Dehydration In Water Research Articles

Dehydration in Water: A Reagentless and Straightforward Synthesis of Tetrahydroquinazolines under Microwave Irradiation or by Stirring at Room Temperature, and Their Subsequent Conversion into Quinazolines in a Micellar Medium

AbstractUsing a reagent- and catalyst-free approach, a series of 2-substituted 1,2,3,4-tetrahydroquinazolines is synthesized by cyclocondensation between aldehydes and 2-aminobenzylamines via dehydration in water. The reactions are complete in 2 minutes under microwave irradiation and proceed well under stirring at room temperature, affording tetrahydroquinazolines in high to excellent yields. The products are water-insoluble and are isolated by simple filtration, avoiding a conventional work-up step and offering an organic-solvent-free process. Furthermore, the tetrahydroquinazolines are efficiently oxidized in a micellar medium derived from cetyltrimethylammonium bromide (CTAB) using a cheap commercial bleaching solution (4% NaOCl in water) to give quinazolines in high yields. This sustainable protocol has a near zero E-factor.

Dehydration in water: solid-supported lipases as green catalysts for esterification

Catalytic esterification in water has been achieved with the aid of a commercially available polymer-supported lipase, Novozym-435.

Thermoresponsive Helical Dendronized Poly(phenylacetylene)s: Remarkable Stabilization of Their Helicity via Photo-Dimerization of the Dendritic Pendants.

Dynamic helical polymers can change their helicity according to external stimuli due to the low helix-inversion barriers, while helicity stabilization for polymers is important for applications in chiral recognition or chiral separations. Here, we present a convenient methodology to stabilize dynamic helical conformations of polymers through intramolecular cross-linking. Thermoresponsive dendronized poly(phenylacetylene)s (PPAs) carrying 3-fold dendritic oligoethylene glycol pendants containing cinnamate moieties were synthesized. These polymers exhibit typical features of dynamic helical structures in different solvents, that is, racemic contracted conformations in less polar organic solvents and predominantly one-handed stretched helical conformations in highly polar solvents. This dynamic helicity can be enhanced through selective solvation by increasing the polarity of the organic solvents or simply via their thermally mediated dehydration in water. However, through photocycloaddition of the cinnamate moieties between the neighboring pendants via UV irradiation, these dendronized PPAs adopt stable helical conformations either below or above their phase transition temperatures in water, and their helical conformations can even be retained in less polar organic solvents. Spectroscopic and atomic force microscopy measurements demonstrate that photocycloaddition between the cinnamate moieties occurs on the individual molecular level, and this is found to be helpful in restraining the photodegradation of the PPA backbones. Molecular dynamics simulations reveal that the spatial orientation of the pendants along the rigid polyene backbone is crucial for the photodimerization of cinnamates within one helix pitch.

In-situ regeneration of NbOX/TiO2 catalyst deteriorated due to coke deposition via supercritical water oxidation

In this study, supercritical oxidation was used as a method for in situ regeneration of deteriorated NbOX/TiO2 catalyst during glycerol dehydration in supercritical water at 400 ℃ and 30 MPa. When the dehydration reaction using NbOX/TiO2 was conducted, coking of the catalyst occurred, and the activity of the catalyst decreased over time. The regeneration process was conducted by simply changing the feed material from an aqueous glycerol solution to an aqueous hydrogen peroxide solution. After regeneration, the catalytic activity was similar to that of the fresh catalyst. The regeneration time can be shortened by increasing the flow rate of the aqueous solution.

