| 摘要 |
<p>Prodn. of diketals of formula (I): (R=H, 1-4C alkyl or halo; R1=1-4C alkyl) comprises anodic oxidn. at -20 to 60 degrees C of benzene or a 1-R1O-(2- or 3-)R-benzene in methanol contg. 5 wt.% water; 0.2-15 wt.% (on the electrolyte) of >=1 conductivity salt (II) and opt. 0.5-10 wt.% (on the electrolyte) of a difficultly-oxidisable base, esp. 2,6-lutidine at pH >=7. Electrolysis is carried out using glassy carbon, bipolar connected electrodes coated on the cathode side with a material which reduces hydrogen overvoltage. (II) are of formula MQ or AxPh4-xZ+ Y-; M = NH4 or alkali metal; Q=F, ClO4, NO3, BF4, SiF6, PF6, benzenesulphonate or p-toluenesulphonate, each A is independently alkyl; x=1-4; Z is N or P, and Y is F or CH3SO4. (I) are converted by hydrolysis to quinones which are intermediates for photographic chemicals, monomer stabilisers, dye intermediates, etc. Bipolar connected electrodes increase space-time yields and by coating with a material to reduce overvoltage the current yield is as good as that in cells with unipolar connected electrodes.</p> |
