Cyclo­penta­none and cyclo­butanone

Crystals of cyclo­penta­none, C₅H₈O, and cyclo­butanone, C₄H₆O, have been grown in situ on a diffractometer. The two compounds are isostructural and contain two crystallographically independent mol­ecules. Mol­ecules sitting across twofold axes form anti­parallel dipole–dipole dimers, while other mol­ecules in general positions are linked together into ribbons by pairs of C—H...O inter­actions.

S1. Comment

Over the last several years there has been a noticable increase of single-crystal X-ray studies of compounds which are liquid or gaseous under ambient conditions. These studies nowadays include not only straightforward structural determinations of pure compounds, sometimes of new potentially important classes such as room-temperature ionic liquids (Choudhury et al., 2005), but also expand into the emerging area of low-temperature polymorphism (Kirchner et al., 2009) and thus provide fascinating insights into the formation of molecular complexes (cocrystals) in liquid mixtures (Kirchner et al., 2010). Despite such interest, there are still a number of chemical classes left almost untouched. Interesting results were reported recently on polymorphism in such simple compounds as cyclohexanone (Shallard-Brown et al., 2005; Ibberson, 2006; Yufit & Howard, 2008) and cyclohexanol (Ibberson et al., 2008). Surprisingly, the Cambridge Structural Database (Version 5.3.1, November 2010; Allen, 2002) contains no information on the structures of other small cyclic ketones and alcohols. In order to close the gap, we have performed a single-crystal X-ray study of two compounds of this class, namely cyclopentanone (CP) and cyclobutanone (CB), and report here the results obtained.

The crystals of the two compounds turned out to be isostructural (but not isomorphous) and, in both cases, contain two crystallographically independent molecules, one in a general position and one in a special position on a twofold axis, which passes through both atoms of carbonyl group. The geometry of the independent molecules in each compound is identical (Fig. 1). The CP molecules adopt a half-chair conformation, while the CB molecules are planar. The bond lengths and angles in CP and CB are close to calculated values (Mukhopadhyay et al., 2009). Slight elongation of the carbonyl bond in CP [1.2109 (15) and 1.2148 (15) Å] in comparison with CB [1.2016 (16) and 1.2028 (14) Å] corresponds to theoretical calculations and reflects a higher polarity of that bond in CP.

As noted above, the crystals of CP and CB are isostructural; however, the difference in one methylene group between these two molecules slightly distorts the packing. As a result, similarity to the CP orientation and position of the CB molecules in the unit cell can be achieved only by refining the CB structure using a cell with an acute monoclinic angle and an opposite direction of the c axis (Fig 2). In order to maintain consistency of the description of intermolecular interactions in these structures and make the comparisons more simple, the structure of CB has been refined in such a nonstandard setting of the C2/c space group.

The packing of molecules in CP and CB is of note: molecules in general positions form dimers with an antiparallel arrangement of the carbonyl groups and with corresponding O1···C1(-x+1/2, -y+3/2, -z+1) distances of 3.1915 (15) and 3.2295 (13) Å in CP and CB, respectively (Fig. 3). Such an arrangement indicates the presence of strong dipole–dipole interactions between these molecules. The geometrical parameters of these and other intermolecular contacts are given in Table 1. In contrast, the molecules in special positions are linked together in ribbons, parallel to the c direction, by pairs of C—H···O interactions. There are short O···C(carbonyl) contacts [3.2425 (12) and 3.0924 (11)Å in CP and CB, respectively] between molecules in ribbons and in dimers, but in these contacts the carbonyl groups are nonparallel and form O1—C1—O2—C11 torsion angles of -46.90 (8) and -47.91 (8)° in CP and CB, respectively, and therefore can not be regarded as dipole–dipole interactions. The planes of the carbonyl groups are at 57.29 (7) (in CP) and 62.58 (8)° (in CB) to each other, so one of the lone pairs of electrons of the O atom is directed towards the carbonyl C atom of one of dimers.

Thus, these small cyclic ketones show several different types of intermolecular interactions within the same structure. The observed packing pattern is quite different from those found in several polymorphs of cyclohexanone, where the molecules are linked by various C—H···O interactions but not by dipole–dipole interactions (Shallard-Brown et al., 2005; Ibberson, 2006; Yufit & Howard, 2008). Interestingly, solvent cyclopentanone molecules in other crystals either do not interact with each other (Toda et al., 2000) or form C—H···O-linked dimers or chains (Bock et al., 1998; Liu et al., 2006), similar to those found in CP, but no dipole–dipole-linked dimers were observed. To the best of our knowledge, no cocrystals containing cyclobutanone molecules have been reported so far.

