L. S. Smirnova

Nitrobenzene oxidation of fractions of cotton-plant dioxane lignin

SummaryAnalysis of the products of alkaline nitrobenzene oxidation of lignin fractions has confirmed their chemical inhomogeneity and has shown that in the various fractions the amounts of condensed syringly and guaiacyl structures differed markedly.

Quantitative 1 H and 13 C NMR spectroscopies of cottonplant dioxane lignin

A comparative analysis has been made of the dioxane lignins of the stems, seedling shoots, and seed coats of the cotton plant. The ratio of p-hydroxyaromatic, guaiacyl, and syringyl units in the macromolecules of the lignins has been determined, and so have the amounts of functional groups and bonds. It has been established that the main difference between the dioxane lignins from seedling shoots and seed coats of the cotton plant, on the one hand, and the lignin from the woody stems, on the other hand is a lower content of syringyl and guaiacyl units in the former.

Cleavage of dioxane lignin of the cotton plant with thioacetic acid

Summary1. It has been established that the dioxane lignin of mature cotton-plant stems is cleaved by thioacetic acid. About 3/4 of the bonds in the lignin are alkyl-aryl ether bonds and only 1/4 are C-C bonds.

A study of the alkaloids of Saussurea salsa and S. elegans

Conclusions1. In the extraction ofS. salsa andS. elegans, the condensation of the neutral substances with ammonia takes place with the formation of products of a basic nature.2. FromS. elegans a new alkaloid elegantine C23H29O5N has been obtained the saponification of which has given tyramine and a sesquiterpene lactone.

COTTON PLANT LIGNINS

This paper generalizes the results of studies on lignins isolated from the stems, bolls, and seed hulls of cotton plants of a number of varieties as functions of the vegetation periods of the plants. The UV, IR and1H and13C NMR spectra of the lignins have been studied. The dioxane lignin (DLA) and the natural lignins have been subjected to nitrobenzene oxidation and to cleavage with sodium in liquid nitrogen. A structure of the lignin macromolecules consisting of 18 phenylpropane structural units has been done up. Information is given on the use of lignins in agriculture, the food industry, and the paint and varnish industry. The anticorrosion and sorption properties of hydrolysis and modified hydrolysis lignins have been studied.

Preparation of dimeric model compounds of lignin

There are a number of reports in the literature on the study of the reactivity of the benzylic hydroxy groups of li~aha [1-4]. These groups have a high chemical activity and play a large role in the formation of the wood substance [5]. We have shown previously that dimeric compounds are formed fromp-hydroxyphenylpropan1-ol, guaiacylpropan1-ol, and syringylpropan-l-ol under comparatively mild conditions [6]. On continuing this work, we have obtained a dimeric substance from guaiacylpropan-l-ol and syringylpropan-l-ol. The reaction was conducted under the same conditions as in the preparation of the dimers synthesized previously: a mixture of one mole of each alcohol, one mole of aqueous ethanol, and one mole of hydrochloric acid was heated in the water bath or was left at room temperature. In the resulting reaction products TLC on Silufol plates in the solvent system hexane--diethyl ether (1:2.5) revealed four components, three of which were identified with the aid of markers as the initial guaiacylpropan-l-ol, diisoeugenol, and a dimer of syringylpropan-l-ol. To identify the fourth substance, the mixture of products was separated preparatively on Silufol plates. From its mass spectrum and its elementary composition, the fourth component proved to be a dimer of guaicylpropan-l-ol and syringyIpropan-l-ol: 6hydroxy-l-(4-hydroxy-3,5-dimethoxyphenyl)-3-methoxy-2-methylindan. Composition C21H2605 . Its mass spectrum (m/z): M + 358, 329, 313, 299, 267, 253, 239, 225, 204, 175, 137) was characteristic for substances of similar nature. When the reaction products were separated on a silica gel column (the eluent being a mixture of hexane and diethyl ether) a dimer of guaiacylpropan-l-ol and syringylpropan-l-ol was isolated. The dimer was purified by reprecipitation from its ethereal solution in hexane. A light yellow resinous substance was obtained that could not be converted into a powder or be recrystallized. It dissolved well in all solvents except water and hexane. Its PMR spectrum was similar to those of diisoeugenol [4] and syringylpropan-l-ol [6]: PMR spectra (ppm, r-scale) 0.09-1.1, doublet and multiplet, 2CH3; 1.4-1.7, triplet, -CH2--; 2.2-2.5, quartet, -C H; 2.75-3.0, quartet, -CH; 3.35-4.0, three singlets, 3OCH 3 and C H ; 5.35-5.5, doublet, 2OH; 6.25-6.8, multiplet, aromatic 4H. Since on TLC no material remained at the start and the spots obtained were sharp and well separated from one another, we calculated the areas of the spots and, from these, the amounts of the components in the mixture. Each reaction mixture was chromatographed in five different concentrations and in triplicate. Thus, the percentage amount of each component was calculated from 15 results (Table 1). When the reaction mixture was not heated but was left to stand for 1-2 days, the mixture of products was shown by TLC to contain the spot of the initial syringylpropan-l-ol, which later disappeared. In the reaction products the amount of

Schematic structure of a fragment of the cottonplant lignin macromolecule

A schematic structure has been proposed for an average fragment of the macromolecule of cottonplant dioxane lignin on the basis of the results of a chemical study and quantitative1H and13C NMR spectroscopy.

Study of the dioxane lignin of a cotton plant of the variety Namangan-77

Dioxane lignin isolated from the stems of a cotton plant of the variety Namangan-77 has been studied. Its structure differs from that of the DLAs of other varieties, being of lower molecular weight and more highly oxidized.

Study of the lignin of a cotton plant of the variety S-6524

The dioxane lignin (DLA) has been isolated from ripe stems of a cotton plant of the variety S-6524, and its empirical formula and molecular mass have been determined. This DLA differed from the DLA of a cotton plant of variety 108-F by a lower degree of hydroxylation and a higher degree of substitution of the aromatic rings.

Synthesis of model dimers of lignin from (1-hydroxyalkyl)phenols

It has been shown that model (1-hydroxyalkyl)phenols of lignin condense in an acid medium with heating to form dimers of the indan and Ar-C3-Ar series, depending on the substituents in the aromatic ring.