Mapping out the reaction network of humin formation at the initial stage of fructose dehydration in water

The formation of humins hampers the large-scale production of 5-hydroxymethylfurfural (HMF) in biorefinery. Here, a detailed reaction network of humin formation at the initial stage of fructose-to-HMF dehydration in water is delineated by combined experimental, spectroscopic, and theoretical studies. Three bimolecular reaction pathways to build up soluble humins are demonstrated. That is, the intermolecular etherification of β-furanose at room temperature initiates the C12 path, whereas the C–C cleavage of α-furanose at 130–150 °C leads to C11 path, and that of open-chain fructose at 180 °C to C11′ path. The successive intramolecular dehydrations and condensations of the as-formed bimolecular intermediates lead to three types of soluble humins. We show that the C12 path could be restrained by using HCl or AlCl3 catalyst, and both the C12 and C11′ paths could be effectively inhibited by adding THF as a co-solvent or accelerating heating rate via microwave heating.

Management of Listeria monocytogenes on Surfaces via Relative Air Humidity: Key Role of Cell Envelope.

Although relative air humidity (RH) strongly influences microbial survival, its use for fighting surface pathogens in the food industry has been inadequately considered. We asked whether RH control could destroy Listeria monocytogenes EGDe by envelope damage. The impact of dehydration in phosphate-buffered saline (PBS) at 75%, 68%, 43% and 11% RH on the bacterial envelope was investigated using flow cytometry and atomic force microscopy. Changes after rehydration in the protein secondary structure and peptidoglycan were investigated by infrared spectroscopy. Complementary cultivability measurements were performed by running dehydration–rehydration with combinations of NaCl (3–0.01%), distilled water, city water and PBS. The main results show that cell membrane permeability and cell envelope were greatly altered during dehydration in PBS at 68% RH followed by rapid rehydration. This damage led cells to recover only 67% of their initial volume after rehydration. Moreover, the most efficient way to destroy cells was dehydration and rehydration in city water. Our study indicates that rehydration of dried, sullied foods on surfaces may improve current cleaning procedures in the food industry.

The mechanism of sorbitol dehydration in hot acidic solutions.

Sugar alcohol dehydration in hot water is an important reaction that allows for environmentally friendly biomass conversion without the use of organic solvents. Here, we report a free-energy analysis by metadynamics (MTD) simulations based on ab initio density functional theory and semiempirical density-functional tight-binding method to understand the mechanism of dehydration reactions of d-sorbitol (SBT) in hot acidic water. Comparing the results of ab initio and semiempirical MTD, it was found that the latter gives a reliable free energy surface of SBT dehydration reaction, although the results vary upon the inclusion of dispersion correction. It was found that the reaction proceeds consistently via an SN 2 mechanism, whereby the free energy of protonation of the hydroxyl group created as an intermediate is affected by the acidic species. This mechanism was further verified by real-time trajectories started from the transition state using ab initio molecular dynamics simulations. The free energy barriers of the reaction pathways leading to five-membered ether products are lower than those leading to six-membered ether products, in agreement with experiment. This outcome can be ascribed, in part, to our finding that the reaction barrier of the pathway is correlated to the stability of the SBT confined conformation at the initial stage of the reaction.

Continuous-Flow Production of Isosorbide from Aqueous-Cellulosic Derivable Feed over Sustainable Heterogeneous Catalysts

Continuous-flow sorbitol dehydration in liquid water was performed on β zeolite (Si/Al molar ratio = 75) with conversion of 94 and 83 mol % isosorbide yield. This efficiency is due to the three-dimension pore architecture, high specific surface area (520 m2 g–1), and Brønsted acid sites of 69 μmol g–1. The pore size of β zeolite (6.6 × 6.7 Å2) is slightly larger than the cross section of sorbitol and isosorbide and enables an efficient diffusion of the reactant and product to/from the pores. Operation in continuous flow allows rapid dehydration of sorbitol to 1,4-sorbitan, after which the latter got converted to isosorbide. The high yield of isosorbide is attributed to the continuous removal of the formed products from the catalyst surface. Finally, direct isosorbide production from aqueous glucose solution via hydrogenation on Ni catalyst supported on nitrogen-doped carbon, followed by dehydration of the formed sorbitol to isosorbide, was pioneered.

