A low-temperature determination of butyramide

The low-temperature structure determination of butyramide, C₄H₉NO, obtained as part of a experimental polymorph screen on adenine, is reported here. Each molecule takes part in four hydrogen bonds to form a three-dimensional ribbon structure.

Comment

The title compound, (I), is one of the n-aliphatic amides and has recently been studied as a possible agent for growth inhibition of human neuroblastoma cell lines (Rocchi et al., 1998) and inhibitory effects on DNA synthesis on hepatoma cells (Lea et al., 1993).

The powder diffractogram data for (I) were reported in 1950 (Matthews et al., 1950), as part of a study on derivatives of fatty acids, and the unit cell was determined five years later (Turner & Lingafelter, 1955) using Weissenberg photographs, to give a = 9.94 Å, b = 5.79 Å, c = 10.02 Å and β = 100.9°. Examination of the systematic absences showed the space group to be P2₁/a; however, no atomic coordinates were published. We have solved and refined the crystal structure of butyramide at 150 K, to give a final R value of 0.041. There is a 12° difference in the β angle between the two determinations. In (I), the bond lengths and angles are within expected values (Allen et al., 1987), with the C—C bond lengths in the range 1.5057 (18)–1.515 (2) Å and with N1—C1 and O2—C1 bond lengths of 1.3257 (15) and 1.2395 (13) Å, respectively. There is a relative twist of the carbon chain from planarity, with torsion angles C1—C2—C3—C4 and N1—C1—C2—C3 of 177.41 (21) and 151.62 (12)°, respectively. The packing consists of centrosymmetric dimers, linked through a pair of N—H⋯O hydrogen bonds [2.9470 (15) Å]. The other amine H atom is used to hydrogen bond to an adjacent dimer unit which is approximately perpendicular (73°), through an N—H⋯O hydrogen bond [2.8496 (14) Å], resulting in the formation of a three-dimensional criss-crossed ribbon structure (Fig. 2).

Figure 1 View of (I), showing the atom labelling scheme. Displacement ellipsoids are drawn at the 50% probability level.

Figure 2 The packing in (I), showing the butyramide dimer unit which forms a hydrogen-bonded (dashed lines) criss-cross ribbon motif.

Experimental

As part of an experimental polymorph screen on adenine, (I) was obtained from a 0.3 M aqueous solution of (I), to which approximately 0.15 g of adenine was added, and which was stirred on a hotplate at 303 K for 3 d. This solution was filtered, then evaporated at room temperature (10 ml solution, in 75 × 25 mm vessels) in an attempt to crystallize adenine, as it has been found that the solubility of purine and pyrimidine bases increases in aqueous amide solutions (Herskovits & Bowen, 1974). Colourless block-like crystals of (I) were formed after a number of days.

Crystal data

• C₄H₉NO

• M_r = 87.12

• Monoclinic, P 2₁ /c

• a = 9.814 (3) Å

• b = 5.9232 (17) Å

• c = 9.701 (3) Å

• β = 112.070 (4)°

• V = 522.6 (3) ų

• Z = 4

• D_x = 1.107 Mg m⁻³

• Mo Kα radiation

• Cell parameters from 1237 reflections

• θ = 2.2–25.4°

• μ = 0.08 mm⁻¹

• T = 150 (2) K

• Block, colourless

• 0.38 × 0.20 × 0.16 mm

Data collection

• Bruker SMART APEX diffractometer

• ω scans

• Absorption correction: multi-scan(SADABS; Sheldrick, 1996)T_min = 0.971, T_max = 0.987

• 4321 measured reflections

• 1244 independent reflections

• 993 reflections with I > 2σ(I)

• R_int = 0.021

• θ_max = 28.3°

• h = −13 → 12

• k = −7 → 7

• l = −12 → 12

Refinement

• Refinement on F²

• R[F² > 2σ(F²)] = 0.041

• wR(F²) = 0.111

• S = 1.01

• 1244 reflections

• 91 parameters

• All H-atom parameters refined

• w = 1/[σ²(F_o²) + (0.064P)² + 0.0651P] where P = (F_o² + 2F_c²)/3

• (Δ/σ)_max < 0.001

• Δρ_max = 0.19 e Å⁻³

• Δρ_min = −0.12 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H1⋯O2^i	0.92 (2)	2.03 (2)	2.9470 (15)	176 (1)
N1—H2⋯O2^ii	0.89 (2)	1.98 (2)	2.8496 (14)	168 (1)
Symmetry codes: (i) -x+1, -y, -z+1; (ii) .

H atoms were refined independently with an isotropic model.

Data collection: SMART (Bruker, 2000); cell refinement: SAINT; data reduction: SAINT (Bruker, 2000); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Bruker, 2000) and MERCURY (Bruno et al., 2002); software used to prepare material for publication: SHELXL97.

Supporting information

Computing details

Data collection: SMART (Bruker, 2000); cell refinement: SAINT; data reduction: SAINT (Bruker, 2000); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Bruker, 2000) and Mercury (Bruno et al., 2002); software used to prepare material for publication: SHELXL97.

