Date of Award
Chemistry and Biochemistry
Pure sciences, Cyclohexane-1, 4-dione, Cyclohexanes
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Part I. The conformational equilibria of cis-1,4-bromochloro-cyclohexane, trans-1,4-dibromo-, trans-1,4-dichloro-, and trans-1,4-bromochlorocyclohexane were measured by integration of the separate axial and equatorial proton signals at low temperature.
The two possible chair forms of the cis compound were shown to exist in equal amounts, contrary to the result of Atkinson and Lunde.
The free energy difference between the diaxial form and the diequatorial form of each of the trans compounds was shown to be roughly one-fifth of what one would expect if additivity of conformational energies was assumed. This was attributed to the greater electrostatic attraction in the di-axial form. Related cases from the literature were also discussed.
Part II. The two bicyclic analogues of cyclohexane-1,4-dione studied were bicyclo[3.2.2] nonan-6,8-dione (11) and bicyclo-[3.3.1] nonan-3,9-dione (28). The first diketone was prepared by the thermal decarboxylation of 1,5-dicarboxybicyclo[3.2.2] nonan-6,8-dione. A discussion of this decarboxylation in relation to Bredt's Rule was presented. The principal mass spectral feature of two derivatives of 11 was presented.
The diketone 11 has two possible conformations each of which has a cyclohexane-1,4-dione ring locked in a flexible form by a trimethylene bridge. The conformational composition of 11 was determined by dipole moment measurement.
The conformations of the diketone 28 and its 9-ethylene ketal were determined by infrared and nmr spectroscopy, and dipole moment measurements. The ethylene ketal was tentatively assigned a non-flattened twin-chair conformation, while 28 was shown to be an equilibrium mixture of 90% of twin-chair and 10% of chair-boat, with the cyclohexane-1,4-dione moiety in the boat form.
Woo, Edmund P., "Part I. Conformational analysis of 1,4-disubstituted cyclohexanes. Part II. Synthesis and conformational analysis of two bicyclic analogues of cyclohexane-1,4-dione" (1968). Electronic Theses and Dissertations. 8048.