DETERMINATION OF CHEMICAL STRUCTURE OF METHYL HYDROXYETHYLCELLULOSE BY 13C NMR SPECTROSCOPY
Abstract
This paper discusses the determination of the structural parameters of methyl hydroxyethylcellulose (MHEC) by 13C NMR spectroscopy. Four samples of methyl hydroxyethylcellulose (MHEC, DS ~ 1.7) of different viscosity aqueous solutions were analyzed to determine the distribution of methyl and hydroxyethyl groups in different positions of the anhydroglucose unit of the polymer chain. For this purpose, MHEC samples were subjected to acid-catalyzed hydrolysis in the presence of sulfuric acid. Optimal conditions for complete hydrolysis leading to methyl and hydroxyethyl substituted D-glucose derivatives were determined. The structure of the hydrolysis products was studied by 13С NMR spectroscopy. The assignment of carbon atom signals in the 13С NMR spectra was made based on chemical shifts calculated using BIOPSEL program. Analysis of the integrated intensities of the C-atom groups of the products of hydrolysis allowed us to determine the distribution of substituents in the anhydroglucose unit. The values of the degree of substitution in 2, 3 and 6 positions (DSC-2, DSC-3 и DSC-6) are calculated, the number of methoxyl (DSMe) and hydroxyethoxyl (DSHE) groups is determined, the total degree of substitution (DStotal) is calculated. The distribution of substituents in different positions of the glucopyranose unit indicates the highest reactivity of 2 and 6 positions, as well as hydroxyl in the hydroxyethyl group. In this paper, the degree of substitution in four different MHEC samples with known DS values is determined. Comparative analysis of the results obtained with the data specified by the manufacturer confirms the high accuracy of the considered method. The proposed method for determining the chemical structure of MHEC is informative since the method allows determining the distribution of substituents for different positions of the anhydroglucose unit and the degree of substitution of each substituent.
References
Kryazhev V.N., Shirokov V.A. Condition of production of cellulose ethers. Khim. Rast. Syrya. 2005. N 3. Р. 7-12 (in Russian).
Vasilik P.G., Golubev I.V. The review of modern cellulose ethers of the trade mark Mecellose for cement-based tile adhesives. Sukh. Stroit. Mat. 2012. N 1. P. 18-21 (in Russian).
Chernykh T.N., Trofimov B.Ya., Kramar L.Ya. Effect of cellulose ethers on the properties of solution mixtures and solutions. Stroit. Mat. 2004. N 4. P. 42-43 (in Russian).
Estemesov Z.A., Vasilchenko N.A., Sultanbekov T.K., Shayakhmetov G.Z. Effect of Tyloza on the processes of cement hydration. Stroit. Mat. 2000. N 7. P. 10-11 (in Russian).
Baumann R., Charlemann S., Noebauer J. Influence of cellulose ethers on the properties of cement plaster mixtures. Alitinform: Tse-ment. Beton. Sukhie Smesi. 2010. N 4-5. P. 80-88 (in Russian).
Khayat K.H. Viscosity-enhancing admixtures for cement-based materials – An overview. Cement Concrete Comp. 1998. V. 20. N 2-3. P. 171-188. DOI: 10.1016/S0958-9465(98)80006-1.
Balan A., Moise A., Grigoriu A. A comparative rheological study of several colloidal systems based on cellulose derivatives. Cellulose Chem. Technol. Cellulose. 2010. V. 44. N 7-8. Р. 231-238.
Mischnick P., Momcilovic D. Chemical Structure Analysis of Starch and Cellulose Derivatives. Adv. Carbohyd. Chem. Biochem. 2010. V. 64. P. 117-210. DOI: 10.1016/S0065-2318(10)64004-8.
Li H., Chai X.-S., Zhan H., Liu M., Fu S. A Novel Method for Determination of Ethoxyl Content in Ethyl Cellulose by Headspace Gas Chromatography. Anal. Lett. 2012. V. 45. N 9. P. 1028-1035. DOI: 10.1080/00032719.2012.670783.
Adden R., Müller R., Mischnick P. Analysis of the substituent distribution in the glucosyl units and along the polymer chain of hydroxypropylmethyl celluloses and statistical evaluation. Cellulose. 2006. V. 13. N 4. P. 459-476. DOI: 10.1007/s10570-005-9028-x.
