Noncatalytic organic rearrangement using supercritical water

Abstract

Significant acceleration of Beckmam and pinacol rearrangements can be achieved by using supercritical water (scH₂O), especially just near the critical point even in the absence of any acid catalysts. A high-pressure, high-temperature flow reactor system with FTlR operable at 500°C and 50 MPa was suaxssfdy developed, wherein the non-catalytic Beckmam and pinacol rearrangements using scH₂O were carried out and monitored. It has been demonstrated that scH₂0 itself acts very effectively in the place of conventional acid catalysts for both the rearrangements. The rate of the pinacol rearrangement using scH₂O is 28,200-fold rate of that in 0.871 M HCl solution at 46.7 MPa under distillation conditions. The high rate of reaction may be attributed to a great increase in the local proton concentration around the organic reactants.

Key Words:

• Supercritical water
• No catalyst
• Pinacol rearrangement
• Beckmann rearrangement
• High-pressure, high-temperature FTIR
• In situ measurement