The Ethynyl Hydrogen Bond

Tyrrell, James (1963) The Ethynyl Hydrogen Bond. PhD thesis, University of Glasgow.

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The nature and properties of the hydrogen bond are discussed with special reference to the ethynyl hydrogen bond. Proof is given of the electron accepting capacity of the C-H group and of the electron donating capacity of the "pi" electron system of aromatic rings. The theory of the calorimetries spectroscopic and diffraction methods of studying the hydrogen bond are discussed in detail especially as it applies to the investigations discussed in this thesis. An investigation of the ethynyl hydrogen bond was conducted in which the chief acatylenic electron acceptor used was benzoyl acetylene. Instruments were constructed for a calorimetric study of the ethynyl hydrogen bond, the apparatus being checked for accuracy by determining the heat of solution of potassium chloride in water. Heats of mixing of benzoyl acetylene in a variety of solvents were obtained and from these the enthalpy of hydrogen bond formation between the benzoyl acetylene and the active solvents was obtained. An infrared investigation of benzoyl acetylene and phenyl acetylene in a wide variety of solvents was carried out, the frequency shifts, half band widths and maximum intensities of the bands being noted. This indicated the wide range of compounds capable of hydrogen bonding and also provided evidence of bonding to the "pi" electron system of aromatic compounds as distinct from bonding to particular electronegative atoms. A quantitative study of benzoyl acetylene in benzene, various methylated benzenes and in n-butyl ether was carried out allowing the determination of association constants and degrees of association. This was repeated at a variety of temperatures allowing the calculation of hydrogen bond strengths. Results obtained using the infrared technique were found to be subject to considerable error. A quantitative study of benazoyl acetylene in the same solvents as above was carried out using the nuclear magnetic resonance method. This provided a very accurate method of determining association constants and degrees of association. It was intended to carry out temperature studies using this technique but this was impossible due to non-delivery of equipment. This method was also applied to the study of 1:4 dichlorobut-2-yne and propargyl chloride in benzene-cyclohexane mixtures and indicated the probable existence of hydrogen bonds between the methylene protons of these molecules and the "pi" electrons of benzene. An X-ray diffraction investigation of the ethynyl hydrogen bond was carried out with Dr. G. Ferguson. For this purpose ortho-bromobesasoylacetylene was prepared and photographed. A two-dimensional Fourier map of the molecule is shown and the first accurate measurement of a known C=H...O hydrogen bond is given.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Organic chemistry
Date of Award: 1963
Depositing User: Enlighten Team
Unique ID: glathesis:1963-79485
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 05 Mar 2020 09:04
Last Modified: 05 Mar 2020 09:04

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