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The title compound, C8H12Cl2O4, lies about an inversion centre. The molecular conformation is characterized by a tgt{\overline g}t conformation for the butane­dioxy moiety and a trans conformation for the ClCH2-C(=O)O bond. The molecular packing is stabilized by a network of weak CH2...O=C intermolecular hydrogen bonds, where each mol­ecule interacts with its four closest neighbours.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270104024709/sx1149sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270104024709/sx1149Isup2.hkl
Contains datablock I

CCDC reference: 259030

Comment top

Polyesters have a wide range of applications as biodegradable materials. Medical uses, such as bioabsorbable surgical sutures and drug delivery systems, are a good example. Most of the speciality polymers actually commercialized as sutures are based on glycolide, which is their major component (Chu, 1997). This group includes sutures such as Dexon or Safil (Schmitt & Polistina, 1967), Vicryl (Schneider, 1955), Maxon (Rosensaft & Webb, 1981), Monocryl (Bezwada et al., 1995) and Monosyn (Erneta & Vhora, 1998), which differ slightly in composition, and obviously in properties (thermal and mechanical) and degradation rates. All of these polymers are prepared by ring-opening polymerization, with the high cost of the cyclic glycolide monomer being one of the most limiting factors.

Considerable efforts are currently focused on identifying alternative syntheses and on obtaining related polymers with enhanced properties. Thus, the solid state polycondensation reaction of halogenated carboxylates appears to be an interesting method for the synthesis of polyglycolide (Herzberg & Epple, 2001), which could then generate the glycolide ring by pyrolysis. We have recently demonstrated that poly(ester amides) of high molecular weight could also be prepared by a condensation reaction between N,N'-bischloroacetyldiamines and dicarboxylate salts (Vera et al., 2004). The driving force of these polymerizations corresponds to the formation of metal halide salts (Epple & Kirschnick, 1997). A similar process could be extended to prepare new polyesters containing glycolic acid residues, characterized by the sequence OCH2COO(CH2)nOCOCH2OCO(CH2)m-2CO.

The title compound, 1,4-bis(chloroacetoxy)butane, (I), is one of the monomers that could be employed to prepare the series derived from 1,4-butanediol (n = 4). It is of interest to determine the crystalline structure of various monomers, since these kinds of reactions sometimes occur in the solid state. Furthermore, knowledge of their molecular conformations is a useful tool for the determination of the polymer structure, since they correspond to small fragments of its sequence. \sch

The molecule of (I) is shown in Fig. 1, and selected torsion angles and hydrogen-bond geometry are reported in Tables 1 and 2, respectively. The ester group is planar to within experimental error, with an r.m.s. deviation of 0.0041 Å for atoms C2, C3, O3 and O4 from the best plane passing through them. The molecule lies on an inversion centre and, consequently, the molecular conformation is symmetric (symmetry code: 1 − x, 1 − y, 1 − z).

The conformations of the chloroacetyl unit and the butanediol moiety, which is a constituent of some synthetic polyesters of commercial interest, such as poly(tetramethylene terephthalate) and poly(tetramethylene succinate), are interesting. A tgt(-g)t conformation was found in (I) for the tetramethylene moiety, a fact that is in agreement with structural studies carried out on poly(tetramethylene succinate). This polymer exists as two polymorphs, the α-form (Chatani et al., 1970), where the butanediol residues adopt a kinked conformation, and the less predominant β-form, characterized by an all-trans conformation (Ichikawa et al., 1994). However, the reported structures for poly(tetramethylene terephthalate) show different conformations for the butanediol unit, namely ggt(-g)(-g) and tst(-s)t for the α-form (Mencik, 1975; Yokouchi et al., 1976) and β-form (Yokouchi et al., 1976), respectively. The short-hand nomenclature (Tadokoro, 1979) refers to the sequence of torsion angles with gauche (g), trans (t) or skew (s) conformations. Furthermore, potential energy calculations (Palmer et al., 1985) demonstrate that, in the case of poly(tetramethylene terephthalate), the ggt(-g)(-g) conformation is stabilized with respect to the tgt(-g)t conformation.

A survey of the Cambridge Structural Data Base (CSD, Version?; Allen, 2002) shows 12 crystal structures containing XCOOCH2CH2CH2CH2OCOX units, with X being an aromatic group (phenyl, chlorophenyl or nitrophenyl) in the majority of cases. The tgt(-g)t conformation was only found in two compounds, tetramethylene glycol o-chlorobenzoate (Bocelli & Grenier-Loustalot, 1984) and tetramethylene glycol p-nitrobenzoate (Palmer at al., 1985). The all-trans conformation was observed in four compounds, with the remainder corresponding to asymmetric conformations where, in general, one of the two OCH2—CH2CH2 torsion angles is close to a gauche conformation. Among the known crystal structures of this class, compound (I) is a unique linear molecule containing aliphatic ester groups, with an observed molecular conformation in agreement with the determined structure of the α-form of poly(tetramethylene succinate).