Related literature

For related literature, see: Bock et al. (1998); Choudhury et al. (2005); Ibberson (2006); Ibberson et al. (2008); Kirchner et al. (2009, 2010); Liu et al. (2006); Mukhopadhyay et al. (2009); Shallard-Brown, Watkin & Cowley (2005); Toda et al. (2000); Yufit & Howard (2005, 2008).

S2. Experimental

The liquids samples were sealed in 0.3 mm borosilicate glass capillaries which were mounted on a diffractometer using a special attachment (Yufit & Howard, 2005). The crystals of both compounds were grown in situ on a diffractometer by flash-freezing of the overcooled liquid at 220 K, followed by partial melting of the resulting polycrystalline material and slow growing of the crystals at 200.5 K. The cylindric crystals formed were then cooled down to 200 K and data were collected at this temperature.

S3. Refinement

As it was mentioned in the Comment, in order to maintain consistency in the description of the structures of CP and CB, the CB structure has been refined in a nonstandard setting of the C2/c space group with an acute β angle. The data have been collected in a standard setting and then the cell parameters in the input file were changed manually. Also the signs of the L indexes in the hkl file have been changed to the opposite ones with the help of a locally written service program.

Computing details

For both compounds, data collection: SMART (Bruker, 2003); cell refinement: SAINT (Bruker, 2003); data reduction: SAINT (Bruker, 2003); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: OLEX2 (Dolomanov et al., 2009); software used to prepare material for publication: OLEX2 (Dolomanov et al., 2009).

Figures

	Fig. 1. The molecular structure and labelling scheme for (a) CP and (b) CB. Displacement ellpsoids are shown at the 50% probability level.
	Fig. 2. The packing of molecules in the structures of (a) CP and (b) CB. The view is along the b axis and H atoms have been omitted for clarity.
	Fig. 3. Fragments of structures of (a) CP and (b) CB, showing the intermolecular contacts. [Symmetry codes: (A) -x+1/2, -y+3/2, -z+1; (B) -x, -y+1, -z+1; (C) x, -y+1, z-1/2.]

(CP) cyclopentan-1-one

Crystal data

C5H8O	F(000) = 552
Mr = 84.11	Dx = 1.152 Mg m^−3
Monoclinic, C2/c	Melting point: 218 K
Hall symbol: -C 2yc	Mo Kα radiation, λ = 0.71073 Å
a = 16.7421 (16) Å	Cell parameters from 1202 reflections
b = 9.7941 (8) Å	θ = 29.6–2.4°
c = 8.8898 (7) Å	µ = 0.08 mm^−1
β = 93.69 (2)°	T = 200 K
V = 1454.7 (2) Å^3	Cylinder, colourless
Z = 12	0.5 × 0.3 × 0.3 mm

Data collection

Bruker SMART CCD 6000 area-detector diffractometer	1336 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.035
Graphite monochromator	θmax = 29.5°, θmin = 2.4°
Detector resolution: 8.0 pixels mm^-1	h = −15→23
ω scans	k = −13→13
6027 measured reflections	l = −9→7
1660 independent reflections

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)] = 0.035	All H-atom parameters refined
wR(F^2) = 0.099	w = 1/[σ^2(Fo^2) + (0.050P)^2 + 0.3P] where P = (Fo^2 + 2Fc^2)/3
S = 1.03	(Δ/σ)max < 0.001
1660 reflections	Δρmax = 0.17 e Å^−3
132 parameters	Δρmin = −0.14 e Å^−3
0 restraints	Extinction correction: SHELXL97 (Sheldrick, 2008), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0115 (18)

