2-Picoline

The crystal structure of 2-picoline (2-methyl­pyridine, C₆H₇N) has been determined at 120 (2) K following in situ crystal growth from the liquid. Molecules pack in a herring-bone-type arrangement in the non-centrosymmetric space group P2₁2₁2₁, with C—H...N contacts indicative of directional hydrogen bonds.

Key indicators

• Single-crystal X-ray study
• T = 120 K
• Mean [sigma](C-C) = 0.003 Å
• Disorder in main residue
• R factor = 0.062
• wR factor = 0.181
• Data-to-parameter ratio = 10.5

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry


 Alert Level C:



RINTA_01  Alert C The value of Rint is greater than 0.10
          Rint given   0.109

PLAT_302  Alert C Anion/Solvent Disorder .......................      12.00 Perc.

General Notes



REFLT_03
         From the CIF: _diffrn_reflns_theta_max           27.46
         From the CIF: _reflns_number_total                749
         Count of symmetry unique reflns          762
         Completeness (_total/calc)             98.29%
         TEST3: Check Friedels for noncentro structure
         Estimate of Friedel pairs measured         0
         Fraction of Friedel pairs measured     0.000
         Are heavy atom types Z>Si present           no
          Please check that the estimate of the number of Friedel pairs is
          correct. If it is not, please give the correct count in the
          _publ_section_exptl_refinement section of the submitted CIF.


 0 Alert Level A = Potentially serious problem

 0 Alert Level B = Potential problem

 2 Alert Level C = Please check

---

S1. Comment

The picolines (methylpyridines) comprise a series of empirical formula C₆H₇N, with weak intermolecular interactions and low melting points. The crystal structure of 4-picoline (4-methylpyridine; m.p. 276 K) has been determined previously from a crystal grown using an elaborate modified Bridgman technique (Ohms et al., 1985). We report here the crystal structure of 2-picoline (m.p. 206 K), determined at 120 (2) K from a crystal grown in situ in a 0.3 mm glass capillary. This work forms part of a study devoted to improving techniques for determining the crystal structures of substances that are liquids at room temperature (see, for example, Bond & Davies, 2001).

Molecules of (I) (Fig. 1) pack in a herring-bone-type arrangement (Fig. 2) in the non-centrosymmetric space group P2₁2₁2₁. Between molecules, C—H···N contacts exist that are close to linear [H4···N1ⁱ = 2.60 Å and C4—H4···N1ⁱ = 146.6°; H6···N1ⁱⁱ = 2.79 Å and C6—H6···N1ⁱⁱ = 170.1°; symmetry codes: (i) 0.5 - x, -y, 0.5 + z; (ii) -0.5 + x, -y, -z], indicative of directional hydrogen bonds.

S2. Experimental

The sample (99%) was obtained from the Aldrich Company and was used without further purification. The crystal was grown in a 0.3 mm glass capillary tube at 206 K (a temperature only slightly less than the melting point of the solid in the capillary tube) using a technique described previously (Davies & Bond, 2001). The crystal was subsequently cooled to 120 (2) K for data collection. The length of the cylindrical crystal was not estimated, but it exceeded the diameter of the collimator (0.35 mm).

S3. Refinement

The methyl H atoms are disordered and modelled as two sets of idealized positions. All H atoms were placed geometrically and allowed to refine with independent isotropic displacement parameters (one common parameter for all methyl H atoms). The methyl groups were allowed to rotate about its local threefold axis. Friedel pairs (486) were merged prior to merging in P2₁2₁2₁; the reported value of R_int corresponds to subsequent merging of equivalent reflections in this space group.

Computing details

Data collection: COLLECT (Nonius, 1998); cell refinement: HKL SCALEPACK (Otwinowski & Minor, 1997); data reduction: HKL DENZO (Otwinowski & Minor 1997) and SCALEPACK; program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); software used to prepare material for publication: SHELXL97.

Figures

	Fig. 1. The molecular structure and atom-labelling scheme for (I) showing displacement ellipsoids at the 50% probability level for non-H atoms (XP; Sheldrick, 1993). Disorder of the H atoms in the methyl group has been omitted for clarity.
	Fig. 2. Projection onto (001) showing the herring-bone packing in (I) (CAMERON; Watkin et al., 1996). C—H···N interactions are shown as dotted lines.

2-methylpyridine

Crystal data

C6H7N	Dx = 1.117 Mg m^−3
Mr = 93.13	Melting point: 206.3 K
Orthorhombic, P212121	Mo Kα radiation, λ = 0.7107 Å
a = 6.6593 (5) Å	Cell parameters from 4571 reflections
b = 7.0878 (6) Å	θ = 1.0–27.5°
c = 11.7358 (7) Å	µ = 0.07 mm^−1
V = 553.93 (7) Å^3	T = 120 K
Z = 4	Cylinder, colourless
F(000) = 200	0.15 mm (radius)

Data collection

Nonius KappaCCD diffractometer	Rint = 0.110
Radiation source: fine-focus sealed tube	θmax = 27.5°, θmin = 3.5°
Thin–slice ω and ϕ scans	h = −4→8
3477 measured reflections	k = −9→7
749 independent reflections	l = −15→10
672 reflections with I > 2σ(I)

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)] = 0.062	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.181	H atoms treated by a mixture of independent and constrained refinement
S = 1.10	w = 1/[σ^2(Fo^2) + (0.1425P)^2] where P = (Fo^2 + 2Fc^2)/3
749 reflections	(Δ/σ)max < 0.001
71 parameters	Δρmax = 0.29 e Å^−3
0 restraints	Δρmin = −0.29 e Å^−3

Special details

Experimental. Grown in situ in a 0.3 mm Lindemann capillary tube at 206 K. Freidel pairs (486) were averaged for the refinement.

