Redetermination of 2-[4-(2-hydroxy-ethyl)piperazin-1-ium-1-yl]ethanesul-fonate at 100 K.

The crystal structure of the title compound (common name HEPES), C(8)H(18)N(2)O(4)S, has been redetermined at 100 K in order to properly elucidate the protonation state of the HEPES molecule. The piperazine ring has a chair conformation and one of the N atoms in the ring is protonated, which was not previously reported [Gao, Yin, Yang, & Xue (2004). Acta Cryst. E60, o1328-o1329]. The change of protonation state of the nitrogen atom significantly affects the intermolecular interactions in the HEPES crystal. The structure is stabilized by N-H⋯O and O-H⋯O hydrogen bonds and ionic inter-actions, as the title compound in solid state is a zwitterion. HEPES mol-ecules pack in layers that are held together by ionic and weak inter-actions, while a hydrogen-bonded network connects the layers.

Related literature

For background to HEPES and analogous compounds, see: Ferguson et al. (1980 ▶); Good & Izawa (1972 ▶); Good et al. (1966 ▶). For the crystal structure of HEPES crystallized from methanol, see: Wouters et al. (1996 ▶) and from water, see: Gao et al. (2004 ▶). For related structures, see: Kubicki et al. (2007 ▶); Chruszcz et al. (2005 ▶); Zhao et al. (2006 ▶).

Experimental

Crystal data

C8H18N2O4S

M = 238.31

Orthorhombic,

a = 8.341 (1) Å

b = 9.567 (1) Å

c = 27.066 (1) Å

V = 2159.8 (4) Å3

Z = 8

Mo Kα radiation

μ = 0.30 mm−1

T = 100 K

0.50 × 0.50 × 0.23 mm

Data collection

Rigaku R-AXIS RAPID diffractometer

Absorption correction: multi-scan (Otwinowski et al., 2003 ▶) T min = 0.86, T max = 0.93

613697 measured reflections

17694 independent reflections

14854 reflections with I > 2σ(I)

R int = 0.036

Refinement

R[F 2 > 2σ(F 2)] = 0.031

wR(F 2) = 0.099

S = 1.04

17694 reflections

208 parameters

All H-atom parameters refined

Δρmax = 0.83 e Å−3

Δρmin = −0.80 e Å−3

Data collection: HKL-2000 (Otwinowski & Minor, 1997 ▶); cell refinement: HKL-2000; data reduction: HKL-2000; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶) and HKL-3000SM (Minor et al., 2006 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶) and HKL-3000SM; molecular graphics: HKL-3000SM, ORTEPIII (Burnett & Johnson, 1996 ▶), ORTEP-3 (Farrugia, 1997 ▶), Mercury (Macrae et al., 2006 ▶) and POV-RAY (The POV-RAY Team, 2004 ▶); software used to prepare material for publication: HKL-3000SM.

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536809042512/fl2269sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809042512/fl2269Isup2.hkl

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

C8H18N2O4S	F(000) = 1024.0
Mr = 238.31	Dx = 1.466 Mg m−3
Orthorhombic, Pbca	Mo Kα radiation, λ = 0.7107 Å
Hall symbol: -P 2ac 2ab	Cell parameters from 613697 reflections
a = 8.341 (1) Å	θ = 2.9–62.9°
b = 9.567 (1) Å	µ = 0.30 mm−1
c = 27.066 (1) Å	T = 100 K
V = 2159.8 (4) Å3	Block, colorless
Z = 8	0.50 × 0.50 × 0.23 mm

Rigaku R-AXIS RAPID diffractometer	17694 independent reflections
Radiation source: fine-focus sealed tube	14854 reflections with I > 2σ(I)
graphite	Rint = 0.036
Detector resolution: 10 pixels mm-1	θmax = 62.9°, θmin = 2.9°
ω scan with χ offset	h = −20→20
Absorption correction: multi-scan (Otwinowski et al., 2003)	k = −23→23
Tmin = 0.86, Tmax = 0.93	l = −67→67
613697 measured reflections

