Payam Kalhor

Deep eutectic solvents (DESs) have emerged as promising green solvents, due to their versatility and properties such as high biodegradability, inexpensiveness, ease of preparation and negligible vapor pressure. Thus, DESs have been used as sustainable media and green catalysts in many chemical processes. On the other hand, lignocellulosic biomass as an abundant source of renewable carbon has received ample interest for the production of biobased chemicals. In this review, the state of the art of the catalytic use of DESs in upgrading the biomass-related substances towards biofuels and value-added chemicals is presented, and the gap in the knowledge is indicated to direct the future research.

Attenuated total reflection–Fourier transform infrared spectroscopy and quantum chemical calculations were performed on tert-butyl alcohol (t-BuOH) and its binary solutions with CCl₄ and CHCl₃. The study was focused on the free-OH stretching bands. Two resolution-enhancing methods, excess spectroscopy and two-dimensional correlation spectroscopy, were employed to examine the structural heterogeneity and search for the detailed contributors to the free-OH bands. Unexpectedly, CCl₄ was found not to be an inert solvent and, similar to CHCl₃, formed hydrogen/halogen bonds (H-/X-bond) with t-BuOH. It was observed that the free-OH band in the t-BuOH–CHCl₃ system is larger and more red-shifted than that in the t-BuOH–CCl₄ system, indicating the stronger intermolecular interactions in the former system. Furthermore, in the t-BuOH–CHCl₃ system, the H-bonds are stronger than the X-bonds, while in the t-BuOH–CCl₄ system, both interactions are similar in strength. To assign the free-OH bands, it was found that they are not only from the free OH of the t-BuOH monomer, but they are also contributed by the quasi-free OH with the oxygen bonded to H or Cl and even the weakly H-bonded OH of t-BuOH molecules. Finally, all the identified species increased simultaneously via cosolvent addition, suggestive of the destabilization of the highly associated t-BuOH clusters.

Deep-eutectic-solvents (DESs) are a new class of green solvents. Here we report the hydrogen bonding and structural properties of the archetypal DES ethaline, a mixture of choline chloride (ChCl) and ethylene glycol (EG) of 1:2 molar ratio, and its pseudo-binary mixtures with acetonitrile. The investigations were carried out employing FTIR combined with quantum chemical calculations. Excess and 2D-correlation spectroscopies were used to identify favorable species in the solutions and to explore the heterogeneity. The results show that the mixing process is the transformation from ethaline, EG tetramer, and CH₃CN dimer to the complexes of ethaline-1CH₃CN and ethaline-2CH₃CN, together with the increased percentages of EG dimer, EG trimer, and CH₃CN monomer with respect to their total amounts in the mixtures. Theoretical calculations show that, for ChCl, the positive charge is located at the methyl groups and methylenes, rendering their ability to form hydrogen bonds. Adding CH₃CN to ethaline can hardly break apart the doubly ionic hydrogen-bonds between Ch⁺ and Cl^-. The co-solvent molecules mainly surround the core-structure of ethaline, forming non-covalent hydrogen bonds with hydroxyl groups of EG/Ch⁺, but not Cl^-. These in-depth studies on the properties of ethaline and CH₃CN/CD₃CN mixed solvents may shed light on exploring their applications.

We propose the concept of local acidity in condensed phase chemistry in this work. The feature is demonstrated in tri-fluoroethanol (TFE) by employing two FTIR nitrile probes, acetonitrile (CH3CN) and benzonitrile (PhCN). Specifically, three positive excess peaks were found in the binary systems composed of TFE and a probe using excess spectroscopy. To characterize the local acidity quantitatively, we have tried to correlate the wavenumbers of positive excess peaks of the probes and the pKa values in water of a series of XH-containing compounds (X=O, N, and C). Good linear relationships were discovered. Accordingly, three different pKa values of TFE were determined based on the three positive excess IR peaks, which are attributed to monomer, dimer, and trimer of TFE with the help of quantum chemical calculations. The concept of local acidity and its quantitative evaluation enrich our knowledge on acid-base chemistry and would shed light on a better understanding of microstructures of solutions.

Valorization of lignocellulosic biomass and food residues to obtain valuable chemicals is essential to the establishment of a sustainable and biobased economy in the modern world. The latest and greenest generation of ionic liquids (ILs) are deep eutectic solvents (DESs) and natural deep eutectic solvents (NADESs); these have shown great promise for various applications and have attracted considerable attention from researchers who seek versatile solvents with pretreatment, extraction, and catalysis capabilities in biomass- and biowaste-to-bioenergy conversion processes. The present work aimed to review the use of DESs and NADESs in the valorization of biomass and biowaste as pretreatment or extraction solvents or catalysis agents.

In this work, quantitative structure-property relationship (QSPR) models for prediction of retention time (RT) of 47 volatile compounds in rosé wines on the basis of their molecular structures were developed by applying multiple linear regression (MLR) and artificial neural network (ANN). A Levenberg- Marquardt algorithm trained feed-forward back-propagation artificial neural network (ANN) was employed. The data were randomly divided into 29 training and 9 validation sets. For comparison purpose, multiple linear regression (MLR) model of the same data was developed. Cross-validation was used to validate the QSPR models. Also, the application of the models for prediction of external set’s retention times of compounds without any contribution to model development steps was another validation process. The MLR model yielded marginally acceptable statistics with test correlation R² = 0.993 and mean squared error (MSE) = 0.0075. Not surprisingly, the ANN model was significantly more accurate with test correlation R² = 0.995 and mean squared error (MSE) = 0.00013.