Solubility oxidative hydroxylation

The octanol/water partition coefficient (log P) indicates the hydrophobiaty of a substrate. Fligher hydrophobicity of a chemical compound will decrease its aqueous solubility. Because hydroxyl radicals have reaction rates that are most likely diffusion controlled, the reaction rates of hydrophobic compounds in aqueous systems, such as Fenton s reaction, will be negatively affected. Figure 6.22 shows the effect of the octanol/partition coefficient on the oxidation rates of 2-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophe-nol, and pentachlorophenol. Pentachlorophenol has the lowest aqueous solubility and correspondingly its reaction rates are significantly affected. 

FTIR and NMR Analysis of Oxidation Products. As expected the FTIR spectra of the soluble oxidation products are dominated by the strong absorptions due to the hydroxyl and carbonyl groups of carboxylic acids. There are absorptions in the spectra which occur in the regions expected for sulfones (1350-1310 and 1160-1120 cm-1) and sulfonic acids (1420-1330 and 1200-1145 cm-1), but these are probably due to non-sulfur containing functional groups, especially carbon-oxygen bonds which are presumably present in much higher concentrations. 

Similar to dissociation of water, all soluble acid phosphates, and soluble oxides dissociate or dissolve in water. When acid phosphates dissociate in water, they lower the pH of the solution by releasing protons (H ), while most of the oxides or hydroxides when mixed with water release hydroxyl ions (OH ) by removing protons from the solution. As a result, initially neutral water becomes richer in protons when acid phosphates are dissolved in it and the pH becomes < 7. On the other hand, for certain oxides such as those of alkaline elements (e.g., Na, K, Mg, and Ca), the pH is increased because the solution becomes deficient in protons. Thus, the pH scale is a good indicator of the extent of release of protons and hydroxyl ions and will be used throughout this book to represent the extent of acid-base reactions. 

Esters. Most acryhc acid is used in the form of its methyl, ethyl, and butyl esters. Specialty monomeric esters with a hydroxyl, amino, or other functional group are used to provide adhesion, latent cross-linking capabihty, or different solubihty characteristics. The principal routes to esters are direct esterification with alcohols in the presence of a strong acid catalyst such as sulfuric acid, a soluble sulfonic acid, or sulfonic acid resins addition to alkylene oxides to give hydroxyalkyl acryhc esters and addition to the double bond of olefins in the presence of strong acid catalyst (19,20) to give ethyl or secondary alkyl acrylates. 

Antimony Oxide as a Primary Flame Retardant. Antimony oxide behaves as a condensed-phase flame retardant in cellulosic materials (2). It can be appHed by impregnating a fabric with a soluble antimony salt followed by a second treatment that precipitates antimony oxide in the fibers. When the treated fabric is exposed to a flame, the oxide reacts with the hydroxyl groups of the cellulose (qv) causing them to decompose endothermically. The decomposition products, water and char, cool the flame reactions while slowing the production and volatilization of flammable decomposition products (see Flaa retardants for textiles). 

Eyrol 51 is a water-soluble Hquid containing about 21% phosphoms. It is made by a multistep process from dimethyl methylphosphonate, phosphoms pentoxide, and ethylene oxide. The end groups are principally primary hydroxyl and the compound can thus be incorporated chemically into aminoplasts, phenoHc resins, and polyurethanes. Eyrol 51, or 58 if diluted with a small amount of isopropanol, is used along with amino resins to produce a flame-retardant resin finish on paper used for automotive air filters, or for backcoating of upholstery fabric to pass the British or California flammabiHty standards. 

Polyethers prepared from propylene oxide are soluble in most organic solvents. The products with the highest hydroxyl number (lowest molecular weight) are soluble in water, not in nonpolar solvents such as hexane. The solubihty of 3000 molecular weight triols is high enough in solvents such as toluene, hexane, and methylene chloride that the triols can be purified by a solvent extraction process. 

Catalytic oxidation ia the presence of metals is claimed as both nonspecific and specific for the 6-hydoxyl depending on the metals used and the conditions employed for the oxidation. Nonspecific oxidation is achieved with silver or copper and oxygen (243), and noble metals with bismuth and oxygen (244). Specific oxidation is claimed with platinum at pH 6—10 ia water ia the presence of oxygen (245). Related patents to water-soluble carboxylated derivatives of starch are Hoechst s on the oxidation of ethoxylated starch and another on the oxidation of sucrose to a tricarboxyhc acid. AH the oxidations are specific to primary hydroxyls and are with a platinum catalyst at pH near neutraUty ia the presence of oxygen (246,247). Polysaccharides as raw materials ia the detergent iadustry have been reviewed (248). 

Surfactants and Dispersants. Castor od can be transformed from an od- to a water-soluble surfactant, depending on the moles of ethylene oxide added to its hydroxyl group. A 40 mole ethylene oxide adduct of castor od, known as PEG-40 castor od, is a surfactant that has cosolvent properties and is utilized as a fragrance solubilizer (118). Glycol hydroxystearate emulsifiers are formulated into shampoos to impart finer peadescence and give better stabdity than gylcol stearates (118) (see Hair preparation). 

The solubility parameter is about 19.2MPa and being amorphous they dissolve in such solvents as tetrahydrofuran, mesityl oxide, diacetone alcohol and dioxane. Since the main chain is composed of stable C—C and C—O—C linkages the polymer is relatively stable to chemical attack, particularly from acids and alkalis. As already mentioned, the pendant hydroxyl groups are reactive and provide a site for cross-linking. 

Mention should also be made here of the extensive use of poly(vinyl alcohol) in potentially biodegradable applications. At appropriate hydroxyl contents these polymers will dissolve in water (see Chapter 14) and can apparently be conveniently washed away after use as a water-soluble packaging. Biodegradation does, however, appear to be slow and first requires an oxidative step involving enzymatic attack to a ketone such as polyenolketone, which then biodegrades more rapidly. 

Step 2 A mixture of 118 parts of the product of Step 1, having hydroxyl number of 260, 2 parts of solid NaH, and 100 parts of toluene was heated to 125° to 150°C In an autoclave. Ethylene oxide was added slowly over a period of 2 /2 hours until 261 parts of ethylene oxide were absorbed. This corresponds to 11 mols of ethylene oxide per mol of phenol in the product of Step 1. The toluene was then removed by steam distillation and the water by vacuum distillation at 10°C. The product was obtained as a viscous paste having a corrected hydroxyl number of 97. It was readily soluble in water and had marked detergent properties. 

The Af-HjO diagrams present the equilibria at various pHs and potentials between the metal, metal ions and solid oxides and hydroxides for systems in which the only reactants are metal, water, and hydrogen and hydroxyl ions a situation that is extremely unlikely to prevail in real solutions that usually contain a variety of electrolytes and non-electrolytes. Thus a solution of pH 1 may be prepared from either hydrochloric, sulphuric, nitric or perchloric acids, and in each case a different anion will be introduced into the solution with the consequent possibility of the formation of species other than those predicted in the Af-HjO system. In general, anions that form soluble complexes will tend to extend the zones of corrosion, whereas anions that form insoluble compounds will tend to extend the zone of passivity. However, provided the relevant thermodynamic data are aveiil-able, the effect of these anions can be incorporated into the diagram, and diagrams of the type Af-HjO-A" are available in Cebelcor reports and in the published literature. 

---