2-Amino-4-methyl­benzothia­zole

The title compound, C₈H₈N₂S, was crystallized from heptane with a minimal amount of toluene. The crystal structure is stabilized by inter­molecular N—H...N and N—H...S hydrogen bonds. The crystal structure viewed down the b axis shows the mol­ecules packed in a bilayer fashion, with alternating hydro­philic and hydro­phobic regions.

Key indicators

• Single-crystal X-ray study
• T = 208 K
• Mean [sigma](C-C) = 0.004 Å
• R factor = 0.047
• wR factor = 0.133
• Data-to-parameter ratio = 16.0

checkCIF/PLATON results

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Alert level C
PLAT322_ALERT_2_C Check Hybridisation of  S      in Main Residue .          ?

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   0 ALERT level B = Potentially serious problem
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   0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
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S1. Comment

The crystal structures of 2-amino-6-fluorobenzothiazole (Jai-nhuknan et al., 1997) and 2-aminobenzothiazole (Goubitz et al., 2001) have been described in the literature. Herein we report the molecular and crystal structure of the title compound (Fig. 1).

The benzothiazole unit is essentially planar, with the a mean deviation of 0.0095 Å from the least-squares plane defined by the nine constituent atoms. The molecular packing is stabilized by N—H···N hydrogen bonds between a H atom of amino group and the N atom of thiazole ring, i.e. N2—H2A···N1ⁱ (Table 1 and Fig. 2). The molecular packing is further stabilized by N—H···S interactions between a H atom of amino group and the S atom of thiazole ring, i.e. N2—H2B···Sⁱⁱ (Table 1 and Fig. 2). The crystal structure viewed down the b axis shows the molecules packed in a bilayer fashion, with alternating hydrophilic and hydrophobic regions (Fig. 2). The geometry of the benzothiazole ring is consistent with other 2-aminobenzothiazoles included in the Cambridge Crystallographic Data Base. The C1—S and C7—S bond distances of 1.773 (3) Å and 1.739 (3) Å respectively, are in between the 1.81 Å average distance for a carbon-sulfur single bond and the 1.61 Å average distance for a carbon-sulfur double bond; this is typical for benzothiazoles.

Related literature

For the crystal structures of similar 2-aminobenzothiazole compounds, see: Jai-nhuknan et al. (1997); Goubitz et al. (2001).

S2. Experimental

A commercial sample of 2-amino-4-methylbenzothiazole was used. Single crystals were obtained by slow evaporation of a heptane solution of a minimal amount of toluene over 24 h.

S3. Refinement

All H atoms were positioned geometrically and refined using a riding model, with C—H = 0.93 Å for aromatic H atoms, 0.96 Å for methyl H atoms and 0.86 Å for amino H atoms, respectively, and with U_iso(H) = 1.2Ueq(C) for aromatic, U_iso(H) = 1.5Ueq(C) for methyl and 1.2Ueq(N) for amino H atoms.

Computing details

Data collection: APEX2 (Bruker, 2006); cell refinement: APEX2 (Bruker, 2006); data reduction: APEX2 (Bruker, 2006); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: CRYSTALS (Betteridge et al., 2003); molecular graphics: CRYSTALS (Betteridge et al., 2003); software used to prepare material for publication: CAMERON (Watkin et al., 1996).

Figures

	Fig. 1. The molecular structure of the title compound, showing displacement ellipsoids drawn at the 30% probability level.
	Fig. 2. N—H···H and N—H···S hydrogen bonds (dotted lines) in the title compound. [Symmetry codes: (i) -x + 2, -y + 1, -z + 1; (ii) -x + 2, y - 1/2, -z + 3/2.]

