2-[(Eth­­oxy­carbono­thio­yl)sulfan­yl]acetic acid

In the title compound, C₅H₈O₃S₂, the C—S and C—O bonds in the xanthate unit are shorter than those linked to it. In the crystal, inversion dimers linked by pairs of O—H⋯O hydrogen bonds occur.

Related literature

For general background to the synthesis and applications of the title compound, see: Stenzel et al. (2003); Moad et al. (2005, 2008). For its applications in polymerization, see: Coote & Radom (2004); Simms et al. (2005); Russum et al. (2005); Assem et al. (2007); Wang et al. (2010). For similar structures, see: Xiao & Charpentier (2010, 2011).

Experimental

Crystal data

• C₅H₈O₃S₂

• M_r = 180.23

• Monoclinic, P 2₁ /n

• a = 4.7387 (2) Å

• b = 14.7836 (8) Å

• c = 11.9013 (6) Å

• β = 100.845 (3)°

• V = 818.86 (7) ų

• Z = 4

• Mo Kα radiation

• μ = 0.60 mm⁻¹

• T = 150 K

• 0.08 × 0.03 × 0.03 mm

Data collection

• Bruker APEXII CCD diffractometer

• Absorption correction: multi-scan (Blessing, 1995) T_min = 0.952, T_max = 0.982

• 39762 measured reflections

• 3582 independent reflections

• 2343 reflections with I > 2σ(I)

• R_int = 0.092

Refinement

• R[F² > 2σ(F²)] = 0.045

• wR(F²) = 0.111

• S = 1.01

• 3582 reflections

• 93 parameters

• H-atom parameters constrained

• Δρ_max = 0.31 e Å⁻³

• Δρ_min = −0.37 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O2—H2⋯O3^i	0.84	1.81	2.645 (2)	175
Symmetry code: (i) -x, -y+1, -z+2.

Data collection: APEX2 (Bruker, 2008); cell refinement: SAINT (Bruker, 2008); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL.

Supporting information

S1. Comment

Reversible-deactivation radical polymerization (RDRP) of vinyl acetate (VAc) has been a challenge. Methyl 2-(ethoxycarbonothioylthio)acetate was investigated for reversible addition-fragmentation chain transfer (RAFT) polymerization of VAc (Moad et al., 2005, 2008; Stenzel et al., 2003; Coote & Radom, 2004), and was successfully applied in emulsion polymerizations (Simms et al., 2005; Russum et al., 2005). Thanks to the similarity of the molecular structures, 2-(ethoxycarbonothioylthio)acetic acid not only provides a carboxylic acid functionality but also works as the RAFT-CTA for VAc in RDRP. This RAFT-CTA has also found applications in the RAFT polymerization of other monomers (Assem et al., 2007; Wang et al., 2010). Compounds of similar structures were reported previously (Xiao & Charpentier, 2010, 2011).

Related literature

For general background to the synthesis and applications of the title compound, see: Stenzel et al. (2003); Moad et al. (2005, 2008). For its applications in polymerization, see: Coote & Radom (2004); Simms et al. (2005); Russum et al. (2005); Assem et al. (2007); Wang et al. (2010). For similar structures, see: Xiao & Charpentier (2010, 2011).

S2. Experimental

Potassium O-ethyl dithiocarbonate 13.6 g was dissolved in THF 50 ml, and then mixed with 2-bromoacetic acid 6.9 g / THF 20 ml. The reaction was carried out at room temperature for 2 days. Excess hexanes was applied to the mixture and the precipitates were filtered off, followed by evaporating the solvents using a rotary evaporator. The light yellow oil was further purified by extraction and recrystallization with hexanes, and colorless crystals were obtained. m.p.: 56.4 °C(DSC). MS: 179.9917.

S3. Refinement

The structure was solved and refined using the Bruker SHELXTL Software Package, using the space group P 1 21/n 1, with Z = 4 for the formula unit, C₅H₈O₃S₂. All of the non-hydrogen atoms were refined with anisotropic thermal parameters. The hydrogen atom positions were calculated geometrically and were included as riding on their respective carbon atoms. The final anisotropic full-matrix least-squares refinement on F² with 93 variables converged at R1 = 4.54%, for the observed data and wR2 = 11.08% for all data. The goodness-of-fit was 1.005. The largest peak in the final difference electron density synthesis was 0.309 e^-/ų and the largest hole was -0.368 e^-/ų with an RMS deviation of 0.077 e^-/ų. On the basis of the final model, the calculated density was 1.462 g/cm³ and F(000), 376 e^-.

Computing details

Data collection: APEX2 (Bruker, 2008); cell refinement: SAINT (Bruker, 2008); data reduction: SAINT (Bruker, 2008); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures

	Fig. 1. View of the title compound (50% probability displacement ellipsoids).
	Fig. 2. Packing diagram of the structure with H-bonds.

