Item

Abstract

A novel 2D proton solid-state NMR experiment is described in which the spins evolve freely during the evolution period, while they are decoupled from each other by a multiple-pulse sequence in the detection period. The resulting 2D spectrum allows the correlation of chemical shifts with dipolar interactions. It is useful for assigning proton chemical shift tensors and for recording simplified wide-line spectra whose meaning is discussed in terms of a “gedanken” experiment. The method is applied to a single crystal of malonic acid (MA). The long-standing problem of assigning the previously measured proton chemical shift tensors in MA to the proton sites is solved. For the first time line splittings are resolved which result from dipolar interactions of the carboxylic protons in MA. They are discussed in terms of the geometry of the hydrogen bonds formed by these protons.