Measurement ofJ(H,H) and long-rangeJ(X,H) coupling constants in small molecules. Broadband XLOC and J-HMBC

New methods for the measurement of homonuclear J(H,H) and heteronuclear long-range J(C,H) coupling constants are presented. The heteronuclear and homonuclear coupling constants are measured by schemes based on J-HMBC and XLOC, respectively, and they all employ a low-pass J filter to eliminate one-bond J(C,H) responses. The J-HMBC experiments are automatically broadband in their excitation over a range of J(C,H) coupling constants whereas the broadband feature for XLOC is achieved by employing the approach used in broadband HMBC.