October 5, 2011
One of the trickiest parts of interpreting a 1H-1H COSY experiment is deciding how to classify the correlations. The goal of this puzzle is to assess the COSY correlations and narrow down a set of fragments that support the data.
An expansion of the aromatic region of a 1H NMR spectrum shows four methine multiplets at 6.61, 7.15, 7.22 and 7.58 ppm with coupling constants less than 2.5 Hz. The 1H-1H COSY spectrum below points to two off-diagonal correlations: between 6.61 and 7.15 ppm and another at 7.22 and 7.58 ppm. Are the correlations on the COSY experiment relating to 3JHH or 4JHH or 5JHH coupling responses?