N-Propyl­urea: the missing link

The title mol­ecule, C₄H₁₀N₂O, is planar and its alkyl chain displays an all-trans configuration, which is typical for n-alkyl­urea structures. Pairs of mol­ecules are hydrogen bonded across crystallographic inversion centres [N...O = 2.962 (4) Å], with each O atom involved in two additional hydrogen bonds, linking adjacent urea molecules into chains along c [N...O = 2.924 (3) and 3.042 (3) Å]. Each chain is propagated by a c-glide operation and planes containing adjacent urea molecules inter­cept at an angle of 50.14 (9)°.

Key indicators

• Single-crystal X-ray study
• T = 150 K
• Mean [sigma](C-C) = 0.005 Å
• R factor = 0.064
• wR factor = 0.172
• Data-to-parameter ratio = 9.8

checkCIF/PLATON results

No syntax errors found



Alert level B
RINTA01_ALERT_3_B  The value of Rint is greater than 0.15
            Rint given   0.167
PLAT020_ALERT_3_B The value of Rint is greater than 0.10 .........       0.17

Alert level C
PLAT088_ALERT_3_C Poor Data / Parameter Ratio ....................       9.78
PLAT340_ALERT_3_C Low Bond Precision on C-C Bonds (x 1000) Ang ...          5

Alert level G
ABSTM02_ALERT_3_G  When printed, the submitted absorption T values will be
            replaced by the scaled T values. Since the ratio of scaled T's
            is identical to the ratio of reported T values, the scaling
            does not imply a change to the absorption corrections used in
            the study.
            Ratio of Tmax expected/reported      0.998
            Tmax scaled      0.998 Tmin scaled      0.923

   0 ALERT level A = In general: serious problem
   2 ALERT level B = Potentially serious problem
   2 ALERT level C = Check and explain
   1 ALERT level G = General alerts; check

   0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   0 ALERT type 2 Indicator that the structure model may be wrong or deficient
   5 ALERT type 3 Indicator that the structure quality may be low
   0 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

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S1. Comment

For the purpose of this paper, n-propylurea will be referred to as C₃—U in compliance with the system used by Hashimoto et al.. (2005) and is derived from the number of carbon atoms in the alkyl group, H₂NCONHC_nH_2n+1.

In common with all the members of the C_4–14—U series, C₃—U is planar and its alkyl chain displays an all-trans configuration (Fig. 1). This contrasts with non-planar C₂—U, in which the terminal methyl group is in a skew position with respect to the N—C bond.

The H-bonding network in the title compound (Fig. 2) is typical for the longer chain n-alkylurea crystal structures and consists of pairs of molecules linked across crystallographic inversion centres (N···O 2.962 (4) Å). Furthermore, each oxygen is involved in two additional H-bonds, which link adjacent urea moieties into chains along c (N···O 2.924 (3), 3.042 (3) Å). All three N···O values agree well with those in the C_5–14—U series, for which the corresponding distances fall in the ranges 2.95 (1), 3.06 (2) and 2.93 (2) Å.

Each chain is propogated by a c-glide operation and planes containing adjacent urea moieties intercept at an angle of 50.14 (9)°. This value is slightly more acute than in the analogous C_5–14—U structures (54.0–55.4°, except for C₅—U, 57.5°). Interestingly, although the crystal packing in C₄—U is somewhat different to the remainder of the series, the structure has retained the above H-bonded chains, albeit with coplanar urea moieties.

Related literature

The title compound is the third member (n = 3) of the straight-chain alkylurea series, H₂NCONHC_nH_{2n + 1}. Crystal structures for the analogous compounds with n = 1 (Huiszoon & Tiemessen, 1976) and n = 2, 4–14 (Hashimoto et al., 2005) have been published previously.

S2. Experimental

The n-propylurea (C₃—U) crystals were grown by evaporation, using 30% weight % H₂O₂ as the solvent. This was a failed attempt at preparing an n-propylurea H₂O₂ adduct.

S3. Refinement

The extremely thin, easily-distorted n-propylurea crystals produced a streaked diffraction pattern, which resulted in an elevated R_int. H atoms were refined isotropically.

Computing details

Data collection: COLLECT (Nonius, 1998); cell refinement: SCALEPACK (Otwinowski & Minor, 1997); data reduction: SCALEPACK and DENZO (Otwinowski & Minor, 1997); program(s) used to solve structure: SIR92 (Altomare et al., 1993); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).

Figures

	Fig. 1. The molecular structure of C3—U, with atom labels and 50% probability displacement ellipsoids for non-H atoms.
	Fig. 2. The packing of C3—U, viewed perpendicular to the c axis, showing the H-bonding scheme (dashed lines).

