2-[4-(2-Hydro­xy­ethyl)­piperazin-1-yl]­ethane­sulfonic acid

The title compound, C₈H₁₈N₂O₄S, is a useful buffer in the physiological pH range. In the crystal structure, the piperazine ring adopts a chair conformation. One weak intramolecular C—H...O hydrogen bond, together with one weak intermolecular C—H...O and two strong intermolecular O—H...N hydrogen bonds are present, the latter linking the mol­ecules into a reticulation framework.

Key indicators

• Single-crystal X-ray study
• T = 298 K
• Mean [sigma](C-C) = 0.003 Å
• R factor = 0.041
• wR factor = 0.115
• Data-to-parameter ratio = 13.6

checkCIF/PLATON results

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Computing details

Data collection: SMART (Bruker, 2000); cell refinement: SAINT (Bruker, 2000); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2000); program(s) used to refine structure: SHELXL97 (Sheldrick, 2000); molecular graphics: SHELXTL/PC (Sheldrick, 1999); software used to prepare material for publication: SHELXTL/PC.

2-[4-(2-Hydroxyethyl)piperazin-1-yl]ethanesulfonic acid

Crystal data

C8H18N2O4S	F(000) = 1024
Mr = 238.30	Dx = 1.445 Mg m^−3
Orthorhombic, Pbca	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ac 2ab	Cell parameters from 12566 reflections
a = 8.3813 (13) Å	θ = 2.4–27.0°
b = 9.6623 (16) Å	µ = 0.29 mm^−1
c = 27.056 (4) Å	T = 298 K
V = 2191.1 (6) Å^3	Sheet, green
Z = 8	0.58 × 0.58 × 0.06 mm

Data collection

SMART 1K CCD area-detector diffractometer	1919 independent reflections
Radiation source: fine-focus sealed tube	1724 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.027
Detector resolution: 100x100 microns pixels mm^-1	θmax = 25.0°, θmin = 1.5°
φ and ω scans	h = −9→7
Absorption correction: multi-scan (SADABS; Sheldrick, 2000)	k = −11→11
Tmin = 0.848, Tmax = 0.983	l = −32→25
9743 measured reflections

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)] = 0.041	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.115	w = 1/[σ^2(Fo^2) + (0.0636P)^2 + 1.4035P] where P = (Fo^2 + 2Fc^2)/3
S = 1.06	(Δ/σ)max = 0.001
1919 reflections	Δρmax = 0.63 e Å^−3
141 parameters	Δρmin = −0.32 e Å^−3
0 restraints	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0033 (6)

