(S)-6-Methyl-∊-caprolactone

The chiral title compound, C₇H₁₂O₂, a lactone derivative, features a seven-membered ring that adopts a chair conformation. The crystal structure is stabilized by weak C—H⋯O inter­actions occurring in the (100) plane. The absolute configuration was assigned on the basis of the enantioselective synthesis.

Related literature

For related literature, see: van As et al. (2005); van Buijtenen et al. (2006). For details of the synthesis, see: van As et al. (2007). For geometry, see: Cremer & Pople (1975).

Experimental

Crystal data

• C₇H₁₂O₂

• M_r = 128.17

• Monoclinic, P 2₁

• a = 6.757 (2) Å

• b = 7.577 (2) Å

• c = 7.586 (2) Å

• β = 110.949 (13)°

• V = 362.71 (17) ų

• Z = 2

• Mo Kα radiation

• μ = 0.08 mm⁻¹

• T = 150 (2) K

• 0.35 × 0.15 × 0.10 mm

Data collection

• Nonius KappaCCD diffractometer

• Absorption correction: none

• 10010 measured reflections

• 889 independent reflections

• 862 reflections with I > 2σ(I)

• R_int = 0.041

Refinement

• R[F² > 2σ(F²)] = 0.027

• wR(F²) = 0.072

• S = 1.10

• 889 reflections

• 83 parameters

• 1 restraint

• H-atom parameters constrained

• Δρ_max = 0.12 e Å⁻³

• Δρ_min = −0.16 e Å⁻³

Table 1
Short-contact C—H⋯O interactions (Å, °) found in the (100) plane

C—H⋯O	C—H	H⋯O	C⋯O	C—H⋯A
C2—H2A⋯O1^i	0.99	2.67	3.573 (2)	152
C5—H5A⋯O1^ii	0.99	2.64	3.616 (2)	166
C5—H5B⋯O1^ii	0.99	2.63	3.601 (2)	168
C6—H6⋯O1^i	1.00	2.54	3.466 (2)	154
Symmetry codes: (i) -x+2, y-1/2, -z; (ii) x, y, z+1.

Data collection: COLLECT (Nonius, 1998); cell refinement: DENZO (Otwinowski & Minor, 1997); data reduction: DENZO; program(s) used to solve structure: SHELXS86 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: PLATON (Spek, 2003); software used to prepare material for publication: PLATON and Mercury (Macrae et al., 2006).

Supporting information

S1. Comment

The enantiomers (R)- and (S)-6-methyl-ε-caprolactone (6-MeCL) have been recently used as monomer units for chiral oligomerization and chiral polymerization reactions (van As et al., 2005; van Buijtenen et al., 2006). A new two-step enantioselective synthesis of (R)- and (S)-6-MeCL from a racemic mixture of 6-MeCL has been described recently (van As et al., 2007). The present paper describes the crystal structure of (S)-6-MeCL, (I).

The structure of (I) (Fig. 1) was solved in the non-centrosymmetric space group P2₁ with Z' = 1. The stereochemistry at the chiral center, C6, was assigned S based on the enantioselective synthesis of (S)-6-MeCL, which was reported to yield an enantiomeric excess greater than 99% (van As et al., 2007).

The seven-membered ring (O2/C1—C6) adopts a chair conformation with puckering parameters: Q₂ = 0.453 (2) Å, ϕ₂ = 130.6 (2)°, Q₃ = 0.653 (2) Å, ϕ₃ = 102.6 (2)° and with a total puckering amplitude Q = 0.795 (2)Å (Cremer & Pople, 1975).

The crystal structure (I) is stabilized by weak C–H···O interactions (Table 1) with the four shortest contacts involving the O1 atom. These short contacts occur between molecules in the (1 0 0) plane, Fig. 2.

Related literature

For related literature, see: van As et al. (2005); van Buijtenen et al. (2006). For details of the synthesis, see: van As et al. (2007). For geometry, see: Cremer & Pople (1975).

S2. Experimental

Details about the synthesis of (S)-6-methyl-ε-caprolactone have been given in a previous paper (van As et al., 2007).

