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The title acid salt, Na+·C4H5O2-·2C4H6O2, contains finite anions in which two cyclopropanoic acid molecules are hydrogen bonded to a cyclopropanoate residue. Each such anion interacts with four different Na+ cations.
Supporting information
CCDC reference: 145518
Crystals were obtained from an aqueous solution of cyclopropanoic acid and
sodium hydroxide in 2:1 mole ratio. Analysis found: C 50.8, H 6.05%;
calculated for C12H17NaO6: C 51.4, H 6.07%. IR (KBr discs): 3439, 3081,
3022, 2860, 2480, 1905, 1692, 1522, 1430, 1362, 1294, 1228 cm-1.
The carboxy H atoms, H2 and H3, were located in a ΔF synthesis. Other H atoms
were positioned using stereochemical criteria and were then constrained to
ride on their parent C atoms. The C32–C34 cyclopropane ring is disordered
over two sites with equal probability and the parameters of the disordered
atoms are therefore subject to some systematic error.
Data collection: CAD-4 EXPRESS (Enraf Nonius, 1992); cell refinement: CAD-4 EXPRESS; data reduction: XCAD4 (Harms & Wocadlo , 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).
Crystal data top
NaH2(C4H5O2)3 | F(000) = 592 |
Mr = 280.25 | Dx = 1.337 Mg m−3 Dm = 1.34 Mg m−3 Dm measured by flotation in heptane/1,2-dichloroethane |
Monoclinic, P21/n | Mo Kα radiation, λ = 0.71073 Å |
a = 12.3629 (7) Å | Cell parameters from 25 reflections |
b = 6.7768 (4) Å | θ = 18.3–23.8° |
c = 16.9374 (12) Å | µ = 0.13 mm−1 |
β = 101.151 (6)° | T = 294 K |
V = 1392.24 (15) Å3 | Needle, colourless |
Z = 4 | 0.49 × 0.21 × 0.11 mm |
Data collection top
Enraf Nonius CAD4 diffractometer | θmax = 27°, θmin = 2.3° |
ω/2θ scans | h = −15→2 |
4477 measured reflections | k = −8→1 |
3357 independent reflections | l = −23→21 |
2175 reflections with I > 2σ(I) | 3 standard reflections every 184 reflections |
Rint = 0.018 | intensity decay: none |
Refinement top
Refinement on F2 | 0 restraints |
Least-squares matrix: full | H atoms treated by a mixture of independent and constrained refinement |
R[F2 > 2σ(F2)] = 0.042 | Calculated w = 1/[σ2(Fo2) + (0.0556P)2 + 0.352P] where P = (Fo2 + 2Fc2)/3 |
wR(F2) = 0.125 | (Δ/σ)max = 0.001 |
S = 1.02 | Δρmax = 0.26 e Å−3 |
3357 reflections | Δρmin = −0.24 e Å−3 |
207 parameters | |
Crystal data top
NaH2(C4H5O2)3 | V = 1392.24 (15) Å3 |
Mr = 280.25 | Z = 4 |
Monoclinic, P21/n | Mo Kα radiation |
a = 12.3629 (7) Å | µ = 0.13 mm−1 |
b = 6.7768 (4) Å | T = 294 K |
c = 16.9374 (12) Å | 0.49 × 0.21 × 0.11 mm |
β = 101.151 (6)° | |
