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The environmental impact of chemical applications can be reduced by using novel solvents with green properties. In this field, Deep Eutectic Solvents (DESs) are promising liquids thanks to their low toxicity, high eco-compatibility and high easiness and “greenness” of preparation. DESs are mixtures of a hydrogen bond donor molecule (HBD) and a hydrogen bond acceptor molecule (HBA) at the proper molar ratio. In this paper, we present the preparation of novel hydrophobic deep eutectic solvents and the studies of their properties: density, eutectic profiles, ranges of water separation, contamination of the separated phases, extraction capabilities of phenol model polluting molecules, capabilities of extraction at acidic and basic conditions. Interesting results emerged about the role of the components of the DESs because of the use of a properly-chosen set of liquids. Their capabilities were dependent on the nature of the HBD molecule, and in particular on its hydrophobicity. Even the DESs with highly water-soluble HBA showed to be easily separable from water and really efficacious as extracting agents when prepared with hydrophobic HBDs. The results of the extractions of pollutants in acid and basic conditions showed the capability of water separation and extraction efficiency of these mixtures even with water at pH = 2 and pH = 9; therefore, the phenols could interact with these liquids without involvement of any acid/base-type of interactions.

Hypothesis Clathrate hydrates of hydrogen form at relatively low pressures (e.g., ca. 10 MPa) when a co-former compound is added. In that case, however, the gravimetric amount of stored hydrogen drops to less than 1 wt% from ca. 5.6 wt% without a co-former. Another factor hindering the entrapment of hydrogen into a clathrate matrix appears to be of a kinetic origin, in that the mass transfer of hydrogen into clathrates is limited by the macroscopic scale of the gas–water interfaces involved in their formation. Thus, the enhanced formation of binary (hydrogen + co-former) hydrates would represent a major achievement in the attempt to exploit those materials as a convenient means for storing hydrogen. Experiments Here, we present a simple process for the enhanced formation of binary hydrates of hydrogen and several co-formers, which is based on the use of reverse micelles for reducing the size of hydrate-forming gas–water interfaces down to tens of nanometers. This reduction of particle size allowed us to reduce the kinetic hindrance to hydrate formation. Findings The present process was able to (i) enhance the kinetics of the formation process; and (ii) assist clathrate formation when using water-insoluble coformers (e.g., cyclopentane, tetrahydrothiophene).

The ability of some zwitterionic natural deep eutectic solvents (NADESs) based on N,N,N-trimethylglycine (TMG) and carboxylic acids (oxalic, glycolic and phenylacetic) to act as environmentally friendly solvents for CO2 capture has been investigated. The solubility of CO2 in the NADESs was measured gravimetrically at different temperatures in the range 298.15–333.15 K, and at different pressures in the range 0.1–4 MPa. The effect of the adopted experimental conditions has been discussed. The highest uptake has been observed for phenylacetic acid/TMG DES at 313.15 K and 4 MPa (45.5 mg CO2/g DES). The efficiency of this NADES as CO2 sorbent when reused in subsequent capture cycles has been evaluated. This work might open new perspectives in developing the most appropriate combination of HBA and HBD components of the DESs and the most appropriate operative conditions for an environmentally friendly CO2 capture.

Deoxydehydration (DODH) reaction on 1,2-propanediol (1,2-PD) catalyzed by rhenium, conducted in 2,4-dimethyl-3-pentanol (DMP) or in neat 1,2-PD, was carried out. The experimental apparatus was planned to recover separately all the reaction products: in one reaction vessel, the gaseous propene was collected while all the other reaction products, above all regarding the transformation of 1,2-PD, were collected in another reaction vessel. The most common commercial high oxidation state rhenium compounds, methytrioxorhenium (MTO), ReO3, Re2O7 and NH4ReO4, were selected as catalysts. Among them, MTO and Re2O7 gave the best performance in terms of propene production even if ReO3 showed a moderate yield of another reaction product, the acetal formed by coupling of 1,2-PD and 1-hydroxypropanone, that can be considered an innovative strategy to make value over the 50% of the diol.

