The correlation of the ~960 cm-1 IR absorption band, frequently observed in Sn-BEA zeolite, to the incorporation of Sn in the zeolite framework has been investigated. IR and NMR spectra of freshly calcined and water treated zeolites combined with first principle calculations indicate that the 960 cm-1 band is not a vibration involving Sn but rather a result of isolated internal silanol groups. Thermogravimetric analysis and temperature-programmed desorption showed the silanol groups condense to form water at temperatures between 400 and 700 °C. These silanol groups form slowly at mild relative humidity (~30-40%) and 25 °C, but in less than an hour at 98 °C in liquid water: they are expected to form in the course of an aqueous phase reaction. The water uptake observed following an one-hour liquid water treatment is 1.2 wt% in Sn-BEA with Si/Sn = 125, equal to 4-5 water molecules per Sn or 1 water molecule per 40 Si, too high for all of it to be directly linked to interaction with Sn atoms. Instead this water uptake can be explained by a site that can be hydroxylated at relatively low temperatures and dehydrated at temperatures typically used for zeolite calcination.

Rearrangement of the tetrahydro-derivative of the heptacyclotetradecane Binor-S in the gas phase in hydrogen chloride over a chlorinated platinurn-alumina catalyst at 150" or in solution in dichloromethane containing aluminium chloride gives diamantane in high yields. Methods for functionalisation of diamantane have been developed. Chlorination at 0" with aluminium chloride-acetyl chloride yields equal amounts of 1and 4-chlorodiamantane (the so-called zonal and apical derivatives) whereas use of chlorosulphonic acid a t -5" yields mainly the 1 -chloroisomer. Hydrolysis of the chlorides yields the corresponding alcohols, which are separable by chromatography over alumina. The chlorides and alcohols can be equilibrated with aluminium chloride and with concentrated sulphuric acid, respectively. Oxidation of diamantane with 96% sulphuric acid at 75" yields diamantanone, 9-hydroxydiamantan-3-one, and diamantane-4.9-diol. Treatment of diamantan-3-01 with 70% sulphuric acid yields a mixture of mono-01s. 9-hydroxydiamantan-3-one, diamantane-3.9-dio1, and diamantane-4,g-diol.A SUBSTANTIAL improvement in the technology of adamantane production was recently reported.2 In this new approach conventional batch techniques are replaced by a gas-phase flow system in which the hydrocarbon precursor in a stream of hydrogen chloride is passed over a chlorinated platinum-alumina catalyst at 168". The advantages of the method lie in the greatly improved yields of adamantane and in the almost total elimination of destructive side reactions. We have now achieved similar improvements in the efficiency of rearrangements leading to diamantane (1) (formerly called congressane), the second member of the diamondoid hydrocarbon homologous series.Schleyer and his co-workers were the first to discover that diamantane could be synthesised from the [2 + 21 norbornene photodimer (2) by rearrangement with an aluminium bromide ' sludge ' catalyst in yields of l-lOyo depending on which stereoisomer of the starting material was employed. Disproportionation and fragmentation reactions predominate with these dimers, no doubt because of the presence of the highly labile cyclobutane ring.l Preliminary report, I).

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We use the conversion of protonated glycerol to acrolein for a case study of the mechanism of acid-catalyzed dehydration of polyols in aqueous environments. We employ hybrid Quamtum Mechanics/Molecular Mechanics Molecular Dynamics (QM/MM MD) simulations with biased sampling and perform free energy calculations for the elementary steps of the reaction. We investigate the effects of solvent dynamics and in particular the role of quantum mechanical water in the dehydration mechanism. We present results supporting a mechanism that proceeds via water-mediated proton transfers and thus through an enol intermediate. We find that the first dehydration may take place by two, low-energy pathways requiring, respectively, 20.9 and 18.8 kcal/mol of activation free energy. The second dehydration requires 19.9 kcal/mol of activation free energy while for the overall reaction we compute a free energy change of -8 kcal/mol.