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1.
Chemistry ; 26(34): 7711-7719, 2020 Jun 18.
Artigo em Inglês | MEDLINE | ID: mdl-32298506

RESUMO

Catenation is common for the light main-group elements whereas it is rare for the heavy elements. Herein, we report the first example of a neutral molecule containing a Bi4 chain. It is prepared in a one-step reaction between bismuth trichloride and bis(diisopropylphosphino)amine in methanol suspension. The same reaction carried out in dichloromethane gives quite different products. All products have been characterized spectroscopically and using single-crystal X-ray analysis.

2.
Environ Sci Process Impacts ; 22(4): 863-872, 2020 Apr 29.
Artigo em Inglês | MEDLINE | ID: mdl-32073072

RESUMO

Canadian bitumen is too viscous to transport by rail and pipeline to markets. One approach to solve this viscosity issue is to dilute the bitumen with a thinning agent to meet transport specifications, but the addition of diluent underutilizes pipeline capacity and increases production cost. A second approach involves the partial refinement of bitumen to produce synthetic crude, which better utilizes pipeline capacity; however, capital and operational costs are high. A third alternative is a new technology that involves wrapping bitumen in a polymer layer to form a solid "puck" termed Canapux, but transportation of this product to coastal ports is limited to rail. Also, greenhouse gas emissions are greater when oil is transported by rail rather than pipeline. In the end, a variety of bitumen products will be transported in Canada, but not all of these products will respond to remediation equally when spilled. In order to ensure effective spill contingency planning, we recommend that engineered bitumen products have physical properties that are resilient to change, within the range of typical response times, after a spill.


Assuntos
Hidrocarbonetos , Canadá , Transportes
3.
Dalton Trans ; 47(30): 10195-10205, 2018 Jul 31.
Artigo em Inglês | MEDLINE | ID: mdl-30014057

RESUMO

In this paper we describe the synthesis, characterization, and X-ray crystal structures of two ligands, diethyl-N,N'-bis(p-tolyl)malonimidate and 1,3-bis(dimethylamino)-N,N'-bis(p-tolyl)propanediimidate. Their corresponding rhodium(i) dicarbonyl, dimethylaluminium, and bis-ligated zinc complexes have also been prepared and characterized. The donor properties of the ligands have been studied and have been compared to those of the traditional anionic N,N'-chelating ligand nacnac.

4.
Dalton Trans ; 47(18): 6299-6303, 2018 May 08.
Artigo em Inglês | MEDLINE | ID: mdl-29670979

RESUMO

Lawesson's reagent (LR) has been shown to react with the N-heterocyclic carbenes [1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMes) and 1,3-bis(2,6-diisopropylphenyl)imidazolidin-2-ylidene (SIPr)] to give adducts of the general form NHC·P(S)2-C6H4OCH3. Full characterizations, including X-ray crystal structures, are provided. The reaction of Woollins' reagent (WR) with IMes gave the known selanone, (IMes)Se.

5.
Angew Chem Int Ed Engl ; 57(3): 749-754, 2018 01 15.
Artigo em Inglês | MEDLINE | ID: mdl-29152832

RESUMO

An extended π-system containing two [3]cumulene fragments separated by a p-carboquinoid and stabilized by two capping N-heterocyclic carbenes (NHCs) has been prepared. Mono- and bis(imidazolidinium ethynyl) cations have also been synthesized from the reaction of an NHC with phenylethynyl bromide or 1,4-bis(bromoethynyl)benzene. Cyclic voltammetry coupled with synthetic and structural studies showed that the dication is readily reduced to a neutral, singlet bis-1,4-([3]cumulene)-p-carboquinoid as a result of the π-accepting properties of the capping NHCs.

6.
Acta Crystallogr E Crystallogr Commun ; 73(Pt 11): 1735-1738, 2017 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-29152362

RESUMO

The title compound, C20H22O3, was formed in the reaction between 2,4,6-tri-methyl-benzoic acid and N,N-diiso-propyl-ethyl-amine in the presence of 1,3-di-chloro-1,3-bis-(di-methyl-amino)-propenium hydrogen dichloride, and was recrystallized from diethyl ether solution. It is the first exclusively alkyl-substituted benzoic anhydride to have been structurally characterized. The asymmetric unit consists of a half mol-ecule, the other half of which is generated by twofold rotation symmetry; the dihedral angle between the symmetry-related aromatic rings is 54.97 (3)°. The geometric parameters of the aromatic ring are typical of those for 2,4,6-tri-methyl-phenyl substituted groups. The C=O and C-O bond lengths are 1.1934 (12) and 1.3958 (11) Å, respectively, and the angle between these three atoms (O=C-O) is 121.24 (9)°. In the crystal, mol-ecules are linked by weak C-H⋯O hydrogen bonds and C-H⋯π inter-actions. The packing features wavy chains that extend parallel to [001].

