PMR spectra of the dioxane lignins of some plants of the family Malvaceae

Analysis of PMR spectra of the dioxane lignins of three species ofAthea, of kenaf, and of the cotton plant has shown that the number of free aromatic protons does not correlate with the number of OCH₃ groups, which indicates different degrees of condensation of the dioxane lignins studied. In all the preparations a very small amount of coumarane structures were found. The aliphatic OH groups have been distinguished as primary (-OH) and secondary (-OH) and their quantitative estimation has been carried out from the PMR spectra.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 560–563, July–August, 1980.     

A comparative study of the dioxane lignins ofAlthea

Summary 1. The dioxane lignins have been extracted from three species ofAlthea for the first time. On the basis of elementary and functional analyses, the semiempirical formulas of the phenylpropane structural units have been calculated.2. The molecular weight distributions have shown that the DLAs of these species ofAlthea are polydisperse, and in the case of the DLAs of the wild-growing species —A. rhyticarpa andA. nudiflora — the high-molecular weight fraction is predominant, while for the DLA ofA. rosea the low-molecular-weight fraction is predominant.3. In a study of the products of nitrobenzene oxidation it has been established that the DLA of all three species ofAlthea includes p-coumaryl, guaiacyl, and syringyl structural units.4. In the products of decomposition with metallic sodium in liquid ammonia 18 phenols have been identified the structures of which show the presence in the initial lignins of guaiacyl- and syringylpropane units with free OH groups in the side chains in the - and -positions to the aromatic nucleus.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 93–100, January–February, 1977.     

PMR spectra of the dioxane lignins of some plants of the family Malvaceae

Analysis of PMR spectra of the dioxane lignins of three species ofAthea, of kenaf, and of the cotton plant has shown that the number of free aromatic protons does not correlate with the number of OCH₃ groups, which indicates different degrees of condensation of the dioxane lignins studied. In all the preparations a very small amount of coumarane structures were found. The aliphatic OH groups have been distinguished as primary (γ-OH) and secondary (α-OH) and their quantitative estimation has been carried out from the PMR spectra.     

PMR spectra of the lignins ofCystoseira barbata at different ages

The PMR spectra of the dioxane lignins from the brown algaCystoseira have been studied. It has been established that the lignins isolated from specimens ofCystoseira of different ages have different degrees of substitution of the C₃ side chain and differ in their degree of condensation. The most highly condensed is the dioxane lignin of young specimens ofCystoseira (age up to one year) and the least condensed the Björkman lignin ofCystoseira aged more than three years. All the PMR spectra of preparations of the lignin of the alga under investigation contain the signals of protons present in coumaran structures, their amount being the greatest in the lignins of the youngest samples and decreasing with increasing age of the alga.Odessa Institute of Structural Engineering. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 91–94, January–February, 1983.     

An investigation of the lignins of healthy and wilt-affected cotton plants of variety Tashkent-1 according to the vegetation periods

Summary 1. The dioxane lignins of healthy and wilt-affected cotton plants of variety Tashkent-1 have been isolated and have been studied comparatively in relation to the vegetation period. On the basis of elementary and functional analysis, semiempirical formulas of the dioxane lignins isolated (DLCT-I to -VII) have been determined and it has been established that the dioxane lignins isolated from the wilt-affected plants contain more OCH₃ groups per phenyl-propane structural unit than the lignins of healthy plants.2. The molecular-weight distributions of the dioxane lignins have been studied and it has been shown that all the dioxane lignins isolated are polydisperse, those of the affected plants to a greater degree.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 260–264, March–April, 1978.     

Lignin of the fine-fibered cotton plant of variety S-6030 affected by fusarial wilt. II

A comparative study of the products of cleavage by sodium in liquid ammonia of the dioxane lignins (DLAs) from healthy and fusarial-wilt-affected stems of the fine-fibered cotton plant of variety S-6030 and a study of the PMR spectra of both lignins has shown that the DLA from the healthy stems is more highly condensed than the DLA of the stems affected by wilt. The main structures of DNA wilt are of the guaiacyl type. In the DLA from the affected stems, the amount of p-coumaryl structures had increased, which confirms the demethylating action of fusarial wilt on cotton-plant lignin.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 364–366, May–June, 1986.     

