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The 20-membered ring of the title compound, C16H24O8, adopts an approximately flat rectangular structure with three- and seven-bond sides and lies across a crystallographic center of inversion. The corners of the ring occur at both ends of one of the planar ester segments. All of the carbonyl O atoms are involved in inter­molecular C—H...O hydrogen bonds.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270106024188/ln3015sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270106024188/ln3015Isup2.hkl
Contains datablock I

CCDC reference: 618641

Comment top

The products of step-growth polymerization of bifunctional monomers generally contain a small cyclic oligomer fraction. The title compound is one such cyclic oligomer which was obtained during polyester condensation polymerization of 1,4-butanediol and succinic acid. The cyclic butylene succinate oligomers were also obtained by lipase-catalyzed degradable transformation of poly(butylene succinate) which is a typical biodegradable synthetic polymer (Okajima et al., 2003). In addition, it was found that the produced cyclic oligomers can be repolymerized readily by lipase into a high molecular weight polyester. From the viewpoint of sustainable chemical recycling of polymer materials, it has been recognized in recent years that cyclic oligomers of polyesters are useful starting compounds for repolymerization (Okajima et al., 2003; Takahashi et al., 2004; Osanai et al., 2004; Kaihara et al. 2005). In order to obtain the basic structural features of the cyclic oligomer of poly(butylene succinate), the structure of the title compound, (I), has been determined.

The molecule of (I) lies across a crystallographic center of inversion so that the asymmetric unit contains one-half of the molecule (Fig. 1). The 20-membered rings exist in a nearly flat rectangular shape and the shortest transannular contact, O1···C3 at (1 − x, 1 − y, 1 − z), is 4.063 (1) Å. According to Dale's nomenclature (Dale, 1973), this ring conformation is called a [3737] form (Table 1), where the numbers in brackets indicate the number of bonds along each edge of the ring. The planar ester segment composed of atoms C7—C8—O2—C1i [symmetry code: (i) 1 − x, 1 − y, 1 − z] provides the three-bond edge of the ring. On the other hand, the seven-bond edge is composed of butylene (C1—C2—C3—C4), ester (C4—O1—C5—C6) and ethylene (C6—C7) segments. Similar ring conformations have been observed in the crystal structures of related 20-membered rings, such as 1,4,11,14-tetraoxacycloeicosane-5,10,15,20-tetraone (Shanzer et al., 1981) and 1,11-dioxacycloeicosane-2,4,12,14-tetraone (Chen et al., 1993). The tight hair-pin turn composed of the three-bond planar ester segment with gauche conformations at both ends of the ester segment occurs in each of these three 20-membered rings. In addition, such a hair-pin structure is commonly observed in other macrocyclic ring compounds that possess ester segments, e.g. Cambridge Strcutural Database (Version 5.26; Allen, 2002) refcodes BEDNAZ, BEDNIH (Shanzer et al., 1981), DILVID (Malinovskii et al., 1985), MAJYAX (Ruddick et al., 1999) and ZORKUM (Zaidi et al., 1995). This conformational feature may be related to the reactivity of macrocyclic monomer compounds and the biodegradability of chain-folded lamellar crystals of polyesters.

The macrocyclic rings of (I) are slightly tilted with respect to the ac plane and are stacked along the b axis (Fig. 2). The angle between the normal of the least-squares plane of the 20-membered ring and the b axis is 26.06 (1)°. The crystal packing involves four weak intermolecular CH···O(carbonyl) hydrogen bonds (Table 2). The C6—H6A···O3(x, 1 + y, z), C7—H7A···O4(x, 1 + y, z) and C4—H4A···O3(3/2 − x, 1/2 + y, 3/2 − z) hydrogen bonds connect the molecules parallel to the b axis. The H···O distance of the fourth hydrogen bond, C7—H7B···O4(2 − x, 1 − y, 1 − z), is slightly longer than that of Jeffrey's criterium (Jeffrey, 1997), but is not much longer than the longest of the other three H···O contacts shown in Table 2. Thus, the fourth intermolecular C—H···O interaction is somewhat weaker than the others. The cyclic molecules are linked parallel to the a axis by this hydrogen bond.

