Part I. The Adsorption of Capillary-Active Substances at the Dropping Mercury Electrode. Part II The Polarographic Analysis of Nitrite and of Nitrite-Nitrate Mixtures. Part III. An Electron Diffraction Investigation of the Structure of Some Organic Molecules: a) Some Cyclic Derivatives of Ethylene Glycol. b) Naphthalene and Anthracene

Citation

Keilin, Bertram (1950) Part I. The Adsorption of Capillary-Active Substances at the Dropping Mercury Electrode. Part II The Polarographic Analysis of Nitrite and of Nitrite-Nitrate Mixtures. Part III. An Electron Diffraction Investigation of the Structure of Some Organic Molecules: a) Some Cyclic Derivatives of Ethylene Glycol. b) Naphthalene and Anthracene. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/afvs-3n49. https://resolver.caltech.edu/CaltechTHESIS:10222024-192757047

Abstract

Part I. The Adsorption of Capillary-Active Materials at the Dropping Mercury Electrode

It has been found that the addition of a capillary-active substance to a solution which is to be analyzed at the dropping mercury electrode brings about a decrease in the diffusion current which passes as a result of the discharge of the reducible ion. Molecules of the capillary-active compound, adsorbed on the surface of the growing drop, appear to deactivate a portion of this electrode surface. As a result, some of the reducible ions or molecules which reach the electrode vicinity by diffusion do not actually reach the electrode surface, and the current which passes as a result of the reduction is consequently decreased. As the concentration of capillary-active material is increased, the diffusion current decreases to a limiting value which is apparently dependent upon the amount of surface still left free on the electrode after a monomolecular layer of material has been adsorbed. Experimental verification and theoretical consequences of the foregoing are described in Part I of this thesis.

Part II. The Polarographic Analysis of Nitrite and of Nitrite-Nitrate Mixtures

It has been found that a solution containing both nitrate and nitrite ions can be analyzed for both constituents in two polarographic experiments. With one aliquot part, the diffusion current due to the two constituents in the original solution is measured. In another aliquot part, the nitrite present is quantitatively oxidized to nitrate, and the diffusion current of the resulting solution is measured as before. The two experiments provide sufficient data for determining the quantity of each ion in the solution. The oxidation of nitrite is conveniently carried out with hydrogen peroxide in acid solution and the excess peroxide is destroyed catalytically by manganese dioxide in basic solution.

Part III. An Electron Diffraction Investigation of the Structure of Some Organic Molecules

a) Some Cyclic Derivatives of Ethylene Glycol

The results of an electron diffraction investigation of some cyclic derivatives of ethylene glycol (chlorophosphite ester, sulfite ester, and acetal) confirm the configuration assigned by the organic chemist to these molecules. Non-planarity of the five-membered ring may be demonstrated only in the chlorophosphite ester, in which also there is found an abnormally long phosphorus-to-chlorine bond distance and a subnormally short phosphorus-to-oxygen bond distance. The covalent bond distances in the other molecules were shown to be normal but no conclusion could be drawn concerning the planarity or nonplanarity of the ring systems.

b) Naphthalene and Anthracene

In an electron diffraction investigation of naphthalene, the average carbon-to-carbon bond distance has been found to be 1.39₇ ± 0.02 Å. The limits of error cannot be narrowed sufficiently to permit a definite choice to be made among the theoretical models proposed by various workers, but the configuration suggested by Penney and Coulson appears to be in best agreement with the observations.

In anthracene, the mean carbon-to-carbon bond distance has been found to be 1.41₉ ± 0.02 Å. Although no statement of the limits of error for the individual distances could be made, it was concluded that the best model in the region investigated is different than that proposed by Robertson, in which the atoms lie at the corners of regular hexagons.

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