(13)C AND (29)SI NMR INVESTIGATION OF ACETONE ADSORBED ON SILICA SURFACES (CARBON-13, SILICON-29

$sp{13}$C MAS experimental results have shown that the $rm(CHsb3)sb2COcdots HOSi$ interactions yields a large low-shielding and a small high-shielding shift of the carbonyl and methyl peaks. The number of surface interaction sites, the equilibrium constant, and the chemical shifts of the H-bonded complex have been obtained in the acetone/SiO$sb2$ system.;Relaxation studies $rm(Tsb1sp{C}, Tsb1sp{H}, Tsb{1rho}sp{H}, Tsbsp{2L}{prime}$ and $rm Tsb{CH})$ on the acetone/SiO$sb2$ system gave mutually consistent results. Relaxation results indicate that acetone is in the motional narrowing limit; both carbons rely upon the same set of protons for CP; there is a fast $sp1$H-$sp1$H spin exchange between the methyl protons and silanol protons; and acetone may rotate rapidly about the H-bonding axis and/or jump rapidly from one site to another, reducing the effective $sp1$H-$sp{13}$C dipolar interaction substantially at room temperature.;$sp{13}$C MAS studies of partially deuterated of acetone/SiO$sb2$ and $rmlbrack(CHsb3)sb3Crbracksb2CO/SiOsb2$ including T$rmsb{CH}$ and T$rmsb{1rho}sp{H}$ measurement, indicate that both methyl protons and silanol protons participate in CP to carbonyl carbons. $sp{13}$C MAS spectra obtained with and without proton decoupling on the acetone/SiO$sb2$ system indicate that most acetone molecules are liquid-like in the acetone/SiO$sb2$ system.;Variable temperature $sp{13}$C MAS experiments were carried out on the acetone/SiO$sb2$ system. From studies of the behavior of the chemical shifts of the acetone/SiO$sb2$ system as a function of temperature, it was found that the fraction of H-bonded acetone, the equilibrium constant for formation of H-bonding complex increases as the temperature is decreased. Values of $rmDelta Hspcirc$ and $rmDelta Sspcirc$ for the formation of H-bonded acetone on the silica surface were obtained.;From studies of the behavior of the line widths of (acetone-1-$rmsp{13}C/SiOsb2+$ acetone-1-$rmsp{13}C/SiOsb2)$ ($theta$ = 0.80) as functions of sample temperature, it appears that the line broadening of the methyl and carbonyl peaks at low temperature caused primarily by two factors: (1) multiple-site chemical exchange; and (2) chemical shift dispersion.;From VT $sp{13}$C MAS studies of acetone-1,2,3-$rmsp{13}C/SiOsb2$ and (acetone-1-$rmsp{13}C/SiOsb2+$ acetone-2-$rmsp{13}C/SiOsb2),$ it appears that the line broadening of the methyl and carbonyl peaks at the low temperature is not only caused by chemical exchange and chemical shift dispersion, but also by $sp{13}$C-$sp{13}$C dipolar interactions.