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On treatment with oxidants such as chlorine, hypochlorite anion, chlorine dioxide, oxygen, hydrogen peroxide, and peroxy acids, the aromatic nuclei in lignin typically are converted to o-and p-quinoid structures and oxirane derivatives of quinols. Because of their relatively high reactivity, these structures often appear as transient intermediates rather than as end 2 LIGNIN Vol. 15Reactions that involve the formation and elimination of multiple bond functional groups may significantly effect the color of residual lignin in bleached and unbleached pulps. The ethylenic and carbonyl groups conjugated with phenolic Vol. 15

At high pressures of CO, the Ag+ salt of the weakly coordinating anion [Nb(OTeF&]-takes up three equiv. CO reversibly both in the solid state and in 1,1,2-C2CI3F3 solution; the CO ligands can be removed from [Ag(CO)3][Nb(OTeF5)6] under vacuum at 25°C but none are removed at -78°C; IR v(C0) values are 2192 cm-I for [Ag(C0)3]+, 2198 cm-l for [Ag(CO)2]+, and 2208 cm-l for [AgCOl+.

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