4-Methoxy-3-nitro­pyridinium chloride

The structure of the title compound, C₆H₇N₂O₃⁺·Cl⁻, (I), comprises the hydro­chloride salt of an essentially flat mol­ecule with a single N—H...Cl association. Two additional C—H...Cl close contacts are also observed.

Key indicators

• Single-crystal X-ray study
• T = 150 K
• Mean [sigma](C-C) = 0.003 Å
• R factor = 0.043
• wR factor = 0.121
• Data-to-parameter ratio = 16.1

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry

---

S1. Comment

The basified form of 4-methoxy-3-nitropyridine, i.e. the title compound 4-methoxy-3-nitropyridinium chloride, (I), is a useful intermediate in which the methoxy group of can be readily replaced by nucleophiles. The molecule is also commercially available as the 4-ethoxy derivative but the methoxy version is less expensive. Both derivatives are prepared via the 4-chloro analogue, which is then treated with the appropriate alcohol. The 4-chloro compound has increased reactivity to nucleophiles but it is very lipophilic and corrosive to the skin, so it is much easier to handle as a 4-alkoxy compound.

S2. Experimental

The title compound, (I), was prepared by Spa Contract Synthesis. Crystals of (I) were grown from a methanol solution.

S3. Refinement

All H atoms were included in the refinement at calculated positions as riding models, with C—H set to 0.95 (Ar—H) and 0.98 Å (CH₃), except for the pyridinium H atom, which was located on difference syntheses and for which both positional and displacement parameters were refined.

Computing details

Data collection: DENZO (Otwinowski & Minor, 1997) and COLLECT (Hooft, 1998); cell refinement: DENZO and COLLECT; data reduction: DENZO and COLLECT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); software used to prepare material for publication: SHELXL97.

Figures

Fig. 1. The molecular configuration and atom-numbering scheme for (I), showing 50% probability ellipsoids.

4-Methoxy-3-nitropyridinium chloride

Crystal data

C6H7N2O3^+·Cl^−	F(000) = 392
Mr = 190.59	Dx = 1.576 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
a = 10.6185 (4) Å	Cell parameters from 4004 reflections
b = 7.1517 (4) Å	θ = 2.9–27.5°
c = 11.3701 (5) Å	µ = 0.44 mm^−1
β = 111.523 (3)°	T = 150 K
V = 803.24 (6) Å^3	Block, colourless
Z = 4	0.15 × 0.15 × 0.10 mm

Data collection

Enraf Nonius KappaCCD area-detector diffractometer	1835 independent reflections
Radiation source: Enraf Nonius FR591 rotating anode	1219 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.042
Detector resolution: 9.091 pixels mm^-1	θmax = 27.5°, θmin = 3.3°
ϕ and ω scans	h = −13→13
Absorption correction: multi-scan (SORTAV; Blessing, 1995)	k = −8→9
Tmin = 0.937, Tmax = 0.957	l = −13→14
5993 measured 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)] = 0.043	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.121	H atoms treated by a mixture of independent and constrained refinement
S = 1.00	w = 1/[σ^2(Fo^2) + (0.0664P)^2] where P = (Fo^2 + 2Fc^2)/3
1835 reflections	(Δ/σ)max < 0.001
114 parameters	Δρmax = 0.25 e Å^−3
0 restraints	Δρmin = −0.26 e Å^−3

Special details

Experimental. PLEASE NOTE cell_measurement_ fields are not relevant to area detector data, the entire data set is used to refine the cell, which is indexed from all observed reflections in a 10 degree phi range.