N-Propylurea

Crystal data

C4H10N2O	F(000) = 224
Mr = 102.14	Dx = 1.217 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 3437 reflections
a = 7.8473 (10) Å	θ = 2–26°
b = 7.7271 (10) Å	µ = 0.09 mm^−1
c = 9.2429 (14) Å	T = 150 K
β = 95.777 (6)°	Plate, colourless
V = 557.61 (13) Å^3	0.3 × 0.25 × 0.02 mm
Z = 4

Data collection

Nonius KappaCCD diffractometer	710 reflections with I > 2σ(I)
CCD rotation images, thick slices scans	Rint = 0.167
Absorption correction: multi-scan (SORTAV; Blessing, 1995, 1997)	θmax = 25.5°, θmin = 3.4°
Tmin = 0.925, Tmax = 1.000	h = −9→9
3437 measured reflections	k = −9→9
1017 independent reflections	l = −9→11

Refinement

Refinement on F^2	0 restraints
Least-squares matrix: full	All H-atom parameters refined
R[F^2 > 2σ(F^2)] = 0.064	w = 1/[σ^2(Fo^2) + (0.0469P)^2 + 0.3434P] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.172	(Δ/σ)max = 0.015
S = 1.10	Δρmax = 0.19 e Å^−3
1017 reflections	Δρmin = −0.24 e Å^−3
104 parameters

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
C1	0.1361 (4)	0.2221 (4)	0.5775 (3)	0.0316 (7)
C2	0.2539 (4)	0.5134 (4)	0.5468 (3)	0.0334 (7)
C3	0.3388 (5)	0.6552 (4)	0.6406 (3)	0.0383 (8)
C4	0.3912 (5)	0.8063 (5)	0.5506 (4)	0.0428 (9)
N1	0.0878 (4)	0.1021 (3)	0.6715 (3)	0.0390 (7)
N2	0.2076 (3)	0.3678 (3)	0.6358 (3)	0.0355 (7)
O1	0.1154 (3)	0.2001 (3)	0.44264 (19)	0.0365 (6)
H1A	0.025 (5)	0.005 (5)	0.629 (4)	0.055 (10)*
H1B	0.092 (4)	0.135 (4)	0.772 (4)	0.043 (9)*
H2A	0.221 (4)	0.378 (4)	0.736 (3)	0.029 (7)*
H2B	0.328 (4)	0.469 (4)	0.467 (3)	0.037 (8)*
H2C	0.149 (4)	0.564 (4)	0.486 (3)	0.037 (8)*
H3A	0.437 (4)	0.608 (4)	0.702 (4)	0.047 (9)*
H3B	0.262 (5)	0.691 (5)	0.720 (4)	0.060 (11)*
H4A	0.286 (5)	0.857 (5)	0.492 (4)	0.059 (11)*
H4B	0.474 (5)	0.771 (5)	0.486 (4)	0.061 (11)*
H4C	0.443 (5)	0.903 (6)	0.610 (4)	0.069 (12)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0314 (16)	0.0381 (17)	0.0255 (15)	0.0049 (13)	0.0038 (12)	0.0001 (12)
C2	0.0356 (16)	0.0382 (17)	0.0258 (14)	−0.0018 (14)	0.0008 (12)	0.0017 (12)
C3	0.0464 (19)	0.0381 (17)	0.0293 (15)	−0.0034 (15)	−0.0018 (14)	0.0018 (13)
C4	0.047 (2)	0.0408 (19)	0.0391 (19)	−0.0076 (17)	−0.0011 (16)	−0.0006 (15)
N1	0.0540 (18)	0.0368 (14)	0.0266 (14)	−0.0058 (13)	0.0066 (12)	−0.0001 (11)
N2	0.0480 (16)	0.0379 (14)	0.0205 (13)	−0.0068 (12)	0.0020 (10)	0.0005 (11)
O1	0.0484 (14)	0.0372 (12)	0.0233 (11)	−0.0038 (10)	0.0005 (9)	−0.0012 (8)

Geometric parameters (Å, º)

C1—O1	1.252 (3)	C3—H3A	0.98 (3)
C1—N2	1.346 (4)	C3—H3B	1.03 (4)
C1—N1	1.351 (4)	C4—H4A	1.02 (4)
C2—N2	1.461 (4)	C4—H4B	0.96 (4)
C2—C3	1.510 (4)	C4—H4C	0.99 (4)
C2—H2B	1.05 (3)	N1—H1A	0.96 (4)
C2—H2C	1.03 (3)	N1—H1B	0.96 (3)
C3—C4	1.515 (4)	N2—H2A	0.92 (3)
O1—C1—N2	121.3 (3)	H3A—C3—H3B	100 (3)
O1—C1—N1	122.0 (3)	C3—C4—H4A	110 (2)
N2—C1—N1	116.7 (2)	C3—C4—H4B	111 (2)
N2—C2—C3	110.8 (2)	H4A—C4—H4B	110 (3)
N2—C2—H2B	109.5 (17)	C3—C4—H4C	113 (2)
C3—C2—H2B	113.6 (17)	H4A—C4—H4C	106 (3)
N2—C2—H2C	112.0 (17)	H4B—C4—H4C	107 (3)
C3—C2—H2C	108.6 (18)	C1—N1—H1A	116 (2)
H2B—C2—H2C	102 (2)	C1—N1—H1B	117 (2)
C2—C3—C4	111.9 (3)	H1A—N1—H1B	125 (3)
C2—C3—H3A	109.7 (19)	C1—N2—C2	122.4 (2)
C4—C3—H3A	111 (2)	C1—N2—H2A	118.4 (18)
C2—C3—H3B	110 (2)	C2—N2—H2A	119.1 (18)
C4—C3—H3B	113 (2)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1A···O1^i	0.96 (4)	2.00 (4)	2.962 (4)	175 (3)
N1—H1B···O1^ii	0.96 (3)	2.02 (3)	2.924 (3)	156 (3)
N2—H2A···O1^ii	0.92 (3)	2.24 (3)	3.042 (3)	145 (2)

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