Issue 19, 2022

Chains or rings? Polymorphism of an isoniazid derivative derivatized with diacetone alcohol

Abstract

Isoniazid was derivated with diacetone alcohol in a Schiff-base reaction in order to yield N′-[(2E)-4-hydroxy-4-methylpentan-2-ylidene]pyridine-4-carbohydrazide. The resulting product was determined to be polymorphic, exhibiting two crystal forms: form I and form II. From the crystal structure determination using SC-XRD it was determined that form I crystalizes in the C2/c space group while form II crystalizes in the P21/c space group. The hydrogen bonding patterns of both forms are distinctively different from each other: form I forms a chain hydrogen bond motif by forming a hydrogen bond between the hydroxyl group and the oxygen of the amide group while form II forms dimers with a ring hydrogen bond motif forming between the hydroxyl group and the pyridine group. From DSC analysis form I and form II are enantiotropically related, with form I converting to form II at 132.3 °C before melting at 142.3 °C. Based on both experimental and computational evidence, we conclude that form I is a metastable form, with form II being the most stable form. This is another case of a “disappearing polymorph.”

Graphical abstract: Chains or rings? Polymorphism of an isoniazid derivative derivatized with diacetone alcohol

Supplementary files

Article information

Article type
Paper
Submitted
31 Mar 2022
Accepted
03 Apr 2022
First published
14 Apr 2022
This article is Open Access
Creative Commons BY-NC license

RSC Adv., 2022,12, 11658-11664

Chains or rings? Polymorphism of an isoniazid derivative derivatized with diacetone alcohol

M. C. Scheepers, M. A. Fernandes and A. Lemmerer, RSC Adv., 2022, 12, 11658 DOI: 10.1039/D2RA02057B

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