Methyl 1H-1,2,4-triazole-3-carboxyl­ate

The title compound, C₄H₅N₃O₂, possesses a planar triazole ring and contains two inter­molecular hydrogen bonds in the crystal structure.

Key indicators

• Single-crystal X-ray study
• T = 294 K
• Mean [sigma](C-C)= 0.002 Å
• R factor = 0.037
• wR factor = 0.111
• Data-to-parameter ratio = 13.4

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S1. Comment

Ribavirin (1-D-ribofuranosyl-1,2,4-triazole-3-carboxamide) (Vo et al., 2003) is a nucleoside analogue that has demonstrated efficacy in treating viral diseases both as monotherapy 14 (respiratory syncytial virus) and in combination therapy with interferon alpha (hepatitis C virus). Methyl 1H-1,2,4-triazole-3-carboxylate, (I) (Lin & Liu, 1984), has been used as starting materials for Ribavirin (Ramasamy et al., 2000). The structure of (I) (Fig. 1) displays two types of intermolecular hydrogen-bonding interactions, O1···H1—C1 and N1···H3—N3. The plane-to-plane distance of two molecules is 3.26 (2) Å.

S2. Experimental

5-Amino-1,2,4-triazole-3-carboxylic acid (100 g) and methanol (500 ml) were placed in a 2 l three-necked flask with mechanical stirring. The reaction mixture was slowly added with 98% sulfuric acid (250 g) under stirring and then heated under reflux for 16 h. The reaction mixture was cooled to 278 K for 10 h to afford a light-yellow wet solid. This solid was mixed with 98% surfuric acid (58 g) and water (350 ml), and the resulting mixture cooled to 273–2274 K. 30% aqueous sodium nitrite (150 g) was added slowly and the reaction allowed to continue for a further 2 h to give a grey solid. The grey solid and 350 ml me thanol was then placed in a 1 l flask with stirring and slowly heated to 313 K. When all the diazonium salt had been decomposed by methanol, the reaction solution was filtered and the filtrate was cooled to 283 K to afford the product, (I). Recrystallization from water and methanol gave 49 g of crystalline product of (I) (yield 49%).

S3. Refinement

The vinyl and imine H atoms were restrained on their parent atoms, with C—H distances restrained to 0.93 Å and N—H restrained to 0.95 (3) Å. The methyl H atoms were positioned geometrically and refined using a riding model, with C—H = 0.96 Å and U_iso(H) = 1.2U_eq(C). In absence of significant anomalous dispersion effects, Friedel pair reflections were merged prior to refinement.

Computing details

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

Figures

	Fig. 1. A view of the molecule of (I). Displacement ellipsoids are drawn at the 30% probability level and H atoms are shown as small spheres of arbitrary radii.
	Fig. 2. The packing diagram of (I). Dotted lines represent intermolecular hydrogen-bonding interactions.

Methyl 1H-1,2,4-triazole-3-carboxylate

Crystal data

C4H5N3O2	F(000) = 264
Mr = 127.11	Dx = 1.464 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 1220 reflections
a = 3.9737 (9) Å	θ = 2.2–26.2°
b = 18.160 (4) Å	µ = 0.12 mm^−1
c = 8.1865 (19) Å	T = 294 K
β = 102.596 (4)°	Block, colourless
V = 576.5 (2) Å^3	0.30 × 0.26 × 0.20 mm
Z = 4

Data collection

Bruker SMART CCD area-detector diffractometer	1168 independent reflections
Radiation source: fine-focus sealed tube	846 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.023
ϕ and ω scans	θmax = 26.4°, θmin = 2.2°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −2→4
Tmin = 0.960, Tmax = 0.976	k = −22→21
3192 measured reflections	l = −10→10