S3. Refinement

In the absence of significant anomalous scattering effects, XXX Friedel pairs were merged prior to the refinement. The H atoms were found in difference Fourier maps and subsequently placed at calculated positions with C–H = 0.99–1.00 Å, and with U_iso(H) = 1.2 or 1.5 times U_eq(carrier C).

Computing details

Data collection: COLLECT (Nonius, 1998); cell refinement: DENZO (Otwinowski & Minor, 1997); data reduction: DENZO (Otwinowski & Minor, 1997); program(s) used to solve structure: SHELXS86 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: PLATON (Spek, 2003); software used to prepare material for publication: PLATON (Spek, 2003) and Mercury (Macrae et al., 2006).

Figures

	Fig. 1. Molecular structure of (I) showing atom labelling and displacement ellipsoids at the 50% probability level.
	Fig. 2. The packing of one layer found in the crystal structure of (I) viewed down the a* direction. Molecules are connected by short C–H···O contacts in the (1 0 0) plane. Only one set of short contacts (dashed lines) is shown for clarity. The symmetry codes are: (i) 2 - x, -1/2 + y, -z; (iii) 2 - x, 1/2 + y, -z; (iv) x, y, z - 1.

(S)-3-methyl-2-oxepanone

Crystal data

C7H12O2	F(000) = 140
Mr = 128.17	Dx = 1.174 Mg m^−3
Monoclinic, P21	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2yb	Cell parameters from 7835 reflections
a = 6.757 (2) Å	θ = 1.0–27.5°
b = 7.577 (2) Å	µ = 0.08 mm^−1
c = 7.586 (2) Å	T = 150 K
β = 110.949 (13)°	Prism, colourless
V = 362.71 (17) Å^3	0.35 × 0.15 × 0.10 mm
Z = 2

Data collection

Nonius KappaCCD diffractometer	862 reflections with I > 2σ(I)
Radiation source: rotating anode	Rint = 0.041
Graphite monochromator	θmax = 27.5°, θmin = 3.5°
ϕ and ω scans	h = −8→8
10010 measured reflections	k = −9→9
889 independent reflections	l = −9→9

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.027	H-atom parameters constrained
wR(F^2) = 0.072	w = 1/[σ^2(Fo^2) + (0.0431P)^2 + 0.0282P] where P = (Fo^2 + 2Fc^2)/3
S = 1.10	(Δ/σ)max < 0.001
889 reflections	Δρmax = 0.12 e Å^−3
83 parameters	Δρmin = −0.16 e Å^−3
1 restraint	Absolute structure: known chirality of atom C6(S)
Primary atom site location: structure-invariant direct methods

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 > 2σ(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
O1	1.03545 (16)	0.06828 (15)	−0.16671 (13)	0.0355 (3)
O2	1.11573 (13)	0.04935 (14)	0.13758 (12)	0.0288 (2)
C1	0.9754 (2)	0.03155 (18)	−0.03896 (16)	0.0258 (3)
C2	0.7534 (2)	−0.0285 (2)	−0.07029 (18)	0.0301 (3)
H2A	0.7594	−0.1422	−0.0042	0.036*
H2B	0.6778	−0.0491	−0.2069	0.036*
C3	0.6274 (2)	0.1054 (2)	0.0003 (2)	0.0356 (3)
H3A	0.6603	0.2261	−0.0311	0.043*
H3B	0.4740	0.0849	−0.0669	0.043*
C4	0.6759 (2)	0.0938 (2)	0.2120 (2)	0.0365 (3)
H4A	0.6389	−0.0260	0.2421	0.044*
H4B	0.5841	0.1787	0.2461	0.044*
C5	0.9066 (2)	0.1315 (2)	0.33415 (18)	0.0303 (3)
H5A	0.9423	0.2528	0.3071	0.036*
H5B	0.9205	0.1274	0.4685	0.036*
C6	1.06592 (19)	0.00512 (19)	0.30521 (16)	0.0267 (3)
H6	1.0098	−0.1181	0.2938	0.032*
C7	1.2785 (2)	0.0148 (3)	0.46522 (19)	0.0403 (4)
H7A	1.3333	0.1356	0.4759	0.060*
H7B	1.3783	−0.0660	0.4396	0.060*
H7C	1.2615	−0.0190	0.5837	0.060*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0442 (5)	0.0406 (6)	0.0260 (5)	0.0001 (5)	0.0177 (4)	0.0018 (4)
O2	0.0248 (4)	0.0400 (6)	0.0219 (4)	−0.0028 (4)	0.0087 (3)	0.0022 (4)
C1	0.0305 (6)	0.0245 (6)	0.0221 (6)	0.0029 (5)	0.0093 (5)	−0.0007 (5)
C2	0.0272 (6)	0.0341 (7)	0.0255 (6)	−0.0021 (5)	0.0050 (5)	−0.0041 (6)
C3	0.0242 (6)	0.0431 (9)	0.0365 (7)	0.0058 (6)	0.0074 (5)	0.0002 (7)
C4	0.0298 (6)	0.0451 (9)	0.0382 (7)	0.0031 (6)	0.0166 (5)	−0.0030 (7)
C5	0.0360 (7)	0.0322 (7)	0.0254 (6)	−0.0015 (6)	0.0143 (5)	−0.0026 (5)
C6	0.0265 (6)	0.0330 (7)	0.0202 (6)	−0.0027 (5)	0.0079 (5)	0.0028 (5)
C7	0.0311 (6)	0.0598 (11)	0.0252 (6)	−0.0040 (7)	0.0043 (5)	0.0070 (7)

