1H NMR Chemical shift (δ) depends on molecular structure and solvent

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Presentation transcript:

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)

H2 H4 H3 H3 3 H4 4 H2 2

H6 H8 H2 H4 H7 H3 H3 3 H7 7 H4 4 H8 8 H2 2 H6 6

H1 H6 H8 H2 H4 H7 H3 H3 3 H7 7 H4 4 H8 8 H2 2 H6 6 H1 1

H5 H1 H6 H8 H2 H4 H7 H3 H3 3 H7 7 H4 4 H8 8 H2 2 H6 6 H1 1 H5 5

H11 H9 H5 H1 H10 H6 H8 H2 H4 H7 H3 H3 3 H7 7 H4 4 H10 10 H8 8 H2 2 H6 H9 6 9 H11 11 H1 1 H5 5

H11 H9 H5 H1 H10 H6 H8 H2 H4 H7 H3 H3 3 H7 7 H4 4 H10 10 H8 8 H2 2 H6 H9 6 9 H11 11 H1 1 H5 5

LONG-RANGE COUPLING H11 H9 H10 H5 H1 H8 H6 H2 H4 H7 H3 H3 3 H7 7 H4 4

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

H11 H9 H5 H1 H10 H6 H2 H8 H4 H7 H3 5 1 10 3 7 11 6 2 8 4 9

H11 H9 H5 H1 H10 H6 H2 H8 H4 H7 H3 5 1 10 3 7 11 6 2 8 4 9

# of total peaks: 5 1 3 1 4 2 # of non-H C peaks: 2 1 1 1 ?????????? C12, C13, C14, C15, C17 ?????????? C14, C15, C17 C6 C7 C1 C8 C2 C9 C3 C11 C5 C4 C10 C13 C12

Thank You Any Questions?