26—The Oxidation of the Aldehyde Groups in Periodate Oxycelluloses by Chlorous Acid

Abstract

The effects of pH, temperature, and chlorite concentration on the oxidation of the aldehyde groups in periodate oxycelluloses by acidified chlorite solutions have been investigated . From the results it is concluded that a maximum conversion of aldehyde to carboxyl groups is obtained by tre tment of the oxycelluloses at 2o•c with chlorite solution acidified to pH 3 ; the chlorite concentration and the length of the treatment that are required depend upon the extent of the periodate oxidation. This chlorite treatment has been applied to a series of sixteen periodate oxycelluloses, a.nd it has been found that the fina l products contamed, on the average 1 1·78 carboxyl groups for every atom of oxygen consumed in the perioaate oxidation. This yield of carboxyl, although considerably higher than tho e obtained by earlier workers, is still signjficantly less than the theoretical value of 2 ; possible reasons for the discrepancy are discussed. Evidence is presented which suggests that one of the two aldehyde groups in a chain-unit of a perlodate oxycellulose is preferentially oxidized by chlorous acid, and that this group reduces more copper in the copper number determjnation, and contributes more to the alkali-sensitivity of the oxidized chain-molecule, than the other.Chlorous acid was first used a a reagent in the study of o ycelluloses by Rutherford, Minor, Martin, and Harris\ who showed that the aldehyde groups in periodate oxycelluloses may be oxidized to carboxyl group by means of an acidified solution of sodium chlorite. The chlorite treatment adopted by these workers did not, however, effect oxidation of all the aldehyde groups present in the oxycelluloses except when the initial aldehyde content was very low. Later workers 2 -7 have employed a wide variety of conditions of chlorite treatment, but the reaction appears to have been used without adequate preliminary study of the effects of pH, temperature, and chlorite concentration on its rate. The present paper describes an investigation of the effects of these factors, and uggests conditions for the quantitative oxidation of the aldehyde groups in periodate oxycelluloses. The results of an examination of the action of chlorous acid on an extensive series of period ate oxycelluloses are also recorded, and their implications are discussed. I. DETERMINATION OF OPTIMUM ONDITIONS FOR TilE OXIDATION OF THE ALDEHYDE GROUPSIn order to find the optimum conditions for the oxidation of the aldehyde groups in periodate oxycelluloses by acidified chlorite solutions, the effects of pH, temperature, and chlorite concentration on the rate of the reaction were studied. Most of this work was done with an oxycellulose obtained by relatively slight oxidation of cotton cellulose with metaperiodate, but various more highly oxidized materials were also used in the investigation of the effect of chlorite concentration. The periodate oxycelluloses employed are characterized by their 'oxygen con umption ', that is, the proportion of oxygen, expressed in atoms per glucose unit, consumed...

Part II: The Influence of Functional Groups and the Nature of the Yellowing

“…Carboxyl groups were determined by the method of Davidson [3, 6 J .. Aldehyde groups were determined by oxidizing the samples with sodium chlorite and acetic acid according to Davidson and Nevell [4] and then redetermining the carboxyl group content of the oxidized samples. The difference between the value found and that of the original gives the value of the aldehyde group content of the sample.…”

Thermal Neutron Irradiation of Cotton'

“…The I) P measurements, made in an alkaline reagent like cupriethylene diamine, would be much lower than the true chain length due to chain cleavage at the oxidized units on exposure to this reagent. Conversion of the aldehyde groups in periodate-oxidized cellulose to carboxyl groups is accompanied by almost complete stabilization of the material toward alkalies [ 10 ] . This is reflected in Table III by a very large increase in the DP of the periodate-oxidized cottons after chlorite treatment.…”

“…These samples were then analyzed for DP, carboxyl content, and copper number. The results are given in the first three columns of Table III. Davidson and Nevell [ 10] made an extensive study of the optimum conditions for conversion of the aldehyde groups in periodate-oxidized cellulose to carboxyl groups by sodium chlorite solutions.…”

“…Oxidized Samples Water-washed samples of neutron-irradiated, gamma-ray-irradiated, and periodate-oxidized cottons were treated with sodium chlorite, according to the method of Davidson and Nevell [ 10] . These workers determined the experimental conditions necessary for maximum conversion of the aldehyde groups in periodate-oxidized cellulose to carboxyl groups by the sodium chlorite method.…”

Studies in chemically modified celluloses. IV. Lactones in chemically modified celluloses

“…21 The hydrocellulose samples were treated with 0.2M sodium chlorite in 1M acetic acid at pH 3 for 72 hr at 28"C, keeping the material at a liquor ratio of 1:50. The samples were washed with distilled water, steeped in O.5N hydrochloric acid for 15 min, and washed free from the acid.…”