Data collection top
Enraf Nonius CAD4 diffractometer | Rint = 0.018 |
4477 measured reflections | 3 standard reflections every 184 reflections |
3357 independent reflections | intensity decay: none |
2175 reflections with I > 2σ(I) | |
Refinement top
R[F2 > 2σ(F2)] = 0.042 | 0 restraints |
wR(F2) = 0.125 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.02 | Δρmax = 0.26 e Å−3 |
3357 reflections | Δρmin = −0.24 e Å−3 |
207 parameters | |
Special details top
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. |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | Occ. (<1) |
Na1 | 0.25832 (6) | 0.26125 (9) | 0.75806 (4) | 0.0424 (2) | |
O11 | 0.43738 (10) | 0.16489 (18) | 0.74499 (8) | 0.0480 (3) | |
O12 | 0.38710 (11) | −0.11652 (19) | 0.68568 (8) | 0.0549 (4) | |
C11 | 0.45721 (14) | 0.0169 (2) | 0.70601 (10) | 0.0370 (4) | |
C12 | 0.56531 (15) | −0.0031 (3) | 0.68133 (12) | 0.0482 (5) | |
H12 | 0.5751 | −0.1226 | 0.6509 | 0.058* | |
C13 | 0.66778 (16) | 0.0764 (4) | 0.73416 (15) | 0.0661 (6) | |
H13A | 0.6601 | 0.1396 | 0.7842 | 0.079* | |
H13B | 0.7357 | 0.0029 | 0.7366 | 0.079* | |
C14 | 0.62219 (17) | 0.1788 (4) | 0.65887 (13) | 0.0614 (6) | |
H14A | 0.662 | 0.1682 | 0.615 | 0.074* | |
H14B | 0.5864 | 0.3049 | 0.6626 | 0.074* | |
O21 | 0.23813 (10) | −0.00417 (17) | 0.84734 (7) | 0.0432 (3) | |
O22 | 0.11666 (13) | 0.1073 (2) | 0.91684 (9) | 0.0671 (5) | |
H2 | 0.107 (2) | 0.207 (5) | 0.8780 (17) | 0.107 (10)* | |
C21 | 0.18570 (14) | −0.0252 (2) | 0.90041 (10) | 0.0388 (4) | |
C22 | 0.19714 (15) | −0.2029 (3) | 0.95117 (10) | 0.0452 (4) | |
H22 | 0.2424 | −0.3079 | 0.9345 | 0.054* | |
C23 | 0.20379 (19) | −0.1860 (3) | 1.04051 (11) | 0.0584 (5) | |
H23A | 0.2538 | −0.2739 | 1.0751 | 0.07* | |
H23B | 0.1969 | −0.0556 | 1.0626 | 0.07* | |
C24 | 0.10587 (18) | −0.2725 (4) | 0.99023 (11) | 0.0595 (6) | |
H24A | 0.0384 | −0.1956 | 0.9815 | 0.071* | |
H24B | 0.0954 | −0.4138 | 0.994 | 0.071* | |
O31 | 0.12784 (16) | 0.0376 (2) | 0.66665 (9) | 0.0677 (4) | |
O32 | −0.04255 (14) | −0.0599 (3) | 0.66820 (13) | 0.0839 (6) | |
H3 | −0.011 (3) | −0.145 (5) | 0.7033 (18) | 0.121 (12)* | |
C31 | 0.0311 (3) | 0.0585 (3) | 0.64551 (13) | 0.0683 (7) | |
C32 | 0.0045 (4) | 0.2197 (7) | 0.5908 (3) | 0.0438 (10) | 0.5 |
H32A | 0.0645 | 0.2941 | 0.5744 | 0.053* | 0.5 |
C33 | −0.1061 (4) | 0.1989 (8) | 0.5310 (3) | 0.0599 (12) | 0.5 |
H33A | −0.1122 | 0.2599 | 0.4786 | 0.072* | 0.5 |
H33B | −0.146 | 0.0757 | 0.5311 | 0.072* | 0.5 |
C34 | −0.1004 (4) | 0.3288 (7) | 0.6005 (3) | 0.0556 (11) | 0.5 |
