The influence of water adsorption in AlP04-11 has been studied with X-ray powder diffraction and 27AI and 3IP NMR. With X-ray powder diffraction, a change of the crystal symmetry from ZMA2 to PNA2, is observed upon water adsorption, resulting in a diminished unit-cell volume and more elliptical pores. N M R was used to study the hydration on an atomic scale. With 27Al double rotation (DOR) and magic angle spinning (MAS) NMR, the quadrupole coupling constants (CQ) and asymmetry parameters (7) of the different A1 sites in dry and wet AlPO4-11 were determined and correlated with the symmetry of the A1 site obtained from literature data. In contrast with earlier 27Al DOR measurements,' spectral simulations of 27Al MAS and DOR N M R spectra measured at 7.0 T prove the preferential hydration of one tetrahedral aluminum site in Alp@-1 1 (five crystallographically different sites), transforming this site reversibly into octahedrally coordinated aluminum.* From the observed correlation between the XRD data and CQ, it was concluded that the A12 site becomes preferentially octahedrally coordinated. On the basis of 27Al DORand 31P MAS NMRmeasurements performed on the partially hydrated samples, it is shown that the transformation upon hydration is a local process, comparable to the symmetry change observed upon adsorption of sorbates in

Abstract-13C NMR (CMR) spectra of a number of di-and trisubstituted ethylenes have been measured. Very consistent values are found for the differential shieldings of allylic carbons in a number of linear, (Z)-and (E)-disubstituted ethylenes. The discrepancies between the several structural elements are explained tentatively by assuming different rotational preferences in the (2) It is confirmed, that API's recent relabelling of the isomers of 3-Me-2-hexene was justified. Furthermore, the (E)-configuration is assigned to the high-boiling isomer of 3,4,4-triMe-2-pentene. On the other hand, the high-boiling isomer of 3-Et-4-Me-2-pentene is shown to be the (2)-isomer. For the isomeric pair of geraniol and nerol, the (E)-configuration is assigned to the former and the (2)-configuration to the latter, in agreement with our recent PMR investigations.

Silica gel and Cab-O-Sil were chemically modified (silylated) with 3-aminopropyltriethoxysilane and 3-methacryloxypropyltrimethoxysilane under carefully controlled conditions. Subsequently the products were investigated by elemental analysis, Fourier transform IR spectroscopy, and 13C and 29Si crosspolarization magic angle spinning NMR (CP-MAS NMR). The influence of the reaction conditions of the silylation and the effect of subsequent heat treatment and water addition were studied. The resulting differences shed new light on the combined effects of reaction conditions and silica surface structures on the course of the reactions. Some assignments of 29Si NMR signals to specific structures were confirmed, while in one case a reassignment was proposed.

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Calcined dehydrated AlP04-5 has been studied by X-ray powder diffraction, 31P MAS, and 27Al MAS and double-rotation (DOR) NMR. The results indicate that three crystallographically different sites can be distinguished in the structure of dehydrated AlP04-5 in the ratio 1:l:l. The observed splitting of the N M R spectra is correlated to the line width of the XRD peaks between 219 = 19O and 28 = 23'. Simulations of 27Al DOR (4.7,9.4, and 1 1.7 T) and MAS spectra (7.0 and 9.4 T ) yield theisotropicchemical shifts (6i,),quadrupolar coupling constants (CQ), and the asymmetry parameters ( T ) of the different sites in dry AFI. The interaction of water, methanol, ammonia, and acetonitrile with AlP04-5 and AlPO4-11 is studied by XRD and 27Al DOR and MAS NMR. Both water and ammonia are able to coordinate to part of the framework aluminum, leading to five-and/or six-coordinated aluminum. The relative amounts of five-and six-coordinated aluminum depend on the crystal structure and the interacting sorbate. Whereas water in AlPO4-11 is interacting with one specific aluminum site (Alz), the interaction of water with AlP04-5 occurs randomly. This leads to a broadening of the tetrahedral signals at higher water loading (above 10-12 wt %). At low MAS frequencies some dipolar broadening occurs, whereas at high spinning frequencies or 850-1000 Hz DOR the broadening is caused by site distribution. Methanol and acetonitrile do not interact with framework atoms. These molecules are too big to coordinate to framework aluminum in AFI and AEL type molecular sieves. The broadening of the spectral features observed after methanol adsorption is apparently due to an increase in chemical shift dispersion brought about by nonspecific interactions of methanol with the framework, thereby causing a larger spread in AI-0-P angles.