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
O1	0.17244 (6)	0.63157 (9)	0.50785 (12)	0.0642 (3)
O2	0.0000	0.58323 (9)	0.2500	0.0450 (3)
C1	0.16762 (6)	0.70397 (11)	0.39723 (15)	0.0442 (3)
C2	0.20281 (7)	0.67435 (12)	0.24876 (16)	0.0485 (3)
C3	0.19157 (7)	0.80501 (11)	0.15710 (17)	0.0476 (3)
C4	0.11695 (7)	0.86947 (11)	0.21755 (14)	0.0436 (3)
C5	0.12532 (7)	0.84020 (12)	0.38500 (14)	0.0450 (3)
C11	0.0000	0.45920 (13)	0.2500	0.0346 (3)
C12	0.04221 (7)	0.36976 (10)	0.36852 (14)	0.0423 (3)
C13	0.03880 (7)	0.22685 (10)	0.29943 (14)	0.0442 (3)
H21	0.1714 (8)	0.5987 (15)	0.2000 (18)	0.071 (4)*
H22	0.2574 (9)	0.6471 (14)	0.2676 (17)	0.063 (4)*
H31	0.2383 (8)	0.8620 (13)	0.1776 (16)	0.054 (3)*
H32	0.1873 (8)	0.7885 (14)	0.0485 (19)	0.065 (4)*
H41	0.0689 (8)	0.8226 (13)	0.1728 (16)	0.051 (3)*
H42	0.1128 (7)	0.9662 (14)	0.1943 (15)	0.053 (3)*
H51	0.1617 (8)	0.9040 (14)	0.4380 (17)	0.064 (4)*
H52	0.0766 (9)	0.8365 (15)	0.4355 (18)	0.073 (5)*
H121	0.0958 (8)	0.4046 (14)	0.3968 (16)	0.061 (4)*
H122	0.0096 (8)	0.3744 (13)	0.4567 (17)	0.058 (4)*
H131	0.0836 (8)	0.2158 (13)	0.2380 (15)	0.052 (3)*
H132	0.0412 (8)	0.1537 (14)	0.3772 (16)	0.056 (4)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0652 (6)	0.0616 (5)	0.0631 (8)	−0.0133 (4)	−0.0172 (5)	0.0193 (4)
O2	0.0551 (6)	0.0298 (5)	0.0497 (8)	0.000	0.0006 (5)	0.000
C1	0.0373 (5)	0.0424 (5)	0.0515 (9)	−0.0076 (4)	−0.0084 (5)	0.0014 (5)
C2	0.0397 (5)	0.0410 (5)	0.0645 (9)	0.0051 (4)	0.0008 (5)	−0.0087 (5)
C3	0.0451 (6)	0.0473 (6)	0.0518 (9)	−0.0026 (4)	0.0138 (5)	−0.0053 (5)
C4	0.0470 (6)	0.0397 (5)	0.0446 (8)	0.0055 (4)	0.0068 (5)	0.0013 (4)
C5	0.0445 (5)	0.0489 (6)	0.0420 (8)	0.0027 (4)	0.0055 (5)	−0.0058 (5)
C11	0.0380 (6)	0.0311 (6)	0.0353 (9)	0.000	0.0067 (6)	0.000
C12	0.0526 (6)	0.0339 (5)	0.0395 (8)	0.0016 (4)	−0.0039 (5)	−0.0002 (4)
C13	0.0597 (7)	0.0325 (5)	0.0406 (8)	0.0077 (4)	0.0049 (5)	0.0018 (4)

Geometric parameters (Å, º)

