Acid-base, generally equilibria, characteristics

A final limitation to the interpretation of IGC results is to be noted. In order to favor the establishment of equilibrium conditions between the stationary and mobile phases in an ICjC experiment, the quantities of vapor injected are extremely small (e.g. nanolitre range of concentration). As pointed out by Wesson and Allred, surfaces generally are not energetically uniform. The small amounts of available vapor therefore will tend to adsorb on the most energetic fraction of available sites. Surface energy and acid/base characteristics obtained from IGC will therefore describe the performance of these surface fractions, and not necessarily of the surface as a whole. More detailed descriptions of solid surfaces would necessitate the determination of adsorption isotherms. The suitability of ICjrC for this has... 

One of the most important characteristics of the aldol reaction is its easy reversibility under many conditions. Since this factor has such a generally profound effect, we briefly introduce the topic here. For an aldol addition reaction that is carried out under the influence of a catalytic amount of acid or base in protic medium A//° and AG° can be estimated from thermochemical data. Guthrie has estimated A// and AG for the aldol addition depicted in equation (3) to be -9.8 kcal mol and -2.4 kcal mol , respectively (1 cal = 4.18 J). ° The thermochemical values used in this estimation, and the derived values of A// and AG% refer to species at equilibrium with the covalently hydrated aldehydes. It is not expected that values for the free aldehydes would be greatly different. The equilibrium constant for equation (3) is 4(X) M- ... 

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