Study of the stereochemical and reactivity phenomena of the addition reaction of 8-membered cyclic nitrone by NMR spectroscopy
General Material Designation
[Thesis]
First Statement of Responsibility
S. S. Al-Jaroudi
.PUBLICATION, DISTRIBUTION, ETC
Name of Publisher, Distributor, etc.
King Fahd University of Petroleum and Minerals (Saudi Arabia)
Date of Publication, Distribution, etc.
1996
PHYSICAL DESCRIPTION
Specific Material Designation and Extent of Item
166
DISSERTATION (THESIS) NOTE
Dissertation or thesis details and type of degree
M.S.
Body granting the degree
King Fahd University of Petroleum and Minerals (Saudi Arabia)
Text preceding or following the note
1996
SUMMARY OR ABSTRACT
Text of Note
A study of the regio- and stereo-chemical behavior of the 1, 3-dipolar cycloaddition of 3, 4, 5, 6, 7-pentahydro-2H-undecane 1-oxide with a series of mono- and di-substituted alkenes has been achieved. The high degree of both regiochemical and stereochemical control observed in these reactions has been explained in terms of steric factors and secondary orbital interaction in the transition states. Significant secondary orbital interactions are observed in the addition reaction of alkenes having conjugated methoxycarbonyl substituents or having oxygen at allylic position. Rate constants for the cycloaddition of 3, 4, 5, 6, 7-pentahydro-2H-undecane 1-oxide to methyl acrylate and methyl methacrylate have been determined at different temperatures by H NMR spectroscopy. The activation parameters indicate the concerted nature of the reaction. Differences in the rates of cycloadditions have been explained in terms of combination of various factors such as torsional strain, bond angle bending strain and steric factors (non-bonded repulsion) in the transition state. The reaction of ethylene with 5, 6, 7, and 8-membered nitrones led us to prepare for the first time the very important parent 5-5, 6-5, 7-5, and 8-5 fused ring systems and determine their nitrogen inversion barriers. The nitrogen inversion barrier in the 8-membered nitrone cycloaddition products has been determined by detailed band shape analysis of proton and carbon NMR spectra and were in the range of 53.5 to 57.4 kJ/mol. The major isomer is shown to be the trans isomer which is in equilibrium with the minor isomer (cis conformer) by a relatively slow nitrogen inversion.