Tutorial on 2D-NMR: Using COSY & HSQC to Assist in Assigning 1H & 13C NMR Spectra 1H NMR • Chemical shift (δ) depends on molecular structure and solvent • 1H nuclei sensitive to hybridization of atom to which H is attached and electronic effects – EDG’s shield nuclei shift upfield lower δ – EWG’s deshield nuclei shift downfield higher δ Downfield Deshielded Upfield Shielded 10 ppm 0 ppm 1H NMR • Spin-spin coupling effects: interaction between nuclei through bonds – Causes splitting in observed peak (s, d, dd, t, m…) – Coupling constants: magnitude of splitting (Hz) • Hz (not ppm) since effect is independent of applied mag. fld. • Caused by mag. fld. of another nuclei 2-D NMR • Determine structure (especially for molecules too complicated for 1-D NMR) • Involves series of 1-D NMR experiments • Doesn’t need to use the complicated coupling constants Correlation Spectroscopy (COSY) • Homonuclear: plots 1H NMR on both x and y-axis • Diagonal divides the spectrum into 2 equal halves • Cross-signals: symmetrical to diagonal; contain the relevant info • FAB-FOUR – 1H NMR (~5 min) – COSY (~30 min) – 13C NMR (depends…) – HSQC (~30 min) 3 4 2 H4 H3 H3 H2 3 H4 7 4 H2 8 2 6 H8 H4 H7 H3 H6 H2 H3 H4 H7 3 7 H8 4 H6 H2 8 2 6 1 H6 H2 H8 H4 H7 H3 H1 H3 H4 H7 3 7 H8 4 H6 H2 8 2 H1 6 5 1 H5 H1 H8 H4 H7 H3 H6 H2 H4 H7 3 7 H8 4 8 H6 H2 H5H1 H3 2 9 11 5 1 6 10 H11 H9 H6 H2 H H8 10 H4 H7 H3 H5 H1 H4 H7 3 7 H8 H10 4 H9 H6 H2 8 2 9 H11 H5H1 H3 11 5 1 6 10 H11 H9 H6 H2 H H8 10 H4 H7 H3 H5 H1 LONG-RANGE COUPLING H4 H7 3 7 H8 H10 4 H9 H6 H2 8 2 9 H11 H5H1 H3 11 5 1 6 10 Heteronuclear Single Quantum Coherence (HSQC) • Plots 1H NMR on x-axis and 13C NMR on y-axis • Utilizes 1 bond coupling between H and C • Eliminating all the H containing C’s eliminates many C’s assignments – Leaves only on-H containing C’s to assign HSQC Spectrum H5 H1 H11 H9 H6 H2 H H8 10 H4 H7 H3 51 10 7 11 6 9 2 8 4 3 H5 H1 H11 H9 H6 H2 H H8 10 H4 H7 H3 51 10 7 11 6 9 2 8 4 3 # of total peaks: 5 1 3 1 4 2 # of non-H C peaks: 2 1 1 0 1 0 ?????????? C12, C13 C15 14,, C 14,, C17 15, C17 C9 C8 C4 C13 C12 C6 C2 C11 C7 C1 C3 C10 C5 Thank You Any Questions?