An appreciable increase in spectral resolution in the H-1 nuclear magnetic resonance (NMR) spectra of small organic molecules adsorbed in well-crystallized zeolites is obtained by the application of the magic angle spinning (MAS) technique, which allows to observe slight changes in the proton chemical shifts and to measure well-resolved two-dimensional (2D) NMR spectra. The behavior of 1-butene adsorbed in NaX zeolite is studied by analyzing proton chemical shifts at various temperatures and measuring intramolecular proton-proton distances by means of H-1 NOESY NMR spectroscopy. Drastic changes in the NMR line shape of the protons belonging to the terminal group =CH2 are found at varying temperatures (230-340 K) and pore filling factors (between similar to0.05 and 4 molecules per large cavity). There is clear evidence that 1-butene molecules interacting with the exchangeable Na+ cations in NaX zeolites reveal a change in the conformation in comparison to those in the bulk phase. (C) 2003 American Institute of Physics.