Aqueous solutions green chemistry

BMIm]BF4+water as a case study to model ionic hquid aqueous solutions. Green Chemistry, 2004,6 369-381... 

Rebelo, L., Najdanovic-Visak, V., Visak, Z., da Ponte, M., Szydlowski, J., Cerdeirina, C., Troncoso, J., Romani, L., Esperanga, J., Guedes, H. de Sousa, H. (2004). A detailed thermodynamic analysis of [C(4)mim][BF4] plus water as a case study to model ionic liquid aqueous solutions. Green Chemistry, Vol. 6, No. 8,pp. 369-381. 

Fig. 8.16 Reaction network for tandem reaction of glucose conversion to HMF by CrCI3 and HCI in aqueous phase (FA- furfural, Lewis-catalyzed reaction network is shown by dashed line). (Modified from T. D. Swift, H. Nguyen, A. Anderko, V. Nikolalds, D.G. Vlachos, Tandem Lewis/Bronsted homogeneous acid catalysis conversion of glucose to 5-hydoxymethylfurfural in an aqueous chromium (III) chloride and hydrochloric acid solution. Green Chemistry 17 (2015) 4725—4735. Copyright 2015 Royal Society of Chemistry).

The aqueous solution chemistry of Ir in its higher oxidation states III, IV, and V has been explored by Sykes et al.41,48 Chemical and electrochemical oxidation of Ir(H20)6]3+ gives a brown-green Irv product, which undergoes chemical and electrochemical reduction to a blue and a purple IrIV complex. 170 NMR studies are consistent with double- and single-bridged dimeric structures, with likely formulas [(H20)4Ir(/i-0H)2Ir(H20)4]6+ for the blue complex and [(H20)5Ir(/r-0)Ir(H20)5]6+ for the purple one. 

We start with butane-2,3-dione dioxime, more commonly known as dimethylglyoxime (dmg). It is a classic reagent for the analysis of NP, the green aqueous solution of metal ions transforming into a vibrantly red precipitate of Ni(dmg)2 complex it is one of the stars of the show in Ponikvar and Liebman s analytical chemistry chapter in the current volume. Here the stereochemistry is well-established and well-known—both OH groups are found on the same side as their adjacent CH3 group on the butanedione backbone. There have been several measurements of the enthalpy of formation of this species for which we take the one associated with this inorganic analytical chemistry application, i.e. with diverse metal complexes and chelates . 

The U(IV) chemistry is similar to that of Th4+, except for the difference in the charge/radius ratio of the ions. U4+ solutions are green in color, stable, and slowly oxidized by air to U02+. Solutions of U4+ are generally prepared by reduction of solutions of the uranyl (U02+) ion. U(IV) forms complexes with many anions (C204-,C2H302, C03-, Cl-, and NO3"). The chlorides and bromides of U(IV) are soluble while the fluorides and hydroxides are insoluble. In aqueous solution, U(IV) hydrolyzes via the reaction,... 

Strong bases in dry solvents are usually used in organic synthesis to generate reactive enol anions from ketones. Nevertheless, the kinetic studies discussed here were mostly performed on aqueous solutions. Apart from the relevance of this medium for biochemical reactions and green chemistry, it has the advantage of a well-defined pH-scale permitting quantitative studies of acid and base catalysis. 

Fortunately, radicals are a neutral species in general. Thus, they are not affected by the various kinds of solvents (reaction media), i.e. protic polar solvents such as ethanol and water, aprotic polar solvents such as acetonitrile, dimethyl sulfoxide, and non-polar solvents such as hexane and benzene. Moreover, radicals are not affected fundamentally by basic species or acidic species. Radical reactions should take place not only in benzene, but also in water, and proceed not only in 1 N aqueous HC1 solution, but also in 1 N aqueous NaOH solution. This is the fundamental character of radicals and radical reactions, and is a great advantage an advantage that should be reflected in green chemistry. 

The lanthanide triflate remains in the aqueous phase and can be re-used after concentration. From a green chemistry viewpoint it would be more attractive to perform the reactions in water as the only solvent. This was achieved by adding the surfactant sodium dodecyl sulfate (SDS 20 mol%) to the aqueous solution of e.g. Sc(OTf)3 (10 mol%) [145]. A further extension of this concept resulted in the development of lanthanide salts of dodecyl sulfate, so-called Lewis acid-surfactant combined catalysts (LASC) which combine the Lewis acidity of the cation with the surfactant properties of the anion [148]. These LASCs, e.g. Sc(DS)3, exhibited much higher activities in water than in organic solvents. They were shown to catalyze a variety of reactions, such as Michael additions and a three component a-aminophosphonate synthesis (see Fig. 2.44) in water [145]. 

The chemistry of iron mainly involves its +2 and +3 oxidation states. Typical compounds are shown in Table 20.7. In aqueous solutions, iron(II) salts are generally light green because of the presence of Fe(H20)62 +. Although the Fe(H20)63+ ion is colorless, aqueous solutions of iron(III) salts are usually yellow to brown in color, because of the presence of Fe(0H)(H20)52+. This latter ion results from the acidity of Fe(H20)s3+ (Ka = 6 X 10-3) ... 

Most of the recent literature in this field is concerned with synthetic organic reactions, supramolecular chemistry and crystal engineering. However, solvent free approaches can also be used in the extraction of natural products, although less information is available in the mainstream literature. Juice extractors can be used to afford aqueous solutions of biologically active compounds from undried plant material. An extract of Capsicum annum L. was recently prepared in this way, and then used in the green synthesis of silver nanoparticles. The actual synthesis of the nanoparticles was conducted in the aqueous phase and therefore this work will not be discussed further here. However, this solvent free approach to extraction is probably worthy of greater representation in the green chemistry literature. 

The Future of Glycerol New Uses of a Versatile Raw Material 2 Alternative Solvents for Green Chemistry 3 Eco-Friendly Synthesis of Fine Chemicals 4 Sustainable Solutions for Modern Economies 5 Chemical Reactions and Processes under Flow Conditions 6 Radical Reactions in Aqueous Media... 

Chemistry. Cyanogen chloride s first reported preparation was by French chemist Claude Louis Berthollet (1789). Jennings and Scott observed that various conditions can influence the stability of impure CICN (Jennings and Scott, 1919). A larger-scale synthesis of CK appeared shortly after the end of WWI (Price and Green, 1920). A typical synthesis involves the reaction of chlorine with an aqueous solution of sodium cyanide. A related anhydrous procedure yields the desired product with a density of 1.2 at 0°C. After purification, it can be stored (refrigerated) for months (Coleman et al., 1946). 

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