Compounds In Non-aqueous Solvents Research Articles

Approach for Predicting the Standard Free Energy Solvation of H+ and Acidity Constant in Nonaqueous Organic Solvents

In the present work, the free energy solvation of H+, ΔGsolH+, is estimated in various important nonaqueous solvents including alcohols and polar aprotic solvents, semiempirically. The selected solvents are methanol, ethanol, 2-propanol, 2-methyl-2-propanol, dimethyl sulfoxide, dimethylformamide, and acetonitrile. The value of ΔGsolH+ in 2-propanol and 2-methyl-2-propanol were reported for the first time. The estimated values of ΔGsolH+were used to predict the acidity constants (pKa) of different compounds in the selected solvents. These pKa values had better agreement with the experimental values than the corresponding values obtained using the other ΔGsolH+ reported in literature. This confirmed that the values of ΔGsolH+, predicted in this work, are reasonable. The calculated pKa values of selected compounds in nonaqueous solvents were further corrected by accounting for the error of the applied computational method for predicting the pKa values of the compounds in water. New correlation equations were...

Diffusion of aromatic compounds in nonaqueous solvents: A study of solute, solvent, and temperature dependences

Tracer diffusivities (limiting mutual diffusion coefficients) of nonassociated aromatic compounds in n-hexane and cyclohexane have been measured at 298.2 K by Taylor's dispersion method. These new data, together with other diffusivities of nonassociated pseudoplanar solutes reported in the literature, are used to determine the separate effects of solute and solvent on tracer diffusion. The data show that for a given pseudoplanar solute diffusing in different solvents at 298.2 K, the tracer diffusivity is dependent not only on the fractional viscosity of the solvent but also on a function of the solvent's molar density, molecular mass, and free volume fraction. For different pseudoplanar aromatic solutes diffusing in a particular solvent at a constant temperature, there is a linear relationship between the reciprocal of the tracer diffusivity and the molecular volume of the solutes. The results are discussed in respect to relevant theories and experimental studies in the literature. An idealized relation, developed on the basis of the Einstein equation by incorporating the newly found solute and solvent dependences, is capable of describing a total of 176 diffusivities of nonassociated pseudoplanar solutes in various solvents at different temperatures to within an average error of ±2.8%.

Meta and Para Effects in the Ultrafast Excited-State Dynamics of the Green Fluorescent Protein Chromophores

Femtosecond transient absorption and fluorescence upconversion experiments have been performed to investigate the photoinduced dynamics of the meta isomer of the green fluorescent protein chromophore, m-HBDI, and its O-methylated derivative, m-MeOBDI, in various solvent mixtures at neutral, acidic, and basic pH. The para isomer, p-HBDI, and its O- and N-methylated derivatives, p-MeOBDI and p-HBDIMe(+), were also studied for comparison. In all cases, fast quenching of the excited S1 state by internal conversion (IC) to the ground state was observed. In the para compounds, IC, presumably promoted by the internal twisting, arises in <1 ps. A similar process takes place in the meta compounds in nonaqueous solvents but with notably slower kinetics. In aqueous solutions, the meta compounds undergo ultrafast intermolecular excited-state proton transfer that competes with isomerization.

Separation of Neutral Compounds in Nonaqueous Solvents by Capillary Zone Electrophoresis

ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTSeparation of Neutral Compounds in Nonaqueous Solvents by Capillary Zone ElectrophoresisShu Li and Stephen G. WeberView Author Information Department of Chemistry, University of Pittsburgh Pittsburgh, Pennsylvania 15260 Cite this: J. Am. Chem. Soc. 2000, 122, 15, 3787–3788Publication Date (Web):March 30, 2000Publication History Received9 November 1999Revised8 February 2000Published online30 March 2000Published inissue 1 April 2000https://doi.org/10.1021/ja993949yCopyright © 2000 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views285Altmetric-Citations12LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (37 KB) Get e-AlertsSUBJECTS:Alcohols,Ions,Lanthanides,Solution chemistry,Solvents Get e-Alerts

Anomalies in Faradaic rectification polarography of aromatic compounds in non-aqueous solvents

The electrode reaction of p-dicyanobenzene O/− in N, N-dimethylformamide is studied with the aid of the galvanostatic double pulse (GDP) method and faradaic rectification (FR) polarography. The results of the GDP measurements obey the theoretical requirements in all aspects. Conversely, the FR polarogram can be fitted with the theoretical polarograms only in the potential range ∔-50 mV vs. the reversible half-wave potential of this electrode. Furthermore, the most suitable k 0 values used in this curve-fit analysis depends on the frequency of ac input and differ greatly from the value determined by the GDP method. Attention is called to the fact that the p-dicyanobenzene 0/− system is just one of the 16 redox systems of aromatic compounds which show this type of behaviour in FR and GDP experiments. Their kinetic parameters are also tabulated, with some comments on the anomalies in FR polarography.