Dehydration in water: frustrated Lewis pairs directly catalyzed allylization of electron-rich arenes and allyl alcohols.

A frustrated Lewis pair (FLP)-catalyzed allylation of allyl alcohols with electron-rich arenes has been developed. Interestingly, in this reaction, the electron-rich arenes and allyl alcohols are dehydrated in water. What's more, water was the sole byproduct of the reaction. In this protocol, various allyl alcohols can be converted into allyl cations and attacked by the electron-rich arenes to form aryl cation intermediates. Finally, the aryl cation intermediates are deprotonated to give the 1,3-diarylpropenes. In this protocol, indole allyl alcohols can undergo a bimolecular ring closure reaction, and structurally diverse tetrahydroindolo[3,2-b]carbazoles could be smoothly obtained. The reaction is not sensitive to oxygen and has been performed on a gram-scale.

Effect of extraction on furfural production by solid acid-catalyzed xylose dehydration in water

Production of furfural by means of xylose degradation was investigated at 423 K with zeolites or an ion-exchange resin as a solid acid catalyst in water, water/toluene, or water/CO2. All the catalysts gave higher xylose conversions than did hydrothermal conditions without a catalyst. When the ion-exchange resin (Amberlyst 70) was used as the catalyst, furfural extraction with toluene effectively increased the yield relative to that of the reaction in water alone. The furfural yield obtained with the water/CO2 batch system was lower than that with the biphasic water/toluene system because the solubility of furfural in supercritical CO2 was lower than that in toluene. The furfural yield was increased by using a semibatch reactor system with continuous CO2 flow. The maximum furfural yield (52.3%) was achieved with Amberlyst 70 and a CO2 flow rate of 3.77 g min–1 at 423 K.

The reaction mechanism of polyalcohol dehydration in hot pressurized water.

The use of high-temperature liquid water (HTW) as a reaction medium is a very promising technology in the field of green chemistry. In order to fully exploit this technology, it is crucial to unravel the reaction mechanisms of the processes carried out in HTW. In this work, the reaction mechanism of 2,5-hexanediol dehydration in HTW has been studied by means of three different ab initio simulations: the string method, metadynamics and molecular dynamics in real time. It is found that the whole reaction involving protonation, bond exchange and deprotonation occurs in a single step without a stable intermediate. The hydrogen bonded network of the surrounding water has a vital role in assisting an efficient proton relay at the beginning and at the end of the reaction. It is confirmed that the reaction is energetically most favorable in the SN2 pathway with an estimated barrier of 36 kcal mol-1, which explains the high stereoselectivity and the reaction rate observed in experiment. The mechanistic insights provided by our study are relevant for a prominent class of reactions in the context of sustainable biomass processing, namely dehydration reactions of polyalcohol molecules.

Synthesis of Phenylacetaldehyde from 1-Phenylethan-1,2-diol by Microwave-Assisted Dehydration in Water

A highly efficient, simple and versatile acid catalyst is proposed for the selective dehydration of 1-phenylethan-1,2-diol to the phenylacetaldehyde as an industrial platform molecule. For the first time, common Lewis acids AlCl3 and FeCl3 and mineral acids HCl and H2SO4 had produced the acetaldehyde derivative under microwave irradiation in sub-critical water in good yield starting from the corresponding diol.

Glucose- and cellulose-derived Ni/C-SO3H catalysts for liquid phase phenol hydrodeoxygenation.

