3950-33-2Relevant articles and documents
The Significance of α-Sulfone and α-Sulfonate Groups for the Cleavage of β-Aryl Ether Structures in Lignin
Ljunggren, S.,Ljungquist, P. O.,Wenger, U.
, p. 313 - 320 (2007/10/02)
The kinetics of the alkaline cleavage of the β-aryl ether linkage in lignin containing a sulfonate or a sulfone group in the α-position has been studied by the use of model compounds.In the presence of either of these groups the β-ether cleavage reaction is a first order reaction with respect to the cleavage product.The rate constants and their temperature dependence were determined in each case and compared with data for cleavage in normal structures (α-hydroxyl groups).It was found that the activation energy with a sulfone group is 121 kJ/mol; the rate of cleavage is comparably very fast even at 0 deg C.In the presence of an α-sulfonate group, the activation energy is somewhat lower, 97kJ/mol.The reaction rate is much slower than in the presence of sulfone group but is still faster than cleavage in normal structures.At 110 deg C it is about the same as the rate of cleavage in normal structures at 170 deg C.These results support a β-elimination mechanism induced by the electron-withdrawing power of the sulfone and sulfonate groups as has been previously proposed.It is suggested that the un-ionized nature of the sulfone substitient generates a strong inductive effect whereas the ionized nature of the sulfonate groups gives a weaker effect.