Biologically active prenyoxyphenylpropanoids are well known to be biosynthesized by Citrus species, for which they have been found most abundantly in fruit peels. Although several extraction methodologies have been described, the development of novel and alternative extraction processes is a field of research of current interest. In this preliminary communication, we studied the performance of the subcritical butane promoted extraction of selected oxyprenylated phenylpropanoids from grapefruit peels under a counter-current mode using a handmade extraction apparatus coupled to UHPLC analysis. The application of such a method yielded 7-isopentenyloxycoumarin, auraptene, and boropinic acid in quantities higher than those recorded for other extraction methodologies like the ultrasound- and microwave-assisted macerations (0.234, 1.035, and 0.211 mg/g of dry extract respectively). The use of subcritical butane as the extraction solvent for oxyprenylated phenylpropanoids is reported herein for the first time and can be easily adopted for several other food matrices.

Plants belonging to Artemisia spp. are known to biosynthesize a wide panel of 3,3-dimethylallyl- and sesquiterpenyl- substituted coumarins. In this short communication we applied a novel extraction methodology based on the use of subcritical butane under a counter-current mode to further characterize the presence of selected biologically active oxyprenylated phenylpropanoids, namely coumarins and ferulic acid derivatives, in extracts deriving from aerial parts of Artemisia vulgaris L. (commonly known as "common mugwort") (Asteraceae). In the mean time, we assessed the efficiency of the above mentioned extractive methodology with other routes like maceration and ultrasounds and microwaves-based methods using absolute EtOH as the solvents. UHPLC analysis coupled to UV/Vis detection revealed that, among the 5 pure chemical standard assayed, only umbelliprenin (7-farnesyloxycoumarin) was recorded, while boropinic acid, 4'-geranyloxyferulic acid, 7-isopentenyloxycoumarin, and auraptene were not detected. The best extractive yield (0.18 %) was obtained after extaction with subcritical butane. The presence of umbelliprenin in Artemisia plant species has been reported herein for the first time. This coumarin may represent the biosynthetic precursors of sesquiterpenyloxycoumarins with more complex structures typically found in this genus.

This paper contains data of water capacity (in terms of w0 = molwater/molsurfactant) in reverse micelles formed by several commercial and non-commercial cationic surfactants in cyclopentane, petroleum ether, and iso-octane. Also reported are hydrodynamic diameters of the respective reverse micelles formed. Tested surfactants were (i) single-chained cationics: cetyl benzyl diethanolammonium bromide (CBDB), cetyl benzyl dimethylammonium bromide (CBMB), cetyl dibutyl ethanolammonium bromide (CDBEB), cetyl cyclohexyl dimethylammonium bromide (CCDB); and (ii) twin-chained cationics: didodecyl dimethylammonium chloride (DDMC), didodecyl diethylammonium bromide (DDEB), didodecyl dipropylammonium bromide (DDPB), didodecyl diethylammonium chloride (DDEC), dodecyl benzyl dimethylammonium bromide (DBDMB). Also reported are sizes of reverse micelles as determined by dynamic light scattering. Keywords: Reverse micelles, Cationic surfactants, Water content, Dynamic light scattering

The critical micelle concentration (cmc) and ionisation degree (α), of micelles of cetyltrimethylammonium bromide (CTABr), cetyltrimethylammonium chloride (CTACl), cetyltripropylammonium bromide (CTPABr) and cetyltripropylammonium chloride (CTPACl) have been measured over a narrow temperature range at 2 degree intervals using electrical conductivity. CTPACl and CTPABr are very soluble in water and were measured in the temperature range 275.15-323.15K. The Krafft temperatures for CTABr and for CTACl are 293.15K and 284.15K, respectively and established a lower temperature limit for our studies on these two surfactants. The cmc vs temperature curves have a smooth minimum near room temperature and α linearly increases with temperature. The changes of cmc and α with temperature are smaller than those associated with the modification of head group size or counterion nature. Using these results, basic thermodynamic quantities associated with the phenomena of micellization have been evaluated. Thermodynamic properties of the surfactant solutions were discussed in terms of temperature dependence of the free energy, enthalpy and entropy of micellization. A close similarity between the effects of change in temperature on protein folding and micellization process appears from the data.

