Volume 90, Issue 1

The transformation of glycerol into value-added chemicals is an interesting topic in Green Chemistry. The glycerolysis of urea into glycerol carbonate is an important route of glycerol transformation. In this work, the synthesis of glycerol carbonate from glycerol and urea was performed under microwave irradiation and solvent free conditions. The catalytic properties of ZnSO 4 , ZnCl 2 , CuSO 4 and MgSO 4 were tested and ZnSO 4 showed the best performance. The effects of catalyst amount, temperature, reaction time, microwave power, molar ratio of urea to glycerol on the reaction were studied using ZnSO 4 as the catalyst. It was demonstrated that microwave irradiation could promote the reaction effectively, and the yield of desired product glycerol carbonate could reach 93.7%.

For the first time silica gel was observed to activate peroxides in oxidative coupling reactions. Here we report silica gel mediated oxidative C–O coupling of β-dicarbonyl compounds with cyclic diacyl peroxides affording α-acyloxy derivatives with 100% atom efficiency. The highest yields of coupling products were achieved in solvent free conditions. C–O coupling products were prepared in yields up to 86%.

Green/Sustainable Chemistry is the scientific platform where chemists are contributing from different areas to develop modern and efficient processes aimed at minimizing the environmental impact of chemical production. To reach these goals scientists, from both academia and industry, need to strongly focus their fundamental and innovative research towards the application of modern principles of Green Chemistry. In this contribution a description of our efforts in this direction is presented.

The increase attention in the area of phosphonate metal organic framework is exemplified with a variety of applications and a rich chemistry of these compounds. Water pollution caused by heavy metal ions is a major concern due to their toxicity to many life forms. In order to decrease the heavy metals impact upon the environment various technologies of water treatment such as: chemical sedimentation, ion exchange, redox process are studied. The tendency is to find a versatile and economical method of heavy metals removal from waste waters. Phosphonate metal organic frameworks were obtained by the reaction of Ni(CH 3 COO) 2 ·4H 2 O, phosphonic acid (phosphonoacetic (CP), vinyl phosphonic acid (VP) and N,N-bis(phosphonomethyl)glycine (Gly)) in hydrothermal conditions. Coordination polymers synthesized were characterized by FTIR, XRD, scanning electron microscopy (SEM) and thermal gravimetric analysis (TGA). The adsorption processes represent a very good alternative for heavy metals removal due to low costs and ease of operation. In the present paper the adsorption performance of the mentioned materials in the removal process of heavy metals from aqueous solutions, was studied using the batch method. The adsorption conditions were investigated by varying the initial pH, contact time and adsorbate initial concentration for chromium metal ions removal from aqueous solutions. It was found that the adsorption efficiency of the studied materials in the removal process of Cr(VI) ions from aqueous solutions is in the following order: Ni-CP<Ni-Gly≤Ni-VP.

Simple, efficient, clean, and stereospecific protocols of protection of phosphorus atom with borane and deprotection from the borane complexes of the tertiary phosphines in mild conditions are reported. The proposed protection/deprotection reactions tolerate a range of functional groups and lead to pure products with excellent yield with no need for application of chromatographic or crystallisation purification procedures. For the first time mechanisms of the reactions of phosphine protection and deprotection have been studied based on experimental kinetic data as well as quantumchemical calculations, which allows designing reaction conditions suitable for a given substrate.

Arsenic is classified as one of the most toxic elements for humans by the World Health Organization (WHO). With the tightening drinking water regulation to 10 μg L −1 by the WHO, it is necessary to find efficient sorbent materials for arsenic. In this work, the removal of arsenic(V) from water is achieved with an insoluble chitosan sorbent in the protonated form obtained by a simple heating process. Kinetic studies show a very fast sorption (less than 10 min). The Langmuir isotherm model is best describing experimental data with a capacity of 42 mg g −1 at pH 8. The sorption process is based on anion exchange (chemisorption) determined from the Dubinin-Radushkevich model. The sorption efficiency of the chitosan sorbent is 97% at low concentrations (e.g. 100 μg L −1 ). Thermodynamic analysis reveals that the sorption process is exothermic and is controlled by enthalpic factors. Breakthrough curves (BTC) were acquired in real-time by instrumental chromatography and was better described by the Thomas model. BTC from column sorption and desorption with a salt solution suggest that this sorbent is relevant for large scale applications. With this new renewable product, it will be possible to treat arsenic contaminated water at low cost and with little waste (concentration factor of 1500).

