Vinyl acetate is a chemical compound with the molecular formula (CH3COO)C=CH2. It is a colorless liquid that is used as a monomer for the production of polyvinyl acetate (PVA) and other vinyl polymers. It is a reactive intermediate in the production of other chemicals and has applications in the production of paints, adhesives, and coatings. Vinyl acetate is produced by the reaction of acetylene and acetic acid in the presence of a catalyst, and can also be synthesized from ethylene and acetic anhydride.
Preparation
Vinyl acetate is produced commercially by the reaction of ethylene and acetic acid in the presence of a palladium catalyst and oxygen. This reaction is commonly referred to as the ethylene oxidation process. The palladium catalyst acts to form a complex between the ethylene and the acetic acid, which then reacts with oxygen to form vinyl acetate. The reaction conditions are carefully controlled to minimize the formation of by-products, including combustion of the organic precursors.
Polymerization
Vinyl acetate is a monomer that can be polymerized to form a polymer called polyvinyl acetate (PVAc), also known as vinyl acetate homopolymer. The polymerization process can be initiated by free radicals, cationic, or anionic initiators, and typically takes place in aqueous suspension or emulsion. The resulting PVAc polymer is a water-soluble, thermoplastic material that has various applications, such as in the production of adhesives, coatings, films, and fibers. The properties of PVAc can be altered by copolymerizing it with other monomers, such as ethylene, to form copolymers with improved properties and enhanced applications.
Esterification of starch
Vinyl acetate can be used in esterification of starch as a reagent. The reaction involves the reaction of starch with vinyl acetate in the presence of an acid catalyst to produce a starch ester. The resulting starch ester has different properties compared to native starch, such as reduced viscosity and improved film forming ability. This reaction can be used in various applications, such as the production of biodegradable packaging materials and adhesives.
Note that Vinyl acetate is not a carboxylic acid, but it can react with a hydroxyl group in starch to form an ester bond and generate a molecule of acetic acid as a byproduct. This reaction occurs in the presence of a catalyst and under suitable conditions, such as temperature and pressure. The reaction between vinyl acetate and starch can be considered as a modified form of esterification, where vinyl acetate acts as a source of acetic acid instead of a carboxylic acid. The reaction mechanism involves the nucleophilic attack of the hydroxyl group in starch on the acetate group of vinyl acetate, leading to the formation of the ester bond and the release of acetic acid.