Sulfation of Microcrystalline Cellulose with Sulfamic Acid in N,N-Dimethylformamide and Diglyme

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Journal of Siberian Federal University. Chemistry 2 (2014 7) 162-169 ~ ~ ~

УДК 54.05

Sulfation of Microcrystalline Cellulose with Sulfamic Acid in N,N-Dimethylformamide and Diglyme

Vladimir A. Levdanskya,b, Alexandr S. Kondracenkoa, Alexandr V. Levdanskya, Boris N. Kuznetsova,b*, Laurent Djakovitchc and Catherine Pinelc aInstitute of Chemistry and Chemical Technology SB RAS 50-24 Academgorodok, Krasnoyarsk, 660036, Russia bSiberian Federal University 79 Svobodny, Krasnoyarsk, 660041, Russia cIRCELYON 2 avenue Albert Einstein F-69626 Villeurbanne Cedex, Lyon, France

Received 18.01.2014, received in revised form 21.02.2014, accepted 04.04.2014 Sulfation of MCC by sulfamic acid in DMF or diglyme in the presence of urea was studied for the first time. It was established, that the degree of substitution in sulfated MCC was in the range from 1.40 to 1.54. It was shown, that the most effective sulfation of MCC takes place in diglyme. The yield of cellulose sulfate at sulfation MCC in diglyme was 2.5 times higher than the yield for sulfation MCC in N,N-dimethylformamide

Keywords: microcrystalline cellulose, sulfation, sulfamic acid, urea, N,N-dimethylformamide, diglyme, microcrystalline cellulose sulfates.

Introduction Cellulose sulfates (CS) have a rather wide area of application. Sodium salt of cellulose sulfate is used in the process of fabrics dyeing, as the stabilizer of clay suspensions for drilling oil wells, thickeners, sorbent, ion-exchange material, as a base for cosmetics and perfumes, etc. [1]. Cellulose sulfates possess anticoagulant properties and can be used for prevention and treatment of thromboses. Anticoagulant activity of the CS depends on the degree of substitution and its molecular weight [2, 3]. For sulfation of cellulose various etherifying mixtures on the base of sulfuric acid with aliphatic

© Siberian Federal University. All rights reserved * Corresponding author E-mail address: [email protected] – 162 – Vladimir A. Levdansky, Alexandr S. Kondracenko… Sulfation of Microcrystalline Cellulose with Sulfamic Acid… alcohols are used [1]. Another known group of methods is based on cellulose sulfation by sulfur trioxide in N,N-dimethylformamide (DMF), pyridine, or in the presence of tertiary amines. In [3, 4] cellulose sulfation by chlorosulfonic acid in liquid sulfur dioxide, dichloroethane, acetic anhydride, DMF and pyridine was studied. Sulfation of microcrystalline cellulose (MCC) by chlorosulfonic acid in dioxane was also studied [5]. Sulfur trioxide, sulfuric and chlorosulfonic acid which are widely used in the sulfation reactions are quite aggressive reagents, and ecology dangerous the use of which requires special equipment that causes technical difficulties. In contrast to the above reagents, the sulfamic acid is a stable, non- hygroscopic crystalline solid. Its acidity is comparable with sulfuric acid. Sulfamic acid is commercially produced by urea interaction with an oleum. In [6] was reported that cellulose is degraded at heating with sulfamic acid, but in the presence of urea, which plays the role of basic catalyst, sulfation occurs more satisfactorily. The sulfation of cellulose which has been previously impregnated with a solution of urea and sulfamic acid in DMF, proceeds more easily [7]. In the present study, for the first time the sulfation of microcrystalline cellulose by sulfamic acid in DMF and dimethyl ether of diethyleneglycol (diglyme) in the presence of urea was investigated.

Experimental MCC Vivapur ® Type 101 from JRS Pharma (Weissenborn, Germany) with an average degree of polymerization (DP) 350, crystallinity index 0,75, and a hemicellulose content of 5.2 % wt. was used as the starting material. X-ray diffraction scattering analysis was carried out with DRON-3 diffractometer using Cu-Kα source (λ=0,154 nm) in the 2θ range 5–50°. FTIR analysis was carried out in transmission mode. The mass of sample in matrix KBr was 2 mg. The spectra were recorded with Tensor-27 spectrometer (Bruker, Germany) in range 400-4000 cm-1. Spectral data were processed by program OPUS/YR (version 5.02). NMR 13C spectra were recorded at temperature 25 °C with spectrometer Bruker Avance III 600