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
S	1.04860 (6)	0.27595 (6)	0.443761 (18)	0.0285 (2)
O2	0.90393 (19)	0.35559 (18)	0.43881 (6)	0.0446 (4)
O3	1.0642 (2)	0.16138 (19)	0.40993 (6)	0.0562 (5)
O1	1.18966 (17)	0.36491 (16)	0.44371 (5)	0.0354 (4)
H1	1.2620	0.3280	0.4255	0.080*
O4	0.7746 (2)	0.33570 (17)	0.78314 (6)	0.0369 (4)
H4	0.699 (4)	0.300 (3)	0.7867 (11)	0.055 (10)*
N1	0.96747 (19)	0.25262 (17)	0.59097 (6)	0.0245 (4)
N2	0.97735 (19)	0.20089 (17)	0.69669 (6)	0.0243 (4)
C1	1.0725 (2)	0.1432 (2)	0.61282 (7)	0.0301 (5)
H1A	1.1774	0.1815	0.6195	0.036*
H1B	1.0848	0.0676	0.5895	0.036*
C2	1.0001 (3)	0.0900 (2)	0.66014 (7)	0.0300 (5)
H2B	0.8979	0.0475	0.6529	0.036*
H2C	1.0691	0.0194	0.6740	0.036*
C3	0.8718 (3)	0.3058 (2)	0.67489 (7)	0.0288 (5)
H3B	0.8547	0.3797	0.6986	0.035*
H3C	0.7691	0.2643	0.6675	0.035*
C4	0.9424 (3)	0.3651 (2)	0.62809 (7)	0.0306 (5)
H4B	0.8711	0.4345	0.6146	0.037*
H4C	1.0436	0.4093	0.6355	0.037*
C5	0.9105 (3)	0.1406 (2)	0.74216 (7)	0.0314 (5)
H5B	0.9753	0.0617	0.7516	0.038*
H5C	0.8041	0.1067	0.7351	0.038*
C6	1.0321 (3)	0.3104 (2)	0.54346 (8)	0.0310 (5)
H6A	1.1375	0.3487	0.5493	0.037*
H6B	0.9635	0.3848	0.5322	0.037*
C7	0.9011 (3)	0.2390 (2)	0.78573 (8)	0.0352 (5)
H7A	0.8892	0.1851	0.8157	0.042*
H7B	1.0010	0.2892	0.7881	0.042*
C8	1.0424 (2)	0.2005 (2)	0.50383 (8)	0.0298 (5)
H8A	0.9505	0.1397	0.5062	0.036*
H8B	1.1375	0.1451	0.5090	0.036*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
S	0.0287 (3)	0.0340 (3)	0.0229 (3)	−0.0010 (2)	0.00217 (19)	0.0004 (2)
O2	0.0273 (8)	0.0624 (11)	0.0441 (10)	0.0036 (8)	−0.0059 (6)	0.0122 (8)
O3	0.0884 (14)	0.0468 (10)	0.0334 (9)	−0.0092 (10)	0.0119 (9)	−0.0114 (8)
O1	0.0263 (8)	0.0412 (9)	0.0387 (8)	0.0008 (7)	0.0078 (6)	0.0068 (7)
O4	0.0315 (9)	0.0391 (9)	0.0400 (9)	−0.0023 (7)	0.0075 (7)	−0.0035 (7)
N1	0.0259 (9)	0.0277 (9)	0.0198 (8)	0.0015 (6)	0.0011 (6)	0.0011 (7)
N2	0.0250 (9)	0.0263 (8)	0.0217 (9)	0.0016 (7)	0.0009 (6)	0.0018 (6)
C1	0.0320 (11)	0.0317 (11)	0.0266 (11)	0.0075 (9)	0.0025 (8)	0.0008 (9)
C2	0.0364 (11)	0.0254 (10)	0.0282 (11)	0.0037 (9)	0.0028 (9)	0.0016 (8)
C3	0.0306 (11)	0.0317 (10)	0.0239 (10)	0.0070 (9)	0.0005 (8)	−0.0011 (8)
C4	0.0387 (12)	0.0257 (10)	0.0273 (11)	0.0053 (9)	−0.0008 (8)	0.0008 (8)
C5	0.0332 (11)	0.0326 (11)	0.0284 (11)	−0.0006 (9)	0.0045 (9)	0.0039 (9)
C6	0.0384 (13)	0.0300 (11)	0.0245 (10)	−0.0039 (9)	0.0031 (8)	0.0043 (8)
C7	0.0314 (11)	0.0488 (13)	0.0256 (11)	0.0011 (10)	0.0012 (9)	−0.0007 (9)
C8	0.0332 (12)	0.0316 (11)	0.0245 (11)	−0.0007 (9)	0.0037 (8)	0.0027 (9)

Geometric parameters (Å, º)

