Series Of Binary Solvents Research Articles

Insight into Solvent-Dependent Conformational Polymorph Selectivity: The Case of Undecanedioic Acid

Here we report the polymorph nucleation of undecanedioic acid (UDA) having high solvent-dependent selectivity. Solvents with high hydrogen bond donating (HBD) ability preferred to produce form II, while form I was obtained from solvents with no HBD ability. Cooling experiments in a series of binary solvents with an HBD ability value from 0 to 86 were designed to affirm the strong correlation between solute–solvent interactions and polymorph formation verified by solution Fourier transform infrared (FTIR) spectroscopy and quantitative powder X-ray diffraction. Two crystal structures, evaluated as conformational dimorphs assisted by FTIR, solid-state NMR, and quantum chemistry calculations, were reported. Furthermore, the crystal structures suggest that UDA molecules from various solutions went through different conformation rearrangements resulting in two forms during nucleation. Meanwhile, we reveal that there is no direct connection between the solution chemistry of UDA in solvents with various HBD stren...

Solvent-Mediated Vibrational Energy Relaxation from Vaska’s Complex Adducts in Binary Solvent Mixtures

A vibrational pump-probe and FTIR study was performed on two different adducts of Vaska's complex in two different sets of binary solvent mixtures. The carbonyl vibrational mode in the oxygen adduct exhibits solvatochromic shifts of ~10 cm(-1) in either benzyl alcohol or chloroform relative to benzene-d6, whereas this vibration is nearly unchanged for the iodine adduct for the same three solvents. The width and center frequency of the carbonyl stretch for each adduct are compared to its vibrational lifetime in binary mixtures of benzene-d6 with either benzyl alcohol or chloroform. In neat solvents, the trends in line width, frequency, and vibrational lifetime are consistent for the two adducts, but complex relationships emerge when the trends in each property are compared as a function of mixed solvent composition. ν(CO) is more sensitive to the solvation environment around the trans ligand, whereas the line width and lifetime depend on the environment around the CO group itself. The carbonyl frequency and width vary nonlinearly across the two binary solvent series, indicating preferential solvation. In contrast, the vibrational lifetime changes linearly with solvent composition and is correlated with the mole fraction of chloroform but anticorrelated with the mole fraction of benzyl alcohol. The results are explained by differences in the densities of solvent modes that affect intermolecular relaxation of the carbonyl mode.

ChemInform Abstract: Solvent Effects on the Solvolysis of Neophyl Tosylates

Solvolysis rates of 2-phenyl-2-methylpropyl and 2-(p-methoxyphenyl)-2-methylpropyl p-toluenesulfonates were determined in a wide variety of solvents and the solvent effects were analyzed based on the Winstein–Grunwald equation. The solvent effect on neophyl solvolyses failed to give a single linear correlation with the 2-adamantyl YOTs parameter. There was dispersion behavior for the respective binary solvent series between neophyl kΔ substrates and 2-adamantyl tosylate. The pattern of dispersion could not be interpreted in terms of nucleophilic solvent assistance. The response to the solvent polarity (m value for each binary solvent series) was significantly lower for both the methoxy and the unsubstituted derivatives than the m = 1.0 for the limiting kc solvolysis, and appreciably lower for the methoxy derivative than for the unsubstituted one. Linearity of the solvent effects between both neophyl systems and also between other kΔ substrates implied the existence of a unique kinetic solvent polarity sca...

The γ-Silicon Effect. I. Solvent Effects on the Solvolyses of 2,2-Dimethyl-3-(trimethylsilyl)propyl and 3-(Aryldimethylsilyl)-2,2-dimethylpropyl p-Toluenesulfonates

