Polyethylene glycol oxidation reactions

Other examples of nonionics commonly used in syndets are glycols, glycerols, sugar esters, and alkanolamides. Polyethylene glycol esters of fatty acids are produced by reaction with ethylene oxide or by esterification of the fatty acid with polyethylene glycols. The reaction with ethylene oxide is described as ... 

Because the alkyl chain is typically monodisperse, it is not necessary to characterize the hydrophobe moiety beyond a simple confirmation of identity. It should be noted that even though monodisperse in respect to molecular weight, the alkyl chain may be a mixture of isomers, especially in the case of the triisopropylene product. The surfactant is produced by alkali-catalyzed ethoxylation of the alkylphenol. Normally, a Poisson distribution of ethoxylated oligomers is produced, with some unethoxylated alkylphenol remaining, and perhaps with some polyethylene glycol formed. Reaction residues, such as ethylene oxide, 1,4-dioxane, and acetaldehyde, are removed by vacuum stripping (2). 

A number of polyethylene glycols are also available in molecular weight ranges from commercial suppliers. These are made by initiating the polymerization of ethylene oxide by hydroxide ion. The corresponding monomethyl (or monoalkyl ethers) can be made in a similar fashion by initiating the polymerization with an alcohol. The general reaction is shown below in Eq. (7.2). 

Similarly, esters of fatty acids and polyethylene glycols are produced by the reaction of long-chain fatty acids and ethylene oxide ... 

In our ongoing efforts to develop oxidation catalysts that are functional in water as environmentally berrign solvent, we synthesized a water-soluble pentadentate salen ligand with polyethylene glycol side chairts (8). After coordination of copper(II) ions to the salen ligand, a dinuclear copper(II) complex is obtained that is soluble in water, methanol and mixtures of both solvents. The aerobic oxidation of 3,5-di-tert.-butylcatechol (DTBC) into 3,5-di-terr.-butylqitinone (DTBQ) was used as a model reaction to determine the catalytically active species and initial data on its catalytic activity in 80% methanol. 

Poly(ethylene glycol) supported liquid-phase syntheses by both the reaction of (polyethylene glycol (PEG))-supported imines with nitrile oxides, generated in situ from aldoximes, (300) and 1,3-dipolar cycloadditions of nitrile oxide, generated in situ on soluble polymers with a variety of imines (301, 302) have been described. The solid-phase synthesis of 1,2,4-oxadiazolines via cycloaddition of nitrile oxide generated in situ on solid support with imines has also been elaborated (303). These syntheses of 1,2,4-oxadiazolines provide a library of 1,2,4-oxadiazolines in good yields and purity. 

The Suzuki coupling of soluble polyethylene glycol (PEG)-bound bromothiophene 71 and p-formylphenylboronic acid provided biaryl 72 [56]. Due to the high solubilizing power of PEG, the reaction was conducted as a liquid-phase synthesis. Treatment of 72 with o-pyridinediaminc resulted in a two-step-one-pot heterocyclization through an imine intermediate. Nitrobenzene served as an oxidant in the ring closure step. Finally, transesterification with NaOMe in MeOH resulted in l//-imidazole[4,5-e]pyridine 73. 

In 1904 Bally obtained a bluish violet solid by alkali fusion of benzanthrone at approximately 220 °C. Two isomeric compounds were isolated by vatting the reaction mixture and filtering off a sparingly soluble sodium salt. Oxidation of the filtrate gave a blue vat dye, violanthrone (6.75 Cl Vat Blue 20), as the main component. The less soluble residue similarly afforded a violet product, isoviolanthrone (6.76 Cl Vat Violet 10). The formation of isoviolanthrone can be suppressed by carrying out the fusion in a solvent such as naphthalene or a polyethylene glycol in the presence of sodium acetate and sodium nitrite. Dyes of this type are often referred to as dibenzanthrones. 

As with fullerenes, carbon nanotubes are also hydrophobic and must be made soluble for suspension in aqueous media. Nanotubes are commonly functionalized to make them water soluble although they can also be non-covalently wrapped with polymers, polysaccharides, surfactants, and DNA to aid in solubilization (Casey et al., 2005 Kam et al., 2005 Sinani et al., 2005 Torti et al., 2007). Functionalization usually begins by formation of carboxylic acid groups on the exterior of the nanotubes by oxidative treatments such as sonication in acids, followed by secondary chemical reactions to attach functional molecules to the carboxyl groups. For example, polyethylene glycol has been attached to SWNT to aid in solubility (Zhao et al., 2005). DNA has also been added onto SWNT for efficient delivery into cells (Kam et al., 2005). 

Polyethylene glycols (PEG) have been employed as phase transfer agents (and as solvents) in a number of reactions(11). Application of PEG-400 to the Wacker reaction results in the oxidation of both terminal and internal olefins (e.g., isomeric butenes to butanone) (12). 

Our interest in polyethylene glycols centered on a simple scheme to immobilize these materials onto metal oxide surfaces. The surface of silica gel contains both silanol-OH groups and -0-strained siloxane groups(29). A simple synthetic pathway to produce covalently bonded glycols was proposed where reaction(30) would occur between the OH group of the glycol and the surface of a refractory oxide. 

Nitrates. Thallous nitrate, a convenient source of other thallium(I) derivatives, eg, halides, is prepared from the reaction of the pure metal with dilute nitric acid (9). The solid is stable to 300°C and decomposes at 800°C to Tl O, NO, and N02. Thallic nitrate is obtained as a trihydrate upon dissolving T Oj in cold nitric acid. It decomposes to T C on heating to 100°C or upon hydrolysis. Thallic nitrate, soluble in alcohols and ethers of polyethylene glycols, is often used as an oxidizing agent in oiganic syntheses. 

Polymers usually are prepared by two different types of polymerization reactions — addition and condensation. In addition polymerization all of the atoms of the monomer molecules become part of the polymer in condensation polymerization some of the atoms of the monomer are split off in the reaction as water, alcohol, ammonia, or carbon dioxide, and so on. Some polymers can be formed either by addition or condensation reactions. An example is polyethylene glycol, which, in principle, can form either by dehydration of 1,2-ethanediol (ethylene glycol), which is condensation, or by addition polymerization of oxacyclopropane (ethylene oxide) 1... 

Formaldehyde, along with other short-chain aldehydes such as acetaldehyde, is a low molecular weight, volatile, reactive contaminant that can be present at low levels from a variety of sources (e.g., excipients such as polyethylene oxide, polyethylene glycol (64,65), or from carbohydrate degradation (66), solvent contamination (51), packaging materials (52), etc.). Formaldehyde is known to react with amines (Fig. 33) to form a reactive N-hydroxymethyl compound (a hemiaminal) that can further react with other nucleophiles. Reaction of formaldehyde with amino acids (67) can cause... 

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