Towards a colorimetric spot test for the detection of methylamine. Part 1. Reaction of aliphatic amines with nitro-substituted benzene and toluene compounds to form Meisenheimer Complexes

Hunt, Anya L.; Shen, Yong; Alder, John F.

doi:10.1039/ac9963300323

Cited by 9 publications

(10 citation statements)

References 2 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…First, to determine whether ZnO can deprotonate the MA cation, we utilize an indicator molecule. Aromatic nitro compounds such as dinitrotoluene and dinitrobenzene are sensitive primary amine indicators . 2,4‐dinitrotoluene (DNT) rapidly forms a Meisenheimer complex with methylamine, which has a characteristic blue–green color due to absorption minima between 450 and 500 nm.…”

Section: Resultsmentioning

confidence: 99%

Overcoming Zinc Oxide Interface Instability with a Methylammonium‐Free Perovskite for High‐Performance Solar Cells

Schutt

Nayak

Ramadan

et al. 2019

Adv Funct Materials

150

125

View full text Add to dashboard Cite

Perovskite solar cells have achieved the highest power conversion efficiencies on metal oxide n-type layers, including SnO 2 and TiO 2 . Despite ZnO having superior optoelectronic properties to these metal oxides, such as improved transmittance, higher conductivity, and closer conduction band alignment to methylammonium (MA)PbI 3 , ZnO is largely overlooked due to a chemical instability when in contact with metal halide perovskites, which leads to rapid decomposition of the perovskite. While surface passivation techniques have somewhat mitigated this instability, investigations as to whether all metal halide perovskites exhibit this instability with ZnO are yet to be undertaken. Experimental methods to elucidate the degradation mechanisms at ZnO-MAPbI 3 interfaces are developed. By substituting MA with formamidinium (FA) and cesium (Cs), the stability of the perovskite-ZnO interface is greatly enhanced and it is found that stability compares favorably with SnO 2 -based devices after high-intensity UV irradiation and 85 °C thermal stressing. For devices comprising FA-and Cs-based metal halide perovskite absorber layers on ZnO, a 21.1% scanned power conversion efficiency and 18% steady-state power output are achieved. This work demonstrates that ZnO appears to be as feasible an n-type charge extraction layer as SnO 2 , with many foreseeable advantages, provided that MA cations are avoided.

show abstract

Section: Resultsmentioning

confidence: 99%

Overcoming Zinc Oxide Interface Instability with a Methylammonium‐Free Perovskite for High‐Performance Solar Cells

Schutt

Nayak

Ramadan

et al. 2019

Adv Funct Materials

150

125

View full text Add to dashboard Cite

show abstract

“…In this article, we characterized the interaction of 2,4-dinitrotoluene (DNT) with nucleophilic bases in DMSO. It has long been assumed that polynitroaromatic compounds such as DNT form colored Meisenheimer complexes with nucleophiles, − and the addition of an aliphatic amine to a solution of DNT in DMSO indeed produces an intense blue color. However, the presence of a Meisenheimer complex could not be confirmed by NMR spectroscopy.…”

Section: Resultsmentioning

confidence: 99%

Getting More out of a Job Plot: Determination of Reactant to Product Stoichiometry in Cases of Displacement Reactions and n:n Complex Formation

2011

View full text Add to dashboard Cite

The method of continuous variation (often referred to as Job's method) is an easy and common method for the determination of the reactant stoichiometry of chemical equilibria. The traditional interpretation of Job plots has been limited to complex association equilibria of the type nA + mB ⇌ A(n)B(m), while little focus has been placed upon displacement type reactions (e.g., A + B ⇌ C + D), which can give Job plots that look quite similar. We developed a novel method that allows the user to accurately distinguish between 1:1 complex association, 2:2 complex association, and displacement reactions using nothing more than a pocket calculator. This method involves preparing a Job plot of the system under investigation (using regularly spaced mole fractions), normalizing the measured quantities (such as the concentration of A(n)B(m) or C for the above reactions) to their maximum value (i.e., at mole fraction 0.5), and determining the sum of the normalized values. This sum is then compared with theoretically predicted normalized sum values that depend on the nature of the equilibrium. The relationship between, on the one hand, the sum of the normalized values and, on the other hand, the reaction equilibrium constant and the concentration of the stock solutions used for the preparation of the Job plot is also explored. The use of this new technique for the interpretation of Job plots permits users to readily determine information that can be obtained otherwise only with laborious additional experiments, as illustrated by the analysis of four Job plots taken from the literature.

