A comparative study of two polymorphs of L-aspartic acid hydro­chloride

Two polymorphs of L-aspartic acid hydro­chloride, C₄H₈NO₄⁺·Cl⁻, were obtained from the same aqueous solution. Their crystal structures have been determined from single-crystal data collected at 100 K. The crystal structures revealed three- and two-dimensional hydrogen-bonding networks for the triclinic and ortho­rhom­bic polymorphs, respectively. The cations and anions are connected to one another via N—H...Cl and O—H...Cl inter­actions and form alternating cation–anion layer-like structures. The two polymorphs share common structural features; however, the conformations of the L-aspartate cations and the crystal packings are different. Furthermore, the mol­ecular packing of the orthorhombic polymorph contains more inter­esting inter­actions which seems to be a favourable factor for more efficient charge transfer within the crystal.

Computing details

For both compounds, data collection: CrysAlis PRO (Agilent, 2012); cell refinement: CrysAlis PRO (Agilent, 2012); data reduction: CrysAlis PRO (Agilent, 2012); program(s) used to solve structure: SHELXS2014 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2008) and WinGX (Farrugia, 2012); molecular graphics: Mercury (Macrae et al., 2006) and PLATON (Spek, 2003).; software used to prepare material for publication: enCIFer (Allen et al., 2004).

(I) L-Aspartic acid hydrochloride

Crystal data

C4H8NO4^+·Cl^−	Z = 1
Mr = 169.56	F(000) = 88
Triclinic, P1	Dx = 1.642 Mg m^−3
a = 5.5888 (5) Å	Mo Kα radiation, λ = 0.71073 Å
b = 5.6045 (6) Å	Cell parameters from 4428 reflections
c = 6.1697 (7) Å	θ = 3.7–32.8°
α = 114.57 (1)°	µ = 0.51 mm^−1
β = 97.752 (9)°	T = 100 K
γ = 95.720 (8)°	Prism, colourless
V = 171.52 (3) Å^3	0.14 × 0.09 × 0.06 mm

Data collection

Agilent SuperNova (Dual, Cu at zero, Atlas) diffractometer	2273 independent reflections
Radiation source: SuperNova (Mo) X-ray Source	2259 reflections with I > 2σ(I)
Detector resolution: 10.4508 pixels mm^-1	Rint = 0.020
ω scans	θmax = 32.8°, θmin = 3.7°
Absorption correction: analytical [CrysAlis PRO (Agilent, 2012), using a multifaceted crystal model based on expressions derived by Clark & Reid (1995)]	h = −8→8
Tmin = 0.963, Tmax = 0.981	k = −8→8
4428 measured reflections	l = −9→9

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.022	All H-atom parameters refined
wR(F^2) = 0.054	w = 1/[σ^2(Fo^2) + (0.033P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 1.05	(Δ/σ)max = 0.001
2273 reflections	Δρmax = 0.30 e Å^−3
123 parameters	Δρmin = −0.18 e Å^−3
3 restraints	Absolute structure: Flack x determined using 1069 quotients [(I+)-(I-)]/[(I+)+(I-)] (Parsons et al., 2013)
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: 0.03 (3)

Special details

Experimental. Absorption correction: CrysAlisPro (2012), Agilent Technologies UK Ltd, Oxford, UK, Version 1.171.36.24 (release 03-12-2012 CrysAlis171 .NET) (compiled Dec 3 2012,18:21:49) Analytical numeric absorption correction using a multifaceted crystal model based on expressions derived by Clark & Reid, 1995.

