Faculty of Science

Objectives

To initiates students into structure determination by use of the complementary information afforded by four spectrometric techniques: ultraviolet, infrared, nuclear magnetic resonance and mass, the characterization of organic compounds isolated from natural sources; and purified compounds isolated from complex mixtures.

Contents

The Chemical Shift: definition; theory of chemical shifts, proton chemical shifts, aromatic ring currents; Hydrogen bonding shifts; 13C chemical shifts, substituent effects in cyclohexanes, the gamma effect; Spin-spin coupling: first-order rules; mechanism of spin-spin coupling, vicinal HH couplings (3JHH); geminal HH couplings (2JHH), long range couplings, directly bonded couplings (1JCH, 1JCC); 2JCH and 3JCH couplings; 2JCC and 3JCC couplings; Pulse Fourier Transform Techniques: The sensitivity problem, the rotating frame, nuclear relaxation; Time and frequency domain signals, fourier transformation, pulse FT-NMR spectrometer; Double resonance techniques and relaxation mechanisms: Introduction to homonuclear decoupling, heteronuclear decoupling, noise decoupling, INDOR; Nuclear Overhauser Effect (NOE); Gated decoupling; 13C, relaxation mechanisms; 13C spin relaxation times: T1, T2; chemical significance of T1 values. Multi-pulse NMR techniques spin-echo experiment, spin-echo, Fourier transform (SEFT) experiment; two dimensional (2D) NMR; some properties of the second dimension; J-resolved spectroscopy, basic sequence, hetero-nuclear J-resolved spectroscopy; Heteronuclear chemical shift correlation: COSY-90, COSY-45, enhancing the effect of small coupling; SECSY; Correlation through multiple-quantum coherence – INADEQUATE; Connections through space: Relaxation of a two spin system, the NOE of a two-spin systems, steady state NOEs; transient NOEs, two-dimensional NOEs-NOESY; Applications in spectroscopy assignments; structure determination, conformational studies. Combined COSY/NOESY (COCONOESY, CONOESY) experimental considerations. HMQC, HMBC, COLOC COSY/HOHAHA. One-dimensional FT-NMR: Spin decoupling difference spectroscopy, NOE difference spectroscopy. Selective population transfer (SPT); off-resonance proton decoupling, selective proton decoupling; INEPT and DEPT, spin echo decoupling difference; Pulse width calibration, selective pulse and DANTE. Assignment techniques in 13C spectra; quantitative measurements in 13C NMR.