MHz using D2O as reference. Sulfation of MCC in N,N- dimethylformamide MCC (1.62 g), urea (1.80 g), sulfamic acid (3.40 g) and DMF (40 ml) were placed in a three necked flask (100 ml) equipped with stirrer, thermometer and reflux. The mixture was then boiled on oil bath at vigorous stirring for 1 hour. After that, the reaction mixture was cooled to 15-20 °C, poured into 50 ml of 75 % water-ethanol solution containing 3-4 % sodium hydroxide and stirred until the extinction of ammonia ceasing. The resulting sodium salt of MCC sulfate was separated by filtration, washed with 96 % ethanol, and dried under vacuum. The obtained product was then dissolved in 50-60 ml distilled water, filtered and dialyzed on cellophane against distilled water. After dialysis the aqueous solution of NaCS was concentrated under vacuum until complete removal of water. Yield of sodium salt of MCC sulfate was 0,26 г. Sulfation of MCC in diglyme MCC (1.62 g), urea (1.80 g), sulfamic acid (3.40 g) and diglyme (40 ml) were placed in a three necked flask (100 ml) equipped with stirrer, thermometer and reflux. The procedure of synthesis was the same as in the case of MCC sulfation in N,N-dimethylformamide. Yield of sodium salt of MCC sulfate was 0,98 г. – 163 –

product was then dissolved in 50-60 ml distilled water, filtered and dialyzed on cellophane against distilled water. After dialysis the aqueous solution of NaCS was concentrated under vacuum until complete removal of water. Yield of sodium salt of MCC sulfate was 0,26 г. Sulfation of MCC in diglyme MCC (1.62 g), urea (1.80 g), sulfamic acid (3.40 g) and diglyme (40 ml) were placed in a three necked flask (100 ml) equipped with stirrer, thermometer and reflux. The procedure of synthesis was the same as in the case of MCC sulfation in N,N-dimethylformamide. Yield of sodium salt of MCC sulfate was 0,98 г. MCC sulfate inVladimir the form A. Levdansky, of the ammonium Alexandr S. Kondracenko…salt was prepared Sulfation by of Microcrystallinediluting the reaction Cellulose with Sulfamic Acid… mixture with 70 % ethanol. MCC sulfate in the form of potassium salt was prepared by diluting MCC sulfate in the form of the ammonium salt was prepared by diluting the reaction mixture with the reaction mixture with 75 % water-ethanol solution containing 3-4 % potassium hydroxide. 70 % ethanol. MCC sulfate in the form of potassium salt was prepared by diluting the reaction mixture The sulfur contentwith 75 in% MCCwater-ethanol sulfates solutionwas defined containing by modified 3-4 % potassiummethod [8] hydroxide. (by burning in oxygen stream with the Thesubsequent sulfur content absorption in MCC of products sulfates of was burning defined by hydrogenby modified peroxide method and [8] (by burning in oxygen titration by alkali instream the presencewith the subsequent of the indicator absorption of the of met productshyl red). of burning The average by hydrogen degree peroxide of and titration by substitution (DS) ofalkali MCC in sulfates the presence was calculated of the indicator from the of sulfurthe methyl content red). according The average to a formuladegree of substitution (DS) of MCC sulfates was calculated from the sulfur content according to a formula [4]: [4]: 162×ω DS = S 3200 −103×ωS

где ωS – sulfur content (wt. %). где ωS – sulfur content (wt. %). Results and discussion It is known Results[6] that the and reaction discussion of sulfamic acid with alcohols under heating gives the corresponding ammonium salt with yield about of 22 % wt, according to scheme: It is known [6] that the reaction of sulfamic acid with alcohols under heating gives the corresponding ammonium salt with yieldR–OH about + NH of2 SO223 %H →wt, R–OSO according3NH to4 scheme:

