Studies in the Chemistry of Dyes and Their Adsorption by Fibres

Arshid, F. M (1954) Studies in the Chemistry of Dyes and Their Adsorption by Fibres. PhD thesis, University of Glasgow.

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The work described had the main purpose of gaining a better understanding of the mechanism by which dyes are sorbed by various substrates. A subsidiary aim was the development of new analytical procedures to simplify the determination of purity of the dyes used and for the detection of hydrogen bonding. Broadly, the work is classified into three main sections, dealing respectively with analysis of dyes, methods of detecting hydrogen bonds, and the study of the sorption of certain natural colouring matters by various fibres and of synthetic dyes by alumina (in the form of anodised aluminium) and cellulose. An oxidative method for the analysis of azo dyes and some dyes of other classes is described. The results for the majority of dyes examined, agree closely with those obtained by titanous chloride analysis, and the new method has the advantage of being simple, rapid and clean in use. The procedure involves measurement of the volume of nitrogen produced on boiling the dye with a dilute solution of potassium dichromate and sulphuric acid. A still simpler, colorimetric method of determining water-soluble azo dyes uses ceric sulphate oxidation. It is useful for some dyes, but many do not react in simple proportion with the oxidant. The use of the refractometer for detecting the complex ratios of hydrogen bond interaction in binary solutions of organic compounds is also described. This method appears equally useful for detecting strongly or weakly-bonded complexes. The reality of the existence of many compounds so detected has been demonstrated by a variety of procedures, including molecular weight determination, preparation of solid complexes, and comparison with complexes previously reported, either by preparation in substance or detection by infra-red spectrophotometry. The dielectric constant and refractive index methods of detecting complex-ratios in hydrogen-bond interactions have been applied to nearly two hundred and seventy pairs of compounds in a variety of solvents. Intra- as well as inter-molecular bonds can be detected, and a qualitative estimate of their relative stability may be made. Alcoholic and phenolic hydroxy-, aldehyde, amido-, amino-, azo-, carboxylic and sulphonic acid, ester, keto-, nitro- and quinone groups are amongst those examined. Several compounds have been included to represent models of certain natural and synthetic polymers. A number of inter- and intra-molecular bonds have been detected involving a hydrogen atom attached to carbon and activated by a neighbouring carbonyl oxygen atom. These include intermolecular bonds between certain esters, e. g. , acetates, and azobenzene and quinone. Supporting evidence is quoted showing that this type of bond may be responsible for the sorption of dyes by cellulose acetate. Numerous examples of shielding of groups by the solvent have been noted, e.g., water protects alcoholic groups against combination with a number of other solutes of low affinity, but not against phenol. The carbonyl oxygen atom in ketones, amides, or aldehydes is for the same reason unable to form intermolecular complexes in benzene, ether or water, but it is reactive in carbon tetrachloride or dioxan. This was checked by examining the sorption of benzene-azo-alpha-naphthylamine and benzene-azo-beta-naphthylamine on anodised aluminium. These compounds show little affinity for anodised aluminium, using benzene as a solvent, but on employing carbon tetrachloride or dioxan, sorption proceeds readily. Bonding between water, used as a solute in anhydrous solvents, and several other compounds has been observed. With the amide or azo groups water acts as a cross-linking agent, each of its hydrogen atoms being attached to a separate molecule of the other solute. The reactions of the alkylamide group have been studied in view of their importance in the interpretation of the behaviour of proteins and nylon. This group appears to react, bifunctionally, in the enol form in organic solvents, but water stabilises the keto-form and it is then usually monofunctional, the carbonyl oxygen being protected by the solvent. A hydrogen atom on the carbon adjacent to the carbonyl group in the keto-form is shown also to be reactive and the bearing of this fact on the interpretation of the action of quinones in tanning proteins is discussed. The bonding properties of carbohydrates and their relation to sorption by cellulose, are also considered. The individual hydroxy- or ether groups in mono- and disaccharides in their normal ring structures, can form intermolecular bonds with other solutes in an anhydrous solvent (ethylene glycol), but not in water, even with phenol, on account of shielding by the solvent. The nitrogen atom in some solutes can combine, in water, with the free aldehyde group in the open-chain form of glucose or cellobiose. It is shown that these facts are consistent with the sorption of dyes by cellulose from water being due to van der Waals attraction rather than by hydrogen bonds, as formerly supposed. (Abstract shortened by ProQuest.).

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Organic chemistry
Date of Award: 1954
Depositing User: Enlighten Team
Unique ID: glathesis:1954-79068
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 05 Mar 2020 11:45
Last Modified: 05 Mar 2020 11:45

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