1-Ethyl-2-nitro­guanidine

The structure of the title compound, C₃H₈N₄O₂, is similar to other nitr­imines. The nitro­guanyl group is planar and is stabilized by an intramolecular hydrogen bond. Intermolecular hydrogen bonds hold the mol­ecules together in the crystal.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.002 Å
• R factor = 0.036
• wR factor = 0.106
• Data-to-parameter ratio = 11.5

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry

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S1. Comment

As a continuation of work on the structures of nitrimines (Choi, 1981; Nordenson, 1981a,b; Nordenson & Hvoslef, 1981; Rice et al., 1984; Oyumi et al., 1987; Gao et al., 1991; Astachov et al., 2001; Vasiliev et al., 2001), we report here the structure of crystalline 1-ethyl-2-nitroguanidine, (I). The molecular structure of (I) corresponds to that of previously investigated nitrimines. Like other nitrimines, the delocalization of π-electron density gives values of C—N, N—N and N—O bond lengths intermediate between characteristic values of single and double bonds (Table 1). The formally double bond C1═N2 is in fact longer by 0.052–0.057 Å than the C1—N3 and C1—N4 bonds. The planar geometry of the nitroguanile group (r.m.s. deviation 0.065 Å and maximum deviation 0.104 Å) is stabilized by an O1···H1 intramolecular hydrogen bond (Table 2). In other nitrimines, the N—H···O angles are in the range 105–126° and the O···H distance is in the range 1.72–2.24 Å (Allen & Kennard, 1993). The ethyl group does not participate in conjugation of the nitroguanyl fragment and as a consequence the N4—C2 bond length is close to those observed in compounds with single C—N bond (Allen, 2002).

In the crystal, each molecule of (I) is connected by three intermolecular hydrogen bonds with two neighbouring molecules (Fig. 1 and Table 2). Atom O1 is involved in intramolecular hydrogen bonding and forms a hydrogen bond with H2 of another molecule. Besides that the molecules are connected in pairs by two N2···H3 hydrogen bonds. The second oxygen atom, O2, does not participate in hydrogen bonds and, for this reason, the N1—O2 bond length is shorter by 0.027 Å than the N1—O1 bond. The similar developed hydrogen-bond net is typical for the nitrimines (Allen, 2002).

The structure of (I) corresponds well with the methyl derivative of nitroguanidine-1-methyl-2-nitroguanidine, (II) (Nordenson, 1981a). The low-temperature study of (II) exhibits almost equal geometry and, with the exception of N1—N2, all other differences in bond lengths between (I) and (II) do not exceed 2σ. The molecular packing in (I) and (II) is also very similar: they have the same space-group symmetry and number of molecules in the unit cell, and the same hydrogen bonds with nearly equal geometric parameters.

S2. Experimental

Compound (I) was synthesized as described previously by Fishbein & Gallaghan (1954). Single crystals were obtained by evaporation in air of an aqueous solution of (I).

S3. Refinement

H atoms were found in a difference Fourier map and were refined as riding atoms for CH₂ and CH₃ groups and as free atoms for NH and NH₂ groups. Furthermore, the C—H distance was refined as one parameter for CH₂ and CH₃ groups.

Computing details

Data collection: KM-4 Software (Kuma, 1991); cell refinement: KM-4 Software; data reduction: DATARED in KM-4 Software; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Sheldrick, 1995); software used to prepare material for publication: SHELXL97.

Figures

Fig. 1. The molecular arrangement (I) in a crystal, with the atomic numbering scheme. Dashed lines indicate intra- and intermolecular hydrogen bonds.

1-Ethyl-2-nitroguanidine

Crystal data

C3H8N4O2	F(000) = 280
Mr = 132.13	Dx = 1.423 Mg m^−3
Monoclinic, P21/n	Cu Kα radiation, λ = 1.5418 Å
Hall symbol: -P 2yn	Cell parameters from 25 reflections
a = 8.9336 (9) Å	θ = 20–27°
b = 16.087 (2) Å	µ = 1.02 mm^−1
c = 4.3173 (4) Å	T = 293 K
β = 96.119 (8)°	Transparent lump, colourless
V = 616.92 (11) Å^3	0.32 × 0.27 × 0.26 mm
Z = 4

Data collection

Kuma KM-4 diffractometer	Rint = 0.034
Radiation source: fine-focus sealed tube	θmax = 69.9°, θmin = 5.5°
Graphite monochromator	h = −10→10
θ/2θ scans	k = −19→16
1325 measured reflections	l = 0→5
1168 independent reflections	2 standard reflections every 50 reflections
1049 reflections with I > 2σ(I)	intensity decay: variation 0.5%