However, yield of the salt can be increased to 70 % by the addition of pyridine to the reaction

mixture. TheR–OH catalytic + NH activity2SO3H of → pyridine, R–OSO 3urea,NH4 thiourea, acetamide and picoline was compared in the process of sulfation of higher aliphatic alcohols and the most effective catalyst was urea. The higher However, yieldcatalytic of the activity salt can of be urea increased compared to to70 other% by additives the addition has alsoof pyridine been shown to the for sulfation of starch, cellulose and other polysaccharides [6]. This was the basis for the use of urea in the sulfation of MCC reaction mixture. The catalytic activity of pyridine, urea, thiourea, acetamide and picoline was with sulfamic acid. The mechanism of esterification by sulfamic acid in the presence of urea was compared in the processexplained of sulfation by formation of higher of a donor-acceptoraliphatic alcohols complex and the (I), most which effective has high catalyst reactivity to sulfation [9]: was urea. The higher catalytic activity of urea compared to other additives has also been shown δ1 O δ1 O for sulfation of starch, cellulose and other polysaccharides [6]. This was the basis++δ1 for theO δ use2 of O NH2SO3H+ NH2CONH2 H3N S++δ1NH2 Cδ2 NH2 + urea in the sulfation of MCC with sulfamicNH2SO 3acid.H The NH 2mechanismCONH2 of esterificationOOH3N by SsulfamicNH2 C NH2 δ2 OOδ3 δ2 δ3 I acid in the presence of urea was explained by formation of a donor-acceptor complex (I), which I has high reactivity to sulfation [9]: ReactionReaction of cellulose of cellulose sulfation sulfation by sulfamic by sulfamic acid inacid the in presence the presen ofce urea of urea was wascarried carried out outin boiling in Reaction of cellulose sulfation by sulfamic acid in the presence of3 urea was carried out in solventboiling at vigorous solvent atstirring. vigorous Cellulose stirring. sulfatesCellulose were sulfates isolated were in isolat the formed in ofthe ammonium, form of ammonium, sodium, and potassium salts (Fig. 1). sodium,boiling and solvent potassium at vigorous salts (Fig. stirring. 1). Cellulose sulfates were isolated in the form of ammonium, sodium, and potassium salts (Fig. 1).

OH NH2SO3H OSO3NH4 NaOH OH OR1 O HO (NH2)2CO O R1O (KOH) O OH O NH2SO3H O OSO3NH4 O NaOH HO O OH R O O OR1 O HO O 1. DMF(NH2)2CO 1 O R O O (KOH) O OH O OR 1 O O 2. Digly me 1 O O HO OH O 1. DMF R1O OR1 O OH 2. Digly me OR1 OSO3OHNa(K) OR1 OR2 R1 = H, SO3NH4 O O R2O OSO Na(K) O R2 = H, SO3Na(K) R O 3O OR 2 O 2 R = H, SO NH OR O R2O 1 3 4 O 2 O O OR2 R2 = H, SO3Na(K) R2O O Fig. 1. Scheme of MCC sulfationOR2 with sulfamic acid Fig. 1. Scheme of MCC sulfation with sulfamicOR acid2 Fig. 1. Scheme of MCC sulfation with sulfamic– 164 –acid It was established that the reaction of sulfation of MCC by sulfamic acid in the presence of urea in DMF or diglyme proceeds in a heterogeneous medium. Influence of reaction time on It was established that the reaction of sulfation of MCC by sulfamic acid in the presence the yield of cellulose sulfates, the sulfur content and the degree of substitution are shown in the of urea in DMF or diglyme proceeds in a heterogeneous medium. Influence of reaction time on Tables 1 and 2. the yield of cellulose sulfates, the sulfur content and the degree of substitution are shown in the

Tables 1 and 2. Table 1. Sulfation of MCC by sulfamic acid in boiling DMF

Sample № Reaction time, h MCC sulfate yield, g Sulfur content, % DS Table1 1. Sulfation of 1,0MCC by sulfamic acid0,26 in boiling DMF 13,58 1,22 Sample2 № Reaction2,0 time, h MCC0,51 sulfate yield, g Sulfur14,76 content, % 1,42 DS 3 3,0 0,64 13,35 1,19 1 1,0 0,26 13,58 1,22 4 4,0 0,63 12,47 1,05 2 2,0 0,51 14,76 1,42

3 3,0 0,64 13,35 1,19 Table 2.4 Sulfation of MCC4,0 by sulfamic acid in boiling0,63 diglyme 12,47 1,05 Sample № Reaction time, h MCC sulfate yield, g Sulfur content, % DS Table1 2. Sulfation of 1,0MCC by sulfamic acid0,98 in boiling diglyme 14,00 1,29 2 1,5 1,13 14,42 1,36 Sample3 № Reaction2,0 time, h MCC1,27 sulfate yield, g Sulfur15,17 content, % 1,50 DS 4 1 2,51,0 1,640,98 15,4114,00 1,55 1,29 5 2 3,01,5 1,431,13 14,6414,42 1,40 1,36 3 2,0 1,27 15,17 1,50 4 2,5 1,64 15,41 1,554 5 3,0 1,43 14,64 1,40