Experimental top

The title compound, (I), was extracted with methanol from as-polymerized samples of poly(butylene succinate). Gel-permiation chromatography revealed that the methanol extract contains the cyclic butylene succinate dimer (74%) and other oligomers (26%). Final purification was achieved by recrystallization from aqueous solution. This recrystallization was repeated twice. Crystals of (I) for X-ray measurements were grown by slow evaporation of an acetone solution at room temperature (m.p. 39.5 K). 1H NMR (CDCl3, p.p.m.): δ 4.12 (m, 4H), 2.64 (s, 4H), 1.71 (m, 4H); 13C NMR (CDCl3, p.p.m.): δ 171.9, 64.3, 29.5, 25.3; HRMS(FAB) calculated for C16H25O8 [M+H]+ 345.1549, found 345.1561.

Refinement top

All H atoms were found in difference maps and were subsequently treated as riding atoms, with C—H distances of 0.97 Å and Uiso(H) values of 1.2Ueq(C).

Computing details top

Data collection: PROCESS-AUTO (Rigaku, 1998); cell refinement: PROCESS-AUTO; data reduction: CrystalStructure (Rigaku/MSC, 2004); program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEPIII (Burnett & Johnson, 1996); software used to prepare material for publication: SHELXL97.

Figures top
[Figure 1] Fig. 1. The molecular structure of (I), with the atom-labeling scheme and displacement ellipsoids drawn at the 50% probability level. [Symmetry code: (i) −x + 1, −y + 1, −z + 1.]
[Figure 2] Fig. 2. The molecular packing of (I). Broken lines indicate the C—H···O hydrogen bonding interactions. [Symmetry code: (ii) −x + 3/2, y + 1/2, −z + 3/2; (iii) x, y + 1, z; (iv) −x + 2, −y + 1, −z + 1.]
1,6,11,16-Tetraoxacycloeicosane-2,5,12,15-tetraone top
Crystal data top
C16H24O8F(000) = 368
Mr = 344.35Dx = 1.316 Mg m3
Monoclinic, P21/nMelting point: 391.5 K
Hall symbol: -P 2ynCu Kα radiation, λ = 1.5418 Å
a = 13.1756 (12) ÅCell parameters from 14809 reflections
b = 4.7279 (5) Åθ = 3.2–68.2°
c = 14.8400 (14) ŵ = 0.89 mm1
β = 109.927 (6)°T = 296 K
V = 869.08 (15) Å3Platelet, colorless
Z = 20.52 × 0.24 × 0.16 mm
Data collection top
Rigaku R-AXIS RAPID
diffractometer
1589 independent reflections
Radiation source: rotating anode1508 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.034
Detector resolution: 10.00 pixels mm-1θmax = 68.2°, θmin = 3.9°
ω scansh = 1515
Absorption correction: numerical
(NUMABS; Higashi, 1999)
k = 55
Tmin = 0.700, Tmax = 0.914l = 1717
14440 measured reflections
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.032H-atom parameters constrained
wR(F2) = 0.088 w = 1/[σ2(Fo2) + (0.0461P)2 + 0.1553P]
where P = (Fo2 + 2Fc2)/3
S = 1.04(Δ/σ)max = 0.001
1589 reflectionsΔρmax = 0.14 e Å3
110 parametersΔρmin = 0.12 e Å3
0 restraintsExtinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.0310 (15)
Crystal data top
C16H24O8V = 869.08 (15) Å3
Mr = 344.35Z = 2
Monoclinic, P21/nCu Kα radiation
a = 13.1756 (12) ŵ = 0.89 mm1
b = 4.7279 (5) ÅT = 296 K
c = 14.8400 (14) Å0.52 × 0.24 × 0.16 mm
β = 109.927 (6)°
Data collection top
Rigaku R-AXIS RAPID
diffractometer
1589 independent reflections
Absorption correction: numerical
(NUMABS; Higashi, 1999)
1508 reflections with I > 2σ(I)
Tmin = 0.700, Tmax = 0.914Rint = 0.034
14440 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0320 restraints
wR(F2) = 0.088H-atom parameters constrained
S = 1.04Δρmax = 0.14 e Å3
1589 reflectionsΔρmin = 0.12 e Å3
110 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.

