Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270104024709/sx1149sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270104024709/sx1149Isup2.hkl |
CCDC reference: 259030
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).
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.
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.
C8H12Cl2O4 | F(000) = 252 |
Mr = 243.08 | Dx = 1.450 Mg m−3 |
Monoclinic, P21/c | Melting point: 76 K |
Hall symbol: -P 2ybc | Mo Kα radiation, λ = 0.71073 Å |
a = 7.9765 (16) Å | Cell parameters from 25 reflections |
b = 9.8921 (14) Å | θ = 12–21° |
c = 7.220 (2) Å | µ = 0.57 mm−1 |
β = 102.22 (2)° | T = 293 K |
V = 556.8 (2) Å3 | Prism, colourless |
Z = 2 | 0.4 × 0.3 × 0.2 mm |
Enraf Nonius CAD4 diffractometer | Rint = 0.032 |
Radiation source: fine-focus sealed tube | θmax = 30.0°, θmin = 2.6° |
Graphite monochromator | h = −11→0 |
ω/2θ scans | k = −13→0 |
1717 measured reflections | l = −9→10 |
1621 independent reflections | 3 standard reflections every 120 min |
837 reflections with I > 2σ(I) | intensity decay: none |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.053 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.138 | H-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 parameters | Δρmax = 0.24 e Å−3 |
0 restraints | Δρmin = −0.29 e Å−3 |
C8H12Cl2O4 | V = 556.8 (2) Å3 |
Mr = 243.08 | Z = 2 |
Monoclinic, P21/c | Mo Kα radiation |
a = 7.9765 (16) Å | µ = 0.57 mm−1 |
b = 9.8921 (14) Å | T = 293 K |
c = 7.220 (2) Å | 0.4 × 0.3 × 0.2 mm |
β = 102.22 (2)° |
Enraf Nonius CAD4 diffractometer | Rint = 0.032 |
1717 measured reflections | 3 standard reflections every 120 min |
1621 independent reflections | intensity decay: none |
837 reflections with I > 2σ(I) |
R[F2 > 2σ(F2)] = 0.053 | 0 restraints |
wR(F2) = 0.138 | H-atom parameters constrained |
S = 1.01 | Δρmax = 0.24 e Å−3 |
1621 reflections | Δρmin = −0.29 e Å−3 |
67 parameters |
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. |
x | y | z | Uiso*/Ueq | ||
Cl1 | 1.26845 (10) | 0.59334 (9) | 0.94297 (11) | 0.0782 (3) | |
O3 | 0.9226 (3) | 0.7223 (2) | 0.8761 (3) | 0.0777 (7) | |
O4 | 0.8051 (2) | 0.58074 (16) | 0.6439 (2) | 0.0464 (4) | |
C2 | 1.0966 (4) | 0.5621 (3) | 0.7516 (4) | 0.0632 (8) | |
H2A | 1.1284 | 0.5913 | 0.6355 | 0.113 (9)* | |
H2B | 1.0756 | 0.4655 | 0.7420 | 0.113 (9)* | |
C3 | 0.9344 (3) | 0.6324 (3) | 0.7694 (3) | 0.0486 (6) | |
C5 | 0.6394 (3) | 0.6456 (3) | 0.6273 (4) | 0.0543 (7) | |
H5A | 0.6467 | 0.7401 | 0.5940 | 0.067 (6)* | |
H5B | 0.6025 | 0.6404 | 0.7468 | 0.067 (6)* | |
C6 | 0.5145 (3) | 0.5733 (2) | 0.4755 (4) | 0.0526 (6) | |
H6A | 0.5565 | 0.5758 | 0.3589 | 0.067 (6)* | |
H6B | 0.4056 | 0.6206 | 0.4532 | 0.067 (6)* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Cl1 | 0.0652 (5) | 0.0860 (6) | 0.0727 (5) | −0.0116 (4) | −0.0096 (4) | −0.0015 (4) |
