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~Ie OXIDATION of CELLULOSE Witli CHROMIC ACID

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~Ie OXIDATION of CELLULOSE Witli CHROMIC ACID ~iE OXIDATION OF CELLULOSE WI Tli CHR OMIC ACID A Thesis by Al ber t Richard Reid M.Sc. (Dalhousie) Submitted to the Fa cul t y of Graduate Studies and Research in partial ful­ filment of t he r cquirements for the Degree of Doctor of Philosophy. Di vi sion of Industrial and Cellulose Chemistry, McGi l l University. Ma r ch , 1953. AC ~iliOVffiEDGE IBNTS The author wishes to express sincerc appreciation to Dr. C.B. Purves for his constant encouragement and gui ­ dance which was so generously gi ven dur­ ing the course of t his research. Sincere appreciation is also cxpr e s s ed to Dr . T.E. Timell and to fe1­ low stude~ts of the Department of Indus­ trial and Cellulose Chemistry for their advice and kind intercst. Grat ef ul acknow1edgements are made for the financia1 assistance received from the Department of Veterans Affairs, for the funds made availab1e from the Ha r ol d Hi bb er t Memor i al Fe11owship, and for the aid in the form of summer grants received f r om the Pulp and Paper Research Institute of Canada. TABLE OF CONTENTS GENEPJ~L I NTRODUCTI ŒIJ ................................... l HISTüRICAL INTRODUCTION ................................ l Analytical ~ethcds for carbcxyl and carbonyl Groups ....•........•....•... •. ..... 18 R~SULTS AND DISCUSSION ................................. 29 Cxi da t i on s of Cellulose wi t h Chromic Aci d ••••••••• 29 Ob servations on the Estimation of carbonyl Groups.. 50 Application of the Kiliani Reactions to Oxycelluloses •..•.•..•.•.•......•....••.......•• 61 BXPERItŒ NTAL SECTION ................................... 75 Determination of Reduci ng Sugars by Condensation wi th Cyanide •••.•••••••••.•••••.•.• 75 r~1 e thodA. ..•..•.....•...•.•..................• 75 ~·,~ e th o d .B •••. III ..••••••••••••••••••• •• •••••••••• • 76 Det er mi n& t i on of CarboÂJl Groups in OX7lce11ulos e. .................................•. 77 Estimation of Carbonyl Groups in Ox i di zed Cellulos e •.......••..•...•. ....•.•••.•• 78 Hydr-oxyLam.l.n e Hydr ochl or i de Ii1 e t h od •••••••••••• 78 Cyanide T;:ethod .. •.......................•.. •• . 79 E s ~ ima t i on of the Aldehyde Content of Oxidized Cellulose ••••••••••••••••••••••••.•• 80 Copper Reducing Power of O~Jcellulos es •••••••••••• 83 r:l o i s t ur e Content ............•..•.•...............• 85 A sh Content ...............................•...••.. 85 Pretreatments of Cellulose •.•••••••......••••.•••. 86 Oxi dations with Sulphuric Acid - Dichromate ••••••• 87 Oxidation of Oxalic Acid by Potassium Dichromate ••• 88 Oxidation of Cellulose by Potassium Dichromate -Oxalic Aci d •..••••••••••••••••••••• 91 Change in carbonyl and Carb o ~Tl Content durf.n g Oxidation •......................•.....••. 94 Large-Scale Oxidation of Cellulose (Oxycellulose V-5) ••• •• •• ••.•.•••••• •• • •• • •• • •• • 96 Ni t r a t i on of Oxycellulose V-5 ••.•••. •.•••••••• 97 Estimation of the Aver age Degree of Polymerization ••••••••••••••••••••••••••• 98 Me t hylat i on of oxycellulose V-5 wi th Dia~omcthane ••••.•••••••••••••••••••••• 99 ii Table cf Contents (cont'd) Preparation and Reduction of the Cyanohydrin of Oxycel1u1ose V-5 .............. 101 As cendi ng Me tho d of Paper Chromatography ........... 107 Descen àing Mebh.od of Pa p e r- Chromatography .......... 108 Sm,1IiIARY AND CLAD:IS TO ORIGI NAL RE8EARCH ................. 109 BIBLIOGRAPHY ............................................ 112 iii LIST CF Tl-u3LES T l~13LE Page l Cupra&~onium Fluidity and Tensile Strength of Various Hydrocelluloses and Oxyc e l Lu'Lo s e s •• g ••••••••••••••••••• •• ••• 3 II Copper Reducing Power at Va r i ou s Stages of Oxidation 32 III Oxalic Acid - Dichromate System .................. 37 IV Cxidations of Swollen Cellulose with Dichromate and Cxalic Acid at 25°C. 42 v Al d eh yd e and Ket8~e Contents of O~Tcelluloses .... 46 VI Estimation of Gl u co se by the Cyanohydrin Reaction. 51 VII Esti~ation of Fructose by the Cyanohydrin Reaction ................................ .. •. 54 VIII Es t Lmat Lon of t:1.e Carbonyl Content of Oxy - cellulose by the Cyanohydrin Reaction ••••••• 56 IX Recovery of Amraon5a from Aqueous Cyanide Solutions and from the Corre sp onding Unmodified Cellulose Blanks .••....•..•...••• 58 X Comparison of carbonyl Determinations on Oxycellulose by the Cyanide and Hydrozyla.mine Me t h od s ••.•..•......••.••••• •• 60 B 3 h~vi o ur of Oxycelluloses during Cyanohydration and Saponificatior. ........... 64 XII RF Val1.:.es of Acids by the As cending l'iI ethod ....... 69 XIII RF Values of Acid3 by the Dcsccnding I.~c th o d ...... 71 XIV RD Values of Acids by the Des cend Lng I\icthod ... 72 J. ' .. xv Re-oxidation of Ox y cel l ulo fi e \'V i t h Chlorous FJ. oi d ... 82 XVI Comparis on of Draidy and He y e s Copper Numb e r s •••• 85 iv TABLE Page XVII Chan ge in pH of an Oxa1ic Aci è - Potassium Di chroma t e 301'.1ti01J. 