7.
Environ Sci Process Impacts ; 19(7): 928-938, 2017 Jul 19.
Artigo em Inglês | MEDLINE | ID: mdl-28613323

RESUMO

Canada's production, transport, and sale of diluted bitumen (dilbit) products are expected to increase by a million barrels per day over the next decade. The anticipated growth in oil production and transport increases the risk of oil spills in aquatic areas and places greater demands on oil spill capabilities to respond to spills, which have raised stakeholder concerns. Current oil spill models only predict the transport of bitumen blends that are used in contingency plans and oil spill response strategies, rather than changes in the oil's physical properties that are relevant to spill response. We conducted weathering studies of five oil products (two conventional oils and three bitumen blends) in the Department of Fisheries and Oceans' flume tank. We also considered two initial oil slick thicknesses, 4.0 mm and 7.0 mm. We found that there is a major difference in the time evolution of oil properties (density and viscosity), raising doubts on weathering models that do not consider the thickness of oil. We also developed empirical expressions for the evolution of the density and viscosity of these oil products. The findings from the 4.0 mm results were incorporated with data from the literature to provide an update on the factors to consider during the decision making for spills of diluted bitumen products. The matrix indicated that most response options, including chemical dispersants, work much more effectively within 48 hours of the initiation of weathering. After this window of opportunity closes, natural attenuation or in situ burning is the only option remaining, but containment of oil is a limiting factor for in situ burning.


Assuntos
Recuperação e Remediação Ambiental/métodos , Hidrocarbonetos/análise , Modelos Teóricos , Poluição por Petróleo/análise , Poluentes Químicos da Água/análise , Canadá , Tomada de Decisões , Hidrocarbonetos/química , Viscosidade , Poluentes Químicos da Água/química , Tempo (Meteorologia)
8.
J Mol Graph Model ; 64: 147-152, 2016 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-26851865

RESUMO

RADMAP, an open source program, allows for rapid analysis and visualization of the earliest stages of reactions between any molecule and a monoatomic probe (i.e., H*, H(+), H(-), Br*, or any other monoatomic species) using ab initio methods. This program creates non-planar potential energy surfaces of the initial interaction between a molecule of interest and the monoatomic probe. These surfaces can be used to both predict the site of addition as well as provide a qualitative estimate for the relative proportion of the formation of adducts; therefore, it gives insight into both the reactivity and the kinetic stability of a molecule. The program presents a way to quickly predict the number of signals anticipated in transverse field muon spin resonance spectra as well as their relative intensities.


Assuntos
Hidrogênio/química , Modelos Químicos , Modelos Moleculares , Compostos Orgânicos/química , Software
9.
Inorg Chem ; 54(23): 11121-6, 2015 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-26575798

RESUMO

The P,P-chelated heteroleptic complex bis[bis(diisopropylphosphino)amido]indium chloride [(i-Pr2P)2N]2InCl was prepared in high yield by treating InCl3 with 2 equiv of (i-Pr2P)2NLi in Et2O/tetrahydrofuran solution. Samples of [(i-Pr2P)2N]2InCl in a pentane slurry, a CH2Cl2 solution, or in the solid state were exposed to CO2, resulting in the insertion of CO2 into two of the four M-P bonds to produce [O2CP(i-Pr2)NP(i-Pr2)]2InCl in each case. Compounds were characterized by multinuclear NMR and IR spectroscopy, as well as single-crystal X-ray diffraction. ReactIR solution studies show that the reaction is complete in less than 1 min at room temperature in solution and in less than 2 h in the solid-gas reaction. The CO2 complex is stable up to at least 60 °C under vacuum, but the starting material is regenerated with concomitant loss of carbon dioxide upon heating above 75 °C. The compound [(i-Pr2P)2N]2InCl also reacts with CS2 to give a complicated mixture of products, one of which was identified as the CS2 cleavage product [S═P(i-Pr2)NP(i-Pr2)]2InCl]2(µ-Cl)[µ-(i-Pr2P)2N)].