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)] = 0.036	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.106	w = 1/[σ^2(Fo^2) + (0.0632P)^2 + 0.1271P] where P = (Fo^2 + 2Fc^2)/3
S = 1.04	(Δ/σ)max < 0.001
1168 reflections	Δρmax = 0.19 e Å^−3
102 parameters	Δρmin = −0.16 e Å^−3
0 restraints	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.044 (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
N2	0.57727 (12)	0.09681 (6)	0.0506 (3)	0.0382 (3)
O2	0.77500 (13)	0.12035 (7)	−0.1876 (3)	0.0613 (4)
O1	0.69759 (14)	0.22180 (6)	0.0805 (3)	0.0653 (4)
C1	0.46666 (14)	0.12472 (7)	0.2220 (3)	0.0338 (3)
N4	0.37411 (13)	0.06484 (7)	0.2869 (3)	0.0385 (3)
H3	0.3882 (18)	0.0184 (12)	0.219 (4)	0.048 (4)*
N1	0.68449 (13)	0.14855 (7)	−0.0192 (3)	0.0423 (3)
N3	0.44819 (16)	0.20158 (8)	0.3154 (3)	0.0515 (4)
H2	0.367 (2)	0.2150 (12)	0.399 (5)	0.064 (5)*
H1	0.518 (2)	0.2338 (13)	0.271 (5)	0.068 (6)*
C2	0.24698 (15)	0.07412 (8)	0.4678 (3)	0.0425 (4)
H4	0.2700	0.1168	0.622	0.046 (4)*
H5	0.2329	0.0229	0.576	0.060 (5)*
C3	0.10261 (18)	0.09622 (12)	0.2744 (4)	0.0623 (5)
H6	0.1156	0.1468	0.166	0.074 (6)*
H7	0.0247	0.1029	0.406	0.085 (7)*
H8	0.0761	0.0530	0.128	0.084 (7)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
N2	0.0375 (6)	0.0255 (6)	0.0531 (7)	−0.0023 (4)	0.0122 (5)	−0.0029 (4)
O2	0.0527 (7)	0.0493 (7)	0.0879 (8)	−0.0023 (5)	0.0354 (6)	−0.0077 (6)
O1	0.0680 (8)	0.0315 (6)	0.1025 (9)	−0.0163 (5)	0.0380 (7)	−0.0124 (5)
C1	0.0350 (6)	0.0260 (6)	0.0400 (6)	0.0019 (5)	0.0027 (5)	−0.0004 (4)
N4	0.0413 (6)	0.0268 (6)	0.0490 (7)	−0.0002 (4)	0.0119 (5)	−0.0024 (4)
N1	0.0405 (6)	0.0292 (5)	0.0589 (7)	−0.0016 (4)	0.0125 (5)	0.0005 (5)
N3	0.0491 (8)	0.0283 (6)	0.0813 (9)	−0.0009 (5)	0.0262 (7)	−0.0089 (6)
C2	0.0452 (8)	0.0369 (7)	0.0475 (7)	−0.0008 (6)	0.0150 (6)	0.0017 (5)
C3	0.0420 (9)	0.0712 (12)	0.0736 (11)	−0.0015 (8)	0.0054 (8)	−0.0116 (9)

Geometric parameters (Å, º)

N2—N1	1.3276 (15)	N3—H2	0.87 (2)
N2—C1	1.3718 (16)	N3—H1	0.85 (2)
O2—N1	1.2303 (15)	C2—C3	1.502 (2)
O1—N1	1.2555 (15)	C2—H4	0.9626
C1—N3	1.3164 (17)	C2—H5	0.9626
C1—N4	1.3188 (17)	C3—H6	0.9515
N4—C2	1.4528 (17)	C3—H7	0.9515
N4—H3	0.817 (18)	C3—H8	0.9515
N1—N2—C1	119.72 (10)	N4—C2—C3	113.56 (12)
N3—C1—N4	121.28 (12)	N4—C2—H4	108.9
N3—C1—N2	126.41 (12)	C3—C2—H4	108.9
N4—C1—N2	112.31 (11)	N4—C2—H5	108.9
C1—N4—C2	125.65 (11)	C3—C2—H5	108.9
C1—N4—H3	117.8 (11)	H4—C2—H5	107.7
C2—N4—H3	116.5 (11)	C2—C3—H6	109.5
O2—N1—O1	120.36 (11)	C2—C3—H7	109.5
O2—N1—N2	115.99 (11)	H6—C3—H7	109.5
O1—N1—N2	123.64 (11)	C2—C3—H8	109.5
C1—N3—H2	119.8 (13)	H6—C3—H8	109.5
C1—N3—H1	112.8 (14)	H7—C3—H8	109.5
H2—N3—H1	127 (2)
N1—N2—C1—N3	4.4 (2)	C1—N2—N1—O2	−176.20 (12)
N1—N2—C1—N4	−176.27 (11)	C1—N2—N1—O1	4.9 (2)
N3—C1—N4—C2	−1.5 (2)	C1—N4—C2—C3	89.75 (17)
N2—C1—N4—C2	179.13 (12)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N4—H3···N2^i	0.82 (2)	2.23 (2)	3.035 (2)	170 (1)
N3—H2···O1^ii	0.87 (2)	2.04 (2)	2.896 (2)	165 (1)
N3—H1···O1	0.85 (2)	1.89 (2)	2.565 (2)	136 (1)

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