4 Vladimir A. Levdansky, Alexandr S. Kondracenko… Sulfation of Microcrystalline Cellulose with Sulfamic Acid…

It was established that the reaction of sulfation of MCC by sulfamic acid in the presence of urea in DMF or diglyme proceeds in a heterogeneous medium. Influence of reaction time on the yield of cellulose sulfates, the sulfur content and the degree of substitution are shown in the Tables 1 and 2. According to the obtained results, the maximum yield of CS was 0.5-0.6 g at sulfation MCC in DMF for 2-3 hours. The sulfur content in the MCC sulfates was 13,6-14,8 %, which corresponds to the degree of substitution of 1,2-1,4 (Table 1). Prolongation of the reaction time more than 3 h resulted in a darkening and decomposition of the reaction mixture, the yield of NaCS also was decreased. Sulfation of MCC in diglyme for 2,0-2,5 h allowed to obtain NaCS with an yield to 1,6 g and a sulfur content of 15.4 %, which corresponds to a degree of substitution 1,4-1,5 (Table 2). It has been found that at the same reaction time in spite of on the higher boiling point of diglyme (161 °C) as compared to DMF (152 °C), the sulfation of cellulose in diglyme proceeds easier and results in less cellulose degradation than in DMF. The use of diglyme for sulfation allowed to increase the yield of cellulose sulfate by 2.5 times in comparison with DMF. The increase of temperature of cellulose sulfation reduces the degree of cellulose polymerization regardless of the used method of sulfation [1, 4]. The comparison of XRD patterns of initial MCC and MCC sulfated by sulfamic acid in DMF or diglyme testifies of the disordering of cellulose crystalline structure during sulfation process (Fig. 1). IR spectra of sulfated MCC (Fig. 4-5) are differ from IR spectrum of the initial MCC (Fig. 3) by the presence of strong absorption bands at 800-805 cm-1 (C–O–S) and 1236-1245 cm-1 (O=S=O), confirming the introduction of sulfate groups in the structure of cellulose. It is known [3], that the hydroxyl group at C6 primary carbon atom is predominantly sulfated in a glucopyranose unit of cellulose. The hydroxyl group connected with carbon atom C2 is replaced

Table 1. Sulfation of MCC by sulfamic acid in boiling DMF

Sample № Reaction time, h MCC sulfate yield, g Sulfur content, % DS 1 1,0 0,26 13,58 1,22 2 2,0 0,51 14,76 1,42 3 3,0 0,64 13,35 1,19 4 4,0 0,63 12,47 1,05

Table 2. Sulfation of MCC by sulfamic acid in boiling diglyme

Sample № Reaction time, h MCC sulfate yield, g Sulfur content, % DS 1 1,0 0,98 14,00 1,29 2 1,5 1,13 14,42 1,36 3 2,0 1,27 15,17 1,50 4 2,5 1,64 15,41 1,55 5 3,0 1,43 14,64 1,40

– 165 –

According to the obtained results, the maximum yield of CS was 0.5-0.6 g at sulfation MCC in DMF for 2-3 hours. The sulfur content in the MCC sulfates was 13,6-14,8 %, which corresponds to the degree of substitution of 1,2-1,4 (Table 1). Prolongation of the reaction time more than 3 h resulted in a darkening and decomposition of the reaction mixture, the yield of NaCS also was decreased. Sulfation of MCC in diglyme for 2,0-2,5 h allowed to obtain NaCS with an yield to 1,6 g and a sulfur content of 15.4 %, which corresponds to a degree of substitution 1,4-1,5 (Table 2). It has been found that at the same reaction time in spite of on the higher boiling point of diglyme (161 °C) as compared to DMF (152 °C), the sulfation of cellulose in diglyme proceeds easier and results in less cellulose degradation than in DMF. The use of diglyme for sulfation allowed to increase the yield of cellulose sulfate by 2.5 times in comparison with DMF. The increase of temperature of cellulose sulfation reduces the degree of cellulose polymerization regardless of the used method of sulfation [1, 4]. The comparison of XRD patterns of initial MCC and MCC sulfated by sulfamic acid in DMF or diglyme testifies of the disordering of cellulose crystalline structure during sulfation process (Fig. 1).

