organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
One of the above-mentioned crystalline compounds, bis(2-
ethyl-3-hydroxy-6-methylpyridinium) succinate–succinic acid
(1/1), (I) (Fig. 1), was obtained directly as a result of the
reaction of 2-ethyl-6-methylpyridin-3-ol with succinic acid. A
pure sample of another compound, 2-ethyl-3-hydroxy-6-
methylpyridinium hydrogen succinate, (II) (Fig. 2), can be
prepared by transformation of (I) (see Experimental).
ISSN 0108-2701
Two succinic acid derivatives of
2-ethyl-6-methylpyridin-3-ol
Alexander S. Lyakhov,a* Ludmila S. Ivashkevich,a
Vladimir L. Survilob and Tatjana V. Trukhachovab
aResearch Institute for Physico-Chemical Problems of Belarusian State University,
Leningradskaya Street 14, Minsk 220030, Belarus, and bBelmedpreparaty RUE,
Fabritsius Street 30, Minsk 220007, Belarus
Correspondence e-mail: lyakhov@bsu.by
Received 5 December 2011
Accepted 19 December 2011
Online 23 December 2011
Crystals of bis(2-ethyl-3-hydroxy-6-methylpyridinium) succin-
ate–succinic acid (1/1), C8H12NO+ꢀ0.5C4H4O42ꢁꢀ0.5C4H6O4,
(I), and 2-ethyl-3-hydroxy-6-methylpyridinium hydrogen suc-
cinate, C8H12NO+ꢀC4H5O4ꢁ, (II), were obtained by reaction of
2-ethyl-6-methylpyridin-3-ol with succinic acid. The succinate
anion and succinic acid molecule in (I) are located about
centres of inversion. Intermolecular O—Hꢀ ꢀ ꢀO, N—Hꢀ ꢀ ꢀO
and C—Hꢀ ꢀ ꢀO hydrogen bonds are responsible for the
formation of a three-dimensional network in the crystal
structure of (I) and a two-dimensional network in the crystal
structure of (II). Both structures are additionally stabilized by
ꢀ–ꢀ interactions between symmetry-related pyridine rings,
forming a rod-like cationic arrangement for (I) and cationic
dimers for (II).
The asymmetric unit of (I) comprises one 2-ethyl-6-methyl-
3-hydroxypyridinium cation, half a succinate anion (fully
deprotonated) and half a succinic acid molecule. All atoms
occupy general positions. The succinate anion and succinic
acid molecule are located about centres of inversion, imposing
Ci symmetry on both components. However, their non-H-
atom skeletons show almost planar configurations corre-
sponding to noncrystallographic C2h symmetry, with r.m.s.
˚
deviations from planarity of 0.0056 A for the succinic acid
˚
molecule and 0.0612 A for the succinate anion (Pilati & Forni,
1998).
In (I), the bond lengths and valence angles are in the
expected ranges for all components of the compound (CSD).
In the carboxyl group of the succinic acid molecule, the C12—
Comment
˚
A succinic acid derivative of 2-ethyl-6-methylpyridin-3-ol is
used as a nootropic drug in medical practice (Voronina, 1992,
and references therein). It is also known for its antioxidant
(Klebanov et al., 2001), antihypoxant (Luk’yanova et al., 1990),
cardioprotective (Golikov et al., 2004; Sidorenko et al., 2011)
and antistressor (Tilekeyeva & Sitina, 2005; Sariev & Kravt-
sova, 2005) effects. As no crystal data are available for any
succinic acid derivatives of 2-ethyl-6-methylpyridin-3-ol
[Cambridge Structural Database (CSD), Version 5.32,
November 2010; Allen, 2002], in the present work we intended
to obtain such structural information.
Our preliminary investigation, carried out by X-ray powder
diffraction analysis, revealed that the reaction of 2-ethyl-6-
methylpyridin-3-ol with succinic acid (1:1 molar ratio) could
give either one crystalline compound or its mixture with
another one (the ratio of these products depends on the
reaction conditions). The aim of the present work was to
obtain pure crystalline samples of the compounds and inves-
tigate their crystal structures using single-crystal X-ray
diffraction.
O121(H) bond length of 1.304 (2) A is longer than the
˚
carbonyl-group C12—O122 bond length of 1.196 (2) A. The
C10—O101 and C10—O102 bond lengths of the carboxylate
groups of the succinate anion are close to each other, being
˚
1.2587 (18) and 1.2327 (19) A, respectively.
There are hydrogen bonds in the crystal structure of (I)
(Table 1 and Fig. 3). Intermolecular O—Hꢀ ꢀ ꢀO hydrogen
bonds between the succinic acid molecules and the succinate
anions connect the components into polymeric chains
extending along the [210] direction. Each 2-ethyl-3-hydroxy-6-
methylpyridinium cation is bonded to three such polymeric
chains through three hydrogen bonds, namely N—Hꢀ ꢀ ꢀO, O—
Hꢀ ꢀ ꢀO and C—Hꢀ ꢀ ꢀO, forming a three-dimensional polymeric
network. There are additional ꢀ–ꢀ interactions between the
pyridine rings, with centroid–centroid (Cgꢀ ꢀ ꢀCg) distances of
v
˚
about 3.58 A [Cgꢀ ꢀ ꢀCg ; symmetry code: (v) ꢁx, ꢁy + 1,
ii
˚
ꢁz + 1] and of about 3.74 A [Cgꢀ ꢀ ꢀCg ; symmetry code: (ii)
ꢁx + 1, ꢁy + 1, ꢁz + 1]. These ꢀ–ꢀ interactions result in the
formation of a rod-like cationic arrangement extending along
the a axis (Fig. 3).
Acta Cryst. (2012). C68, o33–o36
doi:10.1107/S0108270111054692
# 2012 International Union of Crystallography o33