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

	x	y	z	Uiso*/Ueq
Cl1	0.14928 (5)	−0.48448 (7)	0.68197 (5)	0.0504 (2)
N1	0.29721 (17)	−0.4262 (3)	0.95746 (18)	0.0483 (5)
H1	0.245 (2)	−0.426 (4)	0.870 (3)	0.078 (8)*
C2	0.3021 (2)	−0.2817 (3)	1.03233 (19)	0.0455 (5)
H2	0.2585	−0.1676	0.9975	0.057*
C3	0.37018 (18)	−0.2979 (3)	1.15977 (17)	0.0387 (5)
N31	0.36643 (19)	−0.1332 (2)	1.23515 (17)	0.0500 (5)
O31	0.29498 (18)	−0.0033 (2)	1.18145 (18)	0.0687 (5)
O32	0.4352 (2)	−0.1318 (2)	1.34665 (16)	0.0872 (6)
C4	0.43571 (18)	−0.4643 (3)	1.21323 (18)	0.0377 (5)
O41	0.49836 (15)	−0.47804 (18)	1.33625 (13)	0.0460 (4)
C42	0.5523 (2)	−0.6580 (3)	1.3888 (2)	0.0584 (6)
H421	0.4788	−0.7501	1.3661	0.073*
H422	0.5939	−0.6482	1.4811	0.073*
H423	0.6205	−0.6977	1.3549	0.073*
C5	0.42871 (19)	−0.6114 (3)	1.12890 (18)	0.0426 (5)
H5	0.4727	−0.7268	1.1597	0.053*
C6	0.35892 (19)	−0.5873 (3)	1.00372 (19)	0.0462 (5)
H6	0.3537	−0.6877	0.9474	0.058*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cl1	0.0667 (4)	0.0442 (4)	0.0359 (3)	−0.0050 (2)	0.0138 (3)	0.0012 (2)
N1	0.0532 (10)	0.0567 (12)	0.0342 (10)	−0.0028 (9)	0.0150 (9)	−0.0030 (9)
C2	0.0552 (12)	0.0428 (12)	0.0408 (12)	0.0066 (10)	0.0203 (10)	0.0073 (9)
C3	0.0499 (11)	0.0323 (10)	0.0374 (11)	−0.0019 (8)	0.0199 (9)	−0.0027 (8)
N31	0.0715 (12)	0.0371 (10)	0.0475 (12)	−0.0018 (9)	0.0289 (10)	−0.0029 (8)
O31	0.0751 (11)	0.0511 (11)	0.0778 (13)	0.0212 (8)	0.0255 (10)	−0.0042 (8)
O32	0.1658 (19)	0.0456 (11)	0.0422 (10)	0.0023 (11)	0.0285 (11)	−0.0065 (8)
C4	0.0420 (10)	0.0394 (11)	0.0328 (11)	−0.0050 (8)	0.0149 (9)	−0.0020 (8)
O41	0.0550 (8)	0.0447 (9)	0.0331 (8)	0.0060 (6)	0.0101 (7)	0.0010 (6)
C42	0.0693 (14)	0.0559 (14)	0.0452 (13)	0.0136 (12)	0.0152 (11)	0.0104 (11)
C5	0.0498 (11)	0.0343 (11)	0.0448 (12)	−0.0022 (9)	0.0187 (10)	−0.0014 (9)
C6	0.0543 (12)	0.0438 (12)	0.0440 (12)	−0.0107 (10)	0.0223 (10)	−0.0109 (10)

Geometric parameters (Å, º)

N1—C2	1.328 (3)	C4—O41	1.314 (2)
N1—C6	1.335 (3)	C4—C5	1.407 (3)
N1—H1	0.94 (3)	O41—C42	1.446 (2)
C2—C3	1.366 (3)	C42—H421	0.98
C2—H2	0.95	C42—H422	0.98
C3—C4	1.400 (3)	C42—H423	0.98
C3—N31	1.466 (2)	C5—C6	1.353 (3)
N31—O32	1.209 (2)	C5—H5	0.95
N31—O31	1.213 (2)	C6—H6	0.95
C2—N1—C6	121.42 (19)	C3—C4—C5	116.50 (18)
C2—N1—H1	123.0 (16)	C4—O41—C42	118.42 (16)
C6—N1—H1	115.4 (16)	O41—C42—H421	109.5
N1—C2—C3	119.7 (2)	O41—C42—H422	109.5
N1—C2—H2	120.2	H421—C42—H422	109.5
C3—C2—H2	120.2	O41—C42—H423	109.5
C2—C3—C4	121.19 (17)	H421—C42—H423	109.5
C2—C3—N31	115.77 (18)	H422—C42—H423	109.5
C4—C3—N31	123.02 (17)	C6—C5—C4	119.58 (18)
O32—N31—O31	123.16 (18)	C6—C5—H5	120.2
O32—N31—C3	118.99 (18)	C4—C5—H5	120.2
O31—N31—C3	117.85 (18)	N1—C6—C5	121.63 (19)
O41—C4—C3	120.20 (17)	N1—C6—H6	119.2
O41—C4—C5	123.30 (17)	C5—C6—H6	119.2
C6—N1—C2—C3	−0.8 (3)	C2—C3—C4—C5	0.7 (3)
N1—C2—C3—C4	0.3 (3)	N31—C3—C4—C5	178.98 (16)
N1—C2—C3—N31	−178.12 (16)	C3—C4—O41—C42	173.49 (18)
C2—C3—N31—O32	−172.9 (2)	C5—C4—O41—C42	−5.8 (3)
C4—C3—N31—O32	8.7 (3)	O41—C4—C5—C6	178.18 (18)
C2—C3—N31—O31	6.2 (3)	C3—C4—C5—C6	−1.2 (3)
C4—C3—N31—O31	−172.20 (18)	C2—N1—C6—C5	0.3 (3)
C2—C3—C4—O41	−178.69 (17)	C4—C5—C6—N1	0.7 (3)
N31—C3—C4—O41	−0.4 (3)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···Cl1	0.94 (3)	2.05 (3)	2.974 (2)	167 (2)
C5—H5···Cl1^i	0.95	2.74	3.629 (2)	157
C6—H6···Cl1^ii	0.95	2.58	3.521 (2)	173

Symmetry codes: (i) x+1/2, −y−3/2, z+1/2; (ii) −x+1/2, y−1/2, −z+3/2.