l-Alanine methyl ester hydro-chloride monohydrate.

Abstract

The enanti-opure title compound, C(4)H(10)NO(2) (+)·Cl(-)·H(2)O, forms a two-dimensional network by inter-molecular hydrogen bonding parallel to (010). Non-merohedral twinning with a twofold rotation about the reciprocal c* axis as twin operation was taken into account during intensity integration and structure refinement. This twinning leads to alternative orientations of the stacked hydrogen-bonded layers.

Full text

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L-Alanine methyl ester hydrochloride
monohydrate
Martin Lutz* and Arie Schouten
Bijvoet Center for Biomolecular Research, Crystal and Structural Chemistry, Faculty
of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
Correspondence e-mail: m.lutz@uu.nl
Received 24 January 2011; accepted 3 February 2011
Key indicators: single-crystal X-ray study; T = 110 K; mean ?(C–C) = 0.001 A ˚;
R factor = 0.015; wR factor = 0.043; data-to-parameter ratio = 24.2.
The enantiopure title compound, C4H10NO2+?Cl??H2O, forms
a two-dimensional network by intermolecular hydrogen
bonding parallel to (010). Non-merohedral twinning with a
twofold rotation about the reciprocal c* axis as twin operation
was taken into account during intensity integration and
structure refinement. This twinning leads to alternative
orientations of the stacked hydrogen-bonded layers.
Related literature
For the related l-serine methyl ester hydrochloride, see:
Schouten & Lutz (2009). For the theory of twin formation, see:
Cahn (1954). Twin integration is based on Schreurs et al.
(2010) and the twin refinement on Herbst-Irmer & Sheldrick
(2002). The methods of Flack (1983) and Hooft et al. (2008)
were used for the absolute structure determination.
Experimental
Crystal data
C4H10NO2+?Cl??H2O
Mr= 157.60
Triclinic, P1
a = 4.9461 (4) A˚
b = 6.0134 (4) A˚
c = 6.6853 (5) A˚
? = 101.833 (4)?
? = 93.533 (3)?
? = 92.112 (4)?
V = 194.00 (2) A˚3
Z = 1
Mo K? radiation
? = 0.44 mm?1
T = 110 K
0.39 ? 0.29 ? 0.12 mm
Data collection
Nonius KappaCCD diffractometer
Absorption correction: multi-scan
(TWINABS-2008/4;
Sheldrick, 2008a)
Tmin= 0.69, Tmax= 0.75
11388 measured reflections
3213 independent reflections
3180 reflections with I > 2?(I)
Rint= 0.019
Refinement
R[F2> 2?(F2)] = 0.015
wR(F2) = 0.043
S = 1.05
3213 reflections
133 parameters
3 restraints
All H-atom parameters refined
??max= 0.20 e A˚?3
??min= ?0.13 e A˚?3
Table 1
Hydrogen-bond geometry (A˚,?).
D—H???A
N1—H1N???Cl1
N1—H2N???Cl1i
N1—H3N???O3
O3—H1O???Cl1ii
O3—H2O???Cl1iii
C2—H2???O2i
Symmetry codes: (i) x ? 1;y;z; (ii) x;y;z þ 1; (iii) x ? 1;y;z þ 1.
D—HH???AD???AD—H???A
0.909 (11)
0.895 (12)
0.908 (12)
0.860 (18)
0.808 (17)
0.901 (11)
2.418 (11)
2.275 (12)
1.888 (12)
2.364 (18)
2.470 (17)
2.385 (10)
3.3007 (7)
3.1665 (6)
2.7519 (9)
3.2220 (7)
3.2613 (7)
3.1302 (9)
163.9 (9)
174.2 (10)
158.2 (9)
175.1 (15)
166.9 (14)
140.0 (8)
Data collection: COLLECT (Nonius, 1999); cell refinement:
PEAKREF (Schreurs, 2008); data reduction: Eval15 (Schreurs et al.,
2010) and TWINABS-2008/4 (Sheldrick, 2008a); program(s) used to
solve structure: SHELXS97 (Sheldrick, 2008b); program(s) used to
refine structure: SHELXL97 (Sheldrick, 2008b); molecular graphics:
PLATON (Spek, 2009); software used to prepare material for
publication: manual editing of SHELXL CIF file.
Supplementary data and figures for this paper are available from the
IUCr electronic archives (Reference: EZ2229).
References
Cahn, R. W. (1954). Adv. Phys. 3, 363–445.
Flack, H. D. (1983). Acta Cryst. A39, 876–881.
Herbst-Irmer, R. & Sheldrick, G. M. (2002). Acta Cryst. B58, 477–481.
Hooft, R. W. W., Straver, L. H. & Spek, A. L. (2008). J. Appl. Cryst. 41, 96–103.
Nonius (1999). COLLECT. Nonius BV, Delft, The Netherlands.
Schouten, A. & Lutz, M. (2009). Acta Cryst. E65, o3026.
Schreurs, A. M. M. (2008). PEAKREF. University of Utrecht, The Nether-
lands.
Schreurs, A. M. M., Xian, X. & Kroon-Batenburg, L. M. J. (2010). J. Appl.
Cryst. 43, 70–82.
Sheldrick, G. M. (2008a). TWINABS. University of Go ¨ttingen, Germany.
Sheldrick, G. M. (2008b). Acta Cryst. A64, 112–122.
Spek, A. L. (2009). Acta Cryst. D65, 148–155.
organic compounds
o586
Lutz and Schoutendoi:10.1107/S160053681100420X
Acta Cryst. (2011). E67, o586
Acta Crystallographica Section E
Structure Reports
Online
ISSN 1600-5368