H34A | −0.137 | 0.2857 | 0.6432 | 0.067* | 0.5 |
H34B | −0.1033 | 0.4699 | 0.5907 | 0.067* | 0.5 |
C32B | −0.0573 (6) | 0.2146 (10) | 0.5948 (4) | 0.0827 (19) | 0.5 |
H32B | −0.1349 | 0.2039 | 0.5992 | 0.099* | 0.5 |
C33B | −0.0323 (8) | 0.2610 (9) | 0.5186 (3) | 0.100 (2) | 0.5 |
H33C | −0.0934 | 0.2834 | 0.4741 | 0.119* | 0.5 |
H33D | 0.0317 | 0.1987 | 0.504 | 0.119* | 0.5 |
C34B | −0.0133 (5) | 0.4075 (7) | 0.5843 (3) | 0.0745 (13) | 0.5 |
H34C | 0.0622 | 0.4346 | 0.6104 | 0.089* | 0.5 |
H34D | −0.063 | 0.5194 | 0.5805 | 0.089* | 0.5 |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
Na1 | 0.0504 (4) | 0.0291 (3) | 0.0528 (4) | 0.0021 (3) | 0.0224 (3) | 0.0055 (3) |
O11 | 0.0455 (7) | 0.0366 (7) | 0.0650 (8) | −0.0007 (6) | 0.0180 (6) | −0.0174 (6) |
O12 | 0.0624 (8) | 0.0398 (7) | 0.0701 (9) | −0.0213 (7) | 0.0317 (7) | −0.0164 (7) |
C11 | 0.0435 (9) | 0.0302 (8) | 0.0394 (8) | −0.0012 (7) | 0.0136 (7) | −0.0009 (7) |
C12 | 0.0481 (10) | 0.0413 (10) | 0.0595 (11) | −0.0009 (9) | 0.0209 (9) | −0.0129 (9) |
C13 | 0.0411 (10) | 0.0747 (15) | 0.0795 (15) | 0.0116 (11) | 0.0043 (10) | −0.0067 (12) |
C14 | 0.0485 (11) | 0.0706 (14) | 0.0689 (13) | −0.0173 (11) | 0.0209 (10) | −0.0040 (12) |
O21 | 0.0553 (7) | 0.0325 (6) | 0.0473 (7) | 0.0061 (6) | 0.0238 (6) | 0.0052 (5) |
O22 | 0.0866 (11) | 0.0563 (9) | 0.0722 (10) | 0.0322 (8) | 0.0497 (9) | 0.0226 (8) |
C21 | 0.0464 (9) | 0.0331 (9) | 0.0383 (8) | 0.0031 (8) | 0.0117 (7) | 0.0014 (7) |
C22 | 0.0544 (11) | 0.0392 (10) | 0.0448 (9) | 0.0046 (8) | 0.0164 (8) | 0.0088 (8) |
C23 | 0.0751 (14) | 0.0576 (12) | 0.0399 (10) | −0.0075 (11) | 0.0043 (9) | 0.0075 (9) |
C24 | 0.0636 (13) | 0.0662 (14) | 0.0492 (11) | −0.0134 (11) | 0.0121 (10) | 0.0140 (10) |
O31 | 0.0902 (12) | 0.0523 (9) | 0.0622 (9) | −0.0228 (9) | 0.0192 (9) | 0.0042 (7) |
O32 | 0.0630 (10) | 0.0610 (11) | 0.1165 (15) | −0.0008 (9) | −0.0106 (10) | 0.0366 (11) |
C31 | 0.115 (2) | 0.0337 (10) | 0.0494 (12) | −0.0105 (13) | −0.0027 (13) | 0.0081 (9) |
C32 | 0.031 (2) | 0.040 (2) | 0.059 (2) | 0.004 (2) | 0.0061 (19) | 0.0160 (17) |
C33 | 0.058 (3) | 0.058 (3) | 0.056 (3) | 0.003 (2) | −0.009 (2) | 0.018 (2) |
C34 | 0.049 (2) | 0.040 (2) | 0.075 (3) | 0.014 (2) | 0.005 (2) | 0.009 (2) |
C32B | 0.063 (4) | 0.058 (4) | 0.117 (5) | −0.005 (4) | −0.006 (4) | 0.036 (3) |
C33B | 0.163 (7) | 0.066 (4) | 0.055 (3) | 0.033 (4) | −0.015 (4) | −0.001 (3) |
C34B | 0.092 (4) | 0.056 (3) | 0.073 (3) | 0.011 (3) | 0.010 (3) | 0.007 (2) |
Geometric parameters (Å, º) top
