Proton Chemical-Shift Spectra

摘要: Abstract Three related methods are explored for obtaining high-resolution proton spectra without spin–spin splittings, termed “chemical-shift spectra.” They based on two-dimensional J spectroscopy, where the F 1 dimension is derived by Fourier transformation of spin-echo modulation. The first technique superimposes spectrum its reflection in = 0 axis, creating multiplet patterns form a St. Andrew's cross. other two techniques purge certain antiphase product-operator terms, either dispersal an inhomogeneous effective radiofrequency field oriented at magic angle (54.7°) or means z filter. In all three cases, multiplets separated symmetry filter and their centers taken as measure respective chemical shifts. 400 MHz chemical-shift 4-androsten-3,17-dione presented illustrative example. Good separation achieved, even interpenetrating spin with near degeneracies Complications due to strong-coupling effects discussed.