Sulfonated carbons were explored as functionalized supports for Ni nanoparticles to hydrodeoxygenate (HDO) phenol. Both hexadecane and water were used as solvents. The dual-functional Ni catalysts supported on sulfonated carbon (Ni/C-SO3H) showed high rates for phenol hydrodeoxygenation in liquid hexadecane, but not in water. Glucose and cellulose were precursors to the carbon supports. Changes in the carbons resulting from sulfonation of the carbons resulted in variations of carbon sheet structures, morphologies and the surface concentrations of acid sites. While the C-SO3H supports were active for cyclohexanol dehydration in hexadecane and water, Ni/C-SO3H only catalysed the reduction of phenol to cyclohexanol in water. The state of 3-5 nm grafted Ni particles was analysed by in situ X-ray absorption spectroscopy. The results show that the metallic Ni was rapidly formed in situ without detectable leaching to the aqueous phase, suggesting that just the acid functions on Ni/C-SO3H are inhibited in the presence of water. Using in situ IR spectroscopy, it was shown that even in hexadecane, phenol HDO is limited by the dehydration step. Thus, phenol HDO catalysis was further improved by physically admixing C-SO3H with the Ni/C-SO3H catalyst to balance the two catalytic functions. The minimum addition of 7 wt % C-SO3H to the most active of the Ni/C-SO3H catalysts enabled nearly quantitative conversion of phenol and the highest selectivity (90%) towards cyclohexane in 6 h, at temperatures as low as 473 K, suggesting that the proximity to Ni limits the acid properties of the support.

Synthesis of biobased succinimide from glutamic acid via silver-catalyzed decarboxylation

Glutamic acid was transformed into succinimide in a two step procedure involving a dehydration in water to pyroglutamic acid followed by an oxidative decarboxylation using a silver catalyst.

Solid Lewis acidity of boehmite γ-AlO(OH) and its catalytic activity for transformation of sugars in water

Aqueous-phase transformation of C3- and C6-sugars toward valuable intermediates such as lactic acid and 5-hydroxymethylfurfural (HMF) using boehmite, an abundant, inexpensive and simple aluminium oxide hydroxide γ-AlO(OH) was demonstrated. Pyridine-adsorbed Fourier transform infrared (FTIR) spectroscopy and trimethylphosphine oxide-adsorbed 31P magic angle spinning (MAS) nuclear magic resonance (NMR) revealed that boehmite had no Bronsted acid sites and a small amount of weak Lewis acid sites. The amount of Lewis acid sites and the initial reaction rate for lactic acid synthesis from dihydroxyacetone increased with increase of calcination temperature of boehmite whereas the selectivity for lactic acid remained unchanged and turnover frequency decreased. Boehmite afforded lactic acid selectively from aqueous C3-sugars solution with the yields of 32% and 42% from dihydroxyacetone and glyceraldehyde, respectively, which were higher than those of hydrotalcite, titanium oxide, tin oxide and tungsten oxide. Moreover, boehmite gave both lactic acid and HMF simultaneously from aqueous glucose solution as well as fructose. The total yields of lactic acid and HMF from aqueous glucose solution reached 40%. Boehmite was found to catalyse a variety of reactions including isomerization, retro-aldol condensation, dehydration and hydration in water.

Analysis of acid-catalyzed dehydration of formic acid in hot compressed water based on density functional theory

An acid-catalyzed dehydration mechanism was investigated for formic acid decomposition through calculations based on density functional theory. In previous experimental investigations, formic acid dehydration in hot compressed water was reported to proceed faster at pressures >30MPa. Higher concentration of hydrogen ions because of the large ion product of water at high pressure was believed to contribute to the acceleration of the dehydration reaction. In this study, the structures and energies of the transition states and intermediates were determined through calculations based on density functional theory with the B3LYP/6-311+G(2d,p) level of theory. A comparison of their threshold energies indicated that the dehydration proceeded via the protonation of hydroxyl oxygen, and that the acid-catalyzed dehydration was energetically more favored than the water-catalyzed mechanism. These results suggested that the abundant hydrogen ions in hot compressed water at high pressure accelerated the dehydration occurring via an acid-catalyzed formic acid dehydration mechanism.