O1—C1	1.2109 (15)	C4—H42	0.972 (13)
O2—C11	1.2148 (15)	C5—H51	0.972 (15)
C1—C2	1.5078 (18)	C5—H52	0.957 (15)
C1—C5	1.5111 (15)	C11—C12^i	1.5103 (14)
C2—C3	1.5223 (18)	C11—C12	1.5103 (14)
C2—H21	0.991 (15)	C12—C13	1.5282 (14)
C2—H22	0.957 (15)	C12—H121	0.978 (14)
C3—C4	1.5279 (14)	C12—H122	0.985 (15)
C3—H31	0.968 (14)	C13—C13^i	1.521 (2)
C3—H32	0.977 (16)	C13—H131	0.961 (13)
C4—C5	1.5136 (18)	C13—H132	0.995 (14)
C4—H41	0.987 (13)
O1—C1—C2	126.07 (11)	C1—C5—C4	104.55 (9)
O1—C1—C5	125.59 (12)	C1—C5—H51	104.8 (8)
C2—C1—C5	108.34 (10)	C4—C5—H51	111.7 (9)
C1—C2—C3	105.37 (9)	C1—C5—H52	110.1 (9)
C1—C2—H21	107.5 (9)	C4—C5—H52	116.1 (9)
C3—C2—H21	110.5 (9)	H51—C5—H52	108.9 (12)
C1—C2—H22	108.8 (9)	O2—C11—C12^i	125.45 (6)
C3—C2—H22	114.3 (8)	O2—C11—C12	125.45 (6)
H21—C2—H22	110.0 (11)	C12^i—C11—C12	109.10 (11)
C2—C3—C4	103.58 (9)	C11—C12—C13	104.31 (10)
C2—C3—H31	108.3 (8)	C11—C12—H121	111.0 (8)
C4—C3—H31	111.4 (8)	C13—C12—H121	115.6 (8)
C2—C3—H32	112.8 (8)	C11—C12—H122	105.7 (8)
C4—C3—H32	114.0 (8)	C13—C12—H122	110.7 (8)
H31—C3—H32	106.8 (12)	H121—C12—H122	109.1 (12)
C5—C4—C3	103.98 (10)	C13^i—C13—C12	103.92 (7)
C5—C4—H41	109.2 (8)	C13^i—C13—H131	109.9 (8)
C3—C4—H41	109.2 (7)	C12—C13—H131	108.7 (8)
C5—C4—H42	113.3 (8)	C13^i—C13—H132	113.4 (8)
C3—C4—H42	112.2 (7)	C12—C13—H132	112.5 (8)
H41—C4—H42	108.8 (11)	H131—C13—H132	108.3 (10)
O1—C1—C2—C3	−171.34 (11)	C2—C1—C5—C4	15.14 (12)
C5—C1—C2—C3	8.45 (12)	C3—C4—C5—C1	−32.72 (11)
C1—C2—C3—C4	−28.46 (13)	O2—C11—C12—C13	−168.18 (5)
C2—C3—C4—C5	38.05 (12)	C12^i—C11—C12—C13	11.82 (5)
O1—C1—C5—C4	−165.06 (11)	C11—C12—C13—C13^i	−30.96 (13)

Symmetry code: (i) −x, y, −z+1/2.

(CB) cyclobutan-1-one

Crystal data

C4H6O	Dx = 1.151 Mg m^−3
Mr = 70.09	Melting point: 218 K
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
a = 15.5022 (16) Å	Cell parameters from 1067 reflections
b = 9.0662 (9) Å	θ = 2.6–30.5°
c = 8.6531 (7) Å	µ = 0.08 mm^−1
β = 85.83 (3)°	T = 200 K
V = 1212.9 (2) Å^3	Cylinder, colourless
Z = 12	0.5 × 0.35 × 0.35 mm
F(000) = 456

Data collection

Bruker SMART CCD 6000 area-detector diffractometer	1127 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.036
Graphite monochromator	θmax = 30.5°, θmin = 2.6°
Detector resolution: 5.6 pixels mm^-1	h = −16→22
ω scans	k = −12→12
5379 measured reflections	l = −7→7
1440 independent reflections

