly soluble in polar solvents such as N,N-dimethylformamide, dimethylsulfoxide, N-methylpyrrolidinone and tetrahydrofuran. The ratios of DVS/2 were 1/0, 3/1, 2/1, 1/1, 1/2, 1/3, and 0/1. Molecular weight and physical properties such as solubility, viscosity, and thermal properties of the polymers were examined.

A cascade reaction of pyrrole-2-carbaldehyde substituted Morita–Baylis–Hillman adducts in the presence of tetrabutylammonium hydroxide or acetate to construct aza-heterocycles

The phase-transfer catalyst promoted intramolecular transformation of pyrrole-2-carbaldehyde substituted Morita-Baylis-Hillman adducts has been disclosed, providing an efficient way to construct pyrrolo[1,2-a]azepin-7(6H)-one skeletons in moderate to good yields (up to 92%) under mild conditions.

Redox reaction between m-thiocresol and riboflavin glycosides with 2:1 complex formation; regulation by the steric effect of sugar in the side chain

We investigated the reduction of riboflavin-2′, 3′, 4′, 5′-tetra-acetate (AcB2), riboflavin-1′-glucoside-2″, 3″, 4″, 6″, 2′, 3′, 4′, 5′-hepta-acetate (AcB2gl) and lumiflavin using m-thiocresol (mTc) in the presence of tetrabutylammonium hydroxide. The series of rate constants for AcB2 and AcB2gl reductions indicated that modified Lineweaver–Burk plots were best fit by assuming a 1:2 complex formation. The complex formation in the reaction was supported by the 2-D nuclear Overhauser enhancement spectroscopy and circular dichroism spectra. The modified Michaelis–Menten constants (K m) for AcB2 and AcB2gl with mTc were 1.32 and 0.86 × 10− 3 M2, respectively, and the maximum rate constant k 2 were 4.45 and 4.35 × 10− 2 M− 1 s− 1, respectively. The E 1/2 values of AcB2 and AcB2gl were − 331 and − 341 mV, respectively, which indicated that their reduction activities were almost the same. It was established that the redox function depended on the formation of the complex and was regulated by the steric effect of the sugar in the side chain.

Nanometer-thin layered hydroxide platelets of (Y0.95Eu0.05)2(OH)5NO3·xH2O: exfoliation-free synthesis, self-assembly, and the derivation of dense oriented oxide films of high transparency and greatly enhanced luminescence

Ultra-thin (Y0.95Eu0.05)2(OH)5NO3·xH2O (Y/Eu LRH) nanoplates (down to ∼4 nm thick) have been successfully synthesized in one step, without exfoliation, through hydrothermal treatment of mixed nitrate solution in the presence of tetrabutylammonium hydroxide (TBAOH). Highly [111] oriented, dense (Y0.95Eu0.05)2O3 phosphor films (∼60 nm thick) with excellent optical transparency (∼86%) and a greatly enhanced luminescence intensity (∼4 times that of the powder form) have been constructed via self-assembly of ultra-thin Y/Eu LRHs nanoplates, followed by proper annealing.