2D HMBC

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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. For example ¹H,¹³C-HMBC correlates chemical shifts of protons with carbons separated with two or three bonds, in some cases even the more distant ones.

¹H,¹³C-HMBC is frequently used for assigning of quaternary and carbonyl carbons.

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.