Refinement on F2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.031	Hydrogen site location: difference Fourier map
wR(F2) = 0.099	All H-atom parameters refined
S = 1.04	w = 1/[σ2(Fo2) + (0.060P)2 + 0.0821P] where P = (Fo2 + 2Fc2)/3
17694 reflections	(Δ/σ)max = 0.013
208 parameters	Δρmax = 0.83 e Å−3
0 restraints	Δρmin = −0.80 e Å−3

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.

	x	y	z	Uiso*/Ueq
S1	0.449764 (8)	0.776637 (6)	0.555875 (2)	0.01145 (1)
N2	0.52317 (2)	0.69925 (2)	0.302785 (7)	0.01111 (2)
O2	0.30713 (2)	0.86815 (2)	0.555768 (7)	0.01413 (3)
N1	0.53191 (2)	0.75196 (2)	0.408697 (7)	0.01121 (2)
O4	0.72742 (3)	0.83527 (2)	0.216353 (8)	0.01514 (3)
C1	0.45506 (3)	0.69919 (3)	0.495798 (9)	0.01321 (3)
C5	0.49778 (3)	0.58710 (2)	0.339211 (8)	0.01316 (3)
O1	0.59735 (3)	0.85596 (3)	0.560910 (9)	0.01744 (3)
C3	0.56026 (3)	0.86534 (2)	0.371519 (9)	0.01330 (3)
C6	0.42540 (3)	0.64240 (2)	0.386736 (8)	0.01298 (3)
C4	0.63131 (3)	0.80396 (2)	0.324618 (8)	0.01271 (3)
C2	0.46765 (3)	0.81142 (3)	0.456032 (9)	0.01364 (3)
C8	0.59941 (3)	0.73733 (3)	0.213505 (9)	0.01485 (3)
C7	0.58957 (3)	0.63743 (2)	0.257306 (8)	0.01343 (3)
O3	0.43278 (4)	0.66097 (3)	0.590283 (9)	0.02055 (4)
H1A	0.5416 (10)	0.6363 (10)	0.4955 (4)	0.030 (2)*
H7B	0.5234 (9)	0.5552 (9)	0.2488 (3)	0.0238 (17)*
H2A	0.5445 (9)	0.8874 (10)	0.4673 (3)	0.0253 (19)*
H4B	0.6453 (10)	0.8784 (8)	0.3001 (3)	0.0252 (16)*
H7A	0.7005 (8)	0.5925 (7)	0.2643 (3)	0.0184 (14)*
H3B	0.4576 (9)	0.9063 (10)	0.3665 (3)	0.0253 (19)*
H6A	0.4173 (11)	0.5721 (9)	0.4086 (3)	0.030 (2)*
H6B	0.3201 (9)	0.6878 (8)	0.3822 (3)	0.0199 (15)*
H4A	0.7367 (10)	0.7630 (8)	0.3328 (3)	0.0193 (15)*
H1O4	0.8138 (12)	0.7897 (9)	0.2127 (3)	0.038 (2)*
H5A	0.6006 (9)	0.5394 (8)	0.3472 (3)	0.0175 (14)*
H3A	0.6309 (10)	0.9315 (7)	0.3860 (3)	0.0217 (16)*
H5B	0.4242 (10)	0.5192 (9)	0.3260 (3)	0.0249 (18)*
H1B	0.3616 (9)	0.6429 (8)	0.4933 (3)	0.0220 (16)*
H8B	0.5045 (10)	0.7906 (9)	0.2102 (3)	0.0225 (17)*
H1N	0.6197 (10)	0.7168 (7)	0.4156 (3)	0.0209 (16)*
H2B	0.3673 (10)	0.8534 (8)	0.4489 (3)	0.0235 (17)*
H8A	0.6076 (9)	0.6844 (8)	0.1846 (3)	0.0193 (15)*

