Issue 10, 2018

l-Malic acid crystallization: polymorphism, semi-spherulites, twisting, and polarity

Abstract

L-Malic acid (LMA) is a commodity chemical that was first isolated in the crystalline form in the 18th century, yet it has been troublesome for more than 100 years because of its resistance to forming crystals that are suitable for optical or X-ray analysis. LMA crystallizations from the melt and from solutions are reevaluated here. Indeed, LMA crystallizes poorly from water. However, a flowable solid was produced by growth from ethyl acetate at room temperature to give large well-formed trapezoidal prisms of a new LMA polymorph, form II (space group P21, a = 5.7343(6) Å, b = 6.7990(7) Å, c = 6.9949(7) Å, β = 104.9610(10)°, V = 263.47(5) Å3, Z = 2). The growth of LMA from ethyl acetate at 4 °C produced hard, near-spherical aggregates of the only previously known phase, which also crystallizes in the space group P21 (form I). From the melt, LMA produces spherulites with helicoidal twisting of its individual fibrils. Polycrystalline ensembles are shown to arise from the inequivalent branching of the ends of a polar crystal which adopt semi-spherulitic morphologies as crystallization intermediates. Tailor-made additives were used to assign the absolute growth direction of the polar spherulite radii as +b.

Graphical abstract: l-Malic acid crystallization: polymorphism, semi-spherulites, twisting, and polarity

Supplementary files

Article information

Article type
Paper
Submitted
06 déc. 2017
Accepted
17 janv. 2018
First published
17 janv. 2018

CrystEngComm, 2018,20, 1383-1389

L-Malic acid crystallization: polymorphism, semi-spherulites, twisting, and polarity

J. Yang, C. T. Hu, A. G. Shtukenberg, Q. Yin and B. Kahr, CrystEngComm, 2018, 20, 1383 DOI: 10.1039/C7CE02107K

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements