THE OXIDATION OF POLYALGQHOLS BY PERIODIC ACID BY PETER LESLIE ROGERSON A Thesis submitted to the University of London* Faculty of Science9 for the Degree of Doctor of Philosophyo Battersea College of Technologys July, 1963o ProQuest Number: 10803867 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a com plete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. uest ProQuest 10803867 Published by ProQuest LLC(2018). Copyright of the Dissertation is held by the Author. All rights reserved. This work is protected against unauthorized copying under Title 17, United States C ode Microform Edition © ProQuest LLC. ProQuest LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106- 1346 ACKNOWLEDGMENTS The work described in this thesis was carried out in the Chemistry Department, Battersea College of Technology under the direction of Dr0 GoJo Buist, and the general supervision of Dr» JVEo Salmon, Head of the Department a The author wishes to record his sincere thanks to Dr® Go Jo Buist for his constant help and encouragement during the course of worko The author also wishes to thank the following peoples Dr® CoA o Bunton for his interest in the work® Dre ZoL. Ernst for several helpful discussions, and, his colleagues who timed many fast runs» The Department of Scientific and Industrial Research for a research studentship0 ABSTRACT The mechanism of the periodate oxidation of glycerol, meso- erythritol, glycollic aldehyde, and glyceraldehyde, was investigated over a wide range of pH and reactant concentration at 0°Co Chemical kinetic and polarographic techniques were used, supplemented hy measurements of pH, during reaction,, The work with glycerol established the formation of a glycerol-periodate complex, of greater acid strength than periodic acid and in equilibrium with the reactantso The kinetics of the oxidation of glycollic aldehyde, which is formed byc^=»glyeol cleavage of glycerol, was studied and the results showed that in the oxidation of glycerol, oxidation of the aldehyde must be allowed for at all pH values, except with a very large excess of polyalcoholo The variation of equilibrium constants, for the formation of the complex, and also the rate constants for its decomposition, with pH, is similar to that for 1s2~diols,showing that the monovalent complex is the only decomposing species over the pH rang© studiedo From the results, the dissociation constants for the complex were calculated* Similar studies were made of meso-erythritol and glyceraldehyde, which is formed by initial0^ -glycol cleavage of erythritol* The results showed that the “glycol cleavage of erythritol by periodate is similar to that of glycerol and ls2-diols<> The periodate oxidation of glyceraldehyde occurs via a complex in the pH region 6 - 9<> At lower pH values, the kinetics ABSTRACT (continued) showed that glycollic aldehyde is formed by the initial oxidation of glyceraldehyde« It was possible to follow the formation of polyalcohol” periodate complexes by polarography* Results at high pH suggest that two types of complex may be formed * The equilibrium constants for the formation of the divalent glycerol and meso-erythritol-periodate complexes are much greater than those of ls2-diolso To account for this, a triester structure has been proposed, although it does not altogether explain the variation of the formation and dissociation constants with structural changes* INDEX Part 1 Introduction 1 Part 2 Glycerol and Glycollic aldehyde 29 2a Physical and Chemical Evidence for the Formation of a Glycerol-Periodate Complex 30 2b Kinetic Investigation of Glycerol and Glycollic Aldehyde 37 2c Kinetic Investigation of the Formation of the Glycerol-Periodate Complex at High pH 87 2d Determination of the Thermodynamic Functions for the Formation of the Glyeerol-Periodate Complex 93 2@ The rate of Oxidation of Glycerol by Excess Periodate 96 2f Summary of Results 98 Part 3 Meso-Erythritol and DLrGlyceraldehyde 100 Introduction 101 3a Kinetics of the Oxidation of Dlr-Glyceraldehyde 101 3b Physical and Chemical Evidence for the Formation of an Erythritol-Periodate Complex 119 3o Kinetic Investigation of Meso-Erythritol 122 £ . Kinetic Investigation of the Formation of the Erythritol-Periodate Complex at High pH 138 2* Rate of Oxidation of Erythritol by Excess Periodate 142 3-f Summary of Results 143 Part 4 Discussion and Conclusions 144 INDEX (continued) Part 5 Experimental Work.) 159 5a Preparation and Purification of Materials 160 5b Chemical Kinetic Runs l6l 5o Polarographic Runs 173 5d pH Measurements 178 5e Measurement of the Rate of Liberation of Iodine from Kinetic Solutions with Potassium Iodide 181 Part 6 Examples of Kinetic Runs 