How do you calculate nmr j value for quartet and for multiple?

The J value in NMR spectroscopy represents the coupling constant between nuclei and is measured in hertz (Hz). For a quartet, you can determine the J value by measuring the distance between the peaks of the quartet; this distance corresponds to the J value. For multiplets, you can analyze the spacing between the peaks to identify the couplings involved, often requiring additional analysis of the splitting patterns to extract the J values for each coupling interaction. In both cases, ensure that the peaks are well-resolved for accurate measurements.