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)] = 0.037	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.111	H atoms treated by a mixture of independent and constrained refinement
S = 1.04	w = 1/[σ^2(Fo^2) + (0.0566P)^2 + 0.0868P] where P = (Fo^2 + 2Fc^2)/3
1168 reflections	(Δ/σ)max = 0.002
87 parameters	Δρmax = 0.15 e Å^−3
0 restraints	Δρmin = −0.16 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	0.3505 (4)	0.39535 (7)	0.12670 (17)	0.0685 (5)
O2	0.2107 (3)	0.46242 (7)	0.33138 (17)	0.0597 (4)
N1	0.1973 (4)	0.26613 (8)	0.28949 (17)	0.0487 (4)
N2	0.0297 (4)	0.33867 (8)	0.47971 (17)	0.0486 (4)
N3	−0.0137 (4)	0.26701 (8)	0.51244 (19)	0.0485 (4)
C1	0.0859 (5)	0.22506 (11)	0.4003 (2)	0.0517 (5)
H1	0.0788	0.1739	0.3993	0.062*
C2	0.1574 (4)	0.33524 (9)	0.34415 (19)	0.0412 (4)
C3	0.2501 (4)	0.40039 (9)	0.2544 (2)	0.0457 (4)
C4	0.3033 (6)	0.52920 (11)	0.2565 (3)	0.0732 (6)
H4A	0.5460	0.5289	0.2592	0.110*
H4B	0.2487	0.5709	0.3180	0.110*
H4C	0.1767	0.5323	0.1426	0.110*
H3	−0.100 (6)	0.2543 (14)	0.608 (3)	0.086 (7)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.1045 (11)	0.0556 (9)	0.0588 (8)	0.0018 (7)	0.0469 (8)	0.0036 (6)
O2	0.0812 (9)	0.0453 (8)	0.0596 (8)	−0.0005 (6)	0.0309 (7)	−0.0028 (6)
N1	0.0631 (9)	0.0461 (8)	0.0430 (8)	0.0002 (7)	0.0250 (7)	0.0001 (6)
N2	0.0572 (9)	0.0508 (9)	0.0431 (8)	0.0033 (7)	0.0223 (6)	−0.0002 (6)
N3	0.0556 (9)	0.0545 (10)	0.0411 (8)	0.0012 (7)	0.0227 (7)	0.0038 (7)
C1	0.0640 (11)	0.0470 (10)	0.0492 (10)	0.0008 (8)	0.0231 (9)	0.0016 (8)
C2	0.0438 (9)	0.0469 (10)	0.0355 (8)	0.0032 (7)	0.0146 (7)	−0.0003 (7)
C3	0.0513 (10)	0.0463 (10)	0.0427 (9)	0.0037 (7)	0.0174 (8)	0.0002 (7)
C4	0.0970 (17)	0.0455 (11)	0.0835 (15)	−0.0051 (10)	0.0334 (13)	0.0017 (10)

Geometric parameters (Å, º)

O1—C3	1.2008 (19)	N3—C1	1.318 (2)
O2—C3	1.317 (2)	N3—H3	0.95 (3)
O2—C4	1.442 (2)	C1—H1	0.9300
N1—C1	1.323 (2)	C2—C3	1.481 (2)
N1—C2	1.353 (2)	C4—H4A	0.9600
N2—C2	1.318 (2)	C4—H4B	0.9600
N2—N3	1.347 (2)	C4—H4C	0.9600
C3—O2—C4	116.62 (15)	N1—C2—C3	121.13 (14)
C1—N1—C2	102.43 (14)	O1—C3—O2	125.36 (16)
C2—N2—N3	102.19 (13)	O1—C3—C2	122.46 (15)
C1—N3—N2	110.42 (15)	O2—C3—C2	112.17 (14)
C1—N3—H3	130.6 (15)	O2—C4—H4A	109.5
N2—N3—H3	119.0 (15)	O2—C4—H4B	109.5
N3—C1—N1	110.35 (17)	H4A—C4—H4B	109.5
N3—C1—H1	124.8	O2—C4—H4C	109.5
N1—C1—H1	124.8	H4A—C4—H4C	109.5
N2—C2—N1	114.61 (14)	H4B—C4—H4C	109.5
N2—C2—C3	124.26 (15)
C2—N2—N3—C1	0.12 (18)	C4—O2—C3—O1	−1.3 (3)
N2—N3—C1—N1	−0.2 (2)	C4—O2—C3—C2	178.34 (15)
C2—N1—C1—N3	0.14 (19)	N2—C2—C3—O1	−176.37 (16)
N3—N2—C2—N1	−0.03 (18)	N1—C2—C3—O1	3.1 (3)
N3—N2—C2—C3	179.47 (15)	N2—C2—C3—O2	3.9 (2)
C1—N1—C2—N2	−0.06 (19)	N1—C2—C3—O2	−176.59 (14)
C1—N1—C2—C3	−179.58 (15)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C1—H1···O1^i	0.93	2.57	3.138 (2)	120
N3—H3···N1^i	0.95 (3)	1.88 (3)	2.822 (2)	175 (2)

Symmetry code: (i) x−1/2, −y+1/2, z+1/2.