show abstract

“…13 Similarly, in a study of the reaction of methylamine and diethylamine with DNT in dimethyl sulfoxide (DMSO), the formation of Meisenheimer complexes was assumed only based on the analogy of similar complexes with trinitrobenzene. 14 Also, in a seminal study on the environmental fate of nitroaromatic compounds, DNT adsorption to natural clay materials with large surface concentrations of negative charges was studied. It was assumed that electron donorÀacceptor (EDA) complexes were formed, but the possibility of deprotonation of DNT was not considered.…”

Section: Introductionmentioning

confidence: 99%

“…For the design of DNT receptors, several modes of intermolecular interactions are conceivable. The nitro groups of DNT have been reported to bind to hydrogen bond donors and metal cations, , and there have been several publications suggesting that amines form anionic σ-complexes with DNT (often referred to as Meisenheimer complexes). − With a view to optical sensors, it appeared particularly interesting that solutions of DNT and alkylamines have a deep blue color absent to solutions of DNT or alkylamines alone.…”

Section: Introductionmentioning

confidence: 99%

Interaction of a Weakly Acidic Dinitroaromatic with Alkylamines: Avoiding the Meisenheimer Trap

et al. 2011

View full text Add to dashboard Cite

Polynitroaromatics are well-known to form anionic σ-complexes (Meisenheimer complexes). The formation of such complexes was assumed in the past to explain the blue color of solutions of 2,4-dinitrotoluene (DNT) and amines. However, this work shows that caution is warranted to avoid the hasty misidentification of Meisenheimer complexes. (1)H NMR spectra exhibit no significant shifts in the positions of the DNT protons, indicating that the majority of DNT species in solutions of DNT and amines retain their aromaticity. Density functional calculations on DNT-ethylamine complexes suggest that Meisenheimer complexes are sufficiently high in free energy so that they make up only a very small fraction of the full equilibrium population. While principal component analysis of the UV/vis spectra of the DNT-amine solutions reveals that only one absorbing species of significant concentration is formed, quantitative fits of Job's plots show that 1:1 association of DNT with the amines alone cannot explain the visible absorption spectra. Instead, the Job's plots can be accurately interpreted by deprotonation of DNT, with the amines acting as bases. The deprotonation equilibria lie far on the side of the unreacted DNT, preventing the detection by NMR of the deprotonated minority species that gives the solutions their strong blue color. The analysis of systems with DNT and n-butylamine, diethylamine, triethylamine, or benzylamine provides a consistent pK(a) of DNT in dimethyl sulfoxide of 15.3 ± 0.2.

show abstract

Towards a colorimetric spot test for the detection of methylamine. Part 1. Reaction of aliphatic amines with nitro-substituted benzene and toluene compounds to form Meisenheimer Complexes

Cited by 9 publications

References 2 publications

Overcoming Zinc Oxide Interface Instability with a Methylammonium‐Free Perovskite for High‐Performance Solar Cells

Overcoming Zinc Oxide Interface Instability with a Methylammonium‐Free Perovskite for High‐Performance Solar Cells

Getting More out of a Job Plot: Determination of Reactant to Product Stoichiometry in Cases of Displacement Reactions and n:n Complex Formation

Interaction of a Weakly Acidic Dinitroaromatic with Alkylamines: Avoiding the Meisenheimer Trap

Contact Info

Product

Resources

About