2,2-Dicyclo­prop­ylglycolic acid

The title compound, C₈H₁₂O₃, is the parent acid of a tentative ligand whose binding capability toward a metal ion is modified compared with the smaller and more hydro­philic glycolic acid. In the crystal structure, chains of homodromic rings made up of O—H–π and C=O–π co-operative sequences are lined up along [100]. The homodromic rings are at the centres of tetra­mers of the title compound. They are 12-membered and contain two carb­oxy OH, two alcohol OH and two C=O functions. The rings are connected along the chain direction by the central C—C bond of the acid. The hydro­philic chains are embedded in a lipophilic matrix of hydro­carbon residues.

Key indicators

• Single-crystal X-ray study
• T = 200 K
• Mean [sigma](C-C) = 0.002 Å
• R factor = 0.039
• wR factor = 0.104
• Data-to-parameter ratio = 15.5

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT154_ALERT_1_C The su's on the Cell Angles are Equal  (x 10000)        300 Deg.
PLAT480_ALERT_4_C Long H...A H-Bond Reported H8B    ..  O2      ..       2.61 Ang.

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   2 ALERT level C = Check and explain
   0 ALERT level G = General alerts; check

   1 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   0 ALERT type 2 Indicator that the structure model may be wrong or deficient
   0 ALERT type 3 Indicator that the structure quality may be low
   1 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

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S1. Comment

2,2-Di(cyclopropyl) glycolic acid (I) was prepared as the parent acid of a potentially chelating ligand bearing two conformationally rigid cyclopropane moieties. The cyclopropane rings are oriented askew to each other (Fig. 1). Bond lengths and angles are normal (Yus et al., 2005, Febles et al., 2004).

Fig. 2 shows hydrophilic chains along the viewing direction embedded in a lipophilic matrix. All the contacts between the atoms of the lipophilic matrix arise at distances larger than the sum of the van-der-Waals radii.

Fig. 3 shows an individual hydrogen-bonded chain. Instead of the frequently found carboxylic-acid dimers, pairs of alcoholic OH and C=O functions are the anchoring points for a dimer. If the C1–C2 σ bond is regarded as being incapable of relaying cooperativity, and if the weakly bifurcated part of the bond from the O3–H donor is neglected, there is—contrary to a pure carboxylic acid dimer—no cooperativity in the dimer. Instead, an extended cooperative motif is formed by the mutual lateral contact of two dimers each: 12-membered, homodromic rings that contain O–H vectors as well as π-cooperativity.

Weak interactions below the sum-of-van-der-Waals-radii limit are sparse. The only contact of this kind is a non-classic C–H···O hydrogen bond that supports the hydrophilic chain along the O2···O3 contact.

Related literature

For the synthesis of the title compound, see Zaug et al. (1960). For the crystal structures of some compounds bearing two cyclopropane groups bonded to an O-bonded C atom, see Yus et al. (2005); Febles et al. (2004). For the crystal structures of 1-hydroxycarboxylic acids with the methylene unit of glycolic acid being part of smaller-sized hydrocarbon rings, see: Betz & Klüfers (2007a,b,c) where similar as well as different hydrogen-bonding patterns are observed. For the crystal structures of 1-hydroxycarboxylic acids in which the methylene unit of glycolic acid is substituted with sterically more demanding groups, see: Betz & Klüfers (2007d); Betz et al. (2007).

S2. Experimental

The title compound was prepared according to standard procedures (Zaug et al., 1960) upon aqueous oxidation of 1,1-dicyclopropyl-prop-2-yne-1-ol. Crystals suitable for X-ray analysis were obtained upon the free evaporation of a solution of the compound in diethylether at room temperature.

S3. Refinement

The H atoms were refined as riding on their parent atoms (U_iso as the 1.2-fold of the parent atom's U_eq). The O-bonded H atoms were refined using SHELXL's electron-density-related AFIX 147 statement.

Computing details

Data collection: COLLECT (Nonius, 2004); cell refinement: SCALEPACK (Otwinowski & Minor 1997); data reduction: DENZO and SCALEPACK (Otwinowski & Minor 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEPIII (Burnett & Johnson, 1996); software used to prepare material for publication: SHELXL97 (Sheldrick, 1997).

Figures

	Fig. 1. The molecular structure of (I), with atom labels and anisotropic displacement ellipsoids (drawn at 50% probability level) for non-H atoms.
	Fig. 2. The packing of (I), viewed along [-1 0 0]. One of the hydrogen-bonded chains is centered at x, 0, 0.
	Fig. 3. An individual hydrogen-bonded chain. The [1 0 0] direction is the horizontal axis. Three dimers are shown which give rise to 12-membered homodromic rings by their mutual lateral contact. For the ring in the middle, dashed arrows point to an interaction that may be interpreted as weakly bifurcated.

