Quinone monochlorimide

The absorption spectra of (14) and wood slices treated according to the above sequence are similar, thereby providing evidence that structures (11) and (12) are present in native lignin. Quinone monochlorimide (15) reacts only with p-hydroxybenzyl alcohols (il), forming indophenol (blue) as shown below (Gierer 1954, 1956). 

Wood meal (3 mg) is suspended in 2 ml of ethanol, and 0.2 ml of an ethanolic solution of quinone monochlorimide (1 mg) and 1ml of an 0.04 M sodium hydroxide solution are added. The suspension is shaken for lh at room temperature. After removing the solution by filtration, the residual wood is washed with ethanol, and the blue color which forms is recorded while the material is still wet with ethanol. 

For an isolated lignin, a 20-mg sample is dissolved in 50ml of ethanol or methyl cellosolve. To 2 ml of this solution are added the same amounts of quinone monochlorimide and sodium hydroxide as were used in the above procedure. The solution is allowed to stand for 1 h at room temperature. Two ml of the solution is diluted to 25 ml with methyl cellosolve or ethanol and the absorption spectrum (/max 640 nm) is recorded spectrophotometrically. 

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