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
O10.65848 (6)0.77422 (19)0.59382 (6)0.0542 (3)
O20.70835 (6)0.56423 (18)0.37976 (5)0.0494 (3)
O30.81426 (7)0.5384 (2)0.64361 (7)0.0653 (3)
O40.86579 (7)0.4069 (2)0.37397 (6)0.0636 (3)
C10.34844 (9)0.6163 (3)0.70111 (8)0.0507 (3)
H1A0.33010.56400.75690.061*
H1B0.32860.81260.68580.061*
C20.46739 (9)0.5762 (3)0.72098 (8)0.0532 (3)
H2A0.48410.37620.72990.064*
H2B0.50710.67190.78040.064*
C30.50545 (9)0.6875 (3)0.64180 (8)0.0561 (3)
H3A0.46120.60710.58100.067*
H3B0.49690.89130.63760.067*
C40.62173 (9)0.6136 (3)0.66042 (9)0.0543 (3)
H4A0.66490.66070.72590.065*
H4B0.62880.41250.65110.065*
C50.75781 (8)0.7190 (2)0.59480 (7)0.0438 (3)
C60.79182 (9)0.9139 (2)0.53063 (8)0.0485 (3)
H6A0.82811.07660.56750.058*
H6B0.72810.98140.48010.058*
C70.86681 (9)0.7725 (3)0.48573 (8)0.0503 (3)
H7A0.89980.91890.45910.060*
H7B0.92420.67940.53620.060*
C80.81603 (8)0.5600 (2)0.40864 (8)0.0441 (3)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.0436 (4)0.0619 (5)0.0576 (5)0.0052 (4)0.0178 (4)0.0060 (4)
O20.0379 (4)0.0609 (5)0.0492 (4)0.0026 (3)0.0148 (3)0.0106 (4)
O30.0596 (5)0.0685 (6)0.0728 (6)0.0186 (5)0.0292 (5)0.0217 (5)
O40.0504 (5)0.0744 (6)0.0706 (6)0.0111 (4)0.0266 (4)0.0050 (5)
C10.0497 (6)0.0603 (7)0.0435 (6)0.0045 (5)0.0179 (5)0.0089 (5)
C20.0454 (6)0.0653 (8)0.0447 (6)0.0042 (5)0.0101 (5)0.0055 (5)
C30.0447 (6)0.0691 (8)0.0530 (7)0.0020 (6)0.0147 (5)0.0005 (6)
C40.0487 (6)0.0616 (7)0.0534 (7)0.0014 (5)0.0186 (5)0.0003 (6)
C50.0415 (6)0.0450 (6)0.0417 (5)0.0002 (5)0.0102 (4)0.0071 (5)
C60.0470 (6)0.0449 (6)0.0490 (6)0.0023 (5)0.0106 (5)0.0018 (5)
C70.0386 (6)0.0586 (7)0.0522 (6)0.0051 (5)0.0137 (5)0.0049 (5)
C80.0396 (5)0.0502 (6)0.0447 (6)0.0032 (5)0.0174 (5)0.0102 (5)
Geometric parameters (Å, º) top
C1—C21.5047 (16)C1—H1A0.9700
C2—C31.5201 (16)C1—H1B0.9700
C3—C41.5024 (16)C2—H2A0.9700
C4—O11.4541 (15)C2—H2B0.9700
O1—C51.3298 (13)C3—H3A0.9700
C5—C61.4990 (16)C3—H3B0.9700
C6—C71.5218 (16)C4—H4A0.9700
C7—C81.4980 (16)C4—H4B0.9700
C8—O21.3350 (13)C6—H6A0.9700
O2—C1i1.4549 (13)C6—H6B0.9700
C5—O31.2000 (14)C7—H7A0.9700
C8—O41.2037 (14)C7—H7B0.9700
O2i—C1—C2107.23 (9)C3—C2—H2B108.8
C1—C2—C3113.64 (10)H2A—C2—H2B107.7
C2—C3—C4111.21 (10)C2—C3—H3A109.4
C3—C4—O1107.96 (10)C4—C3—H3A109.4
C4—O1—C5116.40 (9)C2—C3—H3B109.4
O1—C5—C6112.25 (9)C4—C3—H3B109.4
O1—C5—O3123.46 (11)H3A—C3—H3B108.0
O3—C5—C6124.26 (10)C3—C4—H4A110.1
C5—C6—C7112.80 (10)O1—C4—H4A110.1
C6—C7—C8116.19 (9)C3—C4—H4B110.1
C7—C8—O2112.61 (9)O1—C4—H4B110.1
C7—C8—O4124.28 (10)H4A—C4—H4B108.4
O4—C8—O2123.08 (11)C5—C6—H6A109.0
C8—O2—C1i116.59 (9)C7—C6—H6A109.0
O2i—C1—H1A110.3C5—C6—H6B109.0
C2—C1—H1A110.3C7—C6—H6B109.0
O2i—C1—H1B110.3H6A—C6—H6B107.8
C2—C1—H1B110.3C6—C7—H7A108.2
H1A—C1—H1B108.5C8—C7—H7A108.2
C1—C2—H2A108.8C6—C7—H7B108.2
C3—C2—H2A108.8C8—C7—H7B108.2
C1—C2—H2B108.8H7A—C7—H7B107.4
O2i—C1—C2—C367.06 (14)O1—C5—C6—C7147.32 (10)
C1—C2—C3—C4173.80 (11)C5—C6—C7—C872.38 (13)
C2—C3—C4—O1168.37 (10)C6—C7—C8—O4171.01 (11)
C3—C4—O1—C5174.91 (10)C6—C7—C8—O211.03 (14)
C4—O1—C5—O33.59 (16)O4—C8—O2—C1i3.52 (16)
C4—O1—C5—C6174.57 (9)C7—C8—O2—C1i174.47 (9)
O3—C5—C6—C734.54 (15)C8—O2—C1i—C2i179.73 (9)
Symmetry code: (i) x+1, y+1, z+1.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C4—H4A···O3ii0.972.583.3957 (17)142
C6—H6A···O3iii0.972.493.3583 (17)148
C7—H7A···O4iii0.972.603.4252 (17)144
C7—H7B···O4iv0.972.663.5308 (16)149
Symmetry codes: (ii) x+3/2, y+1/2, z+3/2; (iii) x, y+1, z; (iv) x+2, y+1, z+1.