Butyramide

Crystal data

C4H9NO	F(000) = 192
Mr = 87.12	Dx = 1.107 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 9.814 (3) Å	Cell parameters from 1237 reflections
b = 5.9232 (17) Å	θ = 2.2–25.4°
c = 9.701 (3) Å	µ = 0.08 mm^−1
β = 112.070 (4)°	T = 150 K
V = 522.6 (3) Å^3	Plate, colourless
Z = 4	0.38 × 0.20 × 0.16 mm

Data collection

Bruker SMART APEX diffractometer	1244 independent reflections
Radiation source: fine-focus sealed tube	993 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.021
ω rotation with narrow frames scans	θmax = 28.3°, θmin = 2.2°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −13→12
Tmin = 0.971, Tmax = 0.987	k = −7→7
4321 measured reflections	l = −12→12

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)] = 0.041	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.111	All H-atom parameters refined
S = 1.01	w = 1/[σ^2(Fo^2) + (0.064P)^2 + 0.0651P] where P = (Fo^2 + 2Fc^2)/3
1244 reflections	(Δ/σ)max < 0.001
91 parameters	Δρmax = 0.19 e Å^−3
0 restraints	Δρmin = −0.12 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
O2	0.62317 (10)	0.21606 (15)	0.61392 (8)	0.0388 (3)
N1	0.58606 (12)	0.13501 (19)	0.37696 (10)	0.0327 (3)
C1	0.65020 (13)	0.25241 (19)	0.50094 (11)	0.0300 (3)
C2	0.76164 (15)	0.4276 (2)	0.50031 (14)	0.0370 (3)
C3	0.77563 (15)	0.6237 (2)	0.60348 (16)	0.0387 (3)
C4	0.89354 (17)	0.7892 (3)	0.60401 (19)	0.0457 (4)
H1	0.5216 (15)	0.022 (3)	0.3760 (14)	0.042 (4)*
H2	0.6058 (15)	0.164 (2)	0.2966 (16)	0.037 (3)*
H3	0.7428 (17)	0.475 (3)	0.4012 (17)	0.055 (4)*
H4	0.860 (2)	0.344 (3)	0.5341 (19)	0.061 (5)*
H5	0.680 (2)	0.701 (3)	0.5663 (18)	0.054 (4)*
H6	0.7966 (16)	0.564 (2)	0.7050 (18)	0.050 (4)*
H7	0.8744 (19)	0.845 (3)	0.506 (2)	0.063 (5)*
H8	0.898 (2)	0.914 (3)	0.664 (2)	0.070 (5)*
H9	0.9914 (18)	0.716 (3)	0.6376 (16)	0.049 (4)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O2	0.0579 (6)	0.0422 (5)	0.0254 (4)	−0.0114 (4)	0.0263 (4)	−0.0053 (3)
N1	0.0456 (6)	0.0368 (6)	0.0222 (5)	−0.0047 (5)	0.0202 (4)	−0.0012 (4)
C1	0.0398 (6)	0.0317 (6)	0.0240 (5)	0.0024 (5)	0.0183 (5)	0.0006 (4)
C2	0.0475 (7)	0.0403 (7)	0.0297 (6)	−0.0074 (6)	0.0218 (5)	−0.0019 (5)
C3	0.0383 (7)	0.0353 (7)	0.0453 (8)	0.0003 (5)	0.0190 (6)	−0.0028 (5)
C4	0.0435 (8)	0.0382 (8)	0.0549 (9)	−0.0031 (6)	0.0179 (7)	−0.0013 (7)

Geometric parameters (Å, º)

O2—C1	1.2395 (13)	C2—H4	1.022 (18)
N1—C1	1.3257 (15)	C3—C4	1.515 (2)
N1—H1	0.919 (16)	C3—H5	0.985 (18)
N1—H2	0.887 (15)	C3—H6	0.993 (16)
C1—C2	1.5091 (17)	C4—H7	0.954 (18)
C2—C3	1.5057 (18)	C4—H8	0.93 (2)
C2—H3	0.950 (16)	C4—H9	0.990 (16)
C1—N1—H1	118.8 (8)	C2—C3—C4	112.36 (11)
C1—N1—H2	120.7 (9)	C2—C3—H5	106.1 (9)
H1—N1—H2	120.5 (13)	C4—C3—H5	109.0 (9)
O2—C1—N1	121.64 (11)	C2—C3—H6	108.5 (9)
O2—C1—C2	121.28 (10)	C4—C3—H6	110.7 (9)
N1—C1—C2	117.05 (10)	H5—C3—H6	110.0 (13)
C3—C2—C1	114.40 (10)	C3—C4—H7	110.9 (11)
C3—C2—H3	112.4 (10)	C3—C4—H8	111.5 (11)
C1—C2—H3	109.9 (10)	H7—C4—H8	107.2 (16)
C3—C2—H4	108.6 (10)	C3—C4—H9	111.3 (9)
C1—C2—H4	105.5 (10)	H7—C4—H9	106.4 (14)
H3—C2—H4	105.5 (13)	H8—C4—H9	109.4 (14)
O2—C1—C2—C3	−30.35 (18)	C1—C2—C3—C4	177.41 (12)
N1—C1—C2—C3	151.62 (12)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···O2^i	0.919 (16)	2.030 (16)	2.9470 (15)	175.9 (13)
N1—H2···O2^ii	0.887 (15)	1.976 (15)	2.8496 (14)	167.9 (13)

Symmetry codes: (i) −x+1, −y, −z+1; (ii) x, −y+1/2, z−1/2.