The ClCH2—C(O)O torsion angle has a trans conformation, which places the electronegative Cl and O(CH2) atoms as far apart as possible. In fact, 65 crystal structures containing a total of 96 chloroacetoxy fragments have been solved, with the trans conformation observed for the majority (61%, 24%, 13% and 2% for the trans, cis, gauche and skew conformations, respectively). It should be pointed out that this bond tends to a cis conformation in chloroacetamide fragments [ClCH2—C(O)NH] because of the possibility of intramolecular N—H···Cl hydrogen bonds (Rao & Mallikarjunan, 1973; Kalyanaraman et al., 1978; Urpí et al., 2003).

The packing in (I) is characterized by a network of weak intermolecular CH2···OC hydrogen bonds (Fig. 2), where each molecule interacts with its four closest neighbours (Table 2). Hydrogen bonds are established along a direction which, on average, runs parallel to the b crystal axis. The methylene and carbonyl groups that interact belong to asymmetric units related by a twofold screw axis.

Experimental top

The title compound was synthesized by the dropwise addition of a chloroform solution of 2.2 equivalents of chloroacetyl chloride (0.22 mol in 100 ml) to a chloroform solution of 1,4-butanediol (0.1 mol in 150 ml). The reaction mixture was stirred at room temperature for 3 h and then repeatedly washed with water. Finally, the chloroform solvent was evaporated under reduced pressure. The white solid obtained was recrystallized from ethanol to give colourless rhombic crystals of (I) (yield 85%, m.p. 349 K). Analysis: 1H NMR (CDCl3, TMS, internal reference, δ, p.p.m.): 4.26 (m, 4H, OCH2), 4.09 (s, 4H, ClCH2), 1.81 (m, 4H, OCH2CH2); 13C NMR (CDCl3, TMS, internal reference, δ, p.p.m.): 167.33 (CO), 65.53 (OCH2), 40.84 (ClCH2), 25.04 (OCH2CH2).

Refinement top

H atoms were placed in calculated positions and were refined isotropically riding on their attached C atoms, with C—H distances of 0.97 Å. All H atoms belong to CH2 groups. In the asymmetric unit of (I), there are three different CH2 groups. The displacement parameter of the two H atoms of each CH2 group was refined as a free variable.

Computing details top

Data collection: CAD-4 Software (Kiers, 1994); cell refinement: CAD-4 Software; data reduction: local program; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEPII (Johnson, 1976); software used to prepare material for publication: UNIX.

Figures top
[Figure 1] Fig. 1. A view of the molecule of (I), with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii.
[Figure 2] Fig. 2. A view parallel to the crystallographic a axis, showing the crystal packing of (I). Dashed lines illustrate the weak intermolecular hydrogen-bond interactions between the methylene and carbonyl groups.
Butane-1,4-diyl bis(chloroacetate) top
Crystal data top
C8H12Cl2O4F(000) = 252
Mr = 243.08Dx = 1.450 Mg m3
Monoclinic, P21/cMelting point: 76 K
Hall symbol: -P 2ybcMo Kα radiation, λ = 0.71073 Å
a = 7.9765 (16) ÅCell parameters from 25 reflections
b = 9.8921 (14) Åθ = 12–21°
c = 7.220 (2) ŵ = 0.57 mm1
β = 102.22 (2)°T = 293 K
V = 556.8 (2) Å3Prism, colourless
Z = 20.4 × 0.3 × 0.2 mm
Data collection top
Enraf Nonius CAD4
diffractometer
Rint = 0.032
Radiation source: fine-focus sealed tubeθmax = 30.0°, θmin = 2.6°
Graphite monochromatorh = 110
ω/2θ scansk = 130
1717 measured reflectionsl = 910
1621 independent reflections3 standard reflections every 120 min
837 reflections with I > 2σ(I) intensity decay: none
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.053Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.138H-atom parameters constrained
S = 1.01 w = 1/[σ2(Fo2) + (0.0484P)2 + 0.2473P]
where P = (Fo2 + 2Fc2)/3
1621 reflections(Δ/σ)max < 0.001
67 parametersΔρmax = 0.24 e Å3
0 restraintsΔρmin = 0.29 e Å3
Crystal data top
C8H12Cl2O4V = 556.8 (2) Å3
Mr = 243.08Z = 2
Monoclinic, P21/cMo Kα radiation
a = 7.9765 (16) ŵ = 0.57 mm1
b = 9.8921 (14) ÅT = 293 K
c = 7.220 (2) Å0.4 × 0.3 × 0.2 mm
β = 102.22 (2)°
Data collection top
Enraf Nonius CAD4
diffractometer
Rint = 0.032
1717 measured reflections3 standard reflections every 120 min
1621 independent reflections intensity decay: none
837 reflections with I > 2σ(I)
Refinement top
R[F2 > 2σ(F2)] = 0.0530 restraints
wR(F2) = 0.138H-atom parameters constrained
S = 1.01Δρmax = 0.24 e Å3
1621 reflectionsΔρmin = 0.29 e Å3
67 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.