Mischnick P., Unterieser I., Voiges K., Cuers J., Rinken M., Adden R. A new method for the analysis of the substitution pattern of hydroxyethyl(methyl)-celluloses along the polysaccharide chain. Macromolec. Chem. Phys. 2013. V. 214. N 12. P. 1363-1374. DOI: 10.1002/macp.201300070.
Cuers J.A., Rinken M.B., Adden R.C., Mischnick P. Critical investigation of the substituent distribution in the polymer chains of hydroxypropyl methylcelluloses by (LC-)ESI-MS. Analyt. Bioanalyt. Chem. 2013. V. 405. N 28. P. 9021-9032. DOI: 10.1007/s00216-013-7065-0.
Adden R., Niedner W., Müller R., Mischnick P. Com-prehensive analysis of the substituent distribution in the glucosyl units and along the polymer chain of hydroxyethylmethyl celluloses and statistical evaluation. Analyt. Chem. 2006. V. 78. N 4. P. 1146-1157. DOI: 10.1021/ac051484q.
Parfondry A., Perlin A.S. 13C-n.m.r. spectroscopy of cellulose еthers. Carbohyd. Res. 1977. V. 57. P. 39-49. DOI: 10.1016/S0008-6215(00)81918-7.
Nehls I., Wagenknecht W., Philipp B., Stscherbina D. Characterization of cellulose and cellulose derivatives in solution by high resolution 13C-NMR spectroscopy. Pro-gress Polymer Sci. 1994. V. 19. N 1. P. 29-78. DOI: 10.1016/0079-6700(94)90037-X.
Sachinvala N.N.D., Winsor D.L., Niemczura W.P., Maskos K., Vigo T.L., Bertoniere N.R. Synthesis, phys-ical, and NMR characteristics of Di- and Tri-Substituted cellulose ethers. ACS Symp. Ser. 2002. V. 834. P. 306-324.
Kunze J., Ebert A., Fink H.P. Characterization of cellulose and cellulose ethers by means of 13C NMR spectroscopy. Cellulose Chem. Technol. 2000. V. 34. N 1-2. P. 21-34.
Brogly M., Fahs A., Bistac S. Determination of the chemical structure of cellulosebased biopolymers. ARPN J. Eng. Appl. Sci. 2016. V. 11. N 11. P. 7188-7192.
Araslankin S.V., Kostryukov S.G., Petrov P.S. Determination of substitution parameters of hydroxypropylmethylcellulose using 13C NMR spectroscopy. Vestn. Perm. Un-ta. Ser.: Khimiya. 2018. V. 8. N 1. P. 54-67 (in Russian). DOI: 10.17072/2223-1838-2018-1-54-67.
Martínez-Richa A. Determination of molecular size of O-(2-hydroxyethyl)cellulose (HEC) and its relationship to the mechanism of enzymatic hydrolysis by cellulases. Carbohyd. Polymer. 2012. V. 87. N 3. P. 2129-2136. DOI: 10.1016/j.carbpol.2011.10.039.
Saake B., Horner S., Puls J., Heinze T., Koch W. A new approach in the analysis of the substituent distribution of carboxymethyl celluloses. Cellulose. 2001. V. 8. N 1. P. 59-67. DOI: 10.1023/A:1016658307946.
Karrasch A., Jäger C., Saake B., Potthast A., Rosenau T. Solid-state NMR studies of methyl celluloses. Part 2: Determination of degree of substitution and O-6 vs. O-2/O-3 substituent distribution in commercial methyl cellulose samples. Cellulose. 2009. N 16. Р. 1159-1166. DOI: 10.1007/s10570-009-9304-2.
Kostryukov S.G., Araslankin S.V., Petrov P.S. Determination of the degree of substitution (DS) and molecular substitution (MS) of cellulose ethers by solid state 13C NMR spectroscopy. Khim. Rast. Syrya. 2017. N 4. P. 31-40 (in Russian). DOI: 10.14258/jcprm.2017041860.
SE Tylose GmbH & Co. KG https://www.setylose.com (14.06.2019).
BIOPSEL v.3.0 program for structural analysis of biopolymers https://toukach.ru/files/biopsel.zip (14.06.2019).
Toukach F.V., Ananikov V.P. Recent advances in computational predictions of NMR parameters for the structure elucidation of carbohydrates: methods and limitations. Chem. Soc. Rev. 2013. V. 42. P. 8376-8415. DOI: 10.1039/c3cs60073d.