Abstract The solvolysis rates of 2,2-dimethyl-3-(trimethylsilyl)propyl and 3-(aryldimethylsilyl)-2,2-dimethylpropyl p-toluenesulfonates were measured in a wide variety of solvents at 45 °C. The solvent effects were analyzed by using the Winstein–Grunwald equation. The solvent effects observed did not give simple linear correlations with the 2-adamantyl YOTs parameter, but showed dispersion behavior in a series of binary solvents. The m values of 0.59—0.67 were remarkably lower than unity for the limiting kc solvolysis of 2-adamantyl p-toluenesulfonate. The deviation patterns could not be interpreted in terms of nucleophilic assistance by the solvent. The dispersion behavior with reduced m values was found to be more significant for the 3-(aryldimethylsilyl) than for the 3-(trimethylsilyl) derivatives and was compatible with the delocalization of the incipient cationic charge by participation of the Si–Cγ bond in the rate-determining step. An extended dual-parameter treatment, log (k/k80E) = mcYOTs + mΔYΔ, successfully correlated such γ-silyl assisted solvolyses. The MΔ values of 0.24—0.49 so obtained, where MΔ = 0.51mΔ/(mc + 0.51mΔ), are a measure of the extent of charge delocalization, suggesting that the γ-silyl group in the percaudal interaction is more effective in delocalizing the cationic charge than the alkyl group in C–C σ-participation, but less so than π-assisted interaction by the β-aryl group.

Estimation of the solubility parameter of trimethoprim by current methods

Group contribution, the extended Hildebrand solubility (EHS) and the extended Hansen solubility approaches are utilised to estimate the solubility parameter value of trimethoprim. The solubility data in the binary solvent series showed peak solubility at the solubility parameter of solvent, 11.7 H. The regression expression on the lines of the EHS approach yielded 12.06 H. The data on the solubility of trimethoprim in individual solvents was processed as per the extended Hansen approach. The partial solubility parameters were obtained and are used to estimate the solubility parameter, 12.93 H. Extending the Flory-Huggins size correction to this approach gave a value of 10.95 H and improved the correlation coefficient by 3 percent. Partitioning of hydrogen bonding (four parameter approach) didn't improve the value.

Solvent Effects on the Solvolysis of p-Nitrobenzyl and 3,5-Bis(trifluoromethyl)benzyl p-Toluenesulfonates

Abstract Solvolysis rates of p-nitrobenzyl and 3,5-bis(trifluoromethyl)benzyl p-toluenesulfonates were determined in a wide variety of solvents. The solvent effects were analyzed based on the Winstein–Grunwald equation. The solvent effect on these deactivated benzyl solvolyses failed to give a single linear correlation with the 2-adamantyl YOTs parameter. The lower response to the solvent polarity and the pattern of dispersion for respective binary solvent series can be interpreted in terms of nucleophilic solvent assistance. The application of the equation gave a low m value of 0.4 and a large l of close to unity for both derivatives. Furthermore, the l value is also comparable to that for ethyl p-toluenesulfonate and even close to that for the methyl derivative, which has generally been defined as the standard SN2 substrate.

Solvent Effects on the Solvolysis of Benzyl p-Toluenesulfonates

Abstract Solvolysis rates of benzyl p-toluenesulfonate were determined in a wide variety of solvents. The solvent effects were analyzed based on the Winstein–Grunwald equation. The solvent effect on benzyl solvolysis failed to give a single linear correlation with the 2-adamantyl YOTs parameter. The lower response to the solvent polarity and the pattern of dispersion for each binary solvent series can be qualitatively interpreted in terms of nucleophilic solvent assistance. The Winstein–Grunwald analysis gave m = 0.67 and l = 0.36, but with less satisfactory precision. The use of the polarity scale Yneo derived from 2-methyl-2-phenylpropyl solvolysis in place of YOTs gave an improved correlation. A solvent polarity scale Yneo is better applicable to benzyl solvolysis than 2-adamantyl-based YOTs, since the former is compatible with the entire π-delocalization of cationic charge between aryl ring and the reaction center in the transition state.

Solvent Effects on the Solvolysis of Neophyl Tosylates

Abstract Solvolysis rates of 2-phenyl-2-methylpropyl and 2-(p-methoxyphenyl)-2-methylpropyl p-toluenesulfonates were determined in a wide variety of solvents and the solvent effects were analyzed based on the Winstein–Grunwald equation. The solvent effect on neophyl solvolyses failed to give a single linear correlation with the 2-adamantyl YOTs parameter. There was dispersion behavior for the respective binary solvent series between neophyl kΔ substrates and 2-adamantyl tosylate. The pattern of dispersion could not be interpreted in terms of nucleophilic solvent assistance. The response to the solvent polarity (m value for each binary solvent series) was significantly lower for both the methoxy and the unsubstituted derivatives than the m = 1.0 for the limiting kc solvolysis, and appreciably lower for the methoxy derivative than for the unsubstituted one. Linearity of the solvent effects between both neophyl systems and also between other kΔ substrates implied the existence of a unique kinetic solvent polarity scale YΔ characteristic of the β-aryl-assisted (kΔ) solvolysis. The dispersion behavior and reduced m value for the kΔ solvolysis were compatible with the entire π-delocalization of cationic charge between the assisting aryl-ring and the reaction center in the transition state.

