Propyl Bromide Research Articles

Theoretical and experimental study on the recovery of bromide by crystallization from pesticide production wastewater

Brominated wastewater from the propyl bromide pesticide production rich in ammonium, sodium and bromine salts at a high concentration of 11 %. For the recycling of chemical resources of this mixed brine salt system, this paper proposes a method for the separation of bromide from bromine-containing chemical wastewater by crystallization. According to the process design needs of the new method, and because 298 K and 323 K are two common temperatures in industrial practice, in this paper, the solubility data of the NaCl-NH4Cl-NaBr-NH4Br-H2O quaternary system at 298 K and 323 K, as well as its ternary subsystems, NaBr-NH4Br-H2O and NH4Cl-NH4Br-H2O at 323 K were determined by the isothermal solubilization method, and the corresponding phase diagrams were drawn. The solubility of the NaCl-NH4Cl-NaBr-NH4Br-H2O quaternary system at 298 K was also calculated using the Pitzer model, and the calculated results were in good agreement with the experimental measurements. Finally, based on the theoretical analysis of the phase diagrams of the 298 K and 323 K NaCl-NH4Cl-NaBr-NH4Br-H2O quaternary systems and combined with the phase diagrams of the 298 K NaBr-NaCl-CH3OH system, this paper proposes and designs a salt extraction process route for the brominated wastewater of the propyl bromide pesticide production. Through the separation experiment, the new process proved to be technically feasible and produced NaCl with 100 % purity, Na(Br,Cl) with 98.23 % NaBr, and NH4(Cl,Br) with 99.18 % and 97.57 % NH4Cl, respectively. The new process realizes the resourceful utilization of bromine-containing wastewater, and has the significant advantages of production safety and no emission of three wastes.

In situ-Electrochemically reduced graphene oxide integrated with cross-linked supramolecular polymeric network for electrocatalytic hydrogen evaluation reaction

Herein, we report the synthesis of a new supramolecular polymeric network (PCN) assembled through crosslinking of propyl bromide substituted tetraphenyl porphyrin with perhydroxy-cucurbit [8]uril and its use in the electrocatalytic hydrogen evaluation reaction after loading with nickel and integrating with in situ-electrochemically reduced graphene oxide (ERGO). Electrode was prepared by first coating graphene oxide on the FTO substrate followed by layering the nickel loaded PCN and finally by applying an appropriate voltage to reduce the graphene oxide in situ electrochemical reaction. The loading of nickel cocatalyst into PCN together with the integration of ERGO layer substantially improved its HER efficiency. Effect of various concentrations of Ni and GO on the HER activity of the developed electrocatalyst were investigated. Therein, ERGO1/Ni2@PCN catalyst containing 41% Ni and 50% GO (with respect to PCN) with only one layer of each component demonstrated excellent HER activity and stability with low onset and overpotentials of −20 mV, η@10 mA cm−2 of −360 mV, respectively, and remarkable hydrogen generation rate of 27.5 mmol h−1 g−1 in 1 M KOH. This noble-metal-free catalytic system is simple yet highly promising for the efficient hydrogen evolution reaction from water splitting.

Development of efficient solid chiral catalysts with designable linkage for asymmetric transfer hydrogenation of quinoline derivatives

Developing chiral solid catalysts for asymmetric catalysis is desirable for the elimination of homogeneous catalysis flaws but remains an immense challenge. Herein, we report the immo-bilization of TsDPEN on SBA-15 with an ionic liquid (IL) linkage via the one-pot reac-tion of imidazole-TsDPEN-N-Boc with 3-(trimethoxysilyl)propyl bromide in the SBA-15 mesopores. After coordination to Rh, the chiral solid catalysts could efficiently cata-lyze quinoline transfer hydrogenation, achieving 97% conversion with 93% ee, which was comparable to their homogeneous counterparts. The chiral solid catalyst with the IL linkage afforded much higher turnover frequency than that without the IL linkage (93 h–1vs. 33 h–1), attributed to the phase transfer and formate-enriching ability of the IL linkage. Furthermore, the effect of the pH on the reaction rate of the solid catalyst was in-vestigated, preventing reaction rate retardation during the catalytic process. The tuning of the linkage group is an efficient approach for catalytic activity improvement of immobilized chiral catalysts.