Fig. 2. XRD pattern of initial MCC (a) and sulfated MCC (b) Fig. 2. XRD pattern of initial MCC (a) and sulfated MCC (b)

IR spectra of sulfated MCC (Fig. 4-5) are differ from IR spectrum of the initial MCC (Fig. 3) by the presence of strong absorption bands at 800-805 cm-1 (C–O–S) and 1236-1245 cm- 1 (O=S=O), confirming the introduction of sulfate groups in the structure of cellulose.

Fig. 3. FTIR spectrum of initial MCC Fig. 3. FTIR spectrum of initial MCC Fig. 3. FTIR spectrum of initial MCC

Fig. 4. FTIR spectra of MCC sulfated in DMF: 1 – Fig.1 h., 4. 2 FTIR – 2 h., spectra 3 – 3 h., of 4 – MCC4 h sulfated in DMF: 1 – 1 h., 2 – 2 h., 3 – 3 h., 4 – 4 h Fig. 4. FTIR spectra of MCC sulfated in DMF: 1 – 1 h., 2 – 2 h., 3 – 3 h., 4 – 4 h

Fig. 5. FTIR spectra of Fig.MCC 5. FTIR sulfated spectra in diglyme: of MCC1 – sulfated1,0 h., in2 – diglyme: 1,5 h., 3 – 1 –2,0 1,0 h., h., 4 2– –2,5 1,5 h h., 3 – 2,0 h., 4 – 2,5 h

It is known [3], that the hydroxyl group at C6 primary carbon atom is predominantly It is known [3], that the hydroxyl group at C6 primary carbon atom is predominantly sulfated in a glucopyranose unit of cellulose. The hydroxyl group connected with carbon atom sulfated in a glucopyranose unit of cellulose. The hydroxyl group connected with carbon atom C2 is replaced with difficulty. The hydroxyl group at C3 carbon atom is replaced only under hard C2 is replaced with difficulty. The hydroxyl group at C3 carbon atom is replaced only under hard conditions, which leads to a high depolymerization of cellulose [3]. According to 13C NMR [3, conditions, which leads to a high depolymerization of cellulose [3]. According to 13C NMR [3, 10]10] the the chemical chemical shifts shifts corr correspondingesponding to to carbon carbon atoms atoms C1 C1 - C6 - C6 in in glucopyranose glucopyranose units units of of cellulosecellulose are are observed observed at at 102, 102, 74, 73, 79, 79, 77 77 a andnd 66 66 ppm, ppm, respectively. respectively. The The introduction introduction of of sulfatesulfate groups groups to to MCC MCC affected affected the chemical shifts shifts of of carbon carbon atoms atoms to tolower lower magnetic magnetic field. field.

6 6

Fig. 3. FTIR spectrum of initial MCC

Fig. 4. FTIR spectra of MCC sulfated in DMF: 1 –

Vladimir A. Levdansky, Alexandr S. Kondracenko… Sulfation of Microcrystalline Cellulose with Sulfamic Acid…1 h., 2 – 2 h., 3 – 3 h., 4 – 4 h

Studying of 13C NMR spectrum of the obtained cellulose sulfates (Fig. 6) showed that the signal of carbon atom C6 completely moved to 66 ppm. It means that all of the hydroxyl groups Fig. 5. FTIR spectra of at carbon atoms C6 were substituted on sulfate groups. Appearance of a signal of the carbon MCC sulfated in diglyme: atom C2 in the field of 80-82 ppm indicates that the hydroxyl groups at the C2 sulfated partially. 1 – 1,0 h., 2 – 1,5 h., 3 – Similar results were reported by the authors of work [3], in which MCC was sulfated by 2,0 h., 4 – 2,5 h

Fig. 5. FTIRchlorosulfonic spectra of acidMCC in sulfated DMF. Noin diglyme:shift of a1 signal– 1,0 h., of 2atom – 1,5 C3 h., was3 – 2,0observed. h., 4 – 2,5This h indicates the absence of sulfateIt is group known at C3 [3],atom at that sulfated the MCC. hydroxyl group at C6 primary carbon atom is predominantly

sulfated in a glucopyranose unit of cellulose. The hydroxyl group connected with carbon atom a b

C2 is replaced with difficulty. The hydroxyl group at C3 carbon atom is replaced only under hard conditions, which leads to a high depolymerization of cellulose [3]. According to 13C NMR [3, 10] the chemical shifts corresponding to carbon atoms C1 - C6 in glucopyranose units of cellulose are observed at 102, 74, 73, 79, 77 and 66 ppm, respectively. The introduction of sulfate groups to MCC affected the chemical shifts of carbon atoms to lower magnetic field.

