Haijun Wang

Theoretical and experimental investigation on dissolution and regeneration of cellulose in ionic liquid

Density functional theory calculations and atoms in molecules theory were performed to investigate the mechanism of cellulose dissolution and regeneration in 1-ethyl-3-methylimidazolium acetate ([emim]Ac), and (1,4)-dimethoxy-β-D-glucose (Glc) was chosen as the model for cellulose. The theoretical results show that the interaction of [emim]Ac with Glc is stronger than that of Glc with Glc. Further studies indicate that the anion acetate of [emim]Ac forms strong H-bonds with hydroxyl groups of Glc. It is also observed that the H-bonds between [emim]Ac and Glc are weakened or even destroyed by the addition of water. In addition, both the original and regenerated cellulose samples were characterized with FT-IR, XRD, TGA and SEM. The experimental results prove that cellulose can be readily reconstituted from the [emim]Ac-based cellulose solution by the addition of water and the crystalline structure of cellulose is converted to cellulose II from cellulose I in the original cellulose.

Catalytic conversion of cellulose to 5-hydroxymethyl furfural using acidic ionic liquids and co-catalyst.

Efficient catalytic conversion of microcrystalline cellulose (MCC) to 5-hydroxymethyl furfural (HMF), is achieved using acidic ionic liquids (ILs) as the catalysts and metal salts as co-catalysts in the solvent of 1-ethyl-3-methylimidazo-lium acetate ([emim][Ac]). A series of acidic ILs has been synthesized and tested in conversion of MCC to HMF. The effect of reaction conditions, such as reaction time, temperature, catalyst dosage, metal salts, water dosage, Cu(2+) concentration and various acidic ILs are investigated in detail. The results show that CuCl(2) in 1-(4-sulfonic acid) butyl-3-methylimidazolium methyl sulfate ([C(4)SO(3)Hmim][CH(3)SO(3)]), is found to be an efficient catalyst for catalytic conversion of MCC to HMF, and 69.7% yield of HMF is obtained. A mechanism to explain the high activity of CuCl(2) in [C(4)SO(3)Hmim][CH(3)SO(3)] is proposed. To the best of our knowledge, this report first proposes that the Cu(2+) and [C(4)SO(3)Hmim][CH(3)SO(3)] show better catalytic performance in catalytic conversion of MCC to HMF.

Metal-Free Three-Component Oxyazidation of Alkenes with Trimethylsilyl Azide and N-Hydroxyphthalimide

A novel and facile oxyazidation of alkenes under metal-free and mild conditions has been reported. A remarkable feature of the developed procedure is consecutive construction of C-O and C-N bonds in one step. The process allows quick and selective assembly of alkyl azide from readily available starting materials, where N-hydroxyphthalimide was used as an oxygen-radical precursor and TMSN3 as the N3 source. A range of aromatic alkenes bearing synthetically useful functional groups was tolerated.

Theoretical Study on the Structure and Cation−Anion Interaction of Amino Acid Cation Based Amino Acid Ionic Liquid [Pro]+[NO3]−

The proline cation based amino acid ionic liquid [Pro]+[NO3]− was systematically studied by density functional theory at the B3LYP/6-311++G** level. The stable geometries of the cation, anion, ion pair, as well as the ion-pair dimer [Pro]2+[NO3]2− with no imaginary frequencies were obtained and characterized. In the single [Pro]+[NO3]− unit, proton transfer from [Pro]+ to [NO3]− can be observed in some of the configurations and the corresponding proton-transferred products (neutral pairs) are strongly hydrogen bonded. While in the ion-pair dimer [Pro]2+[NO3]2−, proton transfer does not occur and the components are stabilized by ionic interaction and hydrogen bonding interaction jointly. The proton transfer reaction between the cation and the anion in the single ion-pair unit has been investigated, and the role that the proton transfer reaction may play in the physicochemical property change of the ionic liquids has also been discussed. The interactions in the single ion-pair unit [Pro]+[NO3]− and in the ion-pair dimer [Pro]2+[NO3]2− were both carefully studied. The hydrogen bonds (H bonds) between the various fragments were analyzed by the atoms in molecules theory and harmonic vibrational frequency.

