Phosphoric transesterification

On the other hand, phosphorous acid monoesters of lower alcohols easily undergo transesterification [75]. A preferred starting material is the triester of ethylene chlorohydrin, obtained by reaction of phosphorus trichloride with ethylene oxide, according to Eq. (28). 

The development of monoalkyl phosphate as a low skin irritating anionic surfactant is accented in a review with 30 references on monoalkyl phosphate salts, including surface-active properties, cutaneous effects, and applications to paste and liquid-type skin cleansers, and also phosphorylation reactions from the viewpoint of industrial production [26]. Amine salts of acrylate ester polymers, which are physiologically acceptable and useful as surfactants, are prepared by transesterification of alkyl acrylate polymers with 4-morpholinethanol or the alkanolamines and fatty alcohols or alkoxylated alkylphenols, and neutralizing with carboxylic or phosphoric acid. The polymer salt was used as an emulsifying agent for oils and waxes [70]. Preparation of pharmaceutical liposomes with surfactants derived from phosphoric acid is described in [279]. Lipid bilayer vesicles comprise an anionic or zwitterionic surfactant which when dispersed in H20 at a temperature above the phase transition temperature is in a micellar phase and a second lipid which is a single-chain fatty acid, fatty acid ester, or fatty alcohol which is in an emulsion phase, and cholesterol or a derivative. 

Amine salts of acrylate ester polymers, which are physiologically acceptable and useful as surfactants, are prepared by transesterification of alkyl acrylate polymers with 4-morpholinethanol or the alkanolamines and fatty alcohols or alkoxy-lated alkylphenols, and neutralizing with phosphoric acid. The product was used as an emulsifying agent for oils and waxes [60]. 

Acid-Catalyzed Synthesis. - 3.2.1 The Fundamentals. Homogeneous acid catalysts, such as sulfuric acid, phosphoric acid, hydrochloridric acid, organo sulfonic acids and others, can be used to catalyze the transesterification of TGs and the esterification of FFAs to produce biodiesel type monoesters. Nevertheless, because the acid-catalyzed transesterification is about 3 orders of magnitude slower than the alkali-catalyzed reaction for comparable amounts of catalyst, base catalysts have received the most attention in both the academic and industrial sectors. In addition, the corrosiveness of strong liquid acids and... 

Phosphoric acid esters of the type depicted in 51 were described in a Polish patent. 33 Isomannide and isosorbide bis[2,5-(dipropylphosphite)] (52a and 52b) have been obtained134 by transesterification of propyloxydipropyl-phosphane (53) or dipropylamidodipropylphosphane (54) with the isohex-ide for 5 h at 150° and 142 kPa. 

Alkali metal alkoxides such as KOH, NaOH, and CH3ONa are the most effective catalysts in alkali-catalyst transesterification. When using KOH, NaOH, and CH3ONa alkali-catalyst for FAME conversion, the active catalytic species were the methoxide anion (CH 0 ), formed by the reaction between methanol and hydroxide ions of KOH and NaOH. In addition, the methoxide anion was formed by dissolution of sodium methoxide. Sodium methoxide causes the formation of several byproducts, mainly sodium salts, that have to be treated as waste and additionally require high-quality oil (16). However, KOH has an advantage because it can be converted into KOH by reaction with phosphoric acid, which can serve as a fertilizer. Since KOH is more economical than sodium methoxide, it is the preferred choice for large-scale FAME production process. 

Various polyesters derived from phosphorous or phosphoric acids were prepared. Efiicient polyphosphites were synthesised in the early 196(. Polyphosphite prepared from 152 and 4,4 -isopropylidenebis(cyclohexanol) was tested as a thermal stabilizer for PC [199] or as secondary AO for radiation sterilized EPM [200]. Built-in phosphites obtained by transesterification of triallcylphosphite with 4,4 -isopro-pylidenebisphenol or 4,4 -thiobisphenol possess antioxidant properties in polyolefins. Stabilizer containing phosphite moiety 153 was prepared from tris(2-hydroxy-ethyl)isocyanate, decyl alcohol and triphenylphosphite [201]. Various phosphites were derived firom polynuclear phenols or dihydric phenols. For example, a polycondensate prepared by reaction of phosphorus trichloride with 2,5-di-rert-butylhydroquinone was tested as heat and light stabilizer for PP [202], A linear polyester with a built-in phenolic moiety was synthesised from (2,6-di-tm-butyl-4-methylphenyl)bis(6-hydroxyhexyl)phosphite and dimethyl terephthalate [203]. 

In a continuation of their work, however, Heilmann and Maier found that their imprinted silica gels exhibited selective transesterification and lactonisation that was no better than control materials containing phosphoric acid [55]. In fact, the catalytic activity could be removed by rinsing the gel in water. The TSA apparently turns into phosphoric acid during the high temperature treatment and then remains on the gel as a Bronsted acid catalyst (Fig. 8.15). The enhancement of selectivity... 

