Calculation of the Conjugated Carbonyl Contents

As shown in Table 7.4.1, 4-O-isopropylconiferyl aldehyde (18) and 2-(2-methoxyphenoxy)-l-(3,4-dimethoxyphenyl)-3-hydroxy-l-propanone (20) have Aer maxima at 342 and 310 nm with corresponding Aer values of 19800 and 9400 mol 1 cm-1, respectively, at the reduction time of 100 min (see Table 7.4.1 for Aer values and Fig. 7.4.2 for structures of model compounds). In addition, compound (18) has a Aer value of 2020tmol em 1 at 310nm, while compound (20) has a Aer value of 10500 mol-1 cm 1 at 342nm (Adler and Marton 1959). Thus, the quantities of etherified coniferyl aldehyde-type (2) and etherified l-(guaiacyl)-l-propanone-type (JT) structures in lignin can be estimated by simultaneously solving Eqs. (9) and (10)  

Since 2-(2-methoxyphenoxy)-l-(4-hydroxy-3-methoxyphenyl)-l-propanone (19) has a Acr value of only 1200 mol 1 cm-1 at 356 nm for a reduction time of lOOmin and a Asr value of 24300 mol 1 cm-1 at 356 nm for a reduction time of 45 h, it follows that the contribution of l-(guaiacyl)-l-propanone-type (10) 

Model compounds Atr-Maximum at a (nm) Act Reduction time Half-life time (tj) for reduction 

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