The effect of two ammonium salts with a bulky head group, the tetrabutylammonium bromide (TBABr) and the surfactant cetyltributylammonium bromide (CTBABr) on α-chymotrypsin hydrolysis rate toward three peptidyl substrates was investigated. N -Succinyl- l -phenylalanine- p -nitroanilide (SP p NA), N -succinyl- l -alanyl- l -alanyl- l -phenylalanine- p -nitroanilide (SAAP p NA) and N -succinyl- l -alanyl- l -alanyl- l -prolyl- l -phenylalanine- p -nitroanilide (SAAPP p NA), which contain the same chromogenic and N-protecting groups, but a different number of amino acidic residues, were selected. The relative activity showed a bell-shaped dependence on additive concentration, with a maximum which ranged from 1 × 10 −3 M to 5 × 10 −3 M for CTBABr and at 0.3 M for TBABr. Both the additives induced α-chymotrypsin superactivity, but their effect decreased as the peptide chain length of the substrate increased. Analysis of the kinetic parameters indicated that the activation was mainly due to an increase in k cat values, probably caused by enzyme conformational changes induced by the additives, while K M remained almost unchanged. The very notable effect of both CTBABr and TBABr on SP p NA hydrolysis rate and the limited activation with SAAP p NA and SAAPP p NA could be probably due to non-specific interactions between the additives and the subsites next to the catalytic point within α-chymotrypsin active site, not allowed with the longer amino acidic chain substrates.

Comparison of reactivities of methyl naphthalene-2-sulfonate, MeONs, and its 6-sulfonate derivative, MeONsS − , toward H 2 O, OH − , and Br − in water and in cationic micelles of cetyl trialkylammonium surfactants, n -C 16 H 33 N + R 3 X − , R=Me, n -Pr, n -Bu, CTA + , CTPA + , CTBA + , X=OH, Br, and CH 3 SO 3 has been investigated. For reactions in water, the introduction of the negative charge accelerates hydrolysis by a factor of ca. 2, but does not affect reactivity of OH − and Br − . For reactions in micelles, the negative charge decreases values of k M for reactions with water, with OH − and Br − by a factor of ca. 2; differences for the two substrates decrease with bulking the surfactant head group for a reaction with Br − but not for a reaction with OH − .

Reactivities of methyl naphthalene-2-sulfonate, MeONs, and its 6-alkyl derivatives, alkyl=Me, n-C(6)H(13) and n-C(12)H(25), 6-Me-MeONs, 6-Hex-MeONs, and 6-Do-MeONs, respectively, are compared for reactions in cetyl trialkylammonium bromide micelles, n-C(16)H(33)NR(3)Br, R=Me, Et, n-Pr, n-Bu, CTABr, CTEABr, CTPABr, CTBABr, respectively. Similar experiments were made on reactions of Br(-) with n-butyl and n-decyl naphthalene-2-sulfonates, BuONs, and DeONs, respectively. Reactions with OH(-) were followed in cetyl trialkylammonium hydroxide, alkyl=Me, Et, n-Pr, CTAOH, CTEAOH, and CTPAOH, solubility permitting. Some reactions with OH(-) or Br(-) were also followed in mixed-ion systems of CTAOMs or CTPAOMs (OMs=MeSO(3)). Micellar rate effects were analyzed by using pseudophase treatments including interionic competition in mixed-ion systems. Second-order rate constants in the micellar pseudophase increase systematically with increases in substrate hydrophobicity and for reactions with Br(-), but not OH(-), they also increase with bulk of the cationic head group. Copyright 2001 Academic Press.

The interaction of surfactants with proteins in aqueous solutions has been the subject of many investigations to understand the interactions between membrane proteins and lipids, structurally similar to synthetic surfactants. The effect of surfactant on enzyme structure and activity is the result of chemically selective interactions that may be influenced both by the enzyme structure and by the chemistry of the surfactant. For many years, surfactants have been considered as non-specific denaturants of proteins, even if in the literature several of them are reported to enhance activity and/or stability of some enzymes: the detergent can interact with the enzyme and cause a conformational change to a more active form and/or stabilize its native folded structure. Although the surfactant head group seems to have a determining role, other structural features of the detergent are also important in influencing the catalytic properties of an enzyme, i.e. head group size and its hydrophobic/hydrophilic balance. Up to now it is very difficult to predict the molecular features of the surfactant and an extensive investigation on the relationship between the surfactant chemical structure and the catalytic properties of enzyme is still required.

The SN2 reaction of Br- with methylnaphthalene-2-sulfonate (MeONs) in water is accelerated by micelles of tetradecyldialkyl amine oxide (alkyl = methyl, n-propyl) and rates increase sharply in HBr due to increased binding of Br- to the protonated amine oxide. Second-order rate constants at the micellar surface are similar to those at surfaces of trialkylammonium and sulfobetaine micelles. The reaction of OH- with MeONs is weakly inhibited by amine oxide micelles, showing that dispersive, as well as coulombic and charge-dipole, forces play a major role in the association of ions with surfaces of micellar aggregates. Copyright 1999 Academic Press.