1812 Appendices I 190 II 192 Bibliography 195 \ INTRODUCTION 1 2 Malaprade * in 1928 found that periodic acid reacts with certain polyhydric alcohols, containing^-glycol groups and giving as products carbonyl compounds and/or carboxylic acids, for example: rw — r.w h Tn. is Periodate warn reduced to iodate during the reaction. Since then, various workers have shown that periodic acid can oxidise organic compounds containing the following groups besides theo{-glycol structure® 1® -aldols 2® c< «*diketones 3* °(-amino alcohols (the amino group may be primary or secondary)® The reaction with these compounds is rapid and is characterised by cleavage of a carbon-carbon bond, the products being carbonyl compounds and/or carboxylic acids® This type of periodate oxidation will be referred to as Type I in this discussion as there is a second class of reaction which involves compounds containing none of the groups mentioned above and where in general the rate of oxidation is much slower. These will be referred to as Type II® -2- Oxidations of Type I 1 2 3 Malaprade 99 demonstrated the stoichiometry of the reaction for several polyols and sugars. Fleury and Lange^ showed that the reaction only occurs if the hydroxy groups are attached to adjacent carbon atoms, for example, pentaerythritol 5 and monohydrie alcohol^ do not react. Later Fleury and Paris studied the reaction of periodic acid and the<X- andisomers of glycerophosphoric acid and found only the ^ -isomer reacted, -rglycerophosphoric acid being unreactive. The oxidation of -aldol compounds was first noticed as an intermediate stage in the oxidation of some polyhydroxy 3 compounds, for example, Malaprade showed the following reaction mechanism for glycerol: CHp-OH HCHO I H.IO, + CHOH — — — > CHO HcXO/- HCOOH I I CHg-OH CH20H HCHO The glycollic aldehyde being formed in the first stage was later oxidised to formic acid and formaldehyde. The stoichiometry of the oxidation of c*£-aldols and °<^-diketones 6 was established by Clutterbuck and Reuter and they showed, for example, that the following reactions could occur: -3- . i CH, - .C - CH H5I06 k CH^COOH + HCOOH 3 II II ----- > 3 0 0 Fh - C - CH - Fh H5I06 v Ph. COOH + Ph. CHO It I “ — > 0 OH Finally the reaction\ of0 {-amino alcohols with periodate was demonstrated by Nicolet and Shinn^; they found that Serine may be oxidised quantitatively as follows: CH2 - CH - COOH . L I H5I06 . HCHO + H C - COOH + NH, OH NH2------------ * || 3 0 8 Ethanolamine may also be rapidly oxidised yielding ammonia, formic acid and formaldehyde. CH2 ~ CH2 H3I06^ HCHO + HCOOH + NH^ OH NH2 7 9 10. The amino group may also be secondary 9 9 CH„ - CH, % CH, - CH„ 2H5IV 4HCH0 + HH, | \ / | --- OH NH OH Periodate oxidations are important in carbohydrate chemistry and have been used to elucidate the structure of many sugars. It is possible to determine ring sizes and positions of certain substitu%am%by examination of the number of moles of periodate consumed and the products formed. This method was 11 12 I"? H, developed particularly by Jackson and Hudson 9 9 9 However, it is sometimes complicated by the occurrence 18 19 of side reactions and "over-consumption" of periodate. 9 Sometimes iodate is reduced by carbohydrates to iodide which is subsequently oxidised by periodic and to iodine. The methylation of hydroxylgroups usually prevents oxidation occurring, for example, 2-methoxy ethanol gives no reaction,, However, under certain conditions some methylated glucoses are affected although only very slowly®"^* Oxidations of Type II The oxidation ofo(-amino alcohols containing a tertiary amino group hsse been studied and the stoichiometry established® Eleury showed that triethanolamine and N-methyl diethanol^amine react as follows % i:N (CHg - CH2 OH)^ ^H5IQ6 , NH^ + 6 HCHO CH^ - N (CH2 - CH20H)2 2H5I0 6 y CH3NH2 + 4HCH0 The rates of oxidation of these tertiary amino compounds are very slow® Quaternary ammonium salts are not oxidised even at 100°C® It thus seems necessary for a hydrogen atom to be attached to the nitrogen in the amino group to facilitate oxidation® Ethylene diamine ^ reacts with periodate® However, again the reaction is much slower than for primary or secondary^-amino alcohols® -5- CH2 - CH2 H5IQ6 V 2HCH0 + ZBl^ m 2 m 2 Most of the products of oxidation by periodate will undergo further oxidation® However, the rate is generally much slower than the primary reaction,, Sunlight accelerates some of 15 16 these reactions, 9 for example, the oxidation of formic acid>id may be completed in one day in the presence of bright sunlight'15. Similarly, the oxidation of formaldehyde may be speeded up; HCHO H5I°6> HCOOH C02 + H20 20 The reaction