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supplementary materials

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supplementary materials
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Acta Cryst. (2011). E67, o586 [ doi:10.1107/S160053681100420X ]
L-Alanine methyl ester hydrochloride monohydrate
M. Lutz and A. Schouten
Comment
In the context of our ongoing studies of absolute structure determinations of hydrochlorides of amino acid esters, we de-
termined the structure of the title compound (I). The related L-serine methyl ester hydrochloride (Schouten & Lutz, 2009)
has an extended backbone with O–C–C–N and C–O–C–C torsion angles of -175.99 (7) and 179.72 (7)°, respectively. In (I),
the O–C–C–N torsion angle is 155.83 (6)° indicating a significant deviation from an extended backbone. The C–O–C–C
torsion angle of 177.22 (6)° is again close to a trans conformation (Fig. 1).
Two H atoms of the ammonium moiety are involved in hydrogen bonds with chloride anions as acceptors. This results
in a one-dimensional chain in the a-direction. These two hydrogen bonds have significantly different lengths: the N1···Cl1
distance is 3.3007 (7) Å, while the N1···Cl1 (x - 1, y, z) distance is 3.1665 (6) Å. The third ammonium H atom is hydrogen
bonded to the co-crystallized lattice water molecule, which itself donates two hydrogen bonds to chlorides. The water thus
links the one-dimensional chains into a two-dimensional network, which is parallel to the a,c-plane (Fig. 2). In the b-direction
the hydrogen bonded layers of the ammonium moieties, chloride anions and lattice water molecules are alternating with the
organic part of the alanine methyl ester. The O atoms of the ester functionality are not involved in strong intermolecular
interactions, but there is a weak C—H···O bond with the ester O2 as acceptor (Table 1).
The crystal of (I) appeared to be twinned with a twofold rotation about hkl=(0,0,1) as twin operation. This twin relation
was taken into account during the intensity integration with Eval15 (Schreurs et al., 2010) and the refinement (Herbst-Irmer
& Sheldrick, 2002). As can easily be verified in Fig. 2, the twinning operation results in reversed stacking of the two-dimen-
sional hydrogen bonded networks. At the twinning boundaries the polar and ionic groups involved in the hydrogen bonds
must approach each other in the direction of the b axis and the alternation of polar and apolar moieties is broken. These
stacking faults might be accompanied by shifts of the layers for a better structural fit. Such dislocations often depend on the
way the twin was generated (Cahn, 1954), which has not been investigated in the present study of (I). In the macroscopic
shape of the crystal of (I), faces hkl=(0,0,1) and (0,0,1) have the smallest dimensions.
For the determination of the absolute structure, reflections with inverted indices were introduced into the dataset using
the TWINABS software (Sheldrick, 2008a). Thus there were in total four twin domains included in the refinement. The
corresponding twin fractions refined to 0.86 (2) and 0.104 (4) for the non-merohedral domains, and 0.03 (2) and 0.005 (4)
for the corresponding inverted domains. The latter values are very close to zero and we can consider the enantiopurity as
proven, but it should be noted that the two twin fractions of the inverted domains are in the least-squares refinement highly
correlated with each other (correlation -0.999).
Because of this correlation we also performed a single-crystal refinement only on the non-overlapping reflections of the
major twin domain. This dataset has a completeness of 82% (1447 unique reflections) and the coverage of Bijvoet pairs is
80% (712 pairs). Here, the Flack parameter (Flack, 1983) refined to a value of x=0.04 (3). On these data also an analysis
according to Hooft et al. (2008) was performed. Assuming a Gaussian distribution of σ(I) the absolute structure parameter
was calculated as y=0.044 (9). A plot of the Bijvoet differences is shown in Fig. 3.

