What is a doublet of doublets in NMR

The height of the lines may be equal or unequal.A doublet of triplets occurs when jba > jbc.This hydrogen is split by the hydrogen on the same carbon at 4.95 and its 3 bond neighbor, the hydrogen at 5.79:However, aesthetically speaking, it looks like a quartet to me.A quartet is not possible, based on the xylose molecule.

Overview of doublet in nmr.One adjacent proton splits an nmr signal into a doublet and two adjacent protons split the signal into a triplet.A triplet of doublets (td) is a pattern of three doublets, in a 1:2:1 ratio of relative intensities, that results from coupling to two protons (or other spin 1/2 nuclei) with a larger j value and one proton (or other spin 1/2 nucleus) with a smaller j value.The distance between the two pairs of lines on each edge.My gut tells me that this is a doublet of doublets.

Let's examine the hc signal at 6.21 ppm.This hydrogen is split by 2 diastereotopic hydrogens on an adjacent carbon.I would assume this is correct because there are 3hs within 3 bonds to couple with the hydrogen in that environment.There are four separate peaks because hc is coupled to both ha and hb, but with different coupling constants for each.This case assumes neighbouring protons have inequivalent effects (they have differing coupling constants with the observed proton).