Experimental details

Crystal data
Chemical formulaC16H24O8
Mr344.35
Crystal system, space groupMonoclinic, P21/n
Temperature (K)296
a, b, c (Å)13.1756 (12), 4.7279 (5), 14.8400 (14)
β (°) 109.927 (6)
V3)869.08 (15)
Z2
Radiation typeCu Kα
µ (mm1)0.89
Crystal size (mm)0.52 × 0.24 × 0.16
Data collection
DiffractometerRigaku R-AXIS RAPID
diffractometer
Absorption correctionNumerical
(NUMABS; Higashi, 1999)
Tmin, Tmax0.700, 0.914
No. of measured, independent and
observed [I > 2σ(I)] reflections
14440, 1589, 1508
Rint0.034
(sin θ/λ)max1)0.602
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.032, 0.088, 1.04
No. of reflections1589
No. of parameters110
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.14, 0.12

Computer programs: PROCESS-AUTO (Rigaku, 1998), PROCESS-AUTO, CrystalStructure (Rigaku/MSC, 2004), SIR92 (Altomare et al., 1994), SHELXL97 (Sheldrick, 1997), ORTEPIII (Burnett & Johnson, 1996), SHELXL97.

Selected torsion angles (º) top
O2i—C1—C2—C367.06 (14)O1—C5—C6—C7147.32 (10)
C1—C2—C3—C4173.80 (11)C5—C6—C7—C872.38 (13)
C2—C3—C4—O1168.37 (10)C6—C7—C8—O211.03 (14)
C3—C4—O1—C5174.91 (10)C7—C8—O2—C1i174.47 (9)
C4—O1—C5—C6174.57 (9)C8—O2—C1i—C2i179.73 (9)
Symmetry code: (i) x+1, y+1, z+1.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C4—H4A···O3ii0.972.583.3957 (17)142
C6—H6A···O3iii0.972.493.3583 (17)148
C7—H7A···O4iii0.972.603.4252 (17)144
C7—H7B···O4iv0.972.663.5308 (16)149
Symmetry codes: (ii) x+3/2, y+1/2, z+3/2; (iii) x, y+1, z; (iv) x+2, y+1, z+1.
 

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