ポリイミド前駆体調製のためのグリーン混合溶媒の選定法

要約のみTohoku University猪股宏課

Replacement of Hazardous Chemicals Used in Engineering Plastics with Safe and Renewable Hydrogen-Bond Donor and Acceptor Solvent-Pair Mixtures

Mixtures of safe and renewable solvents can replace hazardous solvents presently being used in the manufacture of engineering plastics. In this work, a methodology is proposed for identifying solvent-pair mixtures for preparing polymer precursors, with poly­(amic acid) (PAA) being studied as an example. The methodology uses a chemical safety index, Hansen solubility parameters and Kamlet–Taft solvatochromic parameters of the pure and solvent-pair mixtures to identify hydrogen bond acceptor (HBA)–hydrogen bond donor (HBD) solvent-pair combinations. Ten replacement solvent-pairs for PAA syntheses identified were cyclohexanone–methanol, cyclohexanone–ethanol, cyclopentanone–methanol, cyclopentanone–ethanol, γ-butyrolactone–methanol, γ-butyrolactone–ethanol, γ-butyrolactone–water, γ-valerolactone–methanol, γ-valerolactone–ethanol, and γ-valerolactone–water. Homogeneous PAA solutions could be obtained from HBA–HBD solvent-pair mixtures when their solubility parameters were within 21–29 MPa^0.5 and their Kamlet–Taft solvatochromic parameters were π* (>0.67) and β (>0.67) for nonaqueous solutions and π* (>0.68) and β (>0.59) for aqueous solutions. Replacement solvent-pairs, γ-valerolactone–ethanol, γ-valerolactone–water, and γ-butyrolactone–water gave homogeneous precursor solutions that were comparable with commercial solutions prepared with <i>N</i>-methyl-2-pyrrolidone. The proposed methodology and reported solvatochromic parameters make it is possible to identify other solvent-pair mixtures and new solvent-pairs for preparing polymer precursor solutions used in engineering plastics

Methodology for Replacing Dipolar Aprotic Solvents Used in API Processing with Safe Hydrogen-Bond Donor and Acceptor Solvent-Pair Mixtures

A methodology is presented that allows hazardous dipolar aprotic solvents used in the pharmaceutical processing industries to be replaced with solvent-pair mixtures that consist of a hydrogen-bond donor (HBD) solvent and a hydrogen-bond acceptor (HBA) solvent. The methodology uses the solubility of the active pharmaceutical ingredient (API) in hazardous solvents to estimate the range of required solubility parameters and Kamlet–Taft parameters for the API and then intersects these ranges with the solubility parameters and Kamlet–Taft parameters of the solvent-pair mixtures to identify favorable solvent pairs and possible working compositions. Solvent pairs are ranked according to GSK safety and health scores. The methodology was applied to 13 APIs, where it was found that nonaqueous mixtures (ethanol–isopropyl acetate, ethanol–ethyl acetate, and ethanol–butyl acetate) and aqueous mixtures (water−γ-valerolactone and water–dimethyl sulfoxide) are highly ranked and applicable to many APIs. Solvent pairs were eliminated from consideration due to their inability to simultaneously satisfy Kamlet–Taft acidity, basicity, and polarity parameter constraints. The proposed methodology makes it simple to identify and rank HBD–HBA solvent-pair mixtures for replacement of dipolar aprotic solvents used in the pharmaceutical processing industries

Analysis of the Cybotactic Region of Two Renewable Lactone–Water Mixed-Solvent Systems that Exhibit Synergistic Kamlet–Taft Basicity

Kamlet–Taft solvatochromic parameters (polarity, basicity, acidity) of hydrogen bond donor (HBD)/acceptor (HBA) mixed-solvent systems, water (H₂O)−γ-valerolactone (GVL), methanol (MeOH)–GVL, ethanol (EtOH)–GVL, H₂O−γ-butyrolactone (GBL), MeOH–GBL, and EtOH–GBL, were measured over their entire composition region at 25 °C using UV–vis spectroscopy. Basicity of H₂O–GVL and H₂O–GBL systems exhibited positive deviation from ideality and synergism in the Kamlet–Taft basicity values. The cybotactic region around each indicator in the mixed-solvent systems was analyzed with the preferential solvation model. Both H₂O–GVL and H₂O–GBL mixed-solvent systems were found to be completely saturated with mutual complex molecules and to have higher basicity than pure water because water prefers to interact with GVL or GBL molecules rather than with itself. Formation of H₂O–GVL and H₂O–GBL complex molecules via specific hydrogen bond donor–acceptor interactions were confirmed by infrared spectroscopy. In MeOH–GVL or MeOH–GBL mixed-solvent systems, MeOH molecules prefer self-interaction over that with GVL or GBL so that synergistic basicity was not observed. Synergistic basicity and basicity increase for various functional groups of ten mixed-solvent (water–HBA solvent) systems can be quantitatively explained by considering electrostatic basicity and a ratio of the partial excess HBA solvent basicity with the HBA solvent molar volume that correlate linearly with the preferential solvation model complex molecular parameter (<i>f</i>_12/1). Analysis of the cybotactic region of indicators in aqueous mixtures with the preferential solvation model allows one to estimate the trends of mixed-solvent basicity

