Cellulose Column Chromatographic Separation of Lignin Oxidation Products

Abstract

X brief review is presented of the che~nical nature and the methods of separation of those lignin derivatives obtained by the oxidation and/or alkaline hydrolysis of woody plants and isolated lignin or lignosulphonates. Nine such closely related derivatives, vanillin, syringaldehyde, p-hydroxybenzaldehyde, acetovanillone, acetosyringone, p-hydrosyacetopheno~~e, vanillic acid, syringic acid, and p-hydroxybenzoic acid, were selected for a detailed study of their separation by cellulose column chromatography. Methods are presented whereby, by either a one-or two-stage process, a mixture of from any two to all nine of these compounds may be separated and the components recovered, using solvent systems which are suitable for subsequent quantitative spectrophotolnetric analysis. The applicatioll to a study of lignin chemistry is discussed. INTRODUCTIONIn recent years considerable attention has been given to tlie chro~~~atographic separation of the products of oxidation and/or alltalilie li~~clrolysis of the lignin component of woody plants ancl cereal straws. Froill the earlier \\rorl; the characterization of these various lignin clerivatives has colitributed substantially to the present I<nowledge regarding tlie aromatic nature of lignin. XIore recently this phase of lignin research lias beell stimulated by an increased study of the fate of various C"-labelled coilipouiids \\ihich have been iiltrocluced into growing plants in a study of tlie biosyntlietic pathway leacling to lignin. The 0111~-reliable method whereby proof is obtained tliat tlie C1" lias been incorporated into the lignin lias been to obtain, from this fraction, purifiecl degradation products whose specific activity may be measured. The larger tlie isolatecl lignin fragment the greater the structural significance tliat may be given to it and the inore valuable the information that may be obtainecl from the position of the C1,-labelling. T o clate one of the more fruitful of such degradation studies 11~1s been the oxidation of lignii~ and, in particular, that using all<aliiie nitrobenzene as tlie oxidant systeln (1). By such means substantial yielcls of vailillin and a lliisture of vailillin and syringaldeliyde have been obtainecl froill gymnosperilis and angiosperins respectively. Along nritli both these compouncls much smaller yielcls of p-liydroxj7benzaldehyde have bee11 found in the oxidation products of monocot~~leclons. This technique has been used by several \vorl;ers interested i l l lignin clienlistry and from various lignified materials the followiiig other derivatives liave been isolated and characterized (2, 3, 4 ) : vanillic acid, syringic acicl, P-hydroxybenzoic acid, acetovanillone, acetos)~ringone, 5-carboxyvanilliii, 5-carboxyvanillic acid, 5-foi-iliylvanilliii, 5-formj-lvanillic acid, dehydrodivanillin, and clehydroclivanillic acicl.I11 a series of investigatioils by both Pearl and i\/IcCarthy and their co-worBers (5, 6, 7, 8, 0) using the all<aliiie cupric oside, silver oxide, and mercuric oxicle oxidations of ~igr~osulphonatc...

The Effect of Initial Acid Concentration on the Lignin Isolated by the Acidolysis of Aspen Wood

“…I t has been reported previously that the possible interference of acetovanillone and acetosyringone in the chromatographic procedure did not exist due to the absence of these compounds in the products obtained a t 180' (12). No fi-hydroxybenzaldehyde was detected in the lignin oxidation products.…”

“…The infrared spectra were obtained using a Perkin-Elmer Model 21 spectrophotometer with sodium chloride optics and Nujol mulls. T h e alkaline nitrobenzene oxidations and quantitative estimations of the phenolic aldehydes were conducted according to the procedure of Stone and Blundell (11) with the recent modificatio~ls of Pepper and Siddiqueullah (12).…”