Electrogenerated chemiluminescence. 30. Electrochemical oxidation of oxalate ion in the presence of luminescers in acetonitrile solutions

The electrochemical oxidation of oxalate at a platinum electrode in acetonitrile solutions as studied by cyclic and rotating-ring disk voltammetry and controlled potential coulometry shows an irreversible two-electron oxidation at ca. 0.3 V vs. SCE to CO2 with no intermediates detectable by these techniques. The oxidation of oxalate in the presence of several fluorescers (such as rubrene, 9, IO-diphenylanthracene, and the bipyridyl chelates of ruthenium(l1) and osmium(l1)) does not produce light, but emission characteristic of the fluorescer occurs during the simultaneous oxidation of the additive and oxalate. Studies of the conditions for emission in the presence of thianthrene and naphthalene lead to a mechanism for the oxidation of oxalate and the excitation process based on oxidation of oxalate to CzO4-., which undergoes rapid decomposition to COz and C02--. The C02-e can transfer an electron to the additive molecule to produce a radical anion, which can then undergo an ecl annihilation reaction with the electrogenerated radical cation. There has been much interest in the intense chemiluminescence which results from the reaction of oxalyl chloride or oxalate esters and hydrogen peroxide in the presence of fluorescent compounds in nonaqueous solvents.’-3 In the proposed mechanism for these processes, the reaction between the oxalate ester and H202 produces the dioxetanedione (1) as an

Palladium‐Catalysed reactions of unsaturated compounds in non‐aqueous solvents: The PdII‐catalysed halogen displacement in vinyl chloride by carboxylate and alcoholate

AbstractIn the presence of catalytic amounts of divalent palladium salts vinyl chloride reacts with acetate ions in acetic acid or dimethylformamide solution to produce vinyl acetate in high yield. The reaction was found to be first‐order both in catalyst and in acetate concentration. Chloride anions inhibit the reaction by reducing the effective catalyst concentration by formation of the tetrachloropalladium complex.The mechanism of the reaction is discussed in terms of a displacement of chloride by acetate via a π‐olefin‐PdII complex. The vinylation reaction is considerably accelerated by addition of catalytic amounts of ferric acetate/lithium chloride (molar ratio 1).Also discussed is the influence on the reaction of the solvent and of various transition metal salts. The palladium‐chloride‐catalysed halogen displacement in 2‐chloropropylene by acetate ions in acetic acid was found to produce isopropenyl acetate and acetone + acetic anhydride, which indicates that attack of acetate occurs at the carbon atom carrying the chlorine. Reaction of alcohols with vinyl chloride in the presence of a base (alcoholate or tert‐amine), using palladium chloride as catalyst yields acetaldehyde dialkylacetales. Halogen exchange in vinyl bromide by chloride in dimethylformamide solution using palladium chloride as catalyst proved to be possible.

Relationship between pKa (H&lt;SUB&gt;2&lt;/SUB&gt;O) of 5-Substituted-4-amino-2-methylpyrimidines and Half Neutralization Potential and the Behavior of the Compounds in Nonaqueous Solvents

Relationship between pKa (H&lt;SUB&gt;2&lt;/SUB&gt;O) of 5-Substituted-4-amino-2-methylpyrimidines and Half Neutralization Potential and the Behavior of the Compounds in Nonaqueous Solvents

Studies on the Mechanism of the Direct Acylation of Amino Acids and Related Compounds in Nonaqueous Solvents1

Studies on the Mechanism of the Direct Acylation of Amino Acids and Related Compounds in Nonaqueous Solvents¹

Reactivity of metaphosphate esters prepared from P 4O 10 and ethyl ether

Cyclic tetraethylmetaphosphates are formed by the reaction of P 4O 10 with two moles of ethylether. The metaphosphate ester reacts rapidly with one mole of water. Complete hydrolysis at higher temperature leads to mono- and diesterified phosphates. The reactivity of the metaphosphate ester with OH- and NH- compounds in non-aqueous solvents was determined by potentiometric titrations. The consequences for the preparation of nucleosides and polynucleotides are discussed.