Soon after publication of these reports, Ahmad and Davis attempted to reproduce Heilmann and Maier s initial transesterifications and found that their imprinted materials were considerably weaker in catalytic activity than originally reported [56]. Additionally, selectivities between phenyl and naphthyl carboxylates, as discussed earlier, were not observed. Solid state " P NMR detected phosphate in the gel at different bound states to the matrix. The phosphoric acid, which slowly leaches out of the gel, was identified as the catalyst and the existence of an activated imprinted site was discounted. 

Transesterification (also known as ester exchange, ester interchange, or ester alcoholysis) is the most important of the esterification reactions. Polyesters of relatively low molecular weight (around 2000) prepared from aliphatic dicarboxylic acids and glycols are most commonly made by direct esterification (Section 5.2) with or without addition of an external acidic catalyst. Phosphoric acid, p-toluenesulphonic acid, and antimony pentafluoride have been used as catalysts. The preparation of PET by the direct esterification of TA with ethylene glycol was not practical until the... 

Once the transesterification step is complete, the metal salt is always deactivated by complexation with a phosphate or phosphite compound [18], preventing unwanted side reactions as the reaction temperature is increased during polycondensation. Such side reactions lead to polymer chain scission and loss of molecular weight, as well as development of unwanted discoloration of the polymer. Care has to be taken that excess phosphorous compounds are not added to the reaction, as these compounds can significantly reduce the effectiveness of the polycondensation catalyst. 

Various studies of transesterification of phosphorous esters have been reported. The hexaco-ordinate phosphorus anion (78) has been prepared ... 

Karayannidis and co-workers investigated the effect of various phosphorus-containing compounds on the thermo-oxidative stability of PET [9]. Additives were incorporated in the reaction kettle after the transesterification stage, but before polycondensation. Additives investigated were phosphoric acid, tributylphosphate, triphenylphosphate, phenylphosphonic acid, phenylphosphinic acid and sodium phenylphosphinate. The most effective antioxidants were tributylphosphate, phenylphosphonic acid and phenylphosphinic acid. 

The monomers 2-alko3g - or 2-atylo3y-2-oxo-l,3,2-dioxaphospholanes and 2-alko3Q - or 2-aiylo3g -2-oxo-l,3,2-dioxaphosphorinanes are prepared through reaction of the appropriate 1,2- or 1,3-diol with an allq l or aryl phosphoric dichloride (Scheme 6.8, route A), or with phosphorus trichloride followed by oxidation and reaction with the corresponding alcohol (Scheme 6.8, route B), or via transesterification with a dialkyl phospho-nate ° (Scheme 6.8, route C). 

Phosphorylated derivatives are also available. Cellulose pulp or linters can react with phosphoric acid in a urea melt or with a mixture of phosphoric acid and phosphorus pentoxide in an alcoholic medium to prepare cellulose phosphate. Cellulose phosphites and phosphonates are produced via transesterification with alkyl phosphites. All these compounds have fire-retarding properties and ion-exchange properties and cellulose phosphate is used in textile and paper manufacture, as well as in the treatment of kidney stones. 

Mixed phosphoric acid diesters via transesterification Preferential O-phosphorylation... 

As shown in Figure 4.1, a catalyst is of great importance to the transesterification process. Chemicals (acid and alkali) and enzymes can be used as the catalysts. Most commonly used acids include sulfuric, sulfonic, phosphoric and hydrochloric acids. These strong acids are corrosive and the processes are slow. Alkali-catalyzed transesterification has a better performance than acid, of which the reaction rate is approximately 4000 times faster. Thus, alkali is preferred for industrial production of biofuel. Most... 

An ester is a compound that, on hydrolysis, yields an alcohol R OH and an organic or an inorganic acid (Fig. 1). The reverse reaction is called esterification. Carboxylic acids (R C02H) and phosphoric acid (H3PO4) are examples of common acids that participate in esterification in nature. In spite of mechanistic similarities, ester hydrolysis and esterification should not be mixed with the term transesterification. 

Similar to water, alcohols can also attack phosphorous acid triesters. The reaction can be used for the synthesis of phosphite hgands by transesterification (see above), but they may also play a role in degradation processes, where alcohols produced from the reduction of product aldehydes interfere with the phosphite ligand. 

Thermo-oxidation of PET is catalysed by the metal ions (Zn, Mn etc.) used as catalysts in transesterification of dimethyl terephthalate. Compounds which form complexes with these metal ions inhibit their catalytic action in general and improve the stability of PET towards oxidation. These compounds are mainly esters of phosphoric acid, e.g. triphenyl phosphate (see Table 1). 

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