Na1—O12i | 2.3429 (14) | O22—C21 | 1.305 (2) |
Na1—O11 | 2.3590 (14) | C21—C22 | 1.471 (2) |
Na1—O21 | 2.3939 (13) | C22—C24 | 1.491 (3) |
Na1—O21i | 2.3972 (13) | C22—C23 | 1.504 (2) |
Na1—O31 | 2.5162 (18) | C23—C24 | 1.461 (3) |
Na1—O31i | 2.534 (2) | O31—C31 | 1.189 (3) |
Na1—Na1ii | 3.4024 (2) | O31—Na1ii | 2.534 (2) |
Na1—Na1i | 3.4024 (2) | O32—C31 | 1.325 (3) |
O11—C11 | 1.251 (2) | C31—C32 | 1.429 (5) |
O12—C11 | 1.254 (2) | C31—C32B | 1.639 (7) |
O12—Na1ii | 2.3429 (14) | C32—C34 | 1.529 (6) |
C11—C12 | 1.482 (2) | C32—C33 | 1.542 (6) |
C12—C13 | 1.502 (3) | C33—C34 | 1.459 (7) |
C12—C14 | 1.504 (3) | C32B—C33B | 1.419 (10) |
C13—C14 | 1.465 (3) | C32B—C34B | 1.440 (8) |
O21—C21 | 1.214 (2) | C33B—C34B | 1.477 (8) |
O21—Na1ii | 2.3972 (13) | | |
| | | |
O12i—Na1—O11 | 160.70 (6) | C11—C12—C14 | 119.22 (17) |
O12i—Na1—O21 | 80.02 (5) | C13—C12—C14 | 58.35 (14) |
O11—Na1—O21 | 93.77 (5) | C14—C13—C12 | 60.87 (14) |
O12i—Na1—O21i | 101.21 (5) | C13—C14—C12 | 60.78 (15) |
O11—Na1—O21i | 87.77 (5) | C21—O21—Na1 | 133.77 (11) |
O21—Na1—O21i | 171.08 (5) | C21—O21—Na1ii | 124.26 (11) |
O12i—Na1—O31 | 90.70 (6) | Na1—O21—Na1ii | 90.50 (4) |
O11—Na1—O31 | 106.08 (6) | O21—C21—O22 | 122.81 (16) |
O21—Na1—O31 | 78.66 (5) | O21—C21—C22 | 121.62 (16) |
O21i—Na1—O31 | 92.47 (5) | O22—C21—C22 | 115.57 (15) |
O12i—Na1—O31i | 85.94 (6) | C21—C22—C24 | 121.55 (17) |
O11—Na1—O31i | 79.16 (5) | C21—C22—C23 | 120.41 (17) |
O21—Na1—O31i | 110.67 (5) | C24—C22—C23 | 58.42 (13) |
O21i—Na1—O31i | 78.25 (5) | C24—C23—C22 | 60.34 (13) |
O31—Na1—O31i | 169.29 (6) | C23—C24—C22 | 61.24 (13) |
O12i—Na1—Na1ii | 110.21 (5) | C31—O31—Na1 | 126.97 (16) |
O11—Na1—Na1ii | 76.12 (4) | C31—O31—Na1ii | 131.93 (14) |
O21—Na1—Na1ii | 44.79 (3) | Na1—O31—Na1ii | 84.72 (6) |
O21i—Na1—Na1ii | 127.60 (5) | O31—C31—O32 | 123.2 (2) |
O31—Na1—Na1ii | 47.86 (5) | O31—C31—C32 | 112.2 (3) |
O31i—Na1—Na1ii | 142.70 (5) | O32—C31—C32 | 124.5 (3) |
O12i—Na1—Na1i | 68.98 (4) | O31—C31—C32B | 139.8 (3) |
O11—Na1—Na1i | 108.15 (4) | O32—C31—C32B | 96.8 (3) |
O21—Na1—Na1i | 141.90 (4) | C32—C31—C32B | 28.4 (2) |
O21i—Na1—Na1i | 44.71 (3) | C31—C32—C34 | 113.2 (4) |
O31—Na1—Na1i | 121.94 (5) | C31—C32—C33 | 114.8 (4) |
O31i—Na1—Na1i | 47.42 (4) | C34—C32—C33 | 56.7 (3) |
Na1ii—Na1—Na1i | 169.60 (5) | C34—C33—C32 | 61.2 (3) |
C11—O11—Na1 | 123.69 (11) | C33—C34—C32 | 62.1 (3) |
C11—O12—Na1ii | 133.42 (11) | C33B—C32B—C34B | 62.2 (4) |
O11—C11—O12 | 121.84 (15) | C33B—C32B—C31 | 112.3 (7) |
O11—C11—C12 | 120.10 (15) | C34B—C32B—C31 | 114.9 (5) |
