Water and Organic Solvents

Solvent effects on radical polymerization have been reviewed by Coote and 

Coote et aL, Barton and Borsig, Gromov, and Kamachi A summary of kinetic data is also included in Beuennann and Buback s review. Most literature on solvent effects on the propagation step of radical polymerization deals with influences of the medium on rate of polymerization. 

An attractive feature of using the solvent as an agent to control propagation in solution polymerization is that solvents w hen used are usually present in very large excess in relation to any radical species. Of course, economic, solubility, toxicity, waste disposal, and other considerations limit the range of solvents that can be employed in an industrial polymerization process. 

Solvent effects on the reactions of small radicals have been discussed in general terms in Chapter 2 (see 2.3.6.2 2.4.5). Small, yet easily discernible, solvent effects have been reported for many reactions involving neutral radicals. These effects on the rates of radical reactions often appear insignificant when 

Where monomers or radicals arc charged, readily ionizablc or capable of forming hydrogen bonds, mechanisms whereby the solvent could affect radical reactivity by disruption or involvement of hydrogen bonding may seem obvious. For other systems mechanisms are often still a matter of controversy even in the case of small radicals (Section 2.3.6.2). There are at least three mechanisms whereby the solvent might modify the outcome of a radical process  

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In a second attempt to extend the scope of Lewis-acid catalysis of Diels-Alder reactions in water, we have used the Mannich reaction to convert a ketone-activated monodentate dienophile into a potentially chelating p-amino ketone. The Mannich reaction seemed ideally suited for the purpose of introducing a second coordination site on a temporary basis. This reaction adds a strongly Lewis-basic amino functionality on a position p to the ketone. Moreover, the Mannich reaction is usually a reversible process, which should allow removal of the auxiliary after the reaction. Furthermore, the reaction is compatible with the use of an aqueous medium. Some Mannich reactions have even been reported to benefit from the use of water ". Finally, Lewis-acid catalysis of Mannich-type reactions in mixtures of organic solvents and water has been reported ". Hence, if both addition of the auxiliary and the subsequent Diels-Alder reaction benefit from Lewis-acid catalysis, the possibility arises of merging these steps into a one-pot procedure. 

The metallic salts of trifluoromethanesulfonic acid can be prepared by reaction of the acid with the corresponding hydroxide or carbonate or by reaction of sulfonyl fluoride with the corresponding hydroxide. The salts are hydroscopic but can be dehydrated at 100°C under vacuum. The sodium salt has a melting point of 248°C and decomposes at 425°C. The lithium salt of trifluoromethanesulfonic acid [33454-82-9] CF SO Li, commonly called lithium triflate, is used as a battery electrolyte in primary lithium batteries because solutions of it exhibit high electrical conductivity, and because of the compound s low toxicity and excellent chemical stabiUty. It melts at 423°C and decomposes at 430°C. It is quite soluble in polar organic solvents and water. Table 2 shows the electrical conductivities of lithium triflate in comparison with other lithium electrolytes which are much more toxic (24). 

Diketones. y-Diketones contain two carbonyl groups separated by two carbon atoms. With the exception of 2,5-hexanedione which is a high boiling Hquid, 1,4-diketones ate low melting white soHds with only faint odors. Lower members are soluble in organic solvents and water. Properties of representative 1,4-diketones are shown in Table 14. 

Sephasorb HP (ultrafine, prepared by hydroxypropylation of crossed-linked dextran) can also be used for the separation of small molecules in organic solvents and water, and in addition it can withstand pressures up to 1400 psi making it useful in HPLC. These gels are best operated at pH values between 2 and 12, because solutions with high and low pH values slowly decompose them (see further in Chapter 6). 

Arecoline, CgHj 302N. This, the most important alkaloid of areca nut, is an odourless, alkaline oil, b.p. 209°, volatile in steam, miseible with most organic solvents and water, but extractable from the latter by ether in presence of dissolved salts. The salts are crystalline, but usually deliquescent the hydrobromide, B. HBr, forms slender prisms, m.p. 177-9°, from hot alcohol the aurichloride, B. HAUCI4, is an oil, but the platinichloride, B2. H2PtClg, m.p. 176°, crystallises from water in orange-red rhombs. The methiodide forms glancing prisms, m.p. 173-4°. 

K. Grob and Z. Li, Intr oduction of water and water-containing solvent mixtures in capillary gas cliromatography. II. Wettability of precolumns by mixtures of organic solvents and water retention gas techniques , ]. Chromatogr. 473 391-400 (1989). 

This method also has only limited applications. The reason for this is that the distribution coeffidents of amino adds between organic solvent and water phases are generally small. There are some possibilities given in literature which are based on the alteration of the amino add. 

