The hydrogenation of alkenes by heterogeneous catalysts has been studied for 80 years. The foundational mechanism was proposed by Horiuti and Polanyi in 1934 and consists of three steps: (i) alkene adsorption on the surface of the hydrogenated metal catalyst, (ii) hydrogen migration to the β-carbon of the alkene with formation of a σ-bond between the metal and α-C, and finally (iii) reductive elimination of the free alkane. Hundreds of papers have appeared on the topic, along with a number of variations on the Horiuti–Polanyi mechanism. The second step is highly reversible, leading to extensive deuterium–hydrogen exchange when D2(g) is used. This paper describes the investigation of gas-phase reactions between deuterium and 1-butene using a supported palladium catalyst under ambient laboratory conditions and how the results are consistent with the Horiuti–Polanyi mechanism. An Excel spreadsheet for modeling the extent and distribution of deuteration within butane-d x is described. Interested readers could develop a laboratory or research experience based on results presented here. The results are also suitable for inclusion in an upper-division chemistry course in which organometallic chemistry or reaction mechanisms involving heterogeneous catalysts are discussed. The catalyst tubes are inexpensive and easy to construct. Analysis of the butane produced by 1H NMR and GC–MS leads to numerous conclusions in support of the Horiuti–Polanyi mechanism.

Sorption and diffusion properties were studied for the system disodium salt of 16,17-dimethoxyviolanthrone leuco (I) in cellulose, the solution medium being aqueous sodium hydroxide and sodium hydrosulphite. The sorption equilibrium, over a wide concentration range, was characterized by a distribution coefficient which decreased with increasing concentration. A small degree of irreversible bonding or chemisorption was observed at very low concentrations. The cellulose sorbed large amounts of (I) and this was accompanied by considerable swelling, the degree of which, relative to the original thickness, accelerated with increasing concentration of solute. Diffusion experiments in terms of transport from one solution to another through single and multilayer cellophane membranes afforded concentration gradient and membrane swelling gradient data as well as diffusion coefficients. While the degree of swelling was linear with the distance in the membrane under steady-state diffusion conditions, the diffusion coefficient was markedly concentration dependent, the range of variation being 1000-fold. Interpretation of the sorption, swelling and diffusion data point to greater attraction between .solute molecules and cellulose at lower solute concentrations. By consideration of activity coefficients deduced from the sorption equilibrium data, a concentration-independent difiusion coefficient was obtained.

Equilibrium absorption-desorption isotherms and steady-state diffusion-rate data are reported for the leuco forms of three position isomers of dibenzamido-1 6H-dinaphtho(2,3-a : 2',3'-i)-carbazole-5,10,15,17-tetrone, viz., the 4,9(11), the 4,l l(I1T) and the 6,9(1V) dibenzamidos, and are compared to previously reported data for the leuco form of 16,17-dimethoxy-violanthrone (I). The distribution coefficients and steady-state diffusion rates for the carbazoles are lower than those found for ( I ) , and carbazole (11) showed a unique absorption-desorption hysteresis effect while the other carbazoles and (I) were essentially reversible. The diffusion rates of the carbazoles are correlated with the extent of interaction of the sorbate with the cellulose as deduced from the slopes of the sorption isotherms, steeper slopes indicating more interaction and leading to lower diffusion coefficients. The greater diffusion of (I) can be due to its lower interaction with the cellulose at the higher concentration where comparison is made. Explanations for the differences in sorption and diffusion properties among the carbazoles are explored in terms of thespacing of the benzamido groups in the three isomers. The hysteresis appears to be associated with the dipole moment of (11) arising from the dissymmetry of positioning of the benzamido groups.