Vinyl esters acetals, mixed

Unsaturated vinyl esters for use in polymerization reactions are made by the esterification of olefins. The most important ones are vinyl esters vinyl acetate, vinyl chloride, acrylonitrile, and vinyl fluoride. The addition reaction may be carried out in either the liquid, vapor, or mixed phases, depending on the properties of the acid. Care must be taken to reduce the polymerization of the vinyl ester produced. 

Ethylhexyl isodecyl phthalate (octyl iso-decyl phthalate) n, C8H17-OOCC6H4 COOC10H21. A mixed ester compatible with PVC, vinyl chloride-acetate copolymers, cellulose acetate-butyrates with higher butyrate contents, cellulose nitrate, and, in lower concentrations, with polyvinyl butyral. In vinyls, it is somewhat less volatile than dioctyl phthalate and has equivalent low-temperature properties. 

Butyl Ethylhexyl Phthalate n (butyl octyl phthalate, BOP) A mixed ester of butanol and 2-ethylhexanol, widely used as a primary plasticizer for PVC compounds and plastisols, in which it performs like dioctyl phthalate in most respects. It is also compatible with vinyl chloride-acetate copolymers, cellulose nitrate, ethyl cellulose, polystyrene, chlorinated rubber, and at lower concentrations, with polymethyl methacrylate. 

Titanium—Vanadium Mixed Metal Alkoxides. Titanium—vanadium mixed metal alkoxides, VO(OTi(OR)2)2, are prepared by reaction of titanates, eg, TYZOR TBT, with vanadium acetate ia a high boiling hydrocarbon solvent. The by-product butyl acetate is distilled off to yield a product useful as a catalyst for polymeri2iag olefins, dienes, styrenics, vinyl chloride, acrylate esters, and epoxides (159,160). 

Over the past years considerable attention has been paid to the dispersing system since this controls the porosity of the particle. This is important both to ensure quick removal of vinyl chloride monomer after polymerisation and also to achieve easy processing and dry blendable polymers. Amongst materials quoted as protective colloids are vinyl acetate-maleic anhydride copolymers, fatty acid esters of glycerol, ethylene glycol and pentaerythritol, and, more recently, mixed cellulose ethers and partially hydrolysed polyfvinyl acetate). Much recent emphasis has been on mixed systems. 

Viprostol (81) also incorporates a hydroxy group moved to C-16 and protects this from facile metabolic oxidation by vinylation. It is a potent hypotensive and vasodilatory agent both orally and transdermally. The methyl ester moiety is rapidly hydrolyzed in skin and in the liver so it is essentially a prodrug. It is synthesized from protected E-iodo olefin 78 (compare with 75) by conversion to the mixed organocuprate and this added in a 1,4-sense to olefin 79 to produce protected intermediate 80. The synthesis of viprostol concludes by deblocking with acetic acid and then reesterification with diazomethane to give 81 [19]. 

Another potentially important fermentation is that producing butyric acid. The process is used industrially on only a small scale at present and details have not been disclosed. Many derivatives of butyric acid are used industrially the benzyl, methyl, octyl and terpenyl esters are used in the perfumery and essence trade and amyl butyrate, bornyl and isobornyl butyrates have been described as plasticizers for cellulose esters. Moreover vinyl butyrate is a possible ingredient of polymerizable materials. The mixed acetic and butyric acid esters of polysaccharides are also coming into favor. Cellulose acetate butyrate is marketed as an ingredient of lacquer and is less inflammable than the pure acetate. Dextran (see below) acetate butyrate may have similar uses. 

CA 65, 568(1966) [Fluid nitric esters, nitro aromatic compds or their mixes can be thickened and made plastic by addn of soluble polymers that contain neither nitro nor perchloro groups. The gelled compds are useful in the manuf of expls and propints. Polymers used include poly(Me-methacrylate), poly(vinyl acetate), EtOAc-vinyl chloride, phenol-HCHO, poly-(vinylpyrrolidinone) and poly(vinylpyrrolidi-none)-poly(vlnylacetate)]... 

The permanganate oxidation of axial and equatorial vinyl orthoesters 140 and 141 was carried out in a buffered solution (pH =10) mixed with acetonitrile. The reaction mixture was then esterified with acetic anhydride and pyridine. Both vinyl orthoesters gave an identical result >95% of acetoxy ester J46 and <5% of bicyclic lactone 147. 

Many esters such as butyl acetate and ethyl acetate are used as solvents for vinyl polymers. Figure 19 shows the solubility properties of a carboxyl containing terpolymer in various acetate solvents. These esters can also be used as diluents or to alter evaporation rates in mixed solvent systems. If a primary solvent such as a ketone is present, very high solids can be obtained. 

The allyl vinyl ethers are usually prepared in situ, but it is also possible to isolate the primarily formed mixed acetals or allyl vinyl ethers155-1 57. With low-boiling vinyl ethers the reaction is carried out in a sealed tube with an excess of the vinyl ether. For a tandem Claisen-rearrangc-ment-ene cyclization involving the Saucy-Marbet reaction cf. ref 158. The generation of isopropenyl ethers from esters is described in ref 159. For a related Claisen rearrangement by the reaction of 2-methoxybutadiene with ends and phenols see ref 160. 

Another strategy for in situ activation, used for the s3uithesis of aliphatic cellulose esters, is the exploitation of DCC in combination with 4-pyrrolidinopyridine (PP) [35]. Among the advantages of this method are the high reactivity of the intermediately formed mixed anhydride with PP and a completely homogeneous reaction in DMA/LiCl up to hexanoic acid. If the reaction is carried out with the anhydrides of carboxylic acids, the carboxylic acid liberated is recycled by forming the mixed anhydride with PP, which is applied only in a catalytic amount. The toxic DCC can be recycled from the reaction mixture (Fig. 16.4). In addition, the method is utilized to obtain unsaturated esters (e.g. methacrylic-, cinnamic-, and vinyl acetic acid esters) and esters of aromatic... 

The Claisen-Johnson rearrangement [7] is closely related to both Saucy vinyl allyl ether rearrangement and Eschenmoser rearrangement. The reaction proceeds via a ketene acetal, which results from the condensation between an ortho-ester and an aUylic alcohol giving rise to a mixed orthoester followed by the elimination of the low-boihng-point alcohol. This ketene intermediate forms after rearrangement of a y,d-unsaturated ester (Scheme 6.1). 

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