Substituent distribution of propyl cellulose studied by nuclear magnetic resonance

A series of propyl cellulose (PC) samples with different degrees of substitution (DS) ranging from 0.34 to 2.02 were prepared by a slurry method using propyl bromide as the etherification reagent. Two-dimensional nuclear magnetic resonance (NMR) studies were performed to identify the 1H and 13C chemical shifts of eight anhydroglucose units (AGUs) in PC chains including un-, 2-mono-, 3-mono-, 6-mono-, 2,3-di-, 2,6-di-, 3,6-di-, and 2,3,6-tri-substituted ones. In addition, the mole fractions (χ) of these AGUs in the studied PC samples and their changes with DS were determined from the quantitative 13C NMR spectra. The obtained χ−DS profiles were different from those of methyl and ethyl celluloses prepared by a similar slurry method, indicating that the molecular sizes of the substituent reagents utilized for cellulose ethers strongly affected their substituent distributions.

Технології комплексоутворення в системі краун-етер – KO2 –розчинник, як один з методів отримання стабільної форми аніон-радикалу кисню

Study of reactions of obtaining anion-radical of oxygen: one-electron oxygen reduction and complex formation in the system of crown-ether - potassium superoxide - solvent. Investigation of the possibility of regulating the activity of two different supramolecular structures containing oxygen anion radical to create new antioxidant systems. The oxygen anion radical in solution was obtained by the method of electrochemical oxygen reduction, as well as by complexation in the system of crown ether – potassium superoxide – solvent. The amount of oxygen radical anion obtained was monitored spectrophotometrically using a high-quality reaction with tetrazolium blue and the potentiometric method using an exchange reaction with butyl bromide. The activity of two different supramolecular structures containing oxygen anion radical is compared. It is shown that in the transition from the chemical method of generation of oxygen anion radical to electrochemical, the activity of the anion radical in the reaction with alkyl halide increases slightly. Spectrophotometrically and potentiometrically determined the kinetic parameters of the electrochemical oxygen reduction in the aprotic medium, as well as the process of complexation in the system of crown ether – potassium superoxide – solvent. The activity of two different supramolecular structures containing anion-radical of oxygen with the (Crown-K)+ and (tetraethylammonium)+ ions in reaction with propyl bromide in acetonitrile was compared. The conducted studies allow us to choose the optimal mode and structure of the complex - the sources of oxygen anion radical, depending on the task and goals of the experiment. The study of the complexation reaction in the system of crown ethers - potassium superoxide - solvent, along with the electrochemical method of obtaining active oxygen, is necessary not only in terms of obtaining the most stable form of oxygen anion radical, but also the creation of model systems that allow to analyze the mechanisms and patterns of the processes in biological systems. The obtained results indicate the prospect of using the investigated supramolecular complexes containing oxygen anion radical to create new antioxidant systems that can be used as new classes of antioxidants for engineering, medicine and pharmacy purposes.

Synthesis and Characterization of Ag(I) Complexes Derived from New N-Heterocyclic Carbenes

Two new unsymmetrical imidazolium salts viz., [1-(4-ethylphenyl)-3-propyl-1H-imidazole-3-ium bromide] (3) and [1-(2,6-dimethylphenyl)-3-propyl-1H-imidazole-3-ium bromide] (4) have been synthesized via the reaction of propyl bromide with imidazole derivatives, [1-(4-ethylphenyl)-1Himidazole] (1) and [1-(2,6-dimethylphenyl)-1H-imidazole] (2) in absence of solvent. Then two new N-heterocyclic carbene silver complexes (5 and 6) were prepared through the reaction of imidazoluim salts (3 and 4) as a source of N-heterocyclic carbene with Ag2O by in situ method. These complexes can be used in the future as a transfer agent for preparing other transitional metal carbine complexes (NHCs) via transmetallation method. The formation of these compounds was confirmed by spectral analysis.

Cationic Zn-Porphyrin Immobilized in Mesoporous Silicas as Bifunctional Catalyst for CO2 Cycloaddition Reaction under Cocatalyst Free Conditions

Immobilization of metalloporphyrin onto a solid support is highly desirable in the chemical industry. Herein, we reported for the first time the efficient immobilization of cationic zincporphyrin complexes on mesoporous SBA-15 by a simple one-pot method by refluxing 5,10,15,20-tetrakis(4-pyridyl)porphyrin zinc(II) (Zn-TPy), SBA-15, and 3-(trimethoxysilyl)propyl bromide in toluene, DMF, NMP, or THF. Studies suggest that solid catalyst with high Zn content, stiochiometric Br–/Zn ratio, and uniform distribution of active sites could be obtained using DMF as the solvent, possibly related to its suitable polarity. The bifunctional solid material with both Lewis acid site and nucleophile acts as an efficient catalyst for catalyzing cycloaddition of CO2 and epoxides under cocatalyst free conditions. Compared with the homogeneous counterpart, the solid catalyst is more active (TOF = 1686 h–1 versus 370 h–1). This suggests that the closely connected Lewis acid and Br– in the solid material could enhance their coop...