10.
Angew Chem Int Ed Engl ; 54(26): 7484-7, 2015 Jun 22.
Artigo em Inglês | MEDLINE | ID: mdl-26036318

RESUMO

Out of focus: A recent Communication published in this journal describes the synthesis of [nBu4 N]HCO3 . The authors performed a single-crystal X-ray study that revealed a putative species described as an incipient hydroxide ion engaging in a long, and presumably weak, interaction with CO2 . Our recent exploration of the coordination chemistry of CO2 with small ions leads us to believe that such an exceptional bonding situation is unlikely. Instead, we argue that the crystal structure is that of [nBu4 N]O2 CCH3 and therefore not representative of the bulk powder from the synthesis.


Assuntos
Dióxido de Carbono/química , Cristalografia por Raios X/métodos , Biomimética , Estrutura Molecular
11.
Chem Commun (Camb) ; 51(19): 3942-56, 2015 Mar 07.
Artigo em Inglês | MEDLINE | ID: mdl-25601453

RESUMO

The ability to bind CO2 through the formation of low-energy, easily-broken, bonds could prove invaluable in a variety of chemical contexts. For example, weak bonds to CO2 would greatly decrease the cost of the energy-intensive sorbent-regeneration step common to most carbon capture technologies. Furthermore, exploration of this field could lead to the discovery of novel CO2 chemistry. Reduction of complexed carbon dioxide might generate chemical feedstocks for the preparation of value-added products, particularly transportation fuels or fuel precursors. Implementation on a large scale could help to drastically reduce CO2 concentrations in the atmosphere. However, literature examples of weakly bonded complexes of CO2 are relatively few and true coordination complexes to a 'naked' CO2 fragment are nearly unheard of. In this review article, a variety of complexes of CO2 featuring diverse binding modes and reactivity will be examined. Topics covered include: (A) inclusion complexes of CO2 in porous materials. (B) Zwitterionic carbamates produced from the reaction of CO2 with polyamines. (C) Carbamate salts produced from reaction of CO2 with two equivalents of an amine. (D) Insertion products of CO2 into acid-base adducts (e.g., metal complexes). (E) Lewis acid-base activated CO2, such as frustrated Lewis pair complexes. (F) Simple base-CO2 adducts, wherein the base-CO2 bond is the only interaction formed. Complexes in the last category are of particular interest, and include imidazol-2-carboxylates (N-heterocyclic carbene adducts of CO2) as well as a few other examples that lie outside NHC chemistry.

12.
Science ; 344(6179): 75-8, 2014 Apr 04.
Artigo em Inglês | MEDLINE | ID: mdl-24700853

RESUMO

Why does cyanide not react destructively with the proximal iron center at the active site of 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase, an enzyme central to the biosynthesis of ethylene in plants? It has long been postulated that the cyanoformate anion, [NCCO2](-), forms and then decomposes to carbon dioxide and cyanide during this process. We have now isolated and crystallographically characterized this elusive anion as its tetraphenylphosphonium salt. Theoretical calculations show that cyanoformate has a very weak C-C bond and that it is thermodynamically stable only in low dielectric media. Solution stability studies have substantiated the latter result. We propose that cyanoformate shuttles the potentially toxic cyanide away from the low dielectric active site of ACC oxidase before breaking down in the higher dielectric medium of the cell.


Assuntos
Aminoácido Oxirredutases/metabolismo , Formiatos/isolamento & purificação , Nitrilos/isolamento & purificação , Aminoácido Oxirredutases/química , Dióxido de Carbono/química , Domínio Catalítico , Cristalização , Cianetos/química , Etilenos/metabolismo , Formiatos/química , Espectroscopia de Ressonância Magnética , Estrutura Molecular , Nitrilos/química , Termodinâmica , Difração de Raios X
13.
Inorg Chem ; 52(15): 8312-4, 2013 Aug 05.
Artigo em Inglês | MEDLINE | ID: mdl-23879626

RESUMO

Bis(di-i-propylphosphino)amine 1 reacts with B(C6F5)3 to form an adduct with concomitant N/P H-isomerization. This species reacts smoothly with carbon dioxide. An attempt to prepare an anionic derivative resulted in the formation of a novel heterocycle derived from the PNP ligand and B(C6F5)3.

14.
Mar Pollut Bull ; 71(1-2): 83-91, 2013 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-23623652

RESUMO

Test facilities such as lab basins and wave tanks are essential when evaluating the use of chemical dispersants to treat oil spills at sea. However, these test facilities have boundaries (walls) that provide an ideal environment for surface (interfacial) film formation on seawater. Surface films may form from surfactants naturally present in crude oil as well as dispersant drift/overspray when applied to an oil spill. The objective of this study was to examine the impact of surface film formation on oil spreading rates in a small scale lab basin and on dispersant effectiveness conducted in a large scale wave tank. The process of crude oil spreading on the surface of the basin seawater was influenced in the presence of a surface film as shown using a 1st order kinetic model. In addition, interfacial film formation can greatly influence chemically dispersed crude oil in a large scale dynamic wave tank.


