title: Phenylglyoxylic acid
text: # Phenylglyoxylic acid
  
  Phenylglyoxylic acid is the organic compound with the formula $C_6H_5C(O)CO_2H.$ The conjugate base, known as benzoylformate is the substrate of benzoylformate decarboxylase, a thiamine diphosphate-dependent enzyme:
  
      benzoylformate + $H^+$ ⇌ benzaldehyde + $CO_2$
  
  It is a colourless solid with a melting point of 64–66 °C and is moderately acidic $(pK_a$ = 2.15).
  
  Phenylglyoxylic acid can be synthesized by oxidation of mandelic acid with potassium permanganate. An alternative synthesis involves hydrolysis of benzoyl cyanide.
  
  