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

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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.

Explanation:

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

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is

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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.

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For example, Peak A indicates that the #"H"# at 4.1 ppm is attached to the #"C"# at 60 ppm.

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

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