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 matrix. 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 between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > 2σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Cl1	0.33694 (3)	0.19280 (4)	0.00641 (3)	0.01163 (9)
O1	1.1985 (2)	0.4542 (3)	0.6692 (2)	0.0134 (2)
O2	0.8786 (3)	0.5621 (3)	0.8553 (2)	0.0200 (3)
O3	0.3787 (2)	0.9020 (3)	0.3361 (2)	0.0156 (3)
O4	0.7723 (2)	1.0058 (3)	0.3238 (2)	0.0169 (3)
N1	0.9237 (3)	0.4702 (3)	0.2710 (2)	0.0096 (2)
C1	0.9953 (3)	0.5527 (4)	0.7016 (3)	0.0110 (3)
C2	0.9217 (3)	0.6696 (3)	0.5227 (3)	0.0087 (3)
C3	0.6740 (3)	0.7536 (3)	0.5416 (3)	0.0110 (3)
C4	0.6157 (3)	0.8998 (3)	0.3881 (3)	0.0100 (3)
H1	1.228 (6)	0.381 (7)	0.756 (6)	0.039 (9)*
H2	1.049 (4)	0.826 (5)	0.561 (4)	0.008 (5)*
H3	1.074 (5)	0.403 (6)	0.259 (5)	0.023 (7)*
H4	0.806 (5)	0.331 (6)	0.226 (5)	0.023 (6)*
H5	0.894 (5)	0.539 (6)	0.160 (5)	0.028 (7)*
H6	0.669 (5)	0.880 (5)	0.712 (4)	0.013 (6)*
H7	0.544 (5)	0.609 (6)	0.497 (5)	0.020 (6)*
H8	0.353 (5)	0.978 (6)	0.245 (5)	0.026 (7)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cl1	0.01271 (15)	0.01316 (16)	0.01092 (14)	0.00439 (11)	0.00192 (11)	0.00671 (11)
O1	0.0120 (6)	0.0198 (6)	0.0144 (5)	0.0055 (5)	0.0030 (4)	0.0125 (5)
O2	0.0207 (6)	0.0352 (8)	0.0165 (6)	0.0132 (6)	0.0095 (5)	0.0195 (6)
O3	0.0114 (6)	0.0211 (6)	0.0223 (6)	0.0060 (5)	0.0041 (5)	0.0163 (5)
O4	0.0127 (5)	0.0209 (6)	0.0250 (6)	0.0030 (5)	0.0040 (5)	0.0176 (5)
N1	0.0110 (5)	0.0123 (6)	0.0078 (5)	0.0030 (5)	0.0031 (5)	0.0058 (5)
C1	0.0104 (7)	0.0139 (7)	0.0103 (6)	0.0028 (5)	0.0012 (5)	0.0069 (5)
C2	0.0099 (6)	0.0101 (7)	0.0072 (6)	0.0020 (5)	0.0017 (5)	0.0049 (5)
C3	0.0111 (7)	0.0144 (7)	0.0123 (7)	0.0050 (6)	0.0044 (5)	0.0091 (6)
C4	0.0103 (7)	0.0101 (7)	0.0100 (7)	0.0031 (5)	0.0019 (5)	0.0045 (6)

Geometric parameters (Å, º)

O1—C1	1.315 (2)	N1—H4	0.89 (3)
O1—H1	0.81 (3)	N1—H5	0.92 (3)
O2—C1	1.208 (2)	C1—C2	1.533 (2)
O3—C4	1.323 (2)	C2—C3	1.510 (3)
O3—H8	0.84 (3)	C2—H2	0.99 (2)
O4—C4	1.209 (2)	C3—C4	1.513 (2)
N1—C2	1.492 (2)	C3—H6	1.00 (3)
N1—H3	0.95 (3)	C3—H7	0.95 (3)
C1—O1—H1	111 (2)	C3—C2—C1	111.37 (13)
C4—O3—H8	110 (2)	N1—C2—H2	107.2 (13)
C2—N1—H3	112.2 (16)	C3—C2—H2	110.1 (14)
C2—N1—H4	109.9 (19)	C1—C2—H2	107.7 (13)
H3—N1—H4	106 (3)	C2—C3—C4	111.26 (13)
C2—N1—H5	112 (2)	C2—C3—H6	111.3 (15)
H3—N1—H5	109 (2)	C4—C3—H6	106.2 (15)
H4—N1—H5	107 (2)	C2—C3—H7	113.3 (17)
O2—C1—O1	126.37 (16)	C4—C3—H7	108.9 (16)
O2—C1—C2	121.88 (16)	H6—C3—H7	105 (2)
O1—C1—C2	111.72 (14)	O4—C4—O3	124.22 (14)
N1—C2—C3	111.06 (12)	O4—C4—C3	122.70 (14)
N1—C2—C1	109.32 (13)	O3—C4—C3	113.07 (14)
O2—C1—C2—N1	−131.63 (18)	N1—C2—C3—C4	−64.97 (17)
O1—C1—C2—N1	50.39 (19)	C1—C2—C3—C4	172.92 (13)
O2—C1—C2—C3	−8.5 (2)	C2—C3—C4—O4	−21.3 (2)
O1—C1—C2—C3	173.49 (14)	C2—C3—C4—O3	159.64 (14)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H5···O2^i	0.92 (3)	1.93 (3)	2.8030 (19)	158 (3)
N1—H4···O4^ii	0.89 (3)	2.14 (3)	2.817 (2)	132 (2)
O1—H1···Cl1^iii	0.81 (3)	2.26 (3)	3.0657 (13)	176 (3)
O3—H8···Cl1^iv	0.84 (3)	2.26 (3)	3.0909 (14)	173 (3)
N1—H5···O4	0.92 (3)	2.58 (3)	3.099 (2)	116 (2)
N1—H3···Cl1^v	0.95 (3)	2.33 (3)	3.1682 (15)	147 (2)
N1—H4···Cl1	0.89 (3)	2.66 (3)	3.3562 (15)	136 (2)
C2—H2···O3^v	0.99 (2)	2.56 (2)	3.305 (2)	132.1 (18)
C3—H7···O1^vi	0.95 (3)	2.57 (3)	3.357 (2)	141 (2)

Symmetry codes: (i) x, y, z−1; (ii) x, y−1, z; (iii) x+1, y, z+1; (iv) x, y+1, z; (v) x+1, y, z; (vi) x−1, y, z.

