Acetaldehyde monoperacetate

Oxidation. Acetaldehyde is readily oxidised with oxygen or air to acetic acid, acetic anhydride, and peracetic acid (see Acetic acid and derivatives). The principal product depends on the reaction conditions. Acetic acid [64-19-7] may be produced commercially by the Hquid-phase oxidation of acetaldehyde at 65°C using cobalt or manganese acetate dissolved in acetic acid as a catalyst (34). Liquid-phase oxidation in the presence of mixed acetates of copper and cobalt yields acetic anhydride [108-24-7] (35). Peroxyacetic acid or a perester is beheved to be the precursor in both syntheses. There are two commercial processes for the production of peracetic acid [79-21 -0]. Low temperature oxidation of acetaldehyde in the presence of metal salts, ultraviolet irradiation, or osone yields acetaldehyde monoperacetate, which can be decomposed to peracetic acid and acetaldehyde (36). Peracetic acid can also be formed directiy by Hquid-phase oxidation at 5—50°C with a cobalt salt catalyst (37) (see Peroxides and peroxy compounds). Nitric acid oxidation of acetaldehyde yields glyoxal [107-22-2] (38,39). Oxidations of /)-xylene to terephthaHc acid [100-21-0] and of ethanol to acetic acid are activated by acetaldehyde (40,41). 

Peroxide Determinations. Bawn and Williamson report two iodometric procedures for determining peracetic acid (Methods I and III below) and one method for determining total peroxide (4) (Method II). Bawn and Jolly report another method for total peroxide (5) (Method IV below). The difference between total peroxide and peracetic acid is assumed to be acetaldehyde monoperacetate (AMP). Each method was tested in our preliminary studies. Method III is preferred for peracetic acid because the results are more reproducible. In Method I a large blank titration was always observed, while in Method III the blank titration was very small. Method IV is preferred for total peroxide because it seems to be more sensitive to total peroxide and less sensitive to water content of the acetic acid solvent. 

The kinetics of the noncatalytic reaction were studied by the method of Bawn and Williamson (4). They found 3.3-3.7 moles/liter for the equilibrium constant for the formation of the intermediate acetaldehyde monoperacetate (AMP) and a first-order rate constant for the decomposition of this intermediate to acetic acid of 0.015 min."1 at 25°C. We found difficulty in reproducing our results probably caused mainly by the high values of the blanks in the iodometric methods used. However, as an average of four determinations we obtained 0.03 min."1 at 30°C. 

There are two commercial processes for the production of peracetic acid (1) Low-temperature oxidation of acetaldehyde in the presence of metal salts, ultraviolet irradiation, or treatment with ozone yields acetaldehyde monoperacetate, which can be decomposed to peracetic acid and acetaldehyde. 

Peracetic acid (c), anhydrous. Phillips, Frostick, and Starcher (Union Carbide) describe an efficient two-step synthesis of a water-free solution of peracetic acid in clhyl acetate or acetone. In the first step acetaldehyde is autoxidized at 0° under cnliilysis by ultraviolet light, 0.01% of cobedtous acetate, or ozone to acetaldehyde monoperacetate (AMP). This substance forms crystals (m.p. 20-22°) which explode... 

Acetaldehyde monoperacetate normally decomposes, to yield 97 per cent anhydride and water and 3 per cent add. However, the hydrolysis takes place rapidly, so that acetic anhydride is merely the forerunner of the add in the oxidation of acetaldehyde. The difficulty of the operation, which takes place in the liquid phase with oxygen or air, at moderate temperature (45 to 60°Q and low pressure (0.1 to 0.4.106 Pa absolute), thus consists in preventing the hydrolysis of acetic anhydride from developing. 

Through study of the mechanism by which the catalyzed liquid-phase oxidation of acetaldehyde to acetic proceeds, it has been found, that at temperatures below 15 C and in suitable solvents the acetaldehyde forms an unstable compound, acetaldehyde monoperacetate. At controlled low temperatures this compound can be made to yield peracetic acid and acetaldehyde. Salts of the metals cobalt, copper, and iron catalyze the first-stage reaction, in a manner used in acetic acid manufacture. 

Another process is by catalytic oxidation of acetaldehyde. Acetaldehyde is partially oxidized with air in the liquid phase to acetic acid. The acetic acid reacts with the remaining acetaldehyde to form acetaldehyde monoperacetate, which decomposes quantitative to acetic... 

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