Asymmetrical triesters of phosphoric acid of the general formula ROPO (OR,)2 (R = C8 i4 alkyl R, = C, 3 alkyl) were obtained in approximately 70% yield by treatment of a higher fatty alcohol and a Ci 3 alcohol with P0C13 in hexane or pyridine at <0°C. The products were soluble in nonpolar organic solvents and partially soluble in polar organic solvents and water. But the foamforming ability and foam stability of the compounds in water were low [11]. 

Cured phenol-formaldehydes are resistant to attack by most chemicals. Organic solvents and water have no effect on them, though they will swell in boiling phenols. Simple resins are readily attacked by sodium hydroxide solutions, but resins based on phenol derivatives, such as cresol, tend to be less affected by such solutions. Simple phenol-formaldehyde polymers are resistant to most acids, though formic and nitric acids will tend to attack them. Again, cresol-based polymers have resistance to such attack. 

The zeolite nanocrystals have attracted the considerable attention of many researchers [1-5]. The syntheses of several types of zeolites with different nanometer sizes, such as silicalite-1, ZSM-5, A-type and Y-type, have been reported. Recently, micellar solutions or surfactant-containing solutions have been used for the preparation of zeolite nanoerystals [4,5], We have also successMIy prepared silicalite nanoerystals via hydrothermal synthesis using surfactants. In this study, we demonstrate a method for preparing mono-dispersed silicalite nanoerystals in a solution consisting of surfiictants, organic solvents and water. 

The difference between the surface potentials of two solvents (e.g., an organic solvent and water) may also be measured by means of the following voltaic cells " (Fig. 12) ... 

Supersaturation can also be achieved by adding a liquid that is miscible with the solvent and decreases the solubility of the solute in the mixed solvent. This is called precipitation. In fine chemicals manufacture, the solid is usually dissolved in an organic solvent and water is used as the desalting agent. Precipitation also occurs when a solid product, which is insoluble in the reaction mixture, is formed by chemical reaction. For instance, a phenolic product can be purified by three possible routes ... 

Y. Kubota, Ion-Transfer Voltammetry of Organic Compounds at Organic Solvent/Water Interface. Study on Partition of Organic Compounds between Organic Solvent and Water, MS thesis, Fukui Prefectural University, Fukui 1998. 

These researchers also described [93] the design and synthesis of iron(II) porphyrin dendrimers with triethylene glycol monomethyl, ether surface groups (e.g., 31) which render them soluble in a wide range of organic solvents and water. The potential difference between the first (1 FeCl) and second generation (2 FeCl) Fe-porphryin dendrimers was found to increase more in water than in dichloromethane (0.42 vs 0.08 V). This remarkable potential difference between 2 FeCl and 1 FeCl in water was comparable with that found between cytochrome c and a similarly ligated, more solvent-exposed cytochrome c heme model compound. 

Similar structures were later employed to create original dendronized polymers 485 and 486, based on a chitosan backbone and using such sialodendrons as 484 (Fig. 50).328 Chitosan itself is nontoxic, biodegradable, and has widespread biological activities, but major intrinsic drawbacks such as low solubility in both organic solvents and water have hampered its development as a bioactive polymer. Thus, the synthesis of water-soluble... 

They may be designed to be immiscible with many organic solvents and water, and both the cations and anions can be modified to give specific solubility properties as well as other physical or chemical properties. 

Furthermore, the use of a Lewis acid promoter leads to increased stereoselectivities (Table 19, entry C)252,254. Compared to the aprotic reaction, where allyl silane was used instead of allyl bromide and indium chloride, an almost complete reversal of the diastereos-electivity was found. It was demonstrated recently that the Lewis acid catalysed allylation reaction can be carried out efficiently without any organic solvent in saturated ammonium chloride solution255. Finally, Lewis acid catalysed Mannich reactions can be carried out conveniently in mixtures of organic solvents and water. However, the exact role of the Lewis acid catalyst has not been clarified (Table 19, entry D)253. The same reaction can be carried out in pure water with catalysis by indium trichloride256. 

As would be expected, fluorous compounds are preferentially retained on fluorous silica gel [62]. Similarly, fluorous catalysts can be adsorbed on fluorous silica gel. These materials have been applied to reactions in organic solvents and water, both at room temperature and above [63-69]. The investigators have usually interpreted the transformations as bonded fluorous phase catalysis , which corresponds to sequence B-II in Fig. 1. However, there remains the possibility that at least some catalysis proceeds under homogeneous conditions via desorbed species. To our knowledge, fish-out experiments analogous to that conducted with the Teflon tape in Fig. 8 have not been conducted. 

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