2-[(Ethoxycarbonothioyl)sulfanyl]acetic acid

Crystal data

C5H8O3S2	F(000) = 376
Mr = 180.23	Dx = 1.462 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 4468 reflections
a = 4.7387 (2) Å	θ = 2.2–25.6°
b = 14.7836 (8) Å	µ = 0.60 mm^−1
c = 11.9013 (6) Å	T = 150 K
β = 100.845 (3)°	Cube, colourless
V = 818.86 (7) Å^3	0.08 × 0.03 × 0.03 mm
Z = 4

Data collection

Bruker APEXII CCD diffractometer	3582 independent reflections
Radiation source: fine-focus sealed tube	2343 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.092
ϕ and ω scans	θmax = 35.0°, θmin = 2.2°
Absorption correction: multi-scan (Blessing, 1995)	h = −7→7
Tmin = 0.952, Tmax = 0.982	k = −23→23
39762 measured reflections	l = −19→18

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.045	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.111	H-atom parameters constrained
S = 1.01	w = 1/[σ^2(Fo^2) + (0.0294P)^2 + 0.6076P] where P = (Fo^2 + 2Fc^2)/3
3582 reflections	(Δ/σ)max = 0.001
93 parameters	Δρmax = 0.31 e Å^−3
0 restraints	Δρmin = −0.37 e Å^−3

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
S1	−0.08173 (11)	0.19417 (3)	1.01439 (4)	0.02745 (11)
S2	−0.03755 (11)	0.25308 (3)	0.77468 (4)	0.03030 (12)
O1	0.1868 (3)	0.10724 (9)	0.88947 (11)	0.0300 (3)
O2	−0.3267 (3)	0.44372 (9)	0.93538 (13)	0.0329 (3)
H2	−0.2443	0.4941	0.9464	0.049*
O3	0.0854 (3)	0.39432 (9)	1.04203 (12)	0.0306 (3)
C1	0.4719 (6)	−0.00588 (15)	0.8227 (2)	0.0510 (6)
H1A	0.6206	0.0051	0.8906	0.077*
H1B	0.5624	−0.0255	0.7592	0.077*
H1C	0.3409	−0.0531	0.8396	0.077*
C2	0.3067 (5)	0.07965 (13)	0.79013 (17)	0.0327 (4)
H2A	0.4352	0.1273	0.7699	0.039*
H2B	0.1508	0.0690	0.7234	0.039*
C3	0.0329 (4)	0.18315 (11)	0.88283 (14)	0.0236 (3)
C4	−0.3109 (4)	0.29105 (12)	0.98778 (16)	0.0276 (3)
H4A	−0.4369	0.2837	0.9120	0.033*
H4B	−0.4359	0.2923	1.0457	0.033*
C5	−0.1604 (4)	0.38094 (12)	0.98990 (14)	0.0239 (3)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
S1	0.0365 (2)	0.02475 (19)	0.02263 (19)	−0.00361 (17)	0.00955 (16)	0.00040 (15)
S2	0.0354 (3)	0.0337 (2)	0.02195 (19)	−0.00021 (19)	0.00584 (17)	0.00340 (16)
O1	0.0375 (7)	0.0262 (6)	0.0284 (6)	0.0002 (5)	0.0118 (5)	0.0004 (5)
O2	0.0272 (7)	0.0267 (6)	0.0423 (8)	0.0001 (5)	0.0000 (6)	−0.0006 (6)
O3	0.0266 (6)	0.0272 (6)	0.0356 (7)	−0.0025 (5)	−0.0001 (5)	0.0014 (5)
C1	0.0734 (18)	0.0294 (10)	0.0603 (15)	0.0068 (11)	0.0385 (14)	−0.0004 (10)
C2	0.0384 (11)	0.0299 (9)	0.0332 (9)	−0.0048 (8)	0.0151 (8)	−0.0068 (7)
C3	0.0242 (8)	0.0242 (7)	0.0228 (7)	−0.0060 (6)	0.0050 (6)	−0.0028 (6)
C4	0.0259 (8)	0.0298 (9)	0.0289 (8)	−0.0038 (7)	0.0098 (7)	−0.0011 (7)
C5	0.0237 (8)	0.0269 (8)	0.0223 (7)	−0.0011 (6)	0.0075 (6)	−0.0020 (6)

Geometric parameters (Å, º)

S1—C3	1.7588 (17)	C1—H1A	0.9800
S1—C4	1.789 (2)	C1—H1B	0.9800
S2—C3	1.6356 (18)	C1—H1C	0.9800
O1—C3	1.332 (2)	C2—H2A	0.9900
O1—C2	1.463 (2)	C2—H2B	0.9900
O2—C5	1.308 (2)	C4—C5	1.506 (2)
O2—H2	0.8400	C4—H4A	0.9900
O3—C5	1.228 (2)	C4—H4B	0.9900
C1—C2	1.499 (3)
C3—S1—C4	101.27 (9)	H2A—C2—H2B	108.6
C3—O1—C2	118.58 (14)	O1—C3—S2	127.40 (13)
C5—O2—H2	109.5	O1—C3—S1	106.40 (12)
C2—C1—H1A	109.5	S2—C3—S1	126.20 (11)
C2—C1—H1B	109.5	C5—C4—S1	115.70 (13)
H1A—C1—H1B	109.5	C5—C4—H4A	108.4
C2—C1—H1C	109.5	S1—C4—H4A	108.4
H1A—C1—H1C	109.5	C5—C4—H4B	108.4
H1B—C1—H1C	109.5	S1—C4—H4B	108.4
O1—C2—C1	106.83 (17)	H4A—C4—H4B	107.4
O1—C2—H2A	110.4	O3—C5—O2	124.18 (16)
C1—C2—H2A	110.4	O3—C5—C4	123.47 (16)
O1—C2—H2B	110.4	O2—C5—C4	112.25 (15)
C1—C2—H2B	110.4

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O2—H2···O3^i	0.84	1.81	2.645 (2)	175

Symmetry code: (i) −x, −y+1, −z+2.