'vi th Time of Reaction •• 89 XVIII Fractiona1 Distillation of Aci ds from the Ba.r-Lurn Salt s 106 v LIST OF PIGURLS FIGURE l Oxidations of unswollen linters with chromic acid at 20°C• •.•.•••••••.••..•••• 30 2 Time of oxidations in 0. 2 N oxalic acid - ' 0.04 N po tas s i um di ch r oma te solutions .... 34 3 Rate of oxidation of 0.2 N oxalic acid by 0.1 N p o t a s s i um dichromate ••••••••••••••• 35 1 Changes in the properties of unswollen cellulos e wi t h increased tille of oxidatien ...............•.............••• 49 5 Paper chromatograms of simple fatty acids by a scending method •••••••••••••••••••••• 70 6 Determination of the intrinsic viscosity of nitra tod ozycellulcse V- 5 ••••••••••••• 100 r GENERAL I NTRODUCTI ON Cellulose oxi da t i ons are of interest because t hey i mpair the ~hys i c a l properties of pap er s and cotton textiles and occur, sometimes in bleaching and dyeing, and always dur­ ing exposure to lisht, air, and moi s t ure over long periods of time. With the exception of a few cases, the detailed nature of the r eactions involved in mi l d or drastic oxidations is still obscure, although it h~s long been known that oxidation forms acidic and r educing groups in sorne of the glucose units that comprise the long macromolecules of cellulose. The num­ ber and position of these gr oup s vary with the extent of the oxidation, with the physical sta te of the material and with the oxidant employed. Only Q f ew methods are available for their determination. This Thesis first examines the oxidation of cellulose wi t h aqueous chromic acid with a view ta pr epa r i ng ~~ oxycellu­ lose of high reducing p ower in a minimum time. The oxidation of cellulose induced by dichromate in the presence of oxalic rather than sulphuric acid, wa s p articularly investigated and found to be suitable. Mu Ch time was spent in checking the re­ liability of existing methods for determining total carbonyl, an d also aIdehyde groups, in the oxycelluloses and in de ter­ mining the optimum conditions for the oxidation. A portion of this work, showing how the ke t one gr oup in fructose could be II quantitatively determined by means of the cyanohydrin reaction, has already been accepted for publication in Analytical Chemis­ try. With the experience thus gained, a large batch of the oJ:ycellulose was condensed with the cyanide ion and the result­ ing cyanohydrin was saponified, the whole procedure involving the conversion of the carbonyl groups to a-hydro~J acid units. Reduction of the adduct with hydriodic acid yielded a mixture of low molecular fatty acids. Contrary to expectation, the i n i t i a l oxidation had beeu intensely localized in the cellulose. HISTORICAL INTRODUCTION The first attempt to classify cellulose which had been chemically modified by oxidizing agents was made by Witz (1) in 1883-1884. He described such oxidized products, which still retained the fibrous structure, but not the mechanical strength of unmodified cellulose, under the heading of It oxy_ celluloseslt• At almost the same time, this term was applied by Cross and Bevan (2) to the powdery, non-fibrous, and partly water-soluble products obtained from the drastic oxidation of cellulose with nitric acid. For the next forty years, research on such oxidations was confined largely to empirical tests and observations because of the limited knowledge concerning the chemical structure and the physical nature of cellulose itself. However, the invest­ igations during this period did indicate that the oxidation of cellulose was a very complex chemical reaction yielding oxy­ celluloses which varied in their properties according to the reagent employed. The modern phase of research on oxidized celluloses only spans the past twenty to thirty years, and closely parallels the rapid advancement in the general chemis­ try of cellulose. In technical literature the term Itoxycelluloselt de­ scribes a product that has been chemically modified by oxida­ tive agents in such a limited manner that the fibrous nature of the starting material is still retained, although the mechanical strength is decreased. Thus the definition of Witz (1) is still in use, even though the term "oxycellulose" is actually a misno­ mer, since it implies an addition of oxygen, whereas an abstrac­ tion of hydrogen may also be involved. Parsons (3) and more re­ cently Unruh and Kenyon (4), have suggested the replacement of the term by the more precise riame, "oxLdd z ed celluloseu • How­ ever, both terms have been used interchangeably throUghout the great mass of the literature and the custom will be followed in this thesis. Much of the following information parallels that contained in reviews by purves and co-workers (5)(6)(7), the most recent of which was published only three months ago (October 1952). Extensive work by Clibbens and Ridge (8) showed the re1ationships existing between tensi1e strength, cuprammonium fluidity, (the reciprocal of the viscosity in poises of 0.5 per cent solutions), copper number, and alkali stability of hydrocelluloses were not valid for several types of oxycellu­ 10ses.
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