4,4,4-Tri­fluoro-trans-2-butenoic acid

The title compound, C₄H₃O₂F₃, crystallizes with two mol­ecules in the asymmetric unit. These two mol­ecules form a dimer via a pair of hydrogen-bonding interactions between the carboxyl­ic acid groups of the two mol­ecules. The correspondences of H...O distances and O—H...O angles are 1.77 (3) Å and 179 (3)°, and 1.59 (4) Å and 175 (4)°. The uncertainty in their position indicates disorder in the carboxyl­ic acid H atoms.

Key indicators

• Single-crystal X-ray study
• T = 190 K
• Mean [sigma](C-C) = 0.002 Å
• R factor = 0.039
• wR factor = 0.100
• Data-to-parameter ratio = 13.0

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry

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S1. Comment

The structure of the title compound, (I), was determined as part of a study into the polymorphic forms of the related compound tetrolic acid and an investigation into the structures preferentially formed by small compounds with a single carboxylic acid moiety. Compounds with a double bond α to the C atom of the carboxylic acid group have a strong tendency to form dimers. This compound is no exception, crystallizing in the space group P2₁/c. The two molecules forming the dimer have a non-crystallographic centre of symmetry between the carboxylic acid groups [at x = 0.586 (3), y = 0.360 (3) z = 0.696 (3)]. This can be contrasted with the structure of crotonic acid (Shimizu et al., 1974), which utilizes the crystallographic centre of symmetry to form the dimer. The hydrogen-bonded dimers form ribbons through close contacts involving the F atoms (F···F distances of 3.0, 3.3 and 3.4 Å), and the ribbons lie side-by-side to form sheets. [Please provide correct chemical diagram showing F atoms]

S2. Experimental

A crystal of suitable quality for single-crystal X-ray diffraction was obtained from the sample supplied by Fluorochem. The synthesis of the title compound has been described by Haszeldine (1957).

S3. Refinement

H atoms refined isotropically; C—H distances were in the range 0.88 (2)–0.92 (2) Å and O—H distances were 0.91 (3) and 1.07 (4) Å.

Computing details

Data collection: COLLECT (Nonius, 1997-2001); cell refinement: DENZO/SCALEPACK; data reduction: DENZO/SCALEPACK (Otwinowski & Minor, 1996); program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: CRYSTALS (Watkin et al., 2001); molecular graphics: CAMERON (Watkin et al., 1996); software used to prepare material for publication: CRYSTALS.

Figures

Fig. 1. Crystallographic diagram of the asymmetric unit with atomic numbering. Displacement ellipsoids are drawn at the 50% probability level. H atoms were isotropically refined.

4,4,4-trifluoro-trans-2-butenoic acid

Crystal data

C4H3F3O2	F(000) = 560.000
Mr = 140.06	Dx = 1.727 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 10.8280 (2) Å	Cell parameters from 2437 reflections
b = 9.8064 (2) Å	θ = 5–27°
c = 10.1768 (2) Å	µ = 0.20 mm^−1
β = 94.307 (1)°	T = 190 K
V = 1077.56 (4) Å^3	Plate, colourless
Z = 8	0.30 × 0.30 × 0.15 mm

Data collection

Nonius KappaCCD diffractometer	1961 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.01
ω scans	θmax = 27.5°, θmin = 5.3°
Absorption correction: multi-scan (DENZO/SCALEPACK; Otwinowski & Minor, 1996)	h = −14→14
Tmin = 0.94, Tmax = 0.97	k = −12→12
4700 measured reflections	l = −13→13
2429 independent reflections

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.039	All H-atom parameters refined
wR(F^2) = 0.100	Method = SHELXL 97 (Sheldrick, 1997) W = q / [Sigma^2(F*) + (P(1)p)^2 + P(2)p + P(4) + P(5)Sin(theta)] where the parameter values are: P(1) = 0.388E-01 P(2) = 0.474 P(3) = 0.00 P(4) = 0.00 P(5) = 0.00 P(6) = 0.333
S = 0.99	(Δ/σ)max = 0.001
2429 reflections	Δρmax = 0.35 e Å^−3
187 parameters	Δρmin = −0.31 e Å^−3

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

	x	y	z	Uiso*/Ueq
H1	0.563 (3)	0.460 (3)	0.630 (3)	0.120 (11)*
H101	0.597 (4)	0.251 (5)	0.729 (4)	0.180 (17)*
H4	0.7626 (17)	0.462 (2)	0.3976 (19)	0.047 (5)*
H5	0.8898 (17)	0.234 (2)	0.4887 (19)	0.049 (5)*
H104	0.3885 (17)	0.236 (2)	0.9734 (19)	0.050 (5)*
H105	0.3054 (19)	0.501 (2)	0.922 (2)	0.056 (6)*
O101	0.53815 (11)	0.23484 (12)	0.80720 (11)	0.0447
O102	0.45402 (11)	0.43519 (12)	0.74780 (12)	0.0466
C103	0.46243 (12)	0.33352 (14)	0.82018 (14)	0.0309
C104	0.38178 (13)	0.31879 (16)	0.93103 (15)	0.0333
C105	0.30911 (13)	0.41773 (16)	0.96377 (14)	0.0328
C106	0.22768 (14)	0.40758 (17)	1.07472 (15)	0.0376
F107	0.10915 (8)	0.42248 (13)	1.0338 (1)	0.0576
F108	0.25210 (11)	0.50736 (14)	1.16249 (11)	0.0690
F109	0.2384 (1)	0.29041 (13)	1.13908 (11)	0.0642
O1	0.6191 (1)	0.47338 (11)	0.56840 (11)	0.0378
O2	0.6886 (1)	0.26251 (11)	0.61478 (11)	0.0409
C3	0.69059 (12)	0.37175 (15)	0.55196 (13)	0.0303
C4	0.77927 (14)	0.39228 (16)	0.44974 (14)	0.0331
C5	0.87336 (13)	0.31024 (16)	0.43697 (14)	0.0333
C6	0.96348 (14)	0.33095 (17)	0.33542 (16)	0.0402
F7	0.9771 (1)	0.21884 (11)	0.26449 (11)	0.0577
F8	1.07577 (9)	0.36174 (14)	0.38947 (12)	0.0685
F9	0.93024 (11)	0.42947 (12)	0.25017 (11)	0.0647