S—O2	1.4424 (17)	C2—H2C	0.9700
S—O3	1.4424 (18)	C3—C4	1.511 (3)
S—O1	1.4617 (16)	C3—H3B	0.9700
S—C8	1.782 (2)	C3—H3C	0.9700
O1—H1	0.859	C4—H4B	0.9700
O4—C7	1.415 (3)	C4—H4C	0.9700
O4—H4	0.73 (3)	C5—C7	1.516 (3)
N1—C4	1.495 (3)	C5—H5B	0.9700
N1—C1	1.498 (3)	C5—H5C	0.9700
N1—C6	1.503 (3)	C6—C8	1.512 (3)
N2—C3	1.469 (2)	C6—H6A	0.9700
N2—C2	1.471 (3)	C6—H6B	0.9700
N2—C5	1.472 (3)	C7—H7A	0.9700
C1—C2	1.507 (3)	C7—H7B	0.9700
C1—H1A	0.9700	C8—H8A	0.9700
C1—H1B	0.9700	C8—H8B	0.9700
C2—H2B	0.9700
O2—S—O3	115.27 (11)	H3B—C3—H3C	108.0
O2—S—O1	111.48 (10)	N1—C4—C3	110.04 (16)
O3—S—O1	112.17 (10)	N1—C4—H4B	109.7
O2—S—C8	106.17 (10)	C3—C4—H4B	109.7
O3—S—C8	105.49 (10)	N1—C4—H4C	109.7
O1—S—C8	105.38 (9)	C3—C4—H4C	109.7
S—O1—H1	109.09	H4B—C4—H4C	108.2
C7—O4—H4	110 (2)	N2—C5—C7	114.95 (17)
C4—N1—C1	109.28 (15)	N2—C5—H5B	108.5
C4—N1—C6	110.82 (16)	C7—C5—H5B	108.5
C1—N1—C6	112.84 (15)	N2—C5—H5C	108.5
C3—N2—C2	108.12 (15)	C7—C5—H5C	108.5
C3—N2—C5	112.30 (16)	H5B—C5—H5C	107.5
C2—N2—C5	108.86 (16)	N1—C6—C8	111.47 (17)
N1—C1—C2	109.85 (16)	N1—C6—H6A	109.3
N1—C1—H1A	109.7	C8—C6—H6A	109.3
C2—C1—H1A	109.7	N1—C6—H6B	109.3
N1—C1—H1B	109.7	C8—C6—H6B	109.3
C2—C1—H1B	109.7	H6A—C6—H6B	108.0
H1A—C1—H1B	108.2	O4—C7—C5	114.50 (17)
N2—C2—C1	112.00 (17)	O4—C7—H7A	108.6
N2—C2—H2B	109.2	C5—C7—H7A	108.6
C1—C2—H2B	109.2	O4—C7—H7B	108.6
N2—C2—H2C	109.2	C5—C7—H7B	108.6
C1—C2—H2C	109.2	H7A—C7—H7B	107.6
H2B—C2—H2C	107.9	C6—C8—S	111.14 (14)
N2—C3—C4	111.22 (17)	C6—C8—H8A	109.4
N2—C3—H3B	109.4	S—C8—H8A	109.4
C4—C3—H3B	109.4	C6—C8—H8B	109.4
N2—C3—H3C	109.4	S—C8—H8B	109.4
C4—C3—H3C	109.4	H8A—C8—H8B	108.0
C4—N1—C1—C2	56.4 (2)	C3—N2—C5—C7	−68.2 (2)
C6—N1—C1—C2	−179.83 (17)	C2—N2—C5—C7	172.14 (17)
C3—N2—C2—C1	59.3 (2)	C4—N1—C6—C8	−174.23 (16)
C5—N2—C2—C1	−178.49 (17)	C1—N1—C6—C8	62.8 (2)
N1—C1—C2—N2	−58.8 (2)	N2—C5—C7—O4	76.5 (2)
C2—N2—C3—C4	−59.4 (2)	N1—C6—C8—S	159.09 (14)
C5—N2—C3—C4	−179.54 (17)	O2—S—C8—C6	−59.31 (17)
C1—N1—C4—C3	−57.1 (2)	O3—S—C8—C6	177.90 (15)
C6—N1—C4—C3	177.92 (17)	O1—S—C8—C6	59.06 (16)
N2—C3—C4—N1	59.8 (2)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···N1^i	0.86	1.94	2.755 (2)	158
O4—H4···N2^ii	0.73 (3)	2.14 (3)	2.864 (2)	175 (3)
C1—H1A···O2^i	0.97	2.49	3.109 (3)	121
C3—H3B···O4	0.97	2.42	3.054 (2)	122

Symmetry codes: (i) x+1/2, −y+1/2, −z+1; (ii) x−1/2, y, −z+3/2.