What is the diference between the most common two-dimensional NMR techniques: COSY and HETCOR?

Question

Santiago Alfonso · Accepted Answer

In COSY, the proton spectra are plotted along each axis, while in HETCOR the proton spectrum is on one axis and the #""^13"C"# spectrum is on the other axis.

COSY —#"CO"#rrelation #"S"#pectroscop#"Y"#
(you may also see it written as H,H-COSY)

In COSY, both axes correspond to #""^1"H"# NMR spectra.

The off-diagonal peaks show which protons are coupled to each other.

The COSY spectrum of ethyl but-2-enoate

For example, peak A indicates a coupling between the #"H"# at 6.9 ppm and the #"H"# at 1.8 ppm.

This shows that the #"CH"_3# group is coupled to the adjacent #"H"# on the alkene.

HETCOR — #"HET"#eronuclear #"COR"#relation Spectroscopy

in HETCOR spectra, a proton NMR spectrum is plotted on one axis and the #""^13"C"# NMR spectrum is plotted on the other.

The peaks show which #"H"# is attached to each #"C"#.

Here is the HETCOR spectrum of ethyl but-2-enoate.

at 4.1 ppm is attached to the #"C"# at 60 ppm.

This corresponds to the #"-OCH"_2"-"# group of the ester.

Isabella Acosta · Answer

undefined COSY (correlation spectroscopy) is used to correlate hydrogen atoms that are two to three bonds apart, providing information about which hydrogens are coupled. HETCOR (heteronuclear correlation) correlates signals from different types of nuclei, like hydrogen and carbon, providing information about which hydrogen atoms are attached to which carbon atoms.