2D HMBC

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{{1H}},{{13C}}-HMBC is frequently used for assigning of quaternary and carbonyl carbons. In some cases it can be used for assigning -OH protons, and protons bonded to other heteroatoms also. For example, HMBC spectrum of naringin: [[Image:Naringin hmbc full struct.pdf]].
{{1H}},{{13C}}-HMBC is frequently used for assigning of quaternary and carbonyl carbons. In some cases it can be used for assigning -OH protons, and protons bonded to other heteroatoms also. For example, HMBC spectrum of naringin: [[Image:Naringin hmbc full struct.pdf]].
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HMBC experiment is quite prone to artifacts, like like <sup>1</sup>J<sub>CH</sub> coupling artifacts. Also, due to the different coupling constants, non equivalent protons bonded to the same nucleus can have different pattern of the crosspeaks.
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HMBC experiment is quite prone to artifacts, like for example <sup>1</sup>J<sub>CH</sub> coupling artifacts. Also, due to the different coupling constants, non equivalent protons bonded to the same nucleus (carbon) can have different pattern of the crosspeaks.
Several betterments was proposed to increase sensivity, reduce artifacts (like <sup>1</sup>J<sub>CH</sub> coupling), measure coupling constants, and others.
Several betterments was proposed to increase sensivity, reduce artifacts (like <sup>1</sup>J<sub>CH</sub> coupling), measure coupling constants, and others.

Revision as of 18:05, 8 January 2011

1H,13C-HMBC spectrum of Sudan I dye
1H,13C-HMBC spectrum of Sudan I dye

2D HMBC (Heteronuclear Multiple Bond Correlation) experiment correlates chemical shifts of two types of nuclei separated from each other with two or more chemical bonds. This is an improvement of the old COLOC experiment. For example 1H,13C-HMBC correlates chemical shifts of protons with carbons separated with two or three bonds, in some cases even with the more distant ones. The zero and double quantum coherences with lowpass filtration for elimination of the single quantum coherences are usually applied in this experiment.

Chemical shift of one nucleus - usually 1H is detected in the directly measured dimension, while chemical shift of second nucleus (heteronucleus or X-nucleus) is recorded in the indirect dimension.

1H,13C-HMBC is frequently used for assigning of quaternary and carbonyl carbons. In some cases it can be used for assigning -OH protons, and protons bonded to other heteroatoms also. For example, HMBC spectrum of naringin: Image:Naringin hmbc full struct.pdf. HMBC experiment is quite prone to artifacts, like for example 1JCH coupling artifacts. Also, due to the different coupling constants, non equivalent protons bonded to the same nucleus (carbon) can have different pattern of the crosspeaks.

Several betterments was proposed to increase sensivity, reduce artifacts (like 1JCH coupling), measure coupling constants, and others.

Implementations

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