| 摘要 |
<p>(I): (where R1 and R2 are 1-6C alkyl) are prepd. by condensing a 2,6-dialkylphenol (II) with HCHO, using oxalic acid as catalyst. (I) can be converted to polycarbonates which are very resistant to hydrolysis. Hydrogenation of (I) gives which also form hydrolysis-resistant polyesters. Quantitative yields of (I) are obtd. from aq. HCHO, with short reaction times. The HCHO is quantitatively converted and is not evolved. Use of an additive, e.g. an alcohol, to prevent evolution of HCHO is avoided. Removal of water during the reaction is not necessary, since even very dil. oxalic acid catalyses the condensation. (I) can be hydrogenated without previous purification. (II) is pref. 2,6-Dimethylphenol. Reaction is at 60-140 degrees C, using 0.1-5 wt. % oxalic acid. HCHO is pref. used as 50 (35) wt.% soln. Molar ratio (II): HCHO is esp. 1.8-5:1. (I) can be hydrogenated in presence of a Ni-Cr-Al-Cu catalyst.</p> |