Catalyst-Controlled Dioxygenation of Olefins: An Approach to Peroxides, Alcohols, and Ketones

An efficient catalytic approach for the synthesis of substituted peroxides, alcohols, and ketones through a catalyst-controlled highly selective dioxygenation of olefins has been demonstrated. The reported methods are mild and practical, can be switched by the selection of different catalytic systems, and employ peroxide as an oxidant and a reagent at room temperature.

Silver-Catalyzed Decarboxylative Addition/Cyclization of Activated Alkenes with Aliphatic Carboxylic Acids.

A silver-catalyzed decarboxylative addition/aryl migration/desulfonylation of N-phenyl-N-(phenylsulfonyl)methacrylamide with primary, secondary, and tertiary carboxylic acids was described. The protocol provides an efficient approach for the synthesis of α-all-carbon quaternary stereocenters amides and isoquinolinediones. It was proposed that the radical generated from the silver-catalyzed decarboxylation was involved in the sequence reaction.

Efficient process for the direct transformation of cellulose and carbohydrates to 5-(hydroxymenthyl)furfural with dual-core sulfonic acid ionic liquids and co-catalysts

The direct transformation of cellulose and carbohydrates into 5-(hydroxymethyl)furfural (HMF) in the solvent [BMIM]Cl using dual-core sulfonic acid ionic liquids (ILs) as catalysts and metal salts as co-catalysts was investigated, aiming at a more environmentally friendly process not involving chromium. From the high throughput screening of various metal salts, a combination of [bi-C3SO3HMIM][CH3SO3] (IL-2) and manganese chloride (MnCl2) was found to be the most effective catalyst. HMF was directly afforded from cellulose in 66.5% yield. Thus, synthesis of HMF was successfully performed from cellulose using ILs and MnCl2. Following the principles of green engineering, we recycled the catalyst in our system for cellulose hydrolysis and this catalyst maintained its good performance even after four runs. Furthermore, various sugars and lignocellulosic raw materials could be directly converted into HMF in reasonable yields under these conditions. The mechanism that explains the high activity of ILs in combination with MnCl2 is also proposed.

Novel magnetic lignin composite sorbent for chromium(VI) adsorption

A novel magnetic lignin composite was prepared and modified with diethylenetriamine. The properties of the composite were characterized by SEM, FTIR, XRD, TGA and VSM. Then, the adsorption of chromium(VI) from aqueous solutions using this magnetic lignin composite was investigated. Chromium(VI) removal is pH dependent and the optimum adsorption was observed at pH 2.0. The pseudo-second-order model and the Langmuir adsorption isotherm model were applied to describe the adsorption kinetics and adsorption isotherm, respectively, for the chromium(VI) adsorption. Thermodynamic parameters were calculated, which revealed the adsorption process to be spontaneous and exothermic. Regeneration of the magnetic lignin composite was achieved by using 0.4 M NaCl and 0.2 M NaOH, more than 87% efficiency retention was obtained after 5 cycles.

Theoretical study on the interaction of glutathione with group IA (Li+, Na+, K+), IIA (Be2+, Mg2+, Ca2+), and IIIA (Al3+) metal cations

The structures and energies of complexes obtained upon interaction between glutathione (GSH) and alkali (Li+, Na+, K+), or alkaline earth metal (Be2+, Mg2+, Ca2+), or group IIIA (Al3+) cations were studied using quantum chemical density functional theory. The characteristics of the interactions between GSH and the metal cations at different nucleophilic sites of GSH were examined selecting systematically, both mono- and multi-coordinating were taken into account. The results indicated that the heteroatom of GSH, the radius and charge of metal ion, and the coordination number of the metal cation with the ligand played important roles in determining the stability of these complexes. Moreover, the intramolecular hydrogen migration in GSH could be promoted by the metal cations during coordination reaction. Furthermore, the Al3+ cation might catalyze the decarboxylation reaction and stimulate the formation of covalent bond between S atom and adjacent O atom of GSH.

Copper-catalyzed C–H alkylation of 8-aminoquinolines via 8-amide chelation assistance

A copper-catalyzed 8-amide chelation-assisted C–H alkylation of 8-aminoquinolines is described. The secondary and tertiary alkyl carboxylic acids can be used as alkylating agents. This reaction allows for the highly regioselective preparation of C2-adamantyl 8-aminoquinoline scaffolds by the decarboxylative alkylation catalytic system.