O12—C11—C12 | 118.05 (15) | C32B—C33B—C34B | 59.6 (4) |
C11—C12—C13 | 120.14 (17) | C32B—C34B—C33B | 58.2 (5) |
| | | |
O12i—Na1—O11—C11 | 142.71 (16) | C21—C22—C23—C24 | 110.6 (2) |
O21—Na1—O11—C11 | 72.43 (14) | C21—C22—C24—C23 | −108.6 (2) |
O21i—Na1—O11—C11 | −98.77 (14) | O12i—Na1—O31—C31 | 23.32 (19) |
O31—Na1—O11—C11 | −6.84 (15) | O11—Na1—O31—C31 | −166.32 (18) |
O31i—Na1—O11—C11 | −177.23 (14) | O21—Na1—O31—C31 | 103.00 (18) |
Na1ii—Na1—O11—C11 | 30.92 (13) | O21i—Na1—O31—C31 | −77.93 (18) |
Na1i—Na1—O11—C11 | −139.20 (13) | O31i—Na1—O31—C31 | −48.2 (2) |
Na1—O11—C11—O12 | −16.2 (2) | Na1ii—Na1—O31—C31 | 140.4 (2) |
Na1—O11—C11—C12 | 162.76 (13) | Na1i—Na1—O31—C31 | −42.2 (2) |
Na1ii—O12—C11—O11 | −29.3 (3) | O12i—Na1—O31—Na1ii | −117.06 (5) |
Na1ii—O12—C11—C12 | 151.69 (14) | O11—Na1—O31—Na1ii | 53.30 (5) |
O11—C11—C12—C13 | 33.4 (3) | O21—Na1—O31—Na1ii | −37.38 (4) |
O12—C11—C12—C13 | −147.62 (19) | O21i—Na1—O31—Na1ii | 141.69 (5) |
O11—C11—C12—C14 | −34.9 (3) | O31i—Na1—O31—Na1ii | 171.39 (17) |
O12—C11—C12—C14 | 144.12 (18) | Na1i—Na1—O31—Na1ii | 177.47 (5) |
C11—C12—C13—C14 | −107.8 (2) | Na1—O31—C31—O32 | −112.1 (2) |
C11—C12—C14—C13 | 109.3 (2) | Na1ii—O31—C31—O32 | 9.3 (4) |
O12i—Na1—O21—C21 | −9.52 (16) | Na1—O31—C31—C32 | 70.3 (3) |
O11—Na1—O21—C21 | 152.07 (16) | Na1ii—O31—C31—C32 | −168.3 (2) |
O21i—Na1—O21—C21 | −108.3 (3) | Na1—O31—C31—C32B | 61.9 (6) |
O31—Na1—O21—C21 | −102.27 (17) | Na1ii—O31—C31—C32B | −176.7 (5) |
O31i—Na1—O21—C21 | 72.24 (17) | O31—C31—C32—C34 | −145.5 (3) |
Na1ii—Na1—O21—C21 | −141.99 (18) | O32—C31—C32—C34 | 37.0 (5) |
Na1i—Na1—O21—C21 | 25.9 (2) | C32B—C31—C32—C34 | 23.0 (6) |
O12i—Na1—O21—Na1ii | 132.46 (6) | O31—C31—C32—C33 | 151.9 (3) |
O11—Na1—O21—Na1ii | −65.95 (5) | O32—C31—C32—C33 | −25.7 (5) |
O21i—Na1—O21—Na1ii | 33.7 (2) | C32B—C31—C32—C33 | −39.6 (7) |
O31—Na1—O21—Na1ii | 39.71 (5) | C31—C32—C33—C34 | 102.4 (4) |
O31i—Na1—O21—Na1ii | −145.77 (6) | C31—C32—C34—C33 | −105.3 (5) |
Na1i—Na1—O21—Na1ii | 167.92 (8) | O31—C31—C32B—C33B | 51.3 (8) |
Na1—O21—C21—O22 | 5.0 (3) | O32—C31—C32B—C33B | −133.8 (5) |
Na1ii—O21—C21—O22 | −126.86 (17) | C32—C31—C32B—C33B | 34.6 (7) |
Na1—O21—C21—C22 | −174.44 (12) | O31—C31—C32B—C34B | −17.3 (9) |
Na1ii—O21—C21—C22 | 53.7 (2) | O32—C31—C32B—C34B | 157.6 (6) |
O21—C21—C22—C24 | −153.56 (18) | C32—C31—C32B—C34B | −33.9 (5) |
O22—C21—C22—C24 | 27.0 (3) | C31—C32B—C33B—C34B | −107.4 (5) |
O21—C21—C22—C23 | 137.05 (19) | C31—C32B—C34B—C33B | 103.2 (7) |
O22—C21—C22—C23 | −42.4 (3) | | |
