Etching patterns on the monoclinic and orthorhombic paracetamol

Abstract

The initial stages of etching the monoclinic (I) and the orthorhombic (II) polymorphs of paracetamol crystals by a series of agents (10%-solutions of acetic anhydride, pyridine, 1,4-dioxane, morpholine, N-methylmorpholine in carbon tetrachloride) were studied and the corresponding etching patterns were compared. For the first time, it was possible to observe different etching patterns when dissolving not only the faces of the crystals parallel to molecular layers, but also the faces normal to the molecular layers.

Bulk and Surface-Stabilized Structures of Paracetamol Revisited by Raman Confocal Microscopy

“…The orientation of the single crystal under investigation must be known to extract useful information from the data. Following experimental reports , and computational predictions, the needlelike single crystals lie on the (001) or ab plane, which is also the crystal orientation parallel to the molecular layers ,,, with a growth direction along a , that is, the direction of elongation of paracetamol molecules . With this in mind, we can label all spectra following Porto’s notation, that is, we can identify the matrix element ( ij ) of the polarizability tensor responsible for the Raman scattering in each specific experimental configuration, , as marked in the figure.…”

Solvent-free mechanochemical route for green synthesis of pharmaceutically attractive phenol-hydrazones

“…The mechanisms of solid-state transformations during grinding have been generally attributed to the formation of eutectic melts, 44 molecular transport through surfaces due to sublimation 45,46 or in the bulk of material 47,48 and to reactions mediated by amorphous or metastable crystalline phases. 49,50 In this work we focused on the properties of raw materials that could facilitate a reaction or make it harder.…”

Revisiting paracetamol in a quest for new co-crystals

“…The main difference in the preparation of both paracetamol : morpholine solvates previously reported [38][39][40]43 (1 and 2) is the paracetamol : morpholine ratio used. The relative molar proportion of paracetamol and morpholine used in the preparation of solvate 1 38,39 was 1 : 1 and it was approximately 1 : 2.5 for solvate 2.…”

“…37 Between 2002 and 2004, several multicomponent crystal forms with paracetamol were reported. Co-crystals and solvates with 4,4bipyridine (1 : 1), piperazine (1 : 0.5), N,N-dimethylpiperazine (1 : 0.5), N-methylmorpholine (1 : 0.5), 38,39 acetic anhydride and pyridine 40,41 were successfully prepared and the main interactions responsible for their formation are not only O-H … O and N-H … O, but also N-H … N and O-H … N. With 1,4-dioxane three hemisolvates were disclosed, 38,39,42 two of which are polymorphs that reversibly convert into each other at 230-250 K. 42 Oswald et al 38,39,43 managed to produce two paracetamol : morpholine solvates with different stoichiometries, by modifying the reactant quantities present in solution and using morpholine both as co-former and as solvent. In 2008, Oswald and Pulham produced a paracetamol hemiskis(piperazine) ethanol solvate.…”