Syringaldehyde from lignin

NBO is still probably the most commonly employed chemical degradation technique for lignin analysis. This acceptance is related to the fact that NBO provides in satisfactory yield p-hydroxybenzaldehyde, vanillin, and syringaldehyde from lignin H, G, and S units, together with smaller amounts of the corresponding benzoic acids (Figure 2.2). In addition, NBO yields small amount of 5-carboxyvanillin,... 

Treatment of suberin with nitrobenzene generates vanillin, p-hydroxy benz-aldehyde, but not much syringaldehyde that arises mostly from lignin. 

Vanillin, syringaldehyde, and related phenolic products derived from lignin appear to be important in the desirable odor contributed to beverages by oak barrels (25, 26, 27). These substances are present in the wood, but more appears in the beverage than simple extraction seems to allow. Also the odor of vanillin seems to increase with time and mellowing of the beverage compared with a fresh extract of new wood (25). 

Wu, G. X., Heitz, M., and Chomet, E., Improved alkaline oxidation process for the production of aldehydes (vanillin and syringaldehyde) from steam-explosion Hardwood Lignin. Industrial Eng Chem Res 1994, 33 (3),... 

To correlate these changes in absorption with theory, the ultraviolet spectroscopic behavior of model compounds closely related to the degradation products isolated from bagasse native lignin, i.e., p-hydr-oxybenzaldehyde, vanillin and syringaldehyde, was determined. The compounds used were p-hydroxypropiophenone, vanillin, acetovanillone and acetosyringone and their derivatives. 

As mentioned previously (Chap. 2.2.2.4.1), the major purpose of the GC-MS analysis of a nitrobenzene or cupric oxide oxidation mixture is to verify the identity of the oxidation products established previously by GC or HPLC analysis, and to elucidate the structure of unknown constituents. For example, GC-MS analysis of the nitrobenzene oxidation mixture of milled bamboo lignin from Phyllostachys pubescence showed unequivocally that compounds (l)-(3) in the total ion chromatogram of the oxidation mixture (Fig. 6.2.2) are indeed p-hydroxybenzaldehyde, vanillin, and syringaldehyde, respectively (Tai et al. 1990) (see Chap. 9.1 for a discussion of the GC-MS technique). In addition, the unknown compound in the chromatogram was identified as p-hydroxyazobenzene (15) (Fig. 6.2.1), one of the phenolic reduction products of nitrobenzene. 

The components of lignin obtained are listed in Table 9.1 and labeled alphabetically in Fig. 9.1. The standard solntion for each expected component to be present in lignin was injected into three different concentrations, 10,100 and 1,000 ppm. This was done to ensure that the solution for each similar component at different concentrations had the same retention time. From the HPLC chromatogram, six components were detected in the soda lignin. They are vanillin, syringaldehyde,... 

Catalytic oxidation of beech organosolv lignin in ionic liquid (l-ethyl-3-methylimidazolium trifluoromethanesulfonate) at 100°C and 8 MPa air in the presence of 20% Mn(N03)2 formed DMBQ 25 in 11.5% isolated yield and 21% selectivity. The amount of 25 formed under these conditions depended on the catalyst level. At 2% catalyst, the product slate shifted to a mixture of syringaldehyde, syringyl alcohol, and vanillin, with only trace amounts of DMBQ observed. The authors propose that DMBQ results from syringaldehyde oxidation [100]. 

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