Symmetry codes: (i) −x+1/2, y+1/2, −z+3/2; (ii) −x+1/2, y−1/2, −z+3/2. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O22—H2···O12i | 0.93 (3) | 1.62 (3) | 2.5475 (18) | 171 (3) |
O32—H3···O11ii | 0.86 (3) | 1.72 (3) | 2.567 (2) | 167 (3) |
Symmetry codes: (i) −x+1/2, y+1/2, −z+3/2; (ii) −x+1/2, y−1/2, −z+3/2. |
Experimental details
Crystal data |
Chemical formula | NaH2(C4H5O2)3 |
Mr | 280.25 |
Crystal system, space group | Monoclinic, P21/n |
Temperature (K) | 294 |
a, b, c (Å) | 12.3629 (7), 6.7768 (4), 16.9374 (12) |
β (°) | 101.151 (6) |
V (Å3) | 1392.24 (15) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.13 |
Crystal size (mm) | 0.49 × 0.21 × 0.11 |
|
Data collection |
Diffractometer | Enraf Nonius CAD4 diffractometer |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 4477, 3357, 2175 |
Rint | 0.018 |
(sin θ/λ)max (Å−1) | 0.639 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.042, 0.125, 1.02 |
No. of reflections | 3357 |
No. of parameters | 207 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.26, −0.24 |
Selected geometric parameters (Å, º) topNa1—O12i | 2.3429 (14) | Na1—O21i | 2.3972 (13) |
Na1—O11 | 2.3590 (14) | Na1—O31 | 2.5162 (18) |
Na1—O21 | 2.3939 (13) | Na1—O31i | 2.534 (2) |
| | | |
O12i—Na1—O11 | 160.70 (6) | O31—Na1—O31i | 169.29 (6) |
O21—Na1—O21i | 171.08 (5) | | |
Symmetry code: (i) −x+1/2, y+1/2, −z+3/2. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O22—H2···O12i | 0.93 (3) | 1.62 (3) | 2.5475 (18) | 171 (3) |
O32—H3···O11ii | 0.86 (3) | 1.72 (3) | 2.567 (2) | 167 (3) |
Symmetry codes: (i) −x+1/2, y+1/2, −z+3/2; (ii) −x+1/2, y−1/2, −z+3/2. |
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The title acid salt, (I), was obtained during an attempt to make a conventional acid salt of cyclopropanoic acid. Most monocarboxy acids, HX, form acid salts of the general type MHX2, where M is any singly-charged cation. However, Speakman (1972) noted in his review of the structures of acid salts that more complex compositions are very occasionally found, citing the examples of KH2X3, HX = acetic acid, and RbH2X3, HX = monochloroacetic acid. Salt (I) belongs to this rare class of acid salts. It appears to be identical to the compound whose cell dimensions were reported by Hwang & Donohue (1971). \sch
