Polymorphism of Cinnamic and α-Truxillic Acids:  New Additions to an Old Story

Abstract

X-ray structure determinations have been carried out and analyzed for two conformational polymorphs of α-truxillic acid (2). Polymorph I (cell parameters known since 1959) is isolated upon recrystallization of 2 from acetic acid−petroleum ether solution, while polymorph II (fully characterized in 1993) is the product of a one-phase solid-state reaction of tail-irradiated α-cinnamic acid. For polymorph II, two redeterminations of mixed crystals containing solid solutions of α-cinnamic acid and 2 (68.1 and 89.5%, respectively) were performed. Analysis of the structural parameters of the 1993 and present redeterminations of the polymorph II structures, as well as comparison to data from the Cambridge Structural Database, confirm that claims of errors in the 1993 structure determination of polymorph II are unfounded. X-ray quality crystals of the β-polymorph of trans-cinnamic acid (cell parameters known since 1964) have been obtained from Et2O/petroleum ether solutions; the crystal structure is quite similar to that of 4-chlorocinnamic acid.

Effect of hydrogen bonding in the vibrational spectra of trans‐cinnamic acid

“…However, in a recent determination of β-polymorph [45] the molecule adopts an s-cis conformation. This may raise the question about the polymorph present in the commercial sample.…”

Complexes of the selected transition metal ions with 4-methoxycinnamic acid

“…It has antibacterial, antifungal and antiparasitic properties, and its derivatives are an important pharmaceuticals for high blood pressure and stroke prevention having antitumour activity [2][3][4][5]. From the survey of literature, it follows that there are articles that mainly deal with the study of cinnamic acid structure, its properties, derivatives and complexes with alkali metals, such as Zn(II), Hg(I), Hg(II), Cd(II), and Zn(II) [2][3][4][5][6][7][8][9][10]. Having very important biological activity and specific structure, cinnamic acid has been still extensively and solidly studied.…”

Monitoring photo-induced population dynamics in metastable linkage isomer crystals: a crystallographic kinetic study of [Pd(Bu4dien)NO2]BPh4

“…It has been shown that excitation wavelengths close to the absorption maximum can lead to the pump light being too strongly absorbed in the outer layers of the crystal, effectively blocking it from reaching the centre of the sample and thus limiting the photo-conversion level. 47,48 To avoid this, a wavelength in the tail of the main absorption band is generally preferable. For 1ÁTHF, a series of LED wavelengths between 390 and 500 nm were initially tested (see ESI †).…”