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O101	0.0485 (6)	0.0412 (6)	0.0468 (6)	0.0159 (5)	0.0200 (5)	0.0066 (5)
O102	0.0470 (6)	0.0441 (7)	0.0515 (7)	0.0114 (5)	0.0217 (5)	0.0194 (5)
C103	0.0305 (7)	0.0296 (7)	0.0334 (7)	0.0020 (5)	0.0075 (5)	0.0018 (6)
C104	0.0343 (7)	0.0320 (7)	0.0347 (7)	0.0014 (6)	0.0097 (6)	0.0053 (6)
C105	0.0321 (7)	0.0345 (8)	0.0325 (7)	0.0015 (6)	0.0069 (5)	0.0026 (6)
C106	0.0331 (7)	0.0464 (9)	0.0340 (7)	0.0052 (6)	0.0073 (6)	−0.0005 (7)
F107	0.0310 (5)	0.0887 (8)	0.0544 (6)	0.0097 (5)	0.0103 (4)	0.0021 (6)
F108	0.0706 (7)	0.0885 (9)	0.0500 (6)	−0.0061 (6)	0.0170 (5)	−0.0311 (6)
F109	0.0661 (7)	0.0715 (8)	0.0595 (7)	0.0203 (6)	0.0341 (5)	0.0303 (6)
O1	0.0375 (6)	0.0387 (6)	0.0385 (6)	0.0088 (4)	0.0113 (4)	0.0020 (5)
O2	0.0504 (6)	0.0344 (6)	0.0402 (6)	0.0055 (5)	0.0187 (5)	0.0061 (5)
C3	0.0300 (7)	0.0331 (7)	0.0280 (7)	0.0016 (5)	0.0038 (5)	−0.0010 (6)
C4	0.0357 (7)	0.0347 (8)	0.0296 (7)	−0.0000 (6)	0.0072 (5)	0.0025 (6)
C5	0.0338 (7)	0.0355 (8)	0.0314 (7)	−0.0014 (6)	0.0076 (6)	0.0004 (6)
C6	0.0370 (8)	0.0442 (9)	0.0408 (8)	−0.0011 (7)	0.0131 (6)	−0.0007 (7)
F7	0.0624 (7)	0.0589 (7)	0.0555 (6)	0.0018 (5)	0.0288 (5)	−0.0139 (5)
F8	0.0372 (6)	0.098 (1)	0.0721 (8)	−0.0191 (6)	0.0156 (5)	−0.0146 (7)
F9	0.0720 (7)	0.0632 (7)	0.0637 (7)	0.0109 (6)	0.0376 (6)	0.0247 (6)

Geometric parameters (Å, º)

H1—O1	0.91 (3)	C106—F107	1.327 (2)
H101—O101	1.07 (4)	C106—F108	1.338 (2)
H4—C4	0.88 (2)	C106—F109	1.323 (2)
H5—C5	0.92 (2)	O1—C3	1.281 (2)
H104—C104	0.92 (2)	O2—C3	1.249 (2)
H105—C105	0.92 (2)	C3—C4	1.482 (2)
O101—C103	1.282 (2)	C4—C5	1.312 (2)
O102—C103	1.239 (2)	C5—C6	1.488 (2)
C103—C104	1.485 (2)	C6—F7	1.329 (2)
C104—C105	1.308 (2)	C6—F8	1.331 (2)
C105—C106	1.487 (2)	C6—F9	1.330 (2)
H101—O101—C103	113 (2)	H1—O1—C3	115 (2)
O101—C103—O102	124.4 (1)	O1—C3—O2	124.5 (1)
O101—C103—C104	115.0 (1)	O1—C3—C4	114.6 (1)
O102—C103—C104	120.6 (1)	O2—C3—C4	120.9 (1)
H104—C104—C103	114.3 (10)	H4—C4—C3	114.5 (10)
H104—C104—C105	124.3 (10)	H4—C4—C5	123.1 (10)
C103—C104—C105	121.4 (1)	C3—C4—C5	122.4 (1)
H105—C105—C104	122.9 (10)	H5—C5—C4	123.8 (10)
H105—C105—C106	114.0 (10)	H5—C5—C6	113.5 (10)
C104—C105—C106	123.1 (1)	C4—C5—C6	122.7 (2)
C105—C106—F107	111.7 (1)	C5—C6—F7	111.7 (1)
C105—C106—F108	111.0 (1)	C5—C6—F8	111.7 (1)
F107—C106—F108	105.5 (1)	F7—C6—F8	106.1 (1)
C105—C106—F109	113.5 (1)	C5—C6—F9	113.1 (1)
F107—C106—F109	107.3 (1)	F7—C6—F9	106.4 (1)
F108—C106—F109	107.4 (1)	F8—C6—F9	107.4 (1)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···O102	0.92 (3)	1.76 (3)	2.676 (2)	179 (3)
O101—H101···O2	1.07 (4)	1.59 (4)	2.654 (2)	175 (4)