Determination of toxic lead ions at trace level using solid-based adsorbents has become of interest in recent years. In this work, a novel bio-adsorbent originating from papaya peel waste (PPw) and magnetic nanoparticles (Fe 3 O 4 ) was developed (Fe 3 O 4 /PPw). The new adsorbent was prepared using a one-pot green method and characterized by Fourier transform infrared, X-ray diffractometer, energy-dispersive X-ray spectroscopy and field emission scanning electron microscopy. The synthesized Fe 3 O 4 /PPw was used as a magnetic solid-phase extraction (MSPE) sorbent for extraction of lead ions from waste water prior to assessing by flame atomic absorption spectroscopy. The parameters influencing extraction recovery, including desorption solvent, solvent volume, sample volume, extraction time, desorption time, adsorbent dosage, salt effect and pH were optimized. A linear response for the MSPE method was achieved at concentrations from 10 to 100 ng mL −1 with a good coefficient of determination ( R 2 =0.9987). Detection limits and quantitation limit of the MSPE method were observed around 2 ng mL −1 and 6.6 ng mL −1 , respectively. The intraday and interday precision (%RSD) was in the range 1.6%–4.5% and 2.3%–7.4%, respectively. The recovery amounts obtained were 91% for tap water, 85.9% for river water and 86% for waste water. The synthesized adsorbent showed a minimum reusability of eight cycles without significant change in the lead determination. The results proved that the new bio-adsorbent (Fe 3 O 4 /PPw) is potentially capable to extract the Pb(II) from aqueous media under optimum conditions with a high extraction efficiency.

Cyclization of 2-(2-hydroxyethyl)phenol via DMC chemistry in acidic conditions is herein discussed for the first time. Reaction conditions have been investigated and optimized. This substrate is quite appealing as it incorporates a 2-hydroxyethyl moiety in ortho to the aromatic hydroxyl group capable of stabilizing the related phenonium ion. When the reaction mechanism was investigated via theoretical calculations, the results suggest that the most favorable pathway encompasses a DMC-mediated formation of the phenonium ion that is converted into the 2-(2-methoxyethyl)phenol. The related cyclic ether is then formed via intramolecular cyclization of this intermediate. This peculiar cyclization reaction is another example of the versatility of DMC herein used as solvent, methoxycarbonylation agent and leaving group in the intramolecular cyclization leading to the phenonium ion.

Biomass is a sustainable alternative to fossil fuels, as a source of energy and raw materials for industry. However, this is often criticized, based on an alleged competition with food production due to the presumed scarcity of agricultural land. Data from Brazil and Ethiopia show that the creation and dissemination of new agricultural technology actually allows a significant increase in the production of food as well as energy and raw materials from biomass, bringing economic, social and environmental benefits. Moreover, polymers from biomass display unique features that make them suitable as the basis for making advanced materials, with desirable combinations of chemical and physical properties required for some applications. For instance, natural rubber and cellulose have been used to create new complex nanostructured solids capable of performing new functions. Biomass can thus be exploited as a source of new materials as well as petrochemical-like building blocks.

Despite of the orthogonal reactivity of the N–H aziridines aldehyde, these compounds exist as an equilibrium of three different forms – whereas the dimeric one is mostly observed in a variety of solvents. In this work, we have developed an alternative protocol for the aminoaldehyde dimers synthesis in two steps starting with an organocatalyzed aziridination between α,β-unsaturated aldehydes and a protected amine to afford known isolable and stable N -protected aziridine aldehydes. After Boc-deprotection, dimeric species were immediately formed from monomeric N–H aziridine aldehydes. From this building-block new reduced hydantoins were prepared via [3+2]-annulation with isocyanates.

