| 摘要 |
<p>Methacrylic acid and alkyl esters thereof are manufactured by treating acetone cyanhydrin with an alkyl hydrogen sulphate or a mixture thereof with sulphuric acid at an elevated temperature to produce methacrylamide and heating the product with water or an aliphatic alcohol or preferably with a mixture of water and an aliphatic alcohol. If the alkyl group of the alcohol is identical with that of the alkyl hydrogen sulphate a single ester will be produced, whilst if it is different a mixture of esters will result. The temperature in the first stage is preferably gradually raised to about 130--140 DEG C. The amount of alkyl hydrogen sulphate should be at least one molecular proportion, preferably about 1/ba1/2/be, to one of cyanhydrin, whilst when sulphuric acid is also employed suitable amounts are one molecular proportion of alkyl hydrogen sulphate and /ba1/2/be of acid to one of cyanhydrin. At least 1/ba1/2/be molecular proportions of the hydrolysing or esterifying medium should be used for each molecular proportion of cyanhydrin originally taken, a suitable amount being 2 molecular proportions of an equimolecular mixture of water and alcohol. The products may be recovered by distillation or by addition of water or brine. In examples: (1) and (2) acetone cyanhydrin is reacted with methyl hydrogen sulphate in the presence of copper bronze powder as stabilizer and the product is refluxed with water, yielding methyl methacrylate; (3) and (4) a mixture of water and methyl alcohol is employed in the second stage; (5) and (6) a mixture of methyl hydrogen sulphate and sulphuric acid is employed in the first stage; (7) acetone cyanhydrin is reacted with ethyl hydrogen sulphate and sulphuric acid and the product refluxed with water and ethyl alcohol to produce ethyl methacrylate.</p> |
