Studies of some electron deficient aromatic systems

Wilson, J. A. (1970) Studies of some electron deficient aromatic systems. (PhD thesis), Kingston Polytechnic,


A study has been made of the properties of the electron deficient [pi] -systems in the compounds 3,5,6,8-tetranitro- acenaphthene (T.N.A.), 2,5-dinitro-l,8-naphthalic anhydride (2,5-D.N.N.A.), 3,6-dinitro-I,8-naphthalic anhydride (3,6-D.N.N.A.), 4,5-dinitro-I,8-naphthalic anhydride (4,5-D.N.N.A.), 2,4,5-trinitro-I,8-naphthalic anhydride (Tri.N-I,8-N.A.), 1,6,8-trinitro-2,3-naphthalic anhydride (Tri.N-2,3-N.A.) and 2,4,5,7-tetranitro-I,8-naphthalic anhydride (T.N.N.A.). Measurements on the visible absorption spectra of the donor-acceptor (charge-transfer) complexes formed between aromatic hydrocarbons and the above compounds have shown that the electron acceptor ability increases in the order T.N.A. [less than] 2,5-D.N.N.A. [tilde] 3,6-D.N.N.A. [tilde] 4,5-D.N.N.A. [less than] Tri.N-2,3-N.A. [tilde] Tri.N-l,8-N.A. The electron acceptor ability of T.N.N.A. could not be determined by this method. The extent of electron transfer in the complexes formed with N,N,N',N'-tetramethyl-p-phenylene diamine has been investigated by electron spin resonance spectroscopy and the results have confirmed that T.N.A. is the weakest acceptor. The association constants for the formation of complexes between T.N.A. and various methyl benzenes have been determined by nuclear magnetic resonance spectroscopy and the association constant and the heat of formation of the 3,6-D.N.N.A.-pyrene complex has been determined by visible spectroscopy. The values are comparable with those for other electron donor-acceptor systems. The electron spin resonance spectra of the radical anions of all the compounds, except 3,6-D.N.N.A. and Tri.N-2,3,-N.A., have been analysed and the experimentally determined spin densities have been found to be in good agreement with the values calculated by the Huckel and McLachlan molecular orbital methods. The relative spin densities at the proton sites in 3,6-D.N.N.A. have been estimated by a nuclear magnetic resonance method and found to agree qualitatively with the calculated values. The reactions of the compounds with the bases – methoxide ion, sulphite ion, amines - have been investigated, and the products have been characterised and correlated with the strength of the base used in the reaction. A possible mechanism for the reaction of 3,6-D.N.N.A. with the methoxide ion has been proposed. The preparation of the compounds under study have been described and the nuclear magnetic resonance, infrared and mass spectra have been recorded. The infrared and mass spectra have been discussed in terms of the structure of the compounds. The infrared spectra of the complexes formed with aromatic hydrocarbons have also been recorded and shown to be basically composites of the spectra of the individual components. A number of computer programs relevant to the present work and of general chemical application have been written and are presented as an appendix to the thesis.

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