Geometric parameters (Å, º)

O1—C1	1.2095 (16)	C4—H4A	0.9900
O2—C1	1.3428 (15)	C4—H4B	0.9900
O2—C6	1.4659 (14)	C5—C6	1.5140 (19)
C1—C2	1.5028 (18)	C5—H5A	0.9900
C2—C3	1.539 (2)	C5—H5B	0.9900
C2—H2A	0.9900	C6—C7	1.5152 (18)
C2—H2B	0.9900	C6—H6	1.0000
C3—C4	1.523 (2)	C7—H7A	0.9800
C3—H3A	0.9900	C7—H7B	0.9800
C3—H3B	0.9900	C7—H7C	0.9800
C4—C5	1.5288 (19)
C1—O2—C6	122.88 (10)	C5—C4—H4B	108.6
O1—C1—O2	117.15 (12)	H4A—C4—H4B	107.6
O1—C1—C2	123.02 (11)	C6—C5—C4	114.69 (12)
O2—C1—C2	119.82 (11)	C6—C5—H5A	108.6
C1—C2—C3	112.99 (12)	C4—C5—H5A	108.6
C1—C2—H2A	109.0	C6—C5—H5B	108.6
C3—C2—H2A	109.0	C4—C5—H5B	108.6
C1—C2—H2B	109.0	H5A—C5—H5B	107.6
C3—C2—H2B	109.0	O2—C6—C5	112.13 (11)
H2A—C2—H2B	107.8	O2—C6—C7	103.76 (10)
C4—C3—C2	113.05 (12)	C5—C6—C7	111.89 (12)
C4—C3—H3A	109.0	O2—C6—H6	109.6
C2—C3—H3A	109.0	C5—C6—H6	109.6
C4—C3—H3B	109.0	C7—C6—H6	109.6
C2—C3—H3B	109.0	C6—C7—H7A	109.5
H3A—C3—H3B	107.8	C6—C7—H7B	109.5
C3—C4—C5	114.64 (11)	H7A—C7—H7B	109.5
C3—C4—H4A	108.6	C6—C7—H7C	109.5
C5—C4—H4A	108.6	H7A—C7—H7C	109.5
C3—C4—H4B	108.6	H7B—C7—H7C	109.5
C6—O2—C1—O1	−178.35 (12)	C3—C4—C5—C6	−61.49 (19)
C6—O2—C1—C2	2.78 (18)	C1—O2—C6—C5	−68.78 (16)
O1—C1—C2—C3	−112.90 (16)	C1—O2—C6—C7	170.29 (13)
O2—C1—C2—C3	65.90 (16)	C4—C5—C6—O2	80.45 (14)
C1—C2—C3—C4	−81.25 (16)	C4—C5—C6—C7	−163.43 (12)
C2—C3—C4—C5	61.39 (19)

 

Footnotes

‡Current address: Shell Global Solutions International BV, Badhuisweg 3, 1031 CM Amsterdam, PO Box 38000, 1030 BN Amsterdam, The Netherlands.