Assuntos
Modelos Químicos , Poluição por Petróleo , Petróleo/análise , Tensoativos/química , Poluentes Químicos da Água/química , Laboratórios
15.
Angew Chem Int Ed Engl ; 51(28): 7024-7, 2012 Jul 09.
Artigo em Inglês | MEDLINE | ID: mdl-22685029

RESUMO

Negishi revisited: higher-order alkyl zincates have been subjected to Negishi coupling with alkyl bromides. For the first time, coupling takes place in straight THF, i.e., without a salt additive and a high dielectric co-solvent. This provides evidence that it is the higher-order zincate that undergoes transmetalation to Pd, and not mono-anionic zincates or any of the other species present in the Schlenk equilibrium.

16.
Chem Commun (Camb) ; 48(9): 1227-9, 2012 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-22158693

RESUMO

Amines dissolved in ionic liquids react rapidly with SO(2) to produce new materials. Compounds related to the stepwise conversion of SO(2) to sulfite and sulfate salts have been isolated. Trapping SO(2) in the form of the sulfite anion does not change the oxidation state of sulfur and should maintain the reversibility of the capture system.

17.
Org Biomol Chem ; 9(10): 3672-80, 2011 May 21.
Artigo em Inglês | MEDLINE | ID: mdl-21472176

RESUMO

In this paper, we report a novel synthesis of anhydrous 1-hydroxy-2,2,6,6-tetramethyl-piperidine (TEMPO-H). An X-ray crystal structure and full characterization of the compound are included. Compared to hydrated TEMPO-H, its anhydrous form exhibits improved stability and a differing chemical reactivity. The reactions of anhydrous TEMPO-H with a variety of low-valent carbon centres are described. For example, anhydrous TEMPO-H was reacted with 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMes), an unsaturated NHC. Crystals of [CHNC(6)H(2)(CH(3))(3)](2)C···HO(NC(5)H(6)(CH(3))(4)), IMes···TEMPO-H, were isolated and a crystal structure determined. The experimental structure is compared to the results of theoretical calculations on the hydrogen-bonded dimer. Anhydrous TEMPO-H was also reacted with the saturated NHC, 1,3-bis(2,6-diisopropylphenyl)imidazolidin-2-ylidene (SIPr), giving the product [CH(2)Ni-Pr(2)C(6)H(3)](2)CH···O(NC(5)H(6)(CH(3))(4)). In contrast, the reaction of hydrated TEMPO-H with 1,3-bis(2,6-diisopropylphenyl)imidazolidin-2-ylidene gave small amounts of the hydrolysis product, N-(2,6-diisopropylphenyl)-N-[2-(2,6-diisopropylphenylamino)ethyl]formamide. Finally, anhydrous TEMPO-H was reacted with (triphenylphosphoranylidene)ketene to generate Ph(3)PC(H)C(=O)O(NC(5)H(6)(CH(3))(4)). A full characterization of the product, including an X-ray crystal structure, is described.

20.
J Org Chem ; 73(3): 801-12, 2008 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-18173280

RESUMO

Phosphonium ionic liquids (PhosILs), most notably tetradecyl(trihexyl)phosphonium decanoate (PhosIL-C(9)H(1)9COO), are solvents for bases such as Grignard reagents, isocyanides, Wittig reagents (phosphoranes), and N-heterocyclic carbenes (NHCs). The stability of the organometallic species in PhosIL solution is anion dependent. Small bases, such as hydroxide, react with the phosphonium ions and promote C-H exchange as suggested by deuterium-labeling studies. A method to dry and purify the ionic liquids is described and this step is important for the successful use of basic reagents in PhosIL. NHCs have been generated in PhosIL, and these persistent solutions catalyze organic transformations such as the benzoin condensation and the Kumada-Corriu cross-coupling reaction. Phosphoranes were generated in PhosIL, and their reactivity with various organic reagents was also tested. Inter-ion contacts involving tetraalkylphosphonium ions have been assessed, and the crystal structure of [(n-C(4)H(90)(4)P][CH(3)CO(2).CH(3)CO(2)H] has been determined to aid the discussion. Decomposition of organometallic compounds may also proceed through electron-transfer processes that, inter alia, may lead to decomposition of the IL, and hence the electrochemistry of some representative phosphonium and imidazolium ions has been studied. A radical derived from the electrochemical reduction of an imidazolium ion has been characterized by electron paramagnetic resonance spectroscopy.

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