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	Occ. (<1)
N1	0.3417 (3)	0.0686 (3)	0.05357 (16)	0.0301 (5)
C2	0.4756 (3)	−0.0479 (3)	0.10232 (18)	0.0275 (6)
C3	0.4444 (4)	−0.1249 (3)	0.2101 (2)	0.0335 (6)
H3	0.5432	−0.2040	0.2437	0.071 (12)*
C4	0.2683 (4)	−0.0852 (3)	0.26800 (19)	0.0382 (6)
H4	0.2440	−0.1368	0.3414	0.067 (10)*
C5	0.1293 (4)	0.0306 (3)	0.2168 (2)	0.0356 (6)
H5	0.0061	0.0592	0.2539	0.048 (8)*
C6	0.1716 (4)	0.1045 (3)	0.1109 (2)	0.0337 (6)
H6	0.0751	0.1852	0.0765	0.038 (7)*
C7	0.6606 (4)	−0.0923 (4)	0.0342 (2)	0.0408 (7)	0.80
H7A	0.7359	0.0242	0.0201	0.060 (7)*	0.80
H7B	0.6217	−0.1490	−0.0386	0.060 (7)*	0.80
H7C	0.7449	−0.1810	0.0768	0.060 (7)*	0.80
C7'	0.6606 (4)	−0.0923 (4)	0.0342 (2)	0.0408 (7)	0.20
H7A'	0.6776	0.0026	−0.0257	0.060 (7)*	0.20
H7B'	0.6468	−0.2174	−0.0004	0.060 (7)*	0.20
H7C'	0.7781	−0.0910	0.0845	0.060 (7)*	0.20

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
N1	0.0279 (9)	0.0357 (10)	0.0268 (9)	−0.0009 (9)	−0.0039 (7)	0.0014 (7)
C2	0.0274 (10)	0.0255 (9)	0.0295 (10)	−0.0020 (9)	−0.0028 (9)	−0.0017 (8)
C3	0.0391 (12)	0.0275 (11)	0.0339 (11)	0.0009 (9)	−0.0076 (10)	0.0032 (8)
C4	0.0492 (14)	0.0361 (12)	0.0293 (11)	−0.0055 (12)	0.0022 (10)	0.0033 (10)
C5	0.0308 (11)	0.0399 (12)	0.0360 (12)	−0.0027 (10)	0.0050 (9)	−0.0041 (10)
C6	0.0255 (10)	0.0352 (11)	0.0405 (12)	0.0005 (10)	−0.0036 (10)	0.0033 (10)
C7	0.0321 (11)	0.0448 (13)	0.0456 (14)	0.0058 (11)	0.0036 (11)	−0.0012 (11)
C7'	0.0321 (11)	0.0448 (13)	0.0456 (14)	0.0058 (11)	0.0036 (11)	−0.0012 (11)

Geometric parameters (Å, º)

N1—C6	1.341 (3)	C4—H4	0.9500
N1—C2	1.343 (3)	C5—C6	1.379 (3)
C2—C3	1.394 (3)	C5—H5	0.9500
C2—C7	1.502 (3)	C6—H6	0.9500
C3—C4	1.384 (3)	C7—H7A	0.9800
C3—H3	0.9500	C7—H7B	0.9800
C4—C5	1.375 (4)	C7—H7C	0.9800
C6—N1—C2	117.6 (2)	C4—C5—C6	118.9 (2)
N1—C2—C3	121.9 (2)	C4—C5—H5	120.6
N1—C2—C7	116.5 (2)	C6—C5—H5	120.6
C3—C2—C7	121.6 (2)	N1—C6—C5	123.6 (2)
C4—C3—C2	119.5 (2)	N1—C6—H6	118.2
C4—C3—H3	120.3	C5—C6—H6	118.2
C2—C3—H3	120.3	C2—C7—H7A	109.5
C5—C4—C3	118.5 (2)	C2—C7—H7B	109.5
C5—C4—H4	120.7	C2—C7—H7C	109.5
C3—C4—H4	120.7
C6—N1—C2—C3	−2.1 (3)	C2—C3—C4—C5	−0.3 (3)
C6—N1—C2—C7	177.44 (18)	C3—C4—C5—C6	−0.8 (4)
N1—C2—C3—C4	1.8 (3)	C2—N1—C6—C5	0.9 (3)
C7—C2—C3—C4	−177.7 (2)	C4—C5—C6—N1	0.5 (4)