Atomic force microscopy and Solid‐State rearrangement of benzopinacol

Abstract

The solid-solid chemical reaction of benzopinacol (1) with p-toluenesulphonic acid monohydrate (2) to give a quantitatively proton-catalysed pinacol rearrangement with formation of triphenylacetophenone (3) in the absence of a solvent was studied preparatively and mechanistically using atomic force microscopy (AFM) measurements and known crystal structure data. The reaction rate is dramatically enhanced if the water of reaction is continuously removed. AFM reveals that no reaction occurs on (001) of 1 whereas (100) exhibits distance dependent craters and volcano-like mounds over areas extending to 1.5 m m from the contact edge of the crystals with 1 undergoing phase rebuilding while reacting. A mechanism resembling the formation of membrane potentials is seen for the first time in crystals. Thus it appears that catalytic protons migrate without their counterions from one molecular compartment to the next by proton consumption at its inside and proton liberation at its outside, which is the inside of the next compartment. The uppermost molecular layer determines reactivity or non-reactivity. On (001) of 1 the hydroxyl groups occur with their hydrogens up. Hence no AFM features are found and crystals of 2 do not become adhered to 1. However, on (100) the hydroxyl hydrogens point down (free electron pair up). Protonation is possible, chemical reaction is indicated by the formation of the AFM features and crystals of 2 adhere firmly to the surface of 1 after reaction.

Waste‐free synthesis and production all across chemistry with the benefit of self‐assembled crystal packings

“…This is explained with the crystal packing. [22] Furthermore, molecular steps on an unreactive face exhibit a different crystallographic step face and will therefore be reactive there if the molecules are in the same orientation as on the corresponding extended reactive face of the crystal. For example, crystalline thiohydantoin undergoes ring opening addition of gaseous methylamine with remarkable rate differences between the natural (110) and the cleaved (10À2) face that is 66.078 inclined.…”

Mechanism of solid-solid resolution of pantolactone

“…Therefore, we undertook an atomic force microscopic (AFM) study of the solid-solid * Author to whom correspondence should be addressed. (2) and - [4,5]decane (3) and interpret the experimental results in the light of the crystallographic data for neat 2 and 3. 7 We chose the systems 1-2 and 1-3 for the first mechanistic AFh4 investigation of a solid-solid clathration.…”

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The enantioselective solid-solid clathration of (S)-pantolactone ( I ) into (R,R)-trans-2,3-bis(diphenylhydroxymethyl)-l,4-dioxaspiro[4~4]nonane (2) and -[4.5]decane (3) was studied preparatively and mechanistically using atomic force microscopy (AFM) measurements and crystal packing data. Shortdistance solid-to-solid sublimation mechanisms occur in both cases with initial formation of epitaxial floes along the b-axis in 2 and random craters in 3.

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Atomic force microscopy of reaction of ammonia gas with crystalline substituted benzoic acid

“…Recently, it has been applied to the submicroscopic investigation of chemical reactions on crystal solids. 1,2 These studies have revealed new perspectives in the realm of gas-solid reactions, [3][4][5][6][7] solid-solid reactions, [8][9][10][11] and crystal photolyses. [12][13][14][15][16][17][18][19] AFM measurements on single-crystal sur-faces reveal phase rebuildings with well-directed long-range molecular transports.…”