2,2-Dicyclopropylglycolic acid

Crystal data

C8H12O3	Z = 2
Mr = 156.18	F(000) = 168
Triclinic, P1	Dx = 1.274 Mg m^−3
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 5.8595 (3) Å	Cell parameters from 3975 reflections
b = 7.2955 (3) Å	θ = 3.1–26.0°
c = 10.5515 (5) Å	µ = 0.10 mm^−1
α = 92.107 (3)°	T = 200 K
β = 100.758 (3)°	Block, colourless
γ = 112.263 (3)°	0.16 × 0.13 × 0.08 mm
V = 407.22 (3) Å^3

Data collection

Nonius KappaCCD diffractometer	1221 reflections with I > 2σ(I)
Radiation source: rotating anode	Rint = 0.026
MONTEL, graded multilayered X-ray optics monochromator	θmax = 26.0°, θmin = 3.4°
CCD; rotation images; thick slices scans	h = −7→7
3030 measured reflections	k = −8→8
1594 independent reflections	l = −12→12

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)] = 0.039	H-atom parameters constrained
wR(F^2) = 0.104	w = 1/[σ^2(Fo^2) + (0.0406P)^2 + 0.1023P] where P = (Fo^2 + 2Fc^2)/3
S = 1.04	(Δ/σ)max < 0.001
1594 reflections	Δρmax = 0.19 e Å^−3
103 parameters	Δρmin = −0.18 e Å^−3
0 restraints	Extinction correction: SHELXL, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.096 (12)

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

	x	y	z	Uiso*/Ueq
O3	0.45110 (17)	0.71307 (15)	0.64164 (10)	0.0310 (3)
H83	0.4429	0.6235	0.5865	0.037*
O1	0.78873 (19)	0.61259 (16)	0.55317 (11)	0.0356 (3)
O2	1.11508 (19)	0.85312 (17)	0.68539 (12)	0.0388 (4)
H82	1.1983	0.7962	0.6561	0.047*
C1	0.8731 (3)	0.7539 (2)	0.63559 (14)	0.0237 (4)
C2	0.7095 (2)	0.8385 (2)	0.69426 (14)	0.0231 (4)
C3	0.7557 (3)	1.0442 (2)	0.65394 (15)	0.0304 (4)
H3	0.7210	1.0464	0.5577	0.037*
C4	0.9573 (3)	1.2317 (2)	0.7267 (2)	0.0468 (5)
H4A	1.0446	1.3374	0.6757	0.056*
H4B	1.0650	1.2212	0.8081	0.056*
C5	0.6863 (3)	1.1889 (2)	0.72612 (19)	0.0451 (5)
H5A	0.6063	1.2680	0.6746	0.054*
H5B	0.6267	1.1517	0.8070	0.054*
C6	0.7678 (3)	0.8316 (2)	0.83998 (15)	0.0282 (4)
H6	0.9396	0.9278	0.8863	0.034*
C7	0.6769 (4)	0.6371 (3)	0.89413 (19)	0.0483 (5)
H7A	0.5677	0.5164	0.8328	0.058*
H7B	0.7929	0.6153	0.9674	0.058*
C8	0.5697 (3)	0.7866 (3)	0.91947 (17)	0.0397 (5)
H8A	0.6198	0.8577	1.0083	0.048*
H8B	0.3944	0.7589	0.8736	0.048*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O3	0.0178 (5)	0.0361 (6)	0.0352 (7)	0.0091 (5)	0.0027 (5)	−0.0136 (5)
O1	0.0252 (6)	0.0375 (7)	0.0403 (7)	0.0106 (5)	0.0055 (5)	−0.0140 (5)
O2	0.0188 (6)	0.0469 (7)	0.0477 (8)	0.0137 (5)	0.0024 (5)	−0.0166 (6)
C1	0.0197 (7)	0.0277 (8)	0.0242 (8)	0.0100 (6)	0.0044 (6)	0.0013 (6)
C2	0.0167 (7)	0.0257 (8)	0.0250 (8)	0.0077 (6)	0.0026 (6)	−0.0029 (6)
C3	0.0340 (9)	0.0326 (9)	0.0284 (9)	0.0162 (7)	0.0088 (7)	0.0035 (7)
C4	0.0463 (11)	0.0298 (10)	0.0559 (12)	0.0049 (8)	0.0130 (9)	0.0055 (8)
C5	0.0573 (12)	0.0325 (10)	0.0571 (12)	0.0238 (9)	0.0257 (10)	0.0076 (8)
C6	0.0265 (8)	0.0331 (8)	0.0247 (8)	0.0121 (7)	0.0043 (6)	0.0005 (6)
C7	0.0696 (13)	0.0442 (11)	0.0415 (11)	0.0291 (10)	0.0203 (10)	0.0149 (8)
C8	0.0403 (10)	0.0526 (11)	0.0305 (9)	0.0199 (8)	0.0142 (8)	0.0051 (8)

