β-Glycine

The crystal structure of β-glycine, C₂H₅NO₂, has been refined. Single crystals of the metastable β-polymorph of glycine were obtained by cooling a saturated solution of glycine containing acetic acid. The crystal of the β-polymorph was preserved in dry air for several months. As the humidity of the air increased, a polymorphic transformation into the α-form was observed. The cell parameters of β-glycine have already been determined by Kozhin [Kristallografiya (1978), 23, 1211–1215], but the coordinates have not been published so far.

Key indicators

• Single-crystal X-ray study
• T = 294 K
• Mean [sigma](C-C) = 0.001 Å
• R factor = 0.025
• wR factor = 0.076
• Data-to-parameter ratio = 13.3

checkCIF results

No syntax errors found


 Alert Level B:



PLAT_111  Alert B ADDSYM detects (pseudo) centre of symmetry ...         80 Perc Fit

PLAT_113  Alert B ADDSYM suggests Pseudo/New Spacegroup ........       P21/m

Author response: See response to previous problem (see _publ_section_exptl_refinement).

General Notes



REFLT_03
         From the CIF: _diffrn_reflns_theta_max           37.52
         From the CIF: _reflns_number_total                894
         Count of symmetry unique reflns          894
         Completeness (_total/calc)            100.00%
         TEST3: Check Friedels for noncentro structure
         Estimate of Friedel pairs measured         0
         Fraction of Friedel pairs measured     0.000
         Are heavy atom types Z>Si present           no
          Please check that the estimate of the number of Friedel pairs is
          correct. If it is not, please give the correct count in the
          _publ_section_exptl_refinement section of the submitted CIF.


 0 Alert Level A = Potentially serious problem

 2 Alert Level B = Potential problem

 0 Alert Level C = Please check

---

Computing details

Data collection: STADI4 (Stoe & Cie, 1997); cell refinement: STADI4; data reduction: X-RED (Stoe & Cie, 1998); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: X-STEP (Stoe & Cie, 1998) and Pcw (Kraus & Nolze, 1999); software used to prepare material for publication: SHELXL97.

aminoacetic acid

Crystal data

C2H5NO2	F(000) = 80
Mr = 75.07	Dx = 1.576 Mg m^−3
Monoclinic, P21	Mo Kα radiation, λ = 0.71069 Å
a = 5.0935 (11) Å	Cell parameters from 26 reflections
b = 6.274 (2) Å	θ = 15.1–24.7°
c = 5.3847 (12) Å	µ = 0.14 mm^−1
β = 113.19 (2)°	T = 294 K
V = 158.18 (8) Å^3	Prism, colourless
Z = 2	0.5 × 0.4 × 0.2 mm

Data collection

Stoe STADI4 four-circle diffractometer	823 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.039
Planar graphite monochromator	θmax = 37.5°, θmin = 3.3°
Scan width (ω) = 1.42° – 1.87°, scan ratio 2θ:ω = 1.00 I(Net) and sigma(I) calculated according to Blessing (1987)	h = −8→8
Absorption correction: ψ scan (X-RED; Stoe, 1998)	k = −10→10
Tmin = 0.909, Tmax = 0.998	l = −9→9
6548 measured reflections	2 standard reflections every 180 min
894 independent reflections	intensity decay: 4.3%

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.025	All H-atom parameters refined
wR(F^2) = 0.076	w = 1/[σ^2(Fo^2) + (0.0501P)^2 + 0.0031P] where P = (Fo^2 + 2Fc^2)/3
S = 1.12	(Δ/σ)max < 0.001
894 reflections	Δρmax = 0.29 e Å^−3
67 parameters	Δρmin = −0.18 e Å^−3
1 restraint	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.58 (7)

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 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 > σ(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
O1	−0.09265 (13)	0.40990 (13)	0.59741 (13)	0.02586 (16)
N1	0.35024 (16)	0.28161 (13)	0.23730 (13)	0.02090 (14)
H3	0.349 (4)	0.301 (3)	0.071 (3)	0.029 (4)*
H4	0.520 (4)	0.324 (3)	0.353 (4)	0.029 (4)*
H5	0.340 (4)	0.142 (4)	0.266 (3)	0.034 (4)*
C1	0.13352 (15)	0.38405 (13)	0.56103 (15)	0.01851 (13)
O2	0.37739 (15)	0.35815 (17)	0.74274 (12)	0.0298 (2)
C2	0.11150 (17)	0.39417 (16)	0.26993 (14)	0.02195 (15)
H1	0.123 (4)	0.538 (4)	0.222 (4)	0.035 (5)*
H2	−0.063 (4)	0.332 (3)	0.143 (4)	0.029 (4)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0234 (3)	0.0326 (4)	0.0268 (3)	0.0000 (2)	0.0154 (2)	−0.0038 (2)
N1	0.0218 (3)	0.0272 (3)	0.0151 (2)	0.0026 (2)	0.0087 (2)	0.0000 (2)
C1	0.0204 (3)	0.0210 (3)	0.0163 (2)	−0.0023 (3)	0.0096 (2)	−0.0014 (2)
O2	0.0208 (2)	0.0532 (5)	0.0156 (2)	−0.0029 (3)	0.00725 (19)	0.0007 (3)
C2	0.0232 (3)	0.0286 (4)	0.0151 (3)	0.0055 (3)	0.0087 (2)	0.0023 (3)

Geometric parameters (Å, º)

O1—C1	1.2528 (9)	C1—O2	1.2529 (11)
N1—C2	1.4753 (11)	C1—C2	1.5281 (11)
N1—H3	0.899 (16)	C2—H1	0.95 (3)
N1—H4	0.88 (2)	C2—H2	0.964 (18)
N1—H5	0.89 (3)
C2—N1—H3	111.6 (12)	O2—C1—C2	117.15 (7)
C2—N1—H4	113.3 (12)	N1—C2—C1	111.79 (6)
H3—N1—H4	106.5 (16)	N1—C2—H1	106.4 (10)
C2—N1—H5	110.1 (11)	C1—C2—H1	109.3 (11)
H3—N1—H5	109.1 (17)	N1—C2—H2	107.2 (11)
H4—N1—H5	106.1 (17)	C1—C2—H2	112.6 (11)
O1—C1—O2	125.78 (8)	H1—C2—H2	109.4 (16)
O1—C1—C2	117.03 (7)
O1—C1—C2—N1	−157.41 (8)	O2—C1—C2—N1	25.03 (12)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H4···O1^i	0.88 (2)	1.97 (2)	2.8509 (13)	176.6 (17)
N1—H3···O2^ii	0.899 (16)	1.866 (16)	2.7626 (11)	174.4 (17)
N1—H5···O2^iii	0.89 (3)	2.30 (2)	2.9795 (15)	132.6 (14)
N1—H5···O1^iv	0.89 (3)	2.23 (2)	2.9785 (13)	140.7 (16)

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