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)] = 0.039	Hydrogen site location: difference Fourier map
wR(F^2) = 0.121	All H-atom parameters refined
S = 1.06	w = 1/[σ^2(Fo^2) + (0.070P)^2 + 0.150P], where P = (Fo^2 + 2Fc^2)/3
1440 reflections	(Δ/σ)max < 0.001
106 parameters	Δρmax = 0.23 e Å^−3
0 restraints	Δρmin = −0.15 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
O1	0.16529 (5)	0.62858 (10)	0.49939 (11)	0.0558 (3)
O2	0.0000	0.59104 (11)	0.2500	0.0470 (3)
C1	0.16682 (6)	0.70470 (11)	0.38539 (13)	0.0408 (3)
C2	0.20760 (8)	0.68827 (13)	0.22340 (16)	0.0489 (3)
C3	0.16675 (9)	0.83723 (13)	0.18330 (17)	0.0536 (4)
C4	0.12918 (8)	0.85412 (11)	0.35121 (16)	0.0479 (3)
C11	0.0000	0.45850 (15)	0.2500	0.0351 (3)
C12	0.04292 (8)	0.34379 (12)	0.34572 (17)	0.0456 (3)
C13	0.0000	0.22420 (18)	0.2500	0.0561 (5)
H13	0.0421 (9)	0.1647 (17)	0.190 (2)	0.071 (4)*
H21	0.1859 (9)	0.6060 (16)	0.1639 (18)	0.064 (4)*
H22	0.2693 (10)	0.6906 (17)	0.2224 (19)	0.069 (4)*
H31	0.1201 (10)	0.8302 (17)	0.113 (2)	0.072 (5)*
H32	0.2084 (9)	0.9098 (18)	0.1445 (19)	0.069 (4)*
H41	0.0674 (9)	0.8597 (15)	0.3670 (17)	0.059 (4)*
H42	0.1562 (10)	0.9319 (19)	0.413 (2)	0.074 (5)*
H121	0.0225 (9)	0.3462 (15)	0.4496 (19)	0.057 (4)*
H122	0.1040 (9)	0.3508 (16)	0.3344 (17)	0.063 (4)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0602 (5)	0.0582 (5)	0.0500 (7)	−0.0060 (4)	−0.0111 (4)	0.0156 (4)
O2	0.0567 (6)	0.0391 (5)	0.0466 (9)	0.000	−0.0129 (5)	0.000
C1	0.0386 (5)	0.0400 (5)	0.0445 (8)	−0.0075 (3)	−0.0075 (4)	0.0020 (4)
C2	0.0486 (6)	0.0453 (6)	0.0518 (10)	−0.0079 (4)	0.0038 (5)	−0.0043 (5)
C3	0.0719 (8)	0.0447 (6)	0.0449 (10)	−0.0134 (5)	−0.0094 (6)	0.0055 (5)
C4	0.0588 (7)	0.0373 (5)	0.0477 (10)	−0.0017 (4)	−0.0055 (5)	−0.0011 (4)
C11	0.0350 (6)	0.0416 (6)	0.0284 (10)	0.000	−0.0011 (5)	0.000
C12	0.0490 (6)	0.0473 (6)	0.0404 (10)	0.0081 (4)	−0.0030 (5)	0.0047 (4)
C13	0.0820 (12)	0.0387 (8)	0.0462 (13)	0.000	0.0063 (9)	0.000

Geometric parameters (Å, º)

O1—C1	1.2028 (14)	C4—H41	0.959 (13)
O2—C11	1.2016 (16)	C4—H42	0.998 (17)
C1—C2	1.5026 (18)	C11—C12	1.5135 (14)
C1—C4	1.5126 (15)	C11—C12^i	1.5135 (14)
C2—C3	1.5419 (18)	C12—C13	1.5442 (17)
C2—H21	0.980 (14)	C12—H121	0.931 (16)
C2—H22	0.956 (16)	C12—H122	0.947 (14)
C3—C4	1.533 (2)	C13—C12^i	1.5443 (17)
C3—H31	0.981 (16)	C13—H13	0.967 (15)
C3—H32	0.965 (16)
O1—C1—C2	133.63 (11)	C3—C4—H41	116.6 (9)
O1—C1—C4	133.58 (11)	C1—C4—H42	110.1 (9)
C2—C1—C4	92.78 (9)	C3—C4—H42	115.9 (9)
C1—C2—C3	88.35 (9)	H41—C4—H42	109.9 (12)
C1—C2—H21	115.4 (9)	O2—C11—C12	133.41 (6)
C3—C2—H21	112.7 (8)	O2—C11—C12^i	133.40 (6)
C1—C2—H22	111.0 (10)	C12—C11—C12^i	93.19 (12)
C3—C2—H22	113.9 (10)	C11—C12—C13	88.00 (9)
H21—C2—H22	113.2 (12)	C11—C12—H121	112.3 (9)
C4—C3—C2	90.46 (9)	C13—C12—H121	113.9 (9)
C4—C3—H31	110.4 (10)	C11—C12—H122	111.9 (9)
C2—C3—H31	114.6 (9)	C13—C12—H122	117.3 (9)
C4—C3—H32	117.4 (10)	H121—C12—H122	111.4 (12)
C2—C3—H32	113.5 (9)	C12—C13—C12^i	90.80 (12)
H31—C3—H32	109.6 (14)	C12—C13—H13	112.2 (9)
C1—C4—C3	88.31 (9)	C12^i—C13—H13	113.9 (10)
C1—C4—H41	114.5 (8)
O1—C1—C2—C3	178.28 (12)	C2—C3—C4—C1	−2.25 (8)
C4—C1—C2—C3	−2.30 (9)	O2—C11—C12—C13	180.0
C1—C2—C3—C4	2.26 (8)	C12^i—C11—C12—C13	0.0
O1—C1—C4—C3	−178.27 (12)	C11—C12—C13—C12^i	0.0
C2—C1—C4—C3	2.31 (9)

Symmetry code: (i) −x, y, −z+1/2.