Periodic graphics: The chemistry of dry cleaning

Chemical educator and Compound Interest blogger Andy Brunning cycles through the chemistry used to wash our delicates To download a pdf of this article, visit cenm.ag/dryclean. References used to create this graphic: Dry cleaning dreams A chronology of historical developments in dry cleaning Reducing worker exposure to perchloroethylene (perc) in dry cleaning Perchloroethylene dry-cleaning facilities required to meet federal regulation Evaluation of glycol ether as an alternative to perchloroethylene in dry cleaning Preliminary study of propyl bromide exposure among New Jersey dry cleaners as a result of pending ban on perchloroethylene A collaboration between C&EN and Andy Brunning, author of the popular graphics blog Compound Interest To see more of Brunning’s work, go to compoundchem.com. To see all of C&EN’s Periodic Graphics, visit http://cenm.ag/periodicgraphics.

Alkylation of microfibrillated cellulose – A green and efficient method for use in fiber-reinforced composites

Microfibrillated cellulose (MFC) fibers were alkylated by propargyl bromide, allyl bromide and propyl bromide in an aqueous medium without any stirring. The chemical modifications were confirmed by Fourier transform infrared spectroscopy (FTIR), solid-state 13C nuclear magnetic resonance spectroscopy (NMR) and X-ray photoelectron spectrometry (XPS). The alkylated MFC fibers were obtained with degrees of substitution (DS) ranging from 0.12 to 0.33. All the samples were combined with low-density polyethylene (LDPE), and then the morphology, mechanical properties and water absorption behavior of the ensuing composites were investigated. Study of the morphology of the composites by Scanning Electron Microscopy (SEM) shows a slight improvement of the MFC/LDPE interface after allylation and propargylation. Moreover, the mechanical properties of the composites were significantly improved and the moisture absorption was reduced compared to unmodified MFC fibers.

Elementary SN2 reaction revisited. Effects of solvent and alkyl chain length on kinetics of halogen exchange in haloalkanes elucidated by Empirical Valence Bond simulation

We studied halogen exchange reactions between chloride ion and three bromoalkanes, namely methyl bromide, propyl bromide and hexyl bromide, by quantum chemistry methods and multiscale Empirical Valence Bond (EVB) simulations. These reactions proceed by the mechanism of bimolecular nucleophilic substitution (SN2). The gas phase reaction which was used as reference was characterized by quantum calculations at the M06-2X/6-31+G(d,p) level; the computed reaction energy and activation barrier were used for the calibration of tunable EVB parameters. Effects of solvent were simulated by the EVB methodology with explicit inclusion of water molecules. The corresponding gas phase barriers are 10.30, 13.25 and 15.61kcal/mol for methyl, propyl and hexyl bromide, respectively. The calculated activation free energies in aqueous solution are 21.15, 23.28 and 26.50kcal/mol, respectively. Aqueous environment dramatically impedes all three reactions relative to the gas phase, which is consistent with previous experimental and computational studies. In agreement with elementary features of SN2 reactions, elongation of the alkyl group increases the barrier and decreases the rate constant both in the gas phase and in the solution.

Design, synthesis and structure determination of new inherently chiral para-bromoalkoxycalix[4]arenes

The preparative method for the synthesis of inherently chiral para-bromoalkoxycalix[4]arenes based on para-bromination, stepwise regioselective debenzoylation and the following alkylation of the readily available 25-propoxy-26,27-dibenzoyloxycalix[4]arene with propyl bromide or (R)-N-(1-phenylethyl)bromoacetamide has been developed. Three types of the inherently chiral calix[4]arenes in cone or partial cone conformations with asymmetrical (AHHHHBHH, AAHHHBHH, AHBHHCHH) substitution of both upper and lower rims have been obtained in racemic, diastereomerically pure or enantiomerically pure forms. Their structure and the absolute configuration have been determined by NMR and X-ray.