O3 | 0.0781 (15) | 0.0736 (14) | 0.0805 (14) | −0.0042 (12) | 0.0144 (12) | −0.0393 (12) |
O4 | 0.0487 (10) | 0.0439 (9) | 0.0471 (9) | −0.0008 (8) | 0.0112 (7) | −0.0077 (7) |
C2 | 0.0497 (16) | 0.074 (2) | 0.0614 (17) | 0.0016 (14) | 0.0020 (13) | −0.0171 (14) |
C3 | 0.0579 (15) | 0.0449 (14) | 0.0438 (12) | −0.0072 (12) | 0.0121 (11) | −0.0056 (11) |
C5 | 0.0521 (15) | 0.0458 (14) | 0.0668 (17) | 0.0045 (12) | 0.0166 (13) | −0.0034 (13) |
C6 | 0.0472 (14) | 0.0471 (14) | 0.0623 (16) | 0.0020 (12) | 0.0089 (12) | 0.0062 (12) |
Cl1—C2 | 1.756 (3) | C5—C6 | 1.498 (3) |
O3—C3 | 1.194 (3) | C5—H5A | 0.9700 |
O4—C3 | 1.323 (3) | C5—H5B | 0.9700 |
O4—C5 | 1.451 (3) | C6—C6i | 1.521 (5) |
C2—C3 | 1.498 (4) | C6—H6A | 0.9700 |
C2—H2A | 0.9700 | C6—H6B | 0.9700 |
C2—H2B | 0.9700 | ||
C3—O4—C5 | 116.75 (19) | O4—C5—H5A | 110.2 |
C3—C2—Cl1 | 113.3 (2) | C6—C5—H5A | 110.2 |
C3—C2—H2A | 108.9 | O4—C5—H5B | 110.2 |
Cl1—C2—H2A | 108.9 | C6—C5—H5B | 110.2 |
C3—C2—H2B | 108.9 | H5A—C5—H5B | 108.5 |
Cl1—C2—H2B | 108.9 | C5—C6—C6i | 113.3 (3) |
H2A—C2—H2B | 107.7 | C5—C6—H6A | 108.9 |
O3—C3—O4 | 125.0 (3) | C6i—C6—H6A | 108.9 |
O3—C3—C2 | 126.1 (3) | C5—C6—H6B | 108.9 |
O4—C3—C2 | 108.9 (2) | C6i—C6—H6B | 108.9 |
O4—C5—C6 | 107.6 (2) | H6A—C6—H6B | 107.7 |
C5—O4—C3—O3 | 4.5 (4) | Cl1—C2—C3—O4 | −166.40 (19) |
C5—O4—C3—C2 | −174.1 (2) | C3—O4—C5—C6 | 178.7 (2) |
Cl1—C2—C3—O3 | 15.0 (4) | O4—C5—C6—C6i | 64.3 (3) |
Symmetry code: (i) −x+1, −y+1, −z+1. |
D—H···A | D—H | H···A | D···A | D—H···A |
C2—H2B···O3ii | 0.97 | 2.55 | 3.480 (4) | 160 |
Symmetry code: (ii) −x+2, y−1/2, −z+3/2. |
Experimental details
Crystal data | |
Chemical formula | C8H12Cl2O4 |
Mr | 243.08 |
Crystal system, space group | Monoclinic, P21/c |
Temperature (K) | 293 |
a, b, c (Å) | 7.9765 (16), 9.8921 (14), 7.220 (2) |
β (°) | 102.22 (2) |
V (Å3) | 556.8 (2) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 0.57 |
Crystal size (mm) | 0.4 × 0.3 × 0.2 |
Data collection | |
Diffractometer | Enraf Nonius CAD4 diffractometer |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 1717, 1621, 837 |
Rint | 0.032 |
(sin θ/λ)max (Å−1) | 0.703 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.053, 0.138, 1.01 |
No. of reflections | 1621 |
No. of parameters | 67 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 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.
C5—O4—C3—O3 | 4.5 (4) | Cl1—C2—C3—O4 | −166.40 (19) |
C5—O4—C3—C2 | −174.1 (2) | C3—O4—C5—C6 | 178.7 (2) |
Cl1—C2—C3—O3 | 15.0 (4) | O4—C5—C6—C6i | 64.3 (3) |
Symmetry code: (i) −x+1, −y+1, −z+1. |
D—H···A | D—H | H···A | D···A | D—H···A |
C2—H2B···O3ii | 0.97 | 2.55 | 3.480 (4) | 160 |
Symmetry code: (ii) −x+2, y−1/2, −z+3/2. |
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···O═C 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.