Ressonancia magnetica nuclear de cetonas monossubstituidas

AUTOR(ES)

Roberto Rittner Neto

DATA DE PUBLICAÇÃO

1983

RESUMO

The aim of the present work has been the investigation of the substituent effects in the carbonyl carbon C chemical shifts of some a-monosubstituted aliphatic and alicyclic ketones. In Part I, bibliographic reviews on the substituent effects in the.Carbon-13 n.m.r. (Chapter 1), on the characteristic features of the Oxygen-17 n.m.r. (Chapter 2), on the rotational and conformational isomerism of aliphatic and alicyclic ketones (Chapter 3) and a brief synopsis of the photoelectron spectroscopy of carbonyl compounds (Chapter 4) are presented. Part II deals with the description and the discussion of the obtained results. Either the synthesis or the purification of the following compounds.. are described. Then, the determination of the H n.m.r. spectra, both as a source of new data as well as to prove the compounds identity, and the recording of. the C n.m.r. spectra fully decoupled, off-resonance decoupled and without decoupling, depending upon the studied compound are described. The determination af the O n.m.r. spectra is examined, in relation to the instrumental conditions and to the isotopic enrichment of the studied samples. The signals assignments in the C n.m.r. spectra, through the common techniques are presented. The a-methylenic and the carbonyl carbons and the carbonyl oxygen C and O chemical shifts, respectively, were analysed according to the empirical effects of the substituents. The a effect is thoroughly discussed and new values for the a, b and gp effects on the a-methylenic and carbonyl carbons and on the carbonyl oxygen, respectively, were proposed. The changes in the Carbon-13 chemical shifts were compared to the corresponding changes in the Oxygen-17 chemical shifts and in the carbonyl oxygen no orbital ionization potentials, leading to the conclusion that only accídental correlations may be observed. The attenuation of the substttuent effects was briefly interpreted in the light of the compounds geometry and of the orbitals interaction.

ASSUNTO(S)

ressonancia magnetica nuclear quimica organica

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