Preliminary Study of Propyl Bromide Exposure among New Jersey Dry Cleaners as a Result of a Pending Ban on Perchloroethylene

Many states are considering, and some states have actively pursued, banning the use of perchloroethylene (PERC) in dry cleaning establishments. Proposed legislation has led many dry cleaners to consider the use of products that contain greater than 90% n-propyl bromide (n-PB; also called 1-bromopropane or 1-BP). Very little information is known about toxicity and exposure to n-PB. Some n-PB-containing products are marketed as nonhazardous and “green” or “organic.” This has resulted in some users perceiving the solvent as nontoxic and has resulted in at least one significant poisoning incident in New Jersey. In addition, many dry cleaning operators may not realize that the machine components and settings must be changed when converting from PERC to n-PB containing products. Not performing these modifications may result in overheating and significant leaks in the dry cleaning equipment. A preliminary investigation was conducted of the potential exposures to n-PB and isopropyl bromide (iso-PB; also called 2-bromopropane or 2-BP) among dry cleaners in New Jersey who have converted their machines from PERC to these new solvent products. Personal breathing zone and area samples were collected using the National Institute for Occupational Safety and Health Sampling and Analytical Method 1025, with a slight modification to gas chromatography conditions to facilitate better separation of n-PB from iso-PB. During the preliminary investigation, exposures to n-PB among some workers in two of three shops were measured that were greater than the American Conference of Governmental Industrial Hygienists (ACGIH) threshold limit value (TLV) for n-PB. The highest exposure measured among a dry cleaning machine operator was 54 parts per million (ppm) as an 8-hr time-weighted average, which is more than 5 times the ACGIH TLV of 10 ppm. The preliminary investigation also found that the work tasks most likely to result in the highest short-term exposures included the introduction of solvent to the machine, maintenance of the machine, unloading and handling of recently cleaned clothes, and interrupting the wash cycle of the machine. In addition, this assessment suggested that leaks may have contributed to exposure and may have resulted from normal machine wear over time, ineffective maintenance, and from the incompatibility of n-PB with gasket materials.

FLAME RETARDANTS Chemtura signs bromine agreements with Albemarle

Chemtura, the specialty chemical maker now under Chapter 11 reorganization, has signed a series of agreements and settled a lawsuit with Albemarle to help pave the way for a restructuring of its business in bromine derivatives. Under the agreement, Albemarle is signing over its 17% stake in a bromine-rich brine field in Union County, Ark., that is managed by Chemtura. The transfer consolidates Chemtura’s ownership of the field, according to Anne Noonan, Chemtura’s vice president of flame retardants. The field is the most productive in South Arkansas, she says, and among the most competitive in the world. As part of the deal, Albemarle will manufacture the plastics flame retardants tetrabromobisphenol A, decabromodiphenyl oxide, and decabromodiphenyl ethane for Chemtura. Albemarle will also supply Chemtura with n -propyl bromide and sodium bromide. In addition, the companies are settling an eight-year-old lawsuit in which Albemarle accused Chemtura of infringing its patents for decabromodiphenyl ethane fla...

Synthesis and anticonvulsant activity of some new bishydrazones derived from 3,4-dipropyloxythiophene

A series of new 3,4-dipropyloxy-N 2,N 5-bis(substituted)thiophene-2,5-dicarbohydrazides ( 4– 30) were synthesized from ethyl thiodiglycolate and diethyloxalate through multistep reactions. Following Dieckmann–Komppa reaction, the required precursor 3,4-dihydroxythiophene-2,5-diester ( 1) was prepared. This was derivatized with propyl bromide and further converted to corresponding hydrazide ( 3), which was finally transformed to targeted hydrazones ( 4– 30) by conventional methods. The newly synthesized compounds were characterized using FT-IR, 1H and 13C NMR, EI-MS and elemental analyses. The anticonvulsant activity of all the title compounds was investigated against maximal electroshock induced seizures (MES) and subcutaneous pentylenetetrazole (scMET) models and their neurotoxicity was also evaluated. Some of the selected compounds were subjected to 6 Hz test in order to evaluate their uncover activities. Compound 3,4-dipropyloxy-N 2,N 5-bis[1-(2-thienyl)ethylidene]thiophene-2,5-dicarbohydrazide ( 15) has emerged as a lead in this series with less neurotoxicity.