(II) L-Aspartic acid hydrochloride

Crystal data

C4H8NO4^+·Cl^−	Dx = 1.535 Mg m^−3
Mr = 169.56	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, P21212	Cell parameters from 17470 reflections
a = 9.7082 (2) Å	θ = 3.2–45.5°
b = 8.9123 (3) Å	µ = 0.48 mm^−1
c = 8.4820 (2) Å	T = 100 K
V = 733.88 (3) Å^3	Prism, colourless
Z = 4	0.20 × 0.14 × 0.12 mm
F(000) = 352

Data collection

Agilent SuperNova (Dual, Cu at zero, Atlas) diffractometer	6012 independent reflections
Radiation source: SuperNova (Mo) X-ray Source	5353 reflections with I > 2σ(I)
Detector resolution: 10.4508 pixels mm^-1	Rint = 0.027
ω scans	θmax = 45.5°, θmin = 3.2°
Absorption correction: analytical [CrysAlis PRO (Agilent, 2012), using a multifaceted crystal model based on expressions derived by Clark & Reid (1995)]	h = −19→19
Tmin = 0.936, Tmax = 0.955	k = −17→12
17470 measured reflections	l = −16→17

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.037	All H-atom parameters refined
wR(F^2) = 0.090	w = 1/[σ^2(Fo^2) + (0.0448P)^2 + 0.017P] where P = (Fo^2 + 2Fc^2)/3
S = 1.04	(Δ/σ)max = 0.003
6012 reflections	Δρmax = 0.46 e Å^−3
123 parameters	Δρmin = −0.57 e Å^−3
0 restraints	Absolute structure: Flack x determined using 2029 quotients [(I+)-(I-)]/[(I+)+(I-)] (Parsons et al., 2013)
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: −0.031 (16)

Special details

Experimental. Absorption correction: CrysAlisPro (2012), Agilent Technologies UK Ltd, Oxford, UK, Version 1.171.36.24 (release 03-12-2012 CrysAlis171 .NET) (compiled Dec 3 2012,18:21:49) Analytical numeric absorption correction using a multifaceted crystal model based on expressions derived by Clark & Reid, 1995.

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 matrix. 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 between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > 2σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Cl1	0.66179 (2)	0.17292 (3)	0.26316 (3)	0.01443 (5)
O1	0.30341 (12)	0.50000 (11)	0.17327 (10)	0.02335 (19)
O2	0.34892 (10)	0.45850 (9)	0.42956 (9)	0.01692 (14)
O3	−0.04610 (10)	0.18092 (13)	0.14412 (12)	0.0262 (2)
O4	0.04221 (9)	0.29182 (10)	0.35986 (10)	0.01801 (15)
N1	0.32151 (10)	0.16396 (11)	0.40818 (11)	0.01400 (13)
C1	0.32323 (10)	0.41414 (12)	0.29825 (12)	0.01320 (15)
C2	0.31630 (9)	0.24865 (11)	0.25713 (12)	0.01193 (13)
C3	0.19377 (10)	0.20373 (12)	0.15602 (12)	0.01299 (15)
C4	0.05605 (10)	0.23073 (11)	0.23259 (13)	0.01351 (15)
H1	0.322 (3)	0.587 (4)	0.200 (4)	0.070 (9)*
H2	0.3993 (18)	0.227 (2)	0.199 (2)	0.020 (4)*
H3	0.3987 (18)	0.184 (2)	0.460 (2)	0.020 (4)*
H4	0.2485 (17)	0.185 (2)	0.465 (2)	0.016 (4)*
H5	0.328 (3)	0.070 (3)	0.386 (3)	0.042 (6)*
H6	0.1978 (19)	0.255 (2)	0.061 (2)	0.020 (4)*
H7	0.201 (2)	0.103 (2)	0.127 (2)	0.019 (4)*
H8	−0.119 (3)	0.192 (3)	0.195 (3)	0.046 (6)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cl1	0.01398 (8)	0.01229 (9)	0.01702 (9)	0.00002 (7)	0.00008 (7)	0.00187 (7)
O1	0.0429 (6)	0.0118 (3)	0.0153 (3)	−0.0024 (3)	−0.0019 (3)	0.0018 (3)
O2	0.0210 (4)	0.0143 (3)	0.0155 (3)	−0.0013 (3)	−0.0019 (3)	−0.0028 (2)
O3	0.0128 (3)	0.0382 (5)	0.0277 (5)	−0.0020 (3)	−0.0017 (3)	−0.0158 (4)
O4	0.0143 (3)	0.0265 (4)	0.0132 (3)	0.0004 (3)	0.0012 (2)	−0.0036 (3)
N1	0.0161 (3)	0.0119 (3)	0.0140 (3)	0.0002 (3)	−0.0025 (3)	0.0010 (3)
C1	0.0132 (3)	0.0121 (3)	0.0142 (3)	−0.0008 (3)	0.0012 (3)	−0.0001 (3)
C2	0.0121 (3)	0.0116 (3)	0.0121 (3)	0.0000 (2)	0.0006 (3)	−0.0003 (3)
C3	0.0136 (3)	0.0141 (4)	0.0113 (3)	0.0003 (3)	−0.0002 (3)	−0.0022 (3)
C4	0.0122 (3)	0.0142 (4)	0.0142 (4)	−0.0005 (3)	−0.0007 (3)	−0.0009 (3)