Investigation of the dioxane lignin of the cotton plant

Summary 1. The dioxane lignins of the stems of cotton plants in the early vegetation period, DLA-I, and in the flowering period, DLA-II, have been investigated. Their developed semiempirical formulas have been established by elementary and functional-group analyses.2. The amounts of catechol structural units in cotton-plant dioxane lignins have been determined for the first time.3. The molecular-weight distribution of the dioxane lignins has been studied and it has been shown that they have high molecular weights (22,000–23,500).Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 80–83, January–February, 1976.     

An investigation of the fractional composition of dioxane lignin of the cotton plant by the PMR method

Analysis of the PMR spectra of six fractions of the dioxane lignins of the cotton plant differing considerably in molecular weight has confirmed their chemical nonidentity. It has been established that the low-molecular-weight fractions are less condensed than the high-molecular-weight fractions. It has been found that aliphatic OH groups are approximately evenly distributed between the - and -C atoms of the lignin side chain.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 116–120, January–February, 1980.     

Study of the lignin of cotton plants of the variety AN Bayaut-2. I

The dioxane lignin has been isolated from ripe stems of a cotton plant of the variety AN Bayaut-2. Its developed empirical formula has been derived, its UV, IR, and PMR spectra have been recorded, and its molecular weight has been determined. It has been shown that the dioxane lignins of the stems of cotton plants of different varieties differ in chemical structure.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 101–104, January–February, 1986.     

Change in the structural elements of cotton-plant lignins in the various vegetation periods

Summary 1. The dioxane lignins of the cottonplant of various vegetation periods have been studied, and it has been shown that the lignin changes in the course of the development of the plant: the amount of methoxy groups increases and the amount of phenolic hydroxy groups decreases.2. Gel chromatography of the lignins has shown that they are all polydisperse with a predominance of the high-molecular-weight fraction.3. The 3,4-diethoxybenzaldehyde detected in the products of the alkaline nitrobenzene oxidation of dioxane lignin of the early vegetation period after its ethylation with diethyl sulfate is a direct proof of the presence of catechol structural units in cotton-plant lignin.4. A quantitative determination of the catechol structures in the lignins of the cottonplant has shown that their amount decreases as the plant develops.5. By decomposing the lignins with sodium and liquid ammonia, the presence in them of guaiacyl, syringyl, and p-coumaryl structural units has been confirmed and it has been shown that the lignin becomes less condensed as the plant grows, which is apparently connected with an increase in the degree of its methoxylation.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 100–107, January–February, 1977.     

Quantitative1H and13C 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.Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 798–808, November–December, 1994.     

The lignin of the sea island cotton plant of variety S-6030 affected by fusarial wilt. I

A comparative study of the dioxane lignins isolated from healthy and wilt-affected cotton plant stems has shown thatFusarium fungi demethylate lignin and make it more oxidized than the lignin from healthy stems.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 825–827, November–December, 1985.     

The lignin of the sea island cotton plant of variety S-6030 affected by fusarial wilt. I

A comparative study of the dioxane lignins isolated from healthy and wilt-affected cotton plant stems has shown thatFusarium fungi demethylate lignin and make it more oxidized than the lignin from healthy stems.     

Reductive cleavage by metallic sodium in liquid ammonia of cotton lignin

Twofold cleavage with sodium in liquid ammonia of the dioxane lignin and fourfold cleavage of the native lignin from cotton stems have shown that the uncleaved parts of lignin have molecular masses 2–4 times lower than the initial lignins and consist of 15–17 phenylpropane structural units.Institute of the Chemistry of Plant Substances, Uzbek SSR Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 412–416, May–June, 1989.     

Kerr constants of some nitrogen-containing heterocycles

The molecular Kerr constants [ (mK₂)] were measured for pyridine, 2- and 4-methylpyridines, quinoline, and acridine in dioxane. The molecular moments of pyridine and 4-methylpyridine are directed along the axis of maximum polarizability. The B = B₁₂—B₁ values for dilute solutions of azaaromatic compounds in dioxane are proportional to T^–2.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 974–976, July, 1971.     