Least-squares planes (x,y,z in crystal coordinates) and deviations from them (* indicates atom used to define plane)

2.3619 (0.0129) x + 6.6444 (0.0115) y − 5.2444 (0.0071) z = 2.3810 (0.0123)

* 0.0020 (0.0006) C2 * −0.0071 (0.0022) C3 * 0.0029 (0.0009) O3 * 0.0022 (0.0007) O4

Rms deviation of fitted atoms = 0.0041

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 (Å2) top
xyzUiso*/Ueq
Cl11.26845 (10)0.59334 (9)0.94297 (11)0.0782 (3)
O30.9226 (3)0.7223 (2)0.8761 (3)0.0777 (7)
O40.8051 (2)0.58074 (16)0.6439 (2)0.0464 (4)
C21.0966 (4)0.5621 (3)0.7516 (4)0.0632 (8)
H2A1.12840.59130.63550.113 (9)*
H2B1.07560.46550.74200.113 (9)*
C30.9344 (3)0.6324 (3)0.7694 (3)0.0486 (6)
C50.6394 (3)0.6456 (3)0.6273 (4)0.0543 (7)
H5A0.64670.74010.59400.067 (6)*
H5B0.60250.64040.74680.067 (6)*
C60.5145 (3)0.5733 (2)0.4755 (4)0.0526 (6)
H6A0.55650.57580.35890.067 (6)*
H6B0.40560.62060.45320.067 (6)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Cl10.0652 (5)0.0860 (6)0.0727 (5)0.0116 (4)0.0096 (4)0.0015 (4)
O30.0781 (15)0.0736 (14)0.0805 (14)0.0042 (12)0.0144 (12)0.0393 (12)
O40.0487 (10)0.0439 (9)0.0471 (9)0.0008 (8)0.0112 (7)0.0077 (7)
C20.0497 (16)0.074 (2)0.0614 (17)0.0016 (14)0.0020 (13)0.0171 (14)
C30.0579 (15)0.0449 (14)0.0438 (12)0.0072 (12)0.0121 (11)0.0056 (11)
C50.0521 (15)0.0458 (14)0.0668 (17)0.0045 (12)0.0166 (13)0.0034 (13)
C60.0472 (14)0.0471 (14)0.0623 (16)0.0020 (12)0.0089 (12)0.0062 (12)
Geometric parameters (Å, º) top
Cl1—C21.756 (3)C5—C61.498 (3)
O3—C31.194 (3)C5—H5A0.9700
O4—C31.323 (3)C5—H5B0.9700
O4—C51.451 (3)C6—C6i1.521 (5)
C2—C31.498 (4)C6—H6A0.9700
C2—H2A0.9700C6—H6B0.9700
C2—H2B0.9700
C3—O4—C5116.75 (19)O4—C5—H5A110.2
C3—C2—Cl1113.3 (2)C6—C5—H5A110.2
C3—C2—H2A108.9O4—C5—H5B110.2
Cl1—C2—H2A108.9C6—C5—H5B110.2
C3—C2—H2B108.9H5A—C5—H5B108.5
Cl1—C2—H2B108.9C5—C6—C6i113.3 (3)
H2A—C2—H2B107.7C5—C6—H6A108.9
O3—C3—O4125.0 (3)C6i—C6—H6A108.9
O3—C3—C2126.1 (3)C5—C6—H6B108.9
O4—C3—C2108.9 (2)C6i—C6—H6B108.9
O4—C5—C6107.6 (2)H6A—C6—H6B107.7
C5—O4—C3—O34.5 (4)Cl1—C2—C3—O4166.40 (19)
C5—O4—C3—C2174.1 (2)C3—O4—C5—C6178.7 (2)
Cl1—C2—C3—O315.0 (4)O4—C5—C6—C6i64.3 (3)
Symmetry code: (i) x+1, y+1, z+1.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C2—H2B···O3ii0.972.553.480 (4)160
Symmetry code: (ii) x+2, y1/2, z+3/2.

Experimental details

Crystal data
Chemical formulaC8H12Cl2O4
Mr243.08
Crystal system, space groupMonoclinic, P21/c
Temperature (K)293
a, b, c (Å)7.9765 (16), 9.8921 (14), 7.220 (2)
β (°) 102.22 (2)
V3)556.8 (2)
Z2
Radiation typeMo Kα
µ (mm1)0.57
Crystal size (mm)0.4 × 0.3 × 0.2
Data collection
DiffractometerEnraf Nonius CAD4
diffractometer
Absorption correction
No. of measured, independent and
observed [I > 2σ(I)] reflections
1717, 1621, 837
Rint0.032
(sin θ/λ)max1)0.703
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.053, 0.138, 1.01
No. of reflections1621
No. of parameters67
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.24, 0.29

Computer programs: CAD-4 Software (Kiers, 1994), CAD-4 Software, local program, SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), ORTEPII (Johnson, 1976), UNIX.

Selected torsion angles (º) top
C5—O4—C3—O34.5 (4)Cl1—C2—C3—O4166.40 (19)
C5—O4—C3—C2174.1 (2)C3—O4—C5—C6178.7 (2)
Cl1—C2—C3—O315.0 (4)O4—C5—C6—C6i64.3 (3)
Symmetry code: (i) x+1, y+1, z+1.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C2—H2B···O3ii0.972.553.480 (4)160
Symmetry code: (ii) x+2, y1/2, z+3/2.
 

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