The asymmetric unit of (I) consists of one Na+ cation and an XH···X···HX- anion formed by linking two cyclopropanoic acid molecules, HX, to the same cyclopropanoate anion through moderate-to-strong (Jeffrey, 1997) O—H···O hydrogen bonds (see Table 2). The geometries of the three independent cyclopropanoic acid residues are consistent with an ordered arrangement of hydrogen bonds: the deprotonated acid contains C11—O bonds of nearly equal length [1.251 (2) and 1.254 (2) Å], whereas the C21—-O and C31–O bonds show the difference in length expected if O22 and O32 are protonated [1.214 (2) and 1.305 (2) Å, and 1.189 (2) and 1.325 (2) Å, respectively]. Disorder of the C32–C34 ring obscures some of its structural details, but the other two cyclopropane units show the expected shortening of the distal C—C bonds [1.465 (3) and 1.461 (3) Å] relative to the others [1.491 (3)–1.504 (3) Å; Allen, 1980].
The Na+ ions lie almost exactly on the 21 screw axes (Fig. 1). In consequence, the operations of the screw axes generate nearly linear chains of regularly spaced Na+ cations which run parallel to the b axis. The distance of 3.402 (2) Å between adjacent Na+ ions in these chains is only 0.014 Å greater than b/2. Each Na+ ion is surrounded by a distorted octahedron of O atoms (Table 1). Adjacent octahedra are linked through the O21···O31 edge and also through the η2-bridging carboxy group containing O11 and O12. Each Na+ ion is bonded to three different XH···X···HX- anions and each XH···X···HX- anion donates six electron pairs to four different Na+ ions. This highly stable arrangement uses all lone pairs on unprotonated O atoms O11, O12, O21 and O31 and the hydrogen-bond-donor properties of the O22 and O32 OH groups for inter-residue bonding.
Since Speakman's (1972) review two MH2X3 structures have been fully described and both contain the finite XH···X···HX- anions also found in (I). The cation in KH2(CH3CO2)3 (Efremov et al., 1986) is eight-coordinate. NaH2(CH3CO2)3 more closely resembles (I), with the finite XH···X···HX- anions stabilizing a chain of octahedrally coordinated Na+ cations related by a 41 screw axis; the Na—O distances [2.316 (4)–2.580 (4) Å] are less regular than those in (I) and the O···O distances in the hydrogen bonds [2.509 (4) and 2.503 (4) Å] are somewhat shorter (Perrotti & Tazzoli, 1981). Interestingly, acetic acid also forms a regular sodium salt, Na(CH3CO2), which crystallizes as a trihydrate (Doxsee & Stevens, 1990) and in two anhydrous forms (Hsu & Nordman, 1983), and a regular acid salt NaHX2 (Barrow et al., 1975); all have been structurally characterized. Though an analysis of potassium dihydrogen tris(o-chlorobenzoate) was successful (Golic & Speakman, 1975) no structural details have been published.