Geometric parameters (Å, º)

O3—C2	1.4273 (16)	C4—H4A	0.9900
O3—H83	0.8400	C4—H4B	0.9900
O1—C1	1.2046 (17)	C5—H5A	0.9900
O2—C1	1.3139 (17)	C5—H5B	0.9900
O2—H82	0.8400	C6—C7	1.492 (2)
C1—C2	1.525 (2)	C6—C8	1.501 (2)
C2—C3	1.513 (2)	C6—H6	1.0000
C2—C6	1.518 (2)	C7—C8	1.489 (2)
C3—C4	1.489 (2)	C7—H7A	0.9900
C3—C5	1.497 (2)	C7—H7B	0.9900
C3—H3	1.0000	C8—H8A	0.9900
C4—C5	1.497 (3)	C8—H8B	0.9900
C2—O3—H83	109.5	C4—C5—H5A	117.8
C1—O2—H82	109.5	C3—C5—H5A	117.8
O1—C1—O2	124.35 (13)	C4—C5—H5B	117.8
O1—C1—C2	123.54 (13)	C3—C5—H5B	117.8
O2—C1—C2	112.11 (12)	H5A—C5—H5B	114.9
O3—C2—C3	108.01 (12)	C7—C6—C8	59.66 (11)
O3—C2—C6	109.26 (12)	C7—C6—C2	120.19 (14)
C3—C2—C6	114.76 (12)	C8—C6—C2	122.65 (13)
O3—C2—C1	108.04 (11)	C7—C6—H6	114.5
C3—C2—C1	109.06 (12)	C8—C6—H6	114.5
C6—C2—C1	107.53 (12)	C2—C6—H6	114.5
C4—C3—C5	60.16 (12)	C8—C7—C6	60.49 (11)
C4—C3—C2	124.26 (14)	C8—C7—H7A	117.7
C5—C3—C2	121.31 (13)	C6—C7—H7A	117.7
C4—C3—H3	113.6	C8—C7—H7B	117.7
C5—C3—H3	113.6	C6—C7—H7B	117.7
C2—C3—H3	113.6	H7A—C7—H7B	114.8
C3—C4—C5	60.20 (11)	C7—C8—C6	59.85 (11)
C3—C4—H4A	117.8	C7—C8—H8A	117.8
C5—C4—H4A	117.8	C6—C8—H8A	117.8
C3—C4—H4B	117.8	C7—C8—H8B	117.8
C5—C4—H4B	117.8	C6—C8—H8B	117.8
H4A—C4—H4B	114.9	H8A—C8—H8B	114.9
C4—C5—C3	59.63 (11)
O1—C1—C2—O3	4.3 (2)	C1—C2—C3—C5	−161.26 (15)
O2—C1—C2—O3	−175.78 (12)	C2—C3—C4—C5	−109.52 (17)
O1—C1—C2—C3	−112.91 (16)	C2—C3—C5—C4	114.25 (17)
O2—C1—C2—C3	67.05 (16)	O3—C2—C6—C7	44.52 (18)
O1—C1—C2—C6	122.07 (16)	C3—C2—C6—C7	165.97 (14)
O2—C1—C2—C6	−57.96 (16)	C1—C2—C6—C7	−72.51 (17)
O3—C2—C3—C4	154.67 (14)	O3—C2—C6—C8	−26.75 (19)
C6—C2—C3—C4	32.5 (2)	C3—C2—C6—C8	94.70 (17)
C1—C2—C3—C4	−88.14 (18)	C1—C2—C6—C8	−143.77 (15)
O3—C2—C3—C5	81.55 (17)	C2—C6—C7—C8	−112.50 (16)
C6—C2—C3—C5	−40.6 (2)	C2—C6—C8—C7	108.48 (17)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O2—H82···O3^i	0.84	1.83	2.6387 (16)	161
O3—H83···O1	0.84	2.15	2.6572 (16)	119
O3—H83···O1^ii	0.84	2.07	2.8067 (15)	146
C8—H8B···O2^iii	0.99	2.61	3.470 (2)	145

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