Mechanical Stress and Reactivity in Organic Solids

Abstract

Organic single crystals provide an ideal model for studying the factors that influence chemical processes in structured media. Reaction trajectories are well defined and reveal the influence of spontaneous mechanical stresses equivalent to tens of thousands of atmospheres. Analysis of molecular and crystal structures helps to explain both local mechanical properties, which influence reactions, and bulk properties such as melting point, compressibility, and surface energy.

Role of excited electronic states in the high-pressure amorphization of benzene

“…A comprehensive picture of these mechanisms is still lacking; studies as a function of pressure are a powerful tool to complement the concepts developed so far (8)(9)(10)(11)(12). Pressure is indeed the most efficient tool to reduce the intermolecular distances, allowing precise and continuous tuning of the corresponding interactions.…”

Retrospective: Radiation damage and its associated “Information Limitations”

“…The sweeping movements of these bend contours occurs at electron exposure levels that are a small fraction of the exposure that causes fading of the electron diffraction pattern. We also know from experiments on photolytically initiated solid-state chemical reactions (McBride et al, 1986) that conversion of parent molecules to daughter products can generate pressures within 3-D crystals that are half the value that can convert graphite to diamond, and that this happens when as little as 5 percent of the parent molecules have undergone photolysis. In the case of thin specimens, this sort of mechanical stress is likely to drive a flexing or bending type of movement, the largest component of which will be perpendicular to the plane of the thin specimen, but some component of which could well be parallel to the plane of the specimen.…”

Organic Solid-State Reactions

“…The small particles are mixed to react, provided the crystal packing allows the release of positive chemical stress by molecular migration. A judgment of local stress upon the di-undecanoyl-peroxide photodecomposition at 20 K by IR measurements is available [33]. In addition, an "elastic multipole theory" considering the chemical pressure for the description of "reaction cavities" or "molecular cavities" has been put forward with the claim to "quantitatively understand" solid-state reactivity [34].…”