New insights on monosaccharides’ isomerization, dehydration and fragmentation in hot-compressed water

Typical monosaccharides, which constitute hemicelluloses and cellulose of lignocellulosic materials, were treated in batch hot compressed water to investigate monosaccharides’ isomerization and decomposition. It was found that glucose and mannose were isomerized to each other while galactose was isomerized to tagatose and talose. On the other hand, arabinose was isomerized to ribulose and ribose while xylose was isomerized to xylulose and lyxose. Additionally, these isomerization products’ formation was not only affected by initial monosaccharides but also the reaction conditions. Similarly the dehydration and the fragmentation reactions also depended on reaction conditions, in which possibly dehydration occurred firstly and fragmentation reaction followed. Furthermore, furfural was also detected when hexoses were treated in hot compressed water and it was proposed that furfural was formed via hexose fragmentation reactions through a pentose and formaldehyde pathway. On the other hand, the detection of 5-HMF when pentoses were treated in hot compressed water provided a hint that not only retro-aldol condensation reaction but also aldol condensation occurred when monosaccharides were treated in hot-compressed water. Based on these experiments, some new isomerization, fragmentation and dehydration reaction pathways were proposed to supplement previous knowledge on monosaccharides’ decomposition scheme in hot compressed water.

Towards a Selective Heterogeneous Catalyst for Glucose Dehydration to 5‐Hydroxymethylfurfural in Water: CrCl2 Catalysis in a Thin Immobilized Ionic Liquid Layer

Sugar it up: Stabilization of the CrCl2 active phase in a thin layer of an ionic liquid covalently grafted to mesoporous silica results in a highly selective catalyst for the dehydration of glucose to 5-hydroxymethylfurfural (HMF) in an aqueous medium. Glucose dehydration in water by using the CrCl2-Im-SBA-15 catalyst leads to a 50 % HMF selectivity that can be further increased to up to 70 % by modifying the solvent system.

Production of C3 Hydrocarbons from Biomass via Hydrothermal Carboxylate Reforming

We demonstrate a route for the production of C3 hydrocarbons from renewable biomass by the hydrothermal conversion of well-known fermentation end-products. Specifically, the major commercial C3 hydrocarbons, propane and propylene, can be obtained from butyric acid and 3-hydroxybutyrate (3HB) in substantial yields and industrially relevant productivities by hydrothermal decarboxylation. Butyric acid decarboxylates in supercritical water to give propane as the major product at 454 °C and 25 MPa. 3HB undergoes joint dehydration and decarboxylation in subcritical water to yield propylene at 371 °C and 25 MPa with yields of up to 48 mol %. Although catalysts may be found that increase yields and selectivities, these processes were demonstrated without any added heterogeneous catalysts, and have the further advantage of requiring no external H2 source.

Sorbitol dehydration in high temperature liquid water

Sorbitol dehydration in high temperature liquid water proceeded at 523–573 K without adding any acid catalysts. Anhydrosorbitols (1,4-anhydrosorbitol (1,4-AHSO), 2,5-anhydrosorbitol (2,5-AHSO) and 1,5-anhydrosorbitol (1,5-AHSO)) were produced by the monomolecular dehydration of sorbitol, and isosorbide was produced by the stepwise dehydration of 1,4-AHSO. The formation rates of 1,4-AHSO and 2,5-AHSO (five-membered cyclic ethers) from sorbitol dehydration were much larger than that of 1,5-AHSO (six-membered cyclic ether), and 1,4-AHSO was the main product of the monomolecular dehydration of sorbitol. The dehydration rate of sorbitol to 1,4-AHSO was faster than that of 1,4-AHSO to isosorbide; therefore, 1,4-AHSO could be obtained as an intermediate product. A kinetic analysis of sorbitol dehydration in high temperature liquid water showed that the maximum yield of 1,4-AHSO from the dehydration of sorbitol increased with decreasing reaction temperature (for example, 80% at 500 K) and that the maximum yield of isosorbide was 57% at 590 K for 1 h. 1,4-AHSO and isosorbide could be produced selectively from sorbitol dehydration in high temperature liquid water by controlling both the reaction temperature and reaction time.