Destruction of aspen wood by the fungusPhanerochaete sanguinea quantitative1H and13C NMR spectroscopies of biologically degraded lignin

The lignin of mechanically ground aspen wood and lignins isolated from aspen wood attacked by the fungusPhanerochaete sanguinea have been investigated by quantitative¹H and¹³C NMR spectroscopies. It has been shown that the biodestruction of the lignin takes place through the cleavage of alkyl-aryl and aryl-aryl bonds and is accompanied by demethylation (demethoxylation) reactions, and the oxidation of C and C atoms. In addition to reactions in which the C—C bonds are cleaved, the formation of ether bonds has been observed. An interconnection has been shown between the variations in the amount of functional groups, fragments, and the bonds in biolignins and the loss in mass of the wood. A method is proposed for evaluating the carbohydrate content in lignin preparations using the NMR method.Wood Chemistry Branch of the Institute of Organic Chemistry, Siberian Division of the Russian Academy of Sciences, Irkutsk. Irkutsk State University. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 547–557, July–August, 1994.     

Determination of the regime in the reverse wilson chamber at critical supersaturation measurements

The pressure in the Reverse Wilson Chamber (RWC) was directly measured at different rates of compression of the gas mixture. It was shown that at compression time in the range from 0.06 to 0.3 s an intermediate, between adiabatic and isothermal, process took place in the chamber. To obtain the relative pressure increase P _m /P _at from the values of the relative gas compression V/V, a calibration of the experimental set-up was carried out. The calibration showed that the values of critical supersaturationSc for water condensation on hexadecane, estimated for intermediate regime of the gas compression, were reduced with respect to the values calculated when the adiabatic regime was assumed. This fact confirmed the conclusions made earlier [1–3] that the classical theory was not applicable in this case of heterogeneous phase formation and that the line tension < 0 should be taken into account. Moreover, in an atmosphere of very pure argon (instead of room air [1–3]) the critical supersaturation turned out to be independent of the initial state of undersaturationS _o . The more accurate values obtained for condensation of water on hexadecane were: lnS _c =0.204 (instead of the maximum value obtained earlier: lnS _c =0.26) and=–1.9×10^–5 dyne (instead of=–1.5×10^–5 dyne).     

Ritter reactions. VIII. Inclusion compounds formed betweenN-(5H-Dibenzo[a,d]cycloheptyl)acetamides and dioxane

5H-Dibenzo[a, d]cyclohepten-5-ol2 and its saturated analogue4 undergo Ritter reactions with acetonitrile and sulfuric acid to afford the acetamide derivatives3 or5 respectively. Both products form unstable inclusion compounds when crystallised from dioxane. The crystal structure of the dioxane compound of3 is reported. This material [(C₁₇H₁₅NO)·(C₄H₈O₂)₂,Pnma,a=9.616(1),b=23.280(2),c=10.298(1) Å,Z=4,R=0.054] has the amide molecules arranged in parallel chains by means of intermolecular –N–HO=C hydrogen bonds. The inclusion compound is stabilised by means of –C–HO-hydrogen bonds. Each dioxane molecule is involved in five such interactions to neighbouring molecules of3 and dioxane.Author for correspondence. Supplementary Data relating to this article are deposited with the British Library as supplementary publication No. SUP 82173 (5 pages).     

Isolation of individual fractions of dioxane lignin from kenaf stems and their study

Summary 1. Three fractions of dioxane lignin have been isolated from kenaf stems of the variety Uzbekskii-15-74 by stepwise extraction with aqueous dioxane containing HCl.2. On the basis of the results of elementary and functional analyses, semiempirical formulas of all the fractions have been derived, and their IR and UV spectra have been recorded.3. It has been shown that an increase in the time of extraction leads to a rise in the molecular weight of the fractions and to a decrease in their degree of polydispersity.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 637–641, September–October, 1978.     

Kinetics and mechanism of bromination of cyclic acetals with 1,4-dioxane dibromide

It is shown that the reactivities of cyclic formals in the case of bromination with dioxane dibromide increase in the order 1,3-dioxepane > 1,3-dioxalane 1,3-dioxane, which is explained not only by steric factors but also by the ease of cleavage of the C₄-O₃ bond of the dioxacyclane ring. The bromination of cyclic acetals takes place through prior enolization of the cyclic acetal with subsequent electrophilic addition of bromine to the double bond.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 176–179, February, 1981.