	U11	U22	U33	U12	U13	U23
S1	0.01147 (2)	0.01296 (2)	0.00992 (2)	0.00039 (1)	0.00046 (1)	0.00017 (1)
N2	0.01141 (5)	0.01171 (5)	0.01023 (5)	−0.00043 (4)	0.00008 (4)	−0.00049 (4)
O2	0.01144 (6)	0.01507 (5)	0.01589 (6)	0.00088 (4)	0.00135 (4)	−0.00176 (4)
N1	0.01141 (5)	0.01222 (5)	0.01001 (5)	0.00009 (4)	0.00001 (4)	−0.00027 (4)
O4	0.01385 (6)	0.01526 (6)	0.01631 (6)	0.00036 (5)	0.00216 (5)	0.00128 (4)
C1	0.01505 (8)	0.01313 (6)	0.01144 (6)	−0.00002 (5)	0.00161 (5)	−0.00042 (5)
C5	0.01598 (8)	0.01164 (6)	0.01185 (6)	−0.00126 (5)	0.00163 (5)	−0.00039 (4)
O1	0.01166 (6)	0.02271 (8)	0.01794 (7)	−0.00175 (5)	−0.00219 (5)	−0.00297 (6)
C3	0.01666 (8)	0.01192 (6)	0.01131 (6)	−0.00133 (5)	0.00028 (5)	−0.00032 (4)
C6	0.01328 (7)	0.01395 (6)	0.01170 (6)	−0.00217 (5)	0.00141 (5)	−0.00079 (5)
C4	0.01330 (7)	0.01364 (6)	0.01120 (6)	−0.00253 (5)	0.00046 (5)	−0.00035 (5)
C2	0.01686 (8)	0.01329 (6)	0.01078 (6)	0.00146 (6)	0.00107 (5)	−0.00046 (5)
C8	0.01395 (8)	0.01909 (8)	0.01151 (6)	−0.00078 (6)	0.00002 (5)	0.00110 (5)
C7	0.01524 (8)	0.01335 (6)	0.01171 (6)	−0.00001 (5)	0.00150 (5)	−0.00108 (5)
O3	0.03015 (11)	0.01750 (7)	0.01399 (6)	0.00248 (7)	0.00373 (6)	0.00455 (5)