Spectroscopic Analysis of Binary Mixed-Solvent-Polyimide Precursor Systems with the Preferential Solvation Model for Determining Solute-Centric Kamlet–Taft Solvatochromic Parameters

Hydrogen bond donor/acceptor mixed-solvent systems for solutes that exhibit strong specific interactions are not readily characterized with methods that depend on solvatochromic parameters. In this work, the reaction of two monomers, 4,4′-oxidianiline (ODA) and pyromellitic dianhydride (PMDA), to form the common engineering plastic precursor, poly­(amic acid) (PAA), are studied for the tetrahydrofuran (THF) mixed-solvent systems (THF-methanol, THF-ethanol, THF-water) with spectroscopy. Solute-centric (SC) Kamlet–Taft solvatochromic (K-T) parameters for the solvent environment around the monomer are determined using a proposed model that incorporates spectroscopically determined local composition (<i>X</i>^L) around the ODA monomer and the preferential solvation model. For the example reaction to occur under homogeneous conditions, mixed-solvent conditions need have HBA-rich local compositions (0.30 < <i>X</i>_HBA^L < 0.83), high solute-centric basicity (β_SC > 0.60), high solute-centric polarity, (π_SC^* > 0.63), and low solute-centric acidity (α_SC < 0.63). The method developed allows characterization of mixed-solvent effects and can be readily extended to other systems that have strong specific interactions

Mechanistic role of protonated polar additives in ethanol for selective transformation of biomass-related compounds

We report on a combined experimental, spectroscopic and theoretical study of acid catalysed dehydration-etherification of fructose in ethanol for understanding the mechanistic role of polar solvent additives and product selectivity. Herein, we show that polar solvent additives (e.g. tetrahydrofuran, acetone, acetonitrile, gamma-valerolactone, dimethyl sulfoxide) protonated with a common solid acid catalyst in ethanol allow transformation of biomass-related compounds into desired dehydration or etherification products. Fructose in ethanol with DMSO additive is selectively transformed into 5-hydroxymethylfurfural with negligible formation of 5-ethoxymethylfurfural due to preferential DMSO protonation according to its polarity. Spectroscopic methods and density functional theory show that additives having higher polarity than ethanol are readily protonated and act as the key catalytic protonation species and as the key stabilization species for reaction intermediates. Understanding the mechanism of protonated polar additives in reaction systems allows one to tailor selectivity in acid-catalyzed dehydration-etherification schemes and to develop sustainable chemistry for biomass resources

Mechanism of Glucose Conversion into 5‑Ethoxymethylfurfural in Ethanol with Hydrogen Sulfate Ionic Liquid Additives and a Lewis Acid Catalyst

Hydrogen sulfate ionic liquid additives with aluminum chloride catalyst in ethanol were found to promote efficient (30 min) one-pot, one-step transformation of glucose into 5-ethoxymethylfurfural (5-EMF) in 37% yields. Spectroscopic measurements (FT-IR, ¹H NMR) showed that ionic liquids form multiple hydrogen bonds with glucose and promote its ring opening through ionic liquid–AlCl₃ complexes to enable formation of 5-EMF via 5-hydroxymethylfurfural (5-HMF). Reactions performed in dimethyl sulfoxide using (protic, aprotic) ionic liquid additives with and without AlCl₃ catalyst showed that both the ionic liquid and AlCl₃ were required for efficient transformation of glucose into 5-EMF. The proposed reaction mechanism for 5-EMF synthesis in the ethanol–1-butyl-3-methylimidazolium hydrogen sulfate–AlCl₃ reaction system consists of ring opening of glucose to form the 1,2-enediol and dehydration to form 5-HMF that is followed by etherification to the 5-EMF product. The reaction system is effective for glucose transformation and has application to biomass-related compounds