Geometric parameters (Å, º)

O1—C1	1.3215 (14)	N1—H4	0.876 (17)
O1—H1	0.83 (3)	N1—H5	0.86 (2)
O2—C1	1.2079 (13)	C1—C2	1.5171 (14)
O3—C4	1.3204 (13)	C2—C3	1.5201 (14)
O3—H8	0.84 (3)	C2—H2	0.963 (18)
O4—C4	1.2165 (13)	C3—C4	1.5058 (14)
N1—C2	1.4879 (14)	C3—H6	0.929 (18)
N1—H3	0.888 (18)	C3—H7	0.937 (18)
C1—O1—H1	107 (2)	C1—C2—C3	114.86 (8)
C4—O3—H8	107.7 (18)	N1—C2—H2	108.0 (12)
C2—N1—H3	110.6 (12)	C1—C2—H2	105.9 (11)
C2—N1—H4	109.7 (12)	C3—C2—H2	108.3 (11)
H3—N1—H4	111.7 (15)	C4—C3—C2	114.17 (8)
C2—N1—H5	107.9 (16)	C4—C3—H6	109.5 (12)
H3—N1—H5	104 (2)	C2—C3—H6	109.2 (12)
H4—N1—H5	113 (2)	C4—C3—H7	109.7 (12)
O2—C1—O1	125.47 (10)	C2—C3—H7	110.0 (12)
O2—C1—C2	122.64 (9)	H6—C3—H7	103.8 (16)
O1—C1—C2	111.84 (8)	O4—C4—O3	124.87 (10)
N1—C2—C1	107.08 (8)	O4—C4—C3	123.53 (9)
N1—C2—C3	112.26 (8)	O3—C4—C3	111.59 (9)
O2—C1—C2—N1	9.71 (13)	N1—C2—C3—C4	60.53 (11)
O1—C1—C2—N1	−172.76 (9)	C1—C2—C3—C4	−62.11 (12)
O2—C1—C2—C3	135.10 (10)	C2—C3—C4—O4	4.49 (15)
O1—C1—C2—C3	−47.36 (13)	C2—C3—C4—O3	−175.92 (10)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H4···O2^i	0.876 (17)	2.400 (18)	2.8257 (13)	110.3 (14)
N1—H3···O4^ii	0.888 (18)	2.078 (18)	2.9354 (12)	162.0 (16)
N1—H4···O4	0.877 (17)	2.390 (17)	2.9696 (13)	123.9 (14)
O3—H8···Cl1^iii	0.84 (3)	2.21 (3)	3.0111 (10)	160 (2)
O1—H1···Cl1^iv	0.83 (3)	2.21 (3)	3.0320 (10)	172 (3)
N1—H5···Cl1^v	0.86 (2)	2.40 (2)	3.2487 (10)	167 (2)
N1—H4···Cl1^vi	0.876 (17)	2.766 (18)	3.5056 (10)	143.1 (14)
C2—H2···Cl1	0.963 (18)	2.650 (18)	3.4217 (10)	137.5 (15)

Symmetry codes: (i) −x+1/2, y−1/2, −z+1; (ii) x+1/2, −y+1/2, −z+1; (iii) x−1, y, z; (iv) −x+1, −y+1, z; (v) −x+1, −y, z; (vi) x−1/2, −y+1/2, −z+1.