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supplementary materials
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Experimental
Crystalline L-alanine methyl ester (Aldrich) was dissolved in technical ethanol. Evaporation at room temperature resulted
in a viscous liquid. Crystallization was initiated by adding a seed crystal of the crystalline starting material.
Refinement
The data set in HKLF-5 format (Herbst-Irmer & Sheldrick, 2002) contains non-overlapping reflections of both twin compon-
ents, respectively, together with the overlapping reflections. Equivalent reflections were merged with TWINABS (Sheldrick,
2008a) prior to the least-squares refinement. The same software was used to introduce the inverted reflections for the ab-
solute structure determination.
Figures
Fig. 1. Molecular structure of (I), with atom labels and 50% probability displacement ellips-
oids for non-H atoms.
Fig. 2. Formation of two-dimensional sheets parallel to (010) by hydrogen bonding in (I).
Hydrogen bonds are drawn as dashed lines. H atoms not involved in hydrogen bonding have
been omitted for clarity.
Fig. 3. Bijvoet pairs in the non-overlapping reflections of the major twin component in (I).
Scatter plot prepared by PLATON (Spek, 2009). 622 pairs are shown with Δobs > 0.25σ(Δobs).
534 Reflections confirming the absolute structure are drawn in black. 88 Reflections with the
wrong sign are shown in red.

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(2R)-1-methoxy-1-oxopropan-2-aminium chloride monohydrate
Crystal data
C4H10NO2+·Cl−·H2O
Mr = 157.60
Z = 1
F(000) = 84
Dx = 1.349 Mg m−3
Mo Kα radiation, λ = 0.71073 Å
Cell parameters from 5169 reflections
θ = 3.5–27.5°
µ = 0.44 mm−1
T = 110 K
Plate, colourless
0.39 × 0.29 × 0.12 mm
Triclinic, P1
Hall symbol: P 1
a = 4.9461 (4) Å
b = 6.0134 (4) Å
c = 6.6853 (5) Å
α = 101.833 (4)°
β = 93.533 (3)°
γ = 92.112 (4)°
V = 194.00 (2) Å3
Data collection
Nonius KappaCCD
diffractometer
Radiation source: rotating anode
graphite
φ and ω scans
Absorption correction: multi-scan
(TWINABS-2008/4; Sheldrick, 2008a)
Tmin = 0.69, Tmax = 0.75
11388 measured reflections
3213 independent reflections
3180 reflections with I > 2σ(I)
Rint = 0.019
θmax = 27.7°, θmin = 3.1°
h = −6→6
k = −7→7
l = −8→8
Refinement
Refinement on F2
Primary atom site location: structure-invariant direct
methods
Secondary atom site location: difference Fourier mapLeast-squares matrix: full
R[F2 > 2σ(F2)] = 0.015
wR(F2) = 0.043
Hydrogen site location: difference Fourier map
All H-atom parameters refined
S = 1.05
w = 1/[σ2(Fo2) + (0.0283P)2 + 0.0041P]
where P = (Fo2 + 2Fc2)/3
(Δ/σ)max = 0.005
Δρmax = 0.20 e Å−3
Δρmin = −0.13 e Å−3
3213 reflections
133 parameters
3 restraints
Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance mat-
rix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations