The effect of magnetic field on the shape of etch pits of paracetamol crystals

Etching patterns on the monoclinic and orthorhombic paracetamol

“…11 The structure of the hydrogen-bonded 2D-network and the mechanism of the selective interaction of the solvent molecules with different functional groups of the paracetamol molecules at the crystal surface were considered when interpreting the etching patterns. 12 As additional arguments in favor of the interpretation proposed in ref.…”

“…9 This manifests itself in the different growth rates of different faces, or in their different wettability, which were studied for paracetamol I. 2,3,9,10,11,12 In a series of our earlier publications we have studied (by optical microscopy 2,3,10,11,12 and by the AFM 13 ) the etching patterns formed on different faces of paracetamol I at the initial stages of the dissolution in different solvents (dichloroethane, nitrobenzene, acetic anhydride, acetone, ethyl acetate, and pyridine in carbon tetrachloride), and also, for a comparison, as a result of thermal treatment (sublimation). 2,3 The shapes of the etching pits formed on different crystal faces were shown to be different for the same etching agent, and also for the chemical 10,11,12 and for the thermal etching.…”

“…2,3 The etching patterns on the same face (010), parallel to the molecular layers, were shown to be different for different etching agents. 2,3,10,11,12 A correlation between the donor numbers of etching agents and the extent of the anisotropy of the etching pits (from lines alongated along one crystallographic direction to almost isometric parallelograms and hexagons) was suggested. 10 The cooperative nature of the dissolution with a positive feed-back accounting for the autolocalization of the process was discussed.…”

“…19 of have completely reproduced all the experimental results published in refs., 2,3,10,11,12 using exactly the same set of solvents and the same experimental techniques (although, strangely, they did not cite any of the previous publications). They have suggested another interpretation of these results, assuming that it is the surface diffusion that plays the key role in forming etching patterns.…”

“…To explain the discrepancy, the above authors 19 were forced to take into consideration the same factors as we did in our previous publications, 2,3,11,12 namely the anisotropy of the crystal structure, the differences in the interaction of solvent molecules with different functional groups at the paracetamol crystal surface (molecular recognition between solvent molecules and crystal molecules), and the changes or the interruption of the original hydrogen-bonded 2D-network in the paracetamol crystals resulting from an adsorption of a solvent molecule. All the above mentioned factors can be important for the dissolution.…”