Methyl methacrylate transesterification

Most large-scale industrial methacrylate processes are designed to produce methyl methacrylate or methacryhc acid. In some instances, simple alkyl alcohols, eg, ethanol, butanol, and isobutyl alcohol, maybe substituted for methanol to yield the higher alkyl methacrylates. In practice, these higher alkyl methacrylates are usually prepared from methacryhc acid by direct esterification or transesterification of methyl methacrylate with the desired alcohol. 

Transesterification of methyl methacrylate with the appropriate alcohol is often the preferred method of preparing higher alkyl and functional methacrylates. The reaction is driven to completion by the use of excess methyl methacrylate and by removal of the methyl methacrylate—methanol a2eotrope. A variety of catalysts have been used, including acids and bases and transition-metal compounds such as dialkjitin oxides (57), titanium(IV) alkoxides (58), and zirconium acetoacetate (59). The use of the transition-metal catalysts allows reaction under nearly neutral conditions and is therefore more tolerant of sensitive functionality in the ester alcohol moiety. In addition, transition-metal catalysts often exhibit higher selectivities than acidic catalysts, particularly with respect to by-product ether formation. 

Acrylic Esters. A procedure has been described for preparation of higher esters from methyl acrylate that illustrates the use of an acid catalyst together with the removal of one of the products by azeotropic distillation (112). Another procedure for the preparation of butyl acrylate, secondary alkyl acrylates, and hydroxyalkyl acrylates using -toluenesulfonic acid as a catalyst has been described (113). Alurninumisopropoxide catalyzes the reaction of amino alcohols with methyl acrylate and methyl methacrylate. A review of the synthesis of acryhc esters by transesterification is given in Reference 114 (see... 

In contrast, allyl methacrylate is produced by the esterification of methacrylic acid and allyl alcohol (13), or by the transesterification of allyl alcohol with an ester of methacrylic acid, preferably with methyl methacrylate. The latter reaction is catalyzed with zirconium acetylacetonate (14). The esterification reactions are shown in Figure... 

Kamat et al. (1992) Batch Transesterification of methyl methacrylate by 2-ethylhexanol Lipase from Candida cylindracea... 

Lanthanide-based initiator systems offer a fourth possibility, permitting the block copolymerization of lactones with compounds such as ethylene,tetrahy-drofuran, l-LA, trimethylene carbonate, and methyl methacrylate. Detrimental side reactions such as macrocyclic formation, transesterification, and racemiza-tion are absent and the reactions are extremely fast. 

Direct esterification of methacrylic acid with alcohols using sulfuric acid or other catalysts can be used to prepare methyl methacrylate (MMA) and other esters. Commercial routes for the direct preparation of MMA and some lower alkyl esters also exist. In the 1990s, researchers at Shell developed a direct route to MMA from propyne (methylacetylene), carbon monoxide, and methanol using a Pd(II) catalyst. The limited availability of propyne may slow the expansion of this highly efficient route to high purity MMA. Transesterification of MMA is often the preferred route for the preparation of other esters. 

Lipase catalysts have been used for functionalization of polymers. A terminal hydroxy group of poly-(e-CL) was reacted with carboxylic acids using lipase CA catalyst to give end-functionalized polyesters.231 Lipase MM catalyzed the regioselective transesterification of the terminal ester group of oligo (methyl methacrylate) with allyl alcohol.232 In the PPL-catalyzed reaction of racemic 2,2,2-trichloroethyl 3,4-epoxybutanoate with hydroxy-terminated PEG, the... 

Berberich et al. used salt hydrate pairs to control water activity in [BMIM][PF6]. The results were in good agreement with that obtained for water activity control using saturated salt solutions. The advantage of pre-equilibration is that the contact of the enzyme with the used salt and thus enzyme deactivation can be avoided. On the other hand it is only applicable for initial rate measurements. This disadvantage can be overcome by controlling water activity with salt hydrate pairs. Berberich et al. measured initial rate - water activities for the transesterification reaction of methyl methacrylate with 2-ethylhexanol in either hexane or [BMIM][PF6]. Both reaction systems gave similar profiles [72],... 

Conversion of the phthalimide to the amine was confirmed by a peak at (5 3.2 ppm corresponding to the hydrogen adjacent to the amine group. The functionalization reaction was also monitored by MALDI-TOF MS. Characterization of the phthalimide-functionalized polymer confirmed the conversion of the bromide group. Characterization of the amine-functionalized polymer showed the presence of the desired product, but other side products were also observed. Upon hydrolysis of the phtha-limide-functionalized polymer, a transesterification reaction occurs converting the initiator moiety (ethyl-2-bromoisobuty-rate) from an ethyl ester to a t-butyl ester due to reaction with t-butyl alcohol. One drawback of this reaction is that the Gabriel reaction is only effective for primary alkyl halides and would not be useful for methyl methacrylates or methyl acrylates. 

Another method, namely the macromonomer (macromer) technique, has also been reported. In this method, the macromer is initially prepared by the reaction of hydroxyl-containing oil specimens with a vinyl monomer such as acrylic acid and methyl methacrylate (Rg. 8.7). This macromer is then homopolymerised and copolymerised with styrene. It is also possible to obtain the macromer by transesterification of linseed oil and castor oil. It may subsequently be homo- and copolymerised by the same method. 

SFO and LO were also styrenated after their transesterification with methyl methacrylate (MMA) in the presence of benzoyl peroxide [37] and the ensuing materials were characterized in terms of drying time, alkali and acid resistance and hardness. A more recent study reported the modification of SOYO and SFO by acrylamide derivatives [38] calling upon the use of Ritter s reaction. This rather fundamental study was limited to the determination of the reactivity ratios between ST and the different moieties of acrylamide derivatives. 

Fig. 8. H-R plot of methoxy resonance data obtained for styrene-methyl methacrylate copolymers derived from styrene-phenyl methacrylate copolymers by transesterification [79]. Plot based on spectra of copolymers in CDCI3 —CCI4 solution...

Compatible blends of PC with certain vinyl polymers have been described (35). The compatibilizer acts in the presence of a transesterification catalyst under conditions that effect transesterification. The compatibilizer is a copolymer containing hydroxyl groups, e.g., made from a-methyl-p-hydroxystyrene and methyl methacrylate. Other hydroxyl groups containing monomers may be p-hydroxy-styrene and p-isopropenyl-o-cresol. 

In preparing the compatible blend, the compatibilizer is reac-tively blended with PC and a blending partner in the presence of a transesterification catalyst. The blending partner can be a poly(ole-fin), styrene acrylonitrile copolymer, acrylonitrile-butadiene-styrene, poly (methyl methacrylate), or poly (styrene). Suitable transesterification catalysts include tetraphenyl phosphonium benzoate, tetraphenyl phosphonium acetate, and tetraphenyl phosphonium... 

Porphyrin-methacryUc acid polymer 48, prepared by polymerization of methyl methacrylate and transesterification as shown in Scheme 3, was also reported to form a stable complex with SWNTs in DMF through polymer wrapping [131]. The complex was found to create a long-lived charge-separated state upon photoexcitation. 

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