Magnetic separation can be considered a green technology because it is fast, efficient, consumes low energy, and minimizes the use of solvents and the generation of waste. It has been successfully used in laboratory scale to facilitate supported catalysts’ handling, separation, recovery, and recycling. Only few materials are intrisically magnetic, hence the application of magnetic materials as catalyst supports has broaden the use of magnetic separation. Iron oxides, silica-coated iron oxides, and carbon-coated-cobalt are among the most studied catalyst supports; however, other metal oxide coatings, such as ceria and titania, are also very interesting for application in catalysis. Here we report the preparation of magnetically recoverable magnetic supports containing silica, ceria, and titania. We found that the silica shell protects the iron oxide core and allows the crystalization of ceria and titania at high temperature without compromising the magnetic properties of the catalyst supports.

The methods to monitor the distribution of chemicals in the biosphere and to estimate the impact of chemicals on the biosphere are necessary to reach Sustainable Development Goals (SDGs). The paper presents the examples of methods to measure the concentration of heavy metals (including rare earth elements) and to rank them by the level of hazard to human health on different scales. The megacity scale presents the investigation of the impact of heavy metals on the small water bodies using water contamination index (WCI); and the investigation of snow contamination to estimate the level of short-term seasonal emission of heavy metals and rare earth elements. The 2 nd part of the paper presents approaches to mitigate the exposure to mercury on the regional scale: the estimation of the current concentrations of mercury in atmospheric air, natural soils, and fresh waters using UNEP/SETAC USEtox model, as well as the estimations of the variations in the concentrations of mercury for the year 2045 in the federal districts of the Russian Federation, based on representative concentration pathways (RCPs) scenario and Minamata Convention scenario.

Solid-phase organic synthesis is an essential method for the rapid synthesis of complex biological structures and libraries of small organic molecules. However, it is often associated with the use of large quantities of problematic solvents for the removal of excess reagents and reaction by-products. Given that solvent will often be the biggest contributor to waste generated in the average pharmaceutical/fine-chemical process, its exchange for a more desirable alternative often presents the biggest gains in terms of reducing environmental impact. This review aims to explore recent approaches to performing solid-phase organic synthesis, and associated solid-phase peptide synthesis, in neoteric solvents and reaction media that present greener alternatives.

A brief account of our recent work on the chemo-, regio- and stereoselective photocatalytic hydrogenolysis of allylic alcohols to alkenes promoted by palladium-loaded titanium oxide (Pd/TiO 2 ) photocatalysts is presented. Since methanol is employed as the reducing agent, the method does not involve stoichiometric generation of salt waste. The photocatalytic hydrogenolysis proceeds at room temperature, and is compatible with the presence of functional groups such as C=C double bonds and hydroxyl groups at non-allylic positions. The regioselectivity is predictable: the hydrogen atom is predominantly incorporated into the sterically less hindered carbon atom of the allylic moiety. This protocol should provide straightforward green access to a range of platform chemicals (exemplified by the two-step synthesis of propylene from glycerol) and fine chemicals [e.g. ( S )-(+)-lavandulol from ( R )-(–)-carvone] without the need for protection/deprotection steps.

In 2011 the General Conference on Weights and Measures (CGPM) noted the intention of the International Committee for Weights and Measures (CIPM) to revise the entire International System of Units (SI) by linking all seven base units to seven fundamental physical constants. Of particular interest to chemists, new definitions for the kilogram and the mole have been proposed. A recent IUPAC Technical Report discussed these new definitions in relation to immediate consequences for the chemical community. This IUPAC Recommendation on the preferred definition of the mole follows from this Technical Report. It supports a definition of the mole based on a specified number of elementary entities, in contrast to the present 1971 definition.

Recommendations are given concerning the terminology of methods of separation in analytical chemistry, including chromatography, electromigration techniques, and field-flow fractionation and related techniques.