Is it possible to fully esterify phenol with oxalic acid in order to get diphenyl oxalate? What catalyst should I use and is the synthesis possible to perform at home with hobby equipment?
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I don't know for sure, but it could work provided some conditions be fulfilled
- use of oxalyl chloride
- use low temperature, in order to try to suppress fragmentation of the intermediate (semi-ester) into the simple monoacyl chloride (by CO loss): in such cases $\ce{(COCl)2}$ behaves much like phosgene ($\ce{COCl2}$.
- use the phenol as a dissociated salt (sodium, potassium) in polar solvents such as sulfolane or acetonitrile, this is optional and possibly risky, due to enhanced competitive "C-acylation" if ortho/para positions are free.
- use Piridine-based solvents as reactivity enhancers (they convert acyl chloride to acyl immonium salts). Optionally, even stronger catalysts such as DMAP (p-dimethylamino pyridine) could work
Anyway, to sum up, the major risks stem from:
- "C-acylation" (which is generally kinetically slower but irreversible and thermodynamically favored over "O-acylation"), if some suitable position is avail.
- formation of diaryl carbonates (on extrusion of CO). I guess this last drawback coul be at least reduced by working at low temperature.
answered Apr 2 '16 at 18:16
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Diphenyl oxalate can be obtained by transesterification of dimethyl oxalate with phenol.