Maskless nanopatterning and formation of nanocorrals and switches, for haloalkanes atSi(111)-7 × 7

Labile self-assembled circular patterns of propyl bromide onSi(111)-7 × 7 at 50 K are shown to convert to corresponding stable circular patterns of atomic brominethrough a maskless process of molecular scale imprinting. The imprinting depends onlocalized chemical reaction induced by either photons or electrons. At 50 K propyl bromideadsorbs in a vertical configuration with lateral attraction. By contrast, at 300 K, octylchloride and bromide adsorbed horizontally, self-assembling spontaneously into the valuableconfigurations of switching corrals (‘type I’) and stable corrals (‘type II’). Both types ofcorral, switching and stable, can be seen to alter the local surface charge distribution.

Making a case for ‘normal’-propyl bromide: Metal finishing cleaning agent positioned as high-performing,cost-effective, and environmentally friendly

Making a case for ‘normal’-propyl bromide: Metal finishing cleaning agent positioned as high-performing,cost-effective, and environmentally friendly

NBO‐based CI/MP through‐space/bond interaction analysis and its application to stereoelectronic effects in SN2 reactions

AbstractNBO‐based CI/MP through‐space/bond interaction analysis was developed to analyze specific orbital interactions under consideration of the effects of electron correlation. This treatment was applied to the analysis of stereoelectronic effects in SN2 reactions of allyl bromide in which the effects of electron correlation play an important role (ammonia was used as the nucleophilic reagent). The SN2 activation energy in allyl bromide is lower than that in propyl bromide, because both the σ–π* and π–σ* interactions in allyl bromide contribute equally to the stabilization of the transition state. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005

A Convergent Method for the Synthesis of Highly Enantiomerically Enriched Cyclic Silanes with Silicon-Centered Chirality

A preparatively straightforward methodology has been developed which allows the assembly of silicon-containing carbocycles as mixtures of diastereomers with silicon as the sole center of stereogenic information. One-step construction of the chiral cyclic silanes is realized by reaction of equimolar amounts of a dibromide and a chirally modified dichlorosilane under Barbier conditions giving access to several monofunctionalized 1-sila-1,2,3,4-tetrahydronaphthalenes and a corresponding phenanthrene derivative. Facile large scale syntheses of 3-(2-bromoaryl)propyl bromides as well as dichlorosilanes have been elaborated. This highly convergent methodology relies on the novel (-)-menthyl-oxy-substituted dichlorosilanes, which have the chiral auxiliary for the subsequent optical resolution installed. These enantiopure dichlorosilanes are useful building blocks for a general and modular one-step approach to silanes with silicon-centered chirality since this strategy avoids the linear sequences reported in literature. The optical resolution has been exemplarily optimized for the 1-phenyl-1-sila-1,2,3,4-tetrahydronaphthalene derivative and the absolute configuration has been established by X-ray crystallography. The chiral auxiliary is stereospecifically displaced by simple reduction providing the highly enantioenriched silane (er = 98:2) which is enantiospecifically chlorinated as verified by a Walden inversion at silicon.

Kinetics of Reaction between Superoxide Anion and Propyl Bromide

Kinetics of Reaction between Superoxide Anion and Propyl Bromide

Experimental and Theoretical Studies of the Reactions of Excited Calcium Atoms with Ethyl and n-Propyl Bromides

To study the effect of the orbital alignment of ca(p-1(1)) on the product alignment, we have probed the cabr-(b(2)sigma (+)) product rotational alignments in the reactions of ca(p-1(1)) with c2h5br and n-c3h7br by means of laser-induced chemiluminescence under single-collision conditions in a beam-gas arrangement. when the laser polarization vector is parallel to the ca beam for the reaction ca(p-1(1)) + c2h5br, the rotation of the cabr(b(2)sigma (+)) product seems to be more strongly aligned in comparison with that when the laser polarization vector is perpendicular to the ca beam but when there is significant overlapping of error bars. however, for the reaction ca(p-1(1)) + n-c3h7br, there is no statistical difference in the product rotational alignment when the ca(p-1(1)) atomic orbital alignment is changed. the values of [p2((j) over cap .(k) over cap)] become less negative as the number of carbons is increased, which is probably attributed to the differences in the mass factors and potential energy surfaces. quasiclassical trajectory (qct) based on a leps potential energy surface (pes) has been employed to interpret the experimental results.