S1—O1	1.4525 (3)	C5—H5A	0.995 (8)
S1—O3	1.4532 (2)	C5—H5B	0.963 (8)
S1—O2	1.4771 (2)	C3—C4	1.5190 (3)
S1—C1	1.7874 (3)	C3—H3B	0.951 (8)
N2—C4	1.4719 (3)	C3—H3A	0.949 (8)
N2—C5	1.4724 (3)	C6—H6A	0.898 (9)
N2—C7	1.4736 (3)	C6—H6B	0.987 (8)
N1—C6	1.4971 (3)	C4—H4B	0.981 (8)
N1—C3	1.4984 (3)	C4—H4A	0.988 (8)
N1—C2	1.5008 (3)	C2—H2A	1.016 (9)
N1—H1N	0.827 (8)	C2—H2B	0.948 (8)
O4—C8	1.4226 (4)	C8—C7	1.5250 (4)
O4—H1O4	0.848 (10)	C8—H8B	0.946 (9)
C1—C2	1.5239 (4)	C8—H8A	0.935 (8)
C1—H1A	0.939 (9)	C7—H7B	0.988 (8)
C1—H1B	0.950 (8)	C7—H7A	1.037 (7)
C5—C6	1.5162 (3)
O1—S1—O3	114.856 (17)	C4—C3—H3A	111.1 (5)
O1—S1—O2	111.907 (17)	H3B—C3—H3A	110.1 (7)
O3—S1—O2	111.966 (15)	N1—C6—C5	110.17 (2)
O1—S1—C1	106.317 (13)	N1—C6—H6A	107.9 (6)
O3—S1—C1	105.650 (15)	C5—C6—H6A	109.1 (6)
O2—S1—C1	105.296 (12)	N1—C6—H6B	105.6 (4)
C4—N2—C5	108.376 (18)	C5—C6—H6B	113.7 (4)
C4—N2—C7	112.22 (2)	H6A—C6—H6B	110.1 (7)
C5—N2—C7	108.719 (19)	N2—C4—C3	111.07 (2)
C6—N1—C3	109.504 (18)	N2—C4—H4B	107.2 (5)
C6—N1—C2	113.10 (2)	C3—C4—H4B	109.3 (5)
C3—N1—C2	110.809 (19)	N2—C4—H4A	111.4 (4)
C6—N1—H1N	109.3 (5)	C3—C4—H4A	108.3 (4)
C3—N1—H1N	107.8 (5)	H4B—C4—H4A	109.5 (6)
C2—N1—H1N	106.1 (5)	N1—C2—C1	111.129 (19)
C8—O4—H1O4	107.0 (6)	N1—C2—H2A	107.6 (5)
C2—C1—S1	110.620 (17)	C1—C2—H2A	109.6 (5)
C2—C1—H1A	113.1 (6)	N1—C2—H2B	107.6 (5)
S1—C1—H1A	106.9 (6)	C1—C2—H2B	112.4 (5)
C2—C1—H1B	113.9 (5)	H2A—C2—H2B	108.4 (7)
S1—C1—H1B	106.2 (5)	O4—C8—C7	114.27 (2)
H1A—C1—H1B	105.5 (8)	O4—C8—H8B	106.2 (5)
N2—C5—C6	111.782 (19)	C7—C8—H8B	111.5 (5)
N2—C5—H5A	110.8 (4)	O4—C8—H8A	110.3 (5)
C6—C5—H5A	108.7 (4)	C7—C8—H8A	108.4 (5)
N2—C5—H5B	109.5 (5)	H8B—C8—H8A	105.8 (7)
C6—C5—H5B	107.3 (5)	N2—C7—C8	114.71 (2)
H5A—C5—H5B	108.7 (7)	N2—C7—H7B	107.7 (5)
N1—C3—C4	110.055 (19)	C8—C7—H7B	110.3 (5)
N1—C3—H3B	104.6 (5)	N2—C7—H7A	110.5 (4)
C4—C3—H3B	113.0 (5)	C8—C7—H7A	110.7 (4)
N1—C3—H3A	107.7 (4)	H7B—C7—H7A	102.1 (5)
O1—S1—C1—C2	−59.26 (2)	C5—N2—C4—C3	−59.66 (2)
O3—S1—C1—C2	178.27 (2)	C7—N2—C4—C3	−179.726 (19)
O2—S1—C1—C2	59.63 (2)	N1—C3—C4—N2	59.63 (3)
C4—N2—C5—C6	59.21 (3)	C6—N1—C2—C1	62.57 (3)
C7—N2—C5—C6	−178.55 (2)	C3—N1—C2—C1	−174.03 (2)
C6—N1—C3—C4	−56.75 (3)	S1—C1—C2—N1	159.105 (18)
C2—N1—C3—C4	177.80 (2)	C4—N2—C7—C8	−68.69 (3)
C3—N1—C6—C5	55.97 (3)	C5—N2—C7—C8	171.44 (2)
C2—N1—C6—C5	−179.911 (19)	O4—C8—C7—N2	76.07 (3)
N2—C5—C6—N1	−58.33 (3)

D—H···A	D—H	H···A	D···A	D—H···A
O4—H1O4···N2i	0.85 (1)	1.99 (1)	2.8368 (4)	173 (1)
N1—H1N···O2ii	0.83 (1)	1.92 (1)	2.7414 (4)	169 (1)

Table 1

Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O4—H1O4⋯N2i	0.85 (1)	1.99 (1)	2.8368 (4)	173 (1)
N1—H1N⋯O2ii	0.83 (1)	1.92 (1)	2.7414 (4)	169 (1)

Symmetry codes: (i) ; (ii) .