Chemical Structure of Coal and Petroleum Pitches

The chemical structure of four pitches is discussed. Each pitch was separated into nine fractions by solvent fractionation at room temperature with pyridine, quinoline and a series of binary solvents consisting of n-hexane and benzene.The average structure of the fractions obtained was estimated by elementary analysis, MW, GPC, IR, UV and NMR.Results of the characterisations of four pitches are as follows:(1) Coal tar pitch, (i) Coal tar pitch contains about 25% of the quinoline soluble and insoluble fractions. It is suggested that this pitch contains a much condensed aromatic ring system from these fractions.(ii) Fractions from n-hexane soluble to pyridine soluble have the largest aromaticity and lowest H/C ratio compared with the corresponding fractions of the other pitches.(iii) On the basis of the parameter Cp/Ca (or Hau/Ca), the average structural unit of each fraction tends to increase in the number of the aromatic rings with increasing fraction number, from 3-4 to 8-9 rings. Moreover, it was suggested from the parameters σ and Ln, that about 10% of the peripheral carbon atoms in the aromatic sheet are replaced by methyl groups.(iv) The average molecule of the fractions appears to consist of less than two average structural units, particularly, the aromatic rings in the average molecule for Fr. 1 to Fr. 4 seem to have nearly equal numbers of average structural units.(2) Naphtha cracking tar pitch; (i) Fractions of this pitch have the largest average molecular weight and lowest H/C ratio of all pitches studied. It is suggested that naphtha cracking tar pitch contains fairly aliphatic structures.(ii) The average structural units of each fraction contain from 3 to 8 rings varying with descending order of the fraction and consisting of condensed aromatic systems. It was suggested from a and Ln that about 20-30% of peripheral carbon atoms in the average structural unit are replaced by ethyl groups.(iii) The average molecule of the fractions appears to consist of condensed aromatic ring systems with 2-3 average structural units for Fr. 1 Fr. 5 and more than 4 average structural units for Fr. 6 and Fr. 7.(3) Catalytic cracking tar pitch of crude oil; The characteristics of this pitch appear to resemble coal tar pitch. However, the H/C ratio and molecular weight were slightly larger than coal tar pitch.(4) Prepared pitch from polymerized naphthalene; This pitch is different from the other pitches described above. The structure of fractions of this pitch appears to consist of a mixture, with more than three units of naphthalene bonded at the 2-and 6-positions of the naphthalene nucleus and perylene type products. Moreover, these products appear to contain some aliphatic structures.

Structural Analysis of Polymerization Product of Naphthalene

Naphthalene was polymerized by the use of anhydrous aluminum chloride-cupric chloride at a reaction temperature of 90 C without solvent.The polymerization prQductwas separated into five fractions(No, 1.to No. 5) by extraction with a series of binary solvents consisting of n-hexane and benzene.The Product yield of polymeriz.ation of naphthalepe was a.bout 40 9% on the, basis of raw naphthalene. Fraction No. 1 soluble in n-hexane was obtained in abbut 400/oyield based on the total product. The added yield of fraction No.1 through No.3 was about 90 /e of the product. It is suggested that the product had a relatively low average degree of polymerlzation.The average molecular structure of each fraction was estimated by the average moleculat weight, gel permeation chroMatography, elementary analysis, IR-, UV- and NMR-spectra.IR- and NMR-spectra showed that product contained some aliphatic struqtures in addition-, to. the aromatic structure, Moreover, the aliphatic structure was found to contain a cycloparaffinic structure.The results of structural analysis of each fraction are as follows. (1) With the descending order of fraction, the average molecular weight increased from 260 for No. 1 to 900 for No.5 and the aromaticity (A) of the fraction a1so showed an increase. (2) Since the numbers of the aromatic carbon (C.) increased gradually, the degree of polymerization of naphthalene was considered to increase with the descending order of fractions.In summary the polymerization product was fractionated to a considerable extent byil the. present fractionation methodwith binary solvents.