Band 3, Heft 2 - Special issue: 1st EuCheMS Congress on Green and Sustainable Chemistry (EuGSC 2013) / Issue editor: Rita Földényi

Three alternatives are discussed in comparison with the classical esterification of phosphinic chlorides by reaction with alcohols. All novel methods, such as microwave (MW)-assisted direct esterification, MW-assisted phase transfer catalyzed alkylating esterification and the propylphosphonic anhydride-promoted esterification, start from phosphinic acids and offer different advantages and disadvantages. The methods are analyzed from green chemical point of view.

According to literature, the synthesis of dronic acid derivatives from the corresponding carboxylic acids using phosphorus trichloride and phosphorous acid as the P -reactants is controversial, due to the wide range of molar ratios and diverse conditions. In this minireview, we summarize our results on the clarification of these problems. For example, with zoledronic acid and risedronic acid, we found that, using methanesulfonic acid (MSA) as the solvent, 3.2 equivalents of phosphorus trichloride was enough. Generalizing this optimized method, etidronate, fenidronate, ibandronate and alendronate were obtained in yields of 38%–57%, which is reasonable for valuable dronates, and in most cases, with high purities. Mechanistic aspects are also discussed.

Fenton’s chemistry has long been useful in industry because of the power of hydrogen peroxide (HP), in the presence of ferrous iron (Fe 2+ ), to produce a highly reactive free radical species capable of oxidizing aqueous materials. However, its application has been limited due to the rapid oxidation of ferrous iron. The rapid oxidation of ferrous iron limits the production of free radicals necessary for a powerful reaction. We developed two ‘green’ iron catalysts using used tea leaves (tea dregs) or coffee grounds as raw material. The new ‘green’ iron catalysts contained iron in a reductive stable status for a Fenton catalyst. The study showed that the developed ‘green’ iron catalysts can be used as iron fertilizer and for the Fenton’s reaction on the degradation of methylene blue (MB), and in the disinfection of Escherichia coli . The tea and coffee polyphenols were estimated to be responsible for the reductive stable state of the iron in the developed catalysts, due to their reducing power and chelating iron ability. The developed new ‘green’ iron catalysts are expected to diffuse in wide fields such as food, medicine, public health, agriculture, the environment, etc.

The new water-soluble complex [RuH(OOc)( m tppms) 3 ] (OOc=octanoate, m tppms=monosulfonated triphenylphosphine) was synthesized and – together with the known [RuH(OAc)( m tppms) 3 ] (OAc=acetate) – applied for aqueous-organic biphasic hydrogenation of cinnamaldehyde as well as for hydrogenation of soybean liposomes under mild conditions. The complexes showed pronounced selectivity (up to 75%) towards the hydrogenation of the C=O function in the α,β-unsaturated aldehyde; the selectivity was influenced by the pH of the aqueous phase and the hydrogen pressure. The C=C double bonds in soybean lecithin were only slowly reduced, however, at 5 bar H 2 pressure the reaction rate was sufficient to achieve substantial conversion (approximately 20% of all double bonds) in the unsaturated fatty acids.

Supported Co 3 O 4 nanoparticles (NPs) on Al-SBA-15 were synthesized by means of a mechanochemical protocol, to yield catalytically active materials in the microwave (MW)-assisted selective oxidation of benzyl alcohols to their corresponding aldehydes, using hydrogen peroxide as green oxidant. The catalysts were found to be relatively stable upon reutilization under the investigated conditions.

A process based on the lixiviant properties of organic mixtures of dihalogen/S,S-ligands, N,N′-dimethyl-perhydrodiazepine-2,3-dithione (Me 2 dazdt) and tetraalkylthiuramdisulphide (Et 4 TDS) in the presence of diiodine, for gold recovery from the non-ferrous metal fraction of real shredded waste electric and electronic equipment (WEEE), is presented here. Selective dissolution of metals is achieved through a sequence of three steps where the oxidation of different kinds of metals is achieved by using: (1) refluxing water solutions of HCl 1:5 under Ar atmosphere (Sn, Zn, etc.); (2) water solutions of NH 3 /(NH 4 ) 2 SO 4 mixtures in the presence of H 2 O 2 on the resting sample(Cu, Ag); and (3) acetone solutions of Me 2 dazdt or Et 4 TDS/I 2 mixtures on the final residue (Au). Each step is followed by a further treatment for: (1) metal recovery, in the case of Au, Cu, Ag; and (2) inertization, in the case of heavy metals. As a whole, the process is very promising for effective recovery of gold and other valuable noble-metals and for using non harmful reagents in mild conditions.

Two-step treatment of birch chips ( Betula pendula ) was tested using diethanolamine (DEA)-1,8-diazabicyclo-[5.4.0]-undec-7-ene (DBU)-CO 2 -switchable ionic liquid (SIL), resulting in a 23% weight reduction in 24 h. The weight of the chips was reduced to 32% of their initial weight upon the second treatment with fresh SIL. SIL to wood ratio of 5:1, at 100°C for 24 h, without stirring, was applied in both steps. The relative amount of wood lignin reduced from 24% to 14% after two treatment cycles. The relative amount of cellulose of the undissolved fraction after SIL treatment increased from 43% (native birch wood) to 68% after the second cycle. Also, the undissolved material was efficiently fibrillated. The dissolved materials recovered from spent SIL, after treatment, contained high xylan content, about 90% of the total hemicelluloses, which was 85% of the recovered material. The powder X-ray diffraction (XRD) results revealed that the crystallinity of the undissolved material increased slightly, indicating dissolution of the amorphous material. Moreover, transformation of cellulose form I to form II in the remaining undissolved chips was not observed.

The binding of the neutral 2,2′-bipyridine (BP) molecule to solid humic acid (HA) was studied in the presence of CaCl 2 background electrolyte (10 -2 mol/l), at pH=6.1–6.3. To investigate the binding, two different methods were used: the well-established static adsorption equilibrium measurements and the technique of equilibrium dialysis (ED). The obtained isotherms were fitted by the Langmuir equation, yielding values for the total binding capacity ( q T ) and the Langmuir constant ( K ). The values obtained from the batch experiment were: q T = 3.3×10 -4 mol/g HA , K =4.1×10 2 l/mol and from the ED experiment were: q T = 5.7×10 -4 mol/g HA , K =2.8×10 2 l/mol. From the linear range of the isotherm, the value of the distribution coefficient K D was calculated as 3.3×10 2 l/kg HA (by both methods). This parameter was used to calculate the value of K OC : 6.6×10 2 l/kg OC ,indicating that BP is a slightly mobile pollutant in the HA dominated soil.