Poly acetaldehyde

Acetaldehyde, an important reagent, is manufactured by four processes. Process 1  

Process 2 Oxidation of a mixture of propane and butane with 95% oxygen in the vapor phase, with the formation of a mixture of CH3OH, CH2O, and CH3CHO. 

Process 4 Oxidation of ethylene with air or oxygen at 20°C with PdCl2 or copper or iron salts. There are few by-products in this reaction. Higher aldehydes can be obtained industrially via the Oxo reaction  

The thermodynamic ceiling temperature of the polymerization is very low, — 60°C. Cationic polymerization leads to atactic (67 % isotactic) rubbery products, while anionic polymerization yields highly syndiotactic. 

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Polyacetaldehyde, a mbbery polymer with an acetal stmcture, was first discovered in 1936 (49,50). More recentiy, it has been shown that a white, nontacky, and highly elastic polymer can be formed by cationic polymerization using BF in Hquid ethylene (51). At temperatures below —75° C using anionic initiators, such as metal alkyls in a hydrocarbon solvent, a crystalline, isotactic polymer is obtained (52). This polymer also has an acetal [poly(oxymethylene)] stmcture. Molecular weights in the range of 800,000—3,000,000 have been reported. Polyacetaldehyde is unstable and depolymerizes in a few days to acetaldehyde. The methods used for stabilizing polyformaldehyde have not been successful with poly acetaldehyde and the polymer has no practical significance (see Acetalresins). 

Figure 1. Potential energy map of isotactic poly acetaldehyde. The energy values are given in units of kilocalories per mole of monomer unit (23).

Williams, G. Dielectric information on chain mobility, chain configuration, and an order-disorder transition in amorphous poly(acetaldehyde), Trans. Farad. Soc., 59, 1397 (1962)... 

Elastomeric poly acetaldehyde is amorphous and atactic. High resolution NMR studies were carried out in order to determine the actual tacticity of the polymer (4, 5, 23). Poly acetaldehyde consists mainly of heterotactic sequences isotactic sequences are also present in the polymer. The ratio of heterotactic to isotactic varies, but it is usually between 2-3 1. A detailed description of the tacticity determination by high resolution NMR will be given in a subsequent paper by Goodman and Brandrup (23). 

Internal friction measurements have also been carried out on amorphous poly acetaldehyde and showed a main amorphous transition at -18° C. Poly-n-butyraldehyde had a transition at room temperature (Figure 1). 

Poly(acetaldehyde) see Poly(oxyethylidene) Poly[3,3-bis(chloromethyl)oxacyclobutane] see Poly[oxy-2,2 Poly( 1,2-dihydroxypropane)... 

Poly(acetaldehyde-co-chloral) Fractional precipitation Poly(acrolein-co-thiophenolmercaptal) Chloroform/methanol 1457 2911... 

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