Рис. 6. 13C NMR spectra of MCC sulfated in DMF (a) and in diglyme (b) Рис. 6. 13C NMR spectra of MCC sulfated in DMF (a) and in diglyme (b) 6

Conclusions with difficulty.Sulfation The hydroxyl of MCC group by sulfamic at C3 acidcarbon in DMFatom isor replaced diglyme inonly the under presence hard of conditions, urea was which leads tostudied a high at depolymerization the first time. It was of cellulose established, [3]. th atAccording the degree to of 13 C substitution NMR [3, of10] sulfated the chemical MCC shifts correspondingreaches to to 1.40-1.54. carbon atoms The most C1 –effective C6 in glucopyranosesulfation of MCC units takes of place cellulose in diglyme. are observed The yield at of 102, 74, 73, 79, MCC77 and sulfate 66 ppm, prepared respectively. in diglyme The wasintroduction by 2.5 times of sulfate higher groups than the to yieldMCC of affected MCC sulfate the chemical shifts ofobtained carbon in atoms N,N-dimethylformamide to lower magnetic field. Studying of 13C NMR spectrum of the obtained cellulose sulfates (Fig. 6) showed that the signal of carbon atom C6 completely moved toAcknowledgments 66 ppm. It means that all of the hydroxyl groups at carbon atoms C6 were substituted on sulfate groups. Appearance of a signal of the carbon atom C2 in the The reported study was partially supported by RFBR, research projects No 12-03-93117 field of 80-82 ppm indicates that the hydroxyl groups at the C2 sulfated partially. Similar results and No 12-03-31433. This work is part of the GDRI “Сatalytic biomass valorization” between were reported by the authors of work [3], in which MCC was sulfated by chlorosulfonic acid in DMF. France and Russia. In this work devices of the Krasnoyarsk regional center of collective using of No shift of a signal of atom C3 was observed. This indicates the absence of sulfate group at C3 atom the Siberian Branch of the Russian Academy of Science were used. at sulfated MCC.

– 167 – References

7 Vladimir A. Levdansky, Alexandr S. Kondracenko… Sulfation of Microcrystalline Cellulose with Sulfamic Acid…

Conclusions Sulfation of MCC by sulfamic acid in DMF or diglyme in the presence of urea was studied at the first time. It was established, that the degree of substitution of sulfated MCC reaches to 1.40-1.54. The most effective sulfation of MCC takes place in diglyme. The yield of MCC sulfate prepared in diglyme was by 2.5 times higher than the yield of MCC sulfate obtained in N,N-dimethylformamide

Acknowledgments The reported study was partially supported by RFBR, research projects No 12-03-93117 and No 12-03-31433. This work is part of the GDRI “Сatalytic biomass valorization” between France and Russia. In this work devices of the Krasnoyarsk regional center of collective using of the Siberian Branch of the Russian Academy of Science were used.

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Сульфатирование микрокристаллической целлюлозы сульфаминовой кислотой в N,N-диметилформамиде и диглиме

В.А. Левданскийа,б, А.С. Кондрасенкоа, А.В. Левданскийа, Б.Н. Кузнецова,б, Л. Дьяковичв, К. Пинельв аИнститут химии и химической технологии СО РАН Россия, 660036, Красноярск, Академгородок, 50-24 бСибирский федеральный университет Россия, 660041, Красноярск, пр. Свободный, 79 вIRCELYON 2 avenue Albert Einstein, F-69626 Villeurbanne Cedex, Lyon, France

Изучено сульфатирование МКЦ сульфаминовой кислотой в присутствии мочевины в ДМФА и диглиме. Установлено, что степень замещения серы в полученных сульфатах МКЦ составляет от 1,40 до 1,54. Показано, что наиболее эффективно происходит сульфатирование МКЦ в диглиме, при этом выход сульфата МКЦ возрастает в 2,5 раза по сравнению с сульфатированием МКЦ в N,N-диметилформамиде.

Ключевые слова: микрокристаллическая целлюлоза, сульфатирование, сульфаминовая кислота, мочевина, N,N-диметилформамид, диглим, сульфат микрокристаллической целлюлозы.