2-Amino-4-methylbenzothiazole

Crystal data

C8H8N2S	F(000) = 344
Mr = 164.22	Dx = 1.421 Mg m^−3
Monoclinic, P21/c	Melting point: 410 K
Hall symbol: -P 2ybc	Mo Kα radiation, λ = 0.71073 Å
a = 12.860 (4) Å	Cell parameters from 1578 reflections
b = 3.931 (1) Å	θ = 3.0–26.7°
c = 15.208 (5) Å	µ = 0.35 mm^−1
β = 92.968 (5)°	T = 208 K
V = 767.8 (4) Å^3	Plate, colorless
Z = 4	0.20 × 0.20 × 0.05 mm

Data collection

Bruker SMART diffractometer	1620 independent reflections
Radiation source: fine-focus sealed tube	1214 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.044
Detector resolution: 10.0 pixels mm^-1	θmax = 27.0°, θmin = 1.6°
ω/2θ scans	h = −15→16
Absorption correction: multi-scan (APEX2; Bruker, 2006)	k = −2→4
Tmin = 0.93, Tmax = 0.98	l = −15→19
4667 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)] = 0.047	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.133	H-atom parameters constrained
S = 1.06	w = 1/[σ^2(Fo^2) + (0.067P)^2 + 0.1789P] where P = (Fo^2 + 2Fc^2)/3
1620 reflections	(Δ/σ)max < 0.001
101 parameters	Δρmax = 0.38 e Å^−3
0 restraints	Δρmin = −0.27 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
S	0.88006 (5)	0.19348 (17)	0.71306 (4)	0.0340 (2)
N1	0.87146 (16)	0.4635 (5)	0.55501 (12)	0.0304 (5)
N2	1.03526 (18)	0.2365 (6)	0.60024 (14)	0.0404 (6)
H2A	1.0624	0.2938	0.5519	0.048*
H2B	1.0724	0.1338	0.6407	0.048*
C1	0.9346 (2)	0.3079 (7)	0.61254 (16)	0.0320 (6)
C2	0.77322 (19)	0.4973 (6)	0.58816 (15)	0.0283 (6)
C3	0.6867 (2)	0.6432 (6)	0.54202 (16)	0.0311 (6)
C4	0.5937 (2)	0.6539 (7)	0.58380 (18)	0.0375 (7)
H4	0.5356	0.7498	0.5545	0.045*
C7	0.7623 (2)	0.3662 (6)	0.67334 (16)	0.0297 (6)
C8	0.6993 (2)	0.7835 (7)	0.45000 (17)	0.0356 (6)
H8A	0.6332	0.8621	0.4259	0.053*
H8B	0.7250	0.6075	0.4131	0.053*
H8C	0.7478	0.9693	0.4529	0.053*
C6	0.6684 (2)	0.3798 (7)	0.71419 (17)	0.0369 (7)
H6	0.6623	0.2935	0.7706	0.044*
C5	0.5843 (2)	0.5256 (7)	0.66839 (19)	0.0398 (7)
H5	0.5205	0.5384	0.6944	0.048*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
S	0.0405 (4)	0.0345 (4)	0.0267 (4)	−0.0020 (3)	−0.0010 (3)	0.0031 (3)
N1	0.0348 (12)	0.0320 (11)	0.0240 (11)	0.0005 (10)	−0.0015 (9)	0.0003 (9)
N2	0.0396 (14)	0.0531 (15)	0.0281 (12)	0.0104 (11)	−0.0015 (10)	0.0077 (10)
C1	0.0389 (15)	0.0308 (13)	0.0262 (13)	0.0003 (11)	0.0001 (11)	−0.0018 (10)
C2	0.0326 (14)	0.0256 (13)	0.0266 (13)	−0.0011 (11)	0.0004 (10)	−0.0044 (10)
C3	0.0357 (14)	0.0270 (13)	0.0301 (13)	0.0036 (11)	−0.0031 (11)	−0.0029 (11)
C4	0.0358 (16)	0.0334 (14)	0.0426 (16)	0.0038 (12)	−0.0041 (13)	−0.0064 (12)
C7	0.0355 (15)	0.0252 (13)	0.0279 (13)	−0.0037 (11)	−0.0019 (11)	−0.0031 (10)
C8	0.0419 (16)	0.0318 (14)	0.0318 (14)	0.0081 (12)	−0.0109 (12)	0.0032 (11)
C6	0.0449 (17)	0.0351 (15)	0.0312 (14)	−0.0062 (13)	0.0073 (12)	−0.0039 (11)
C5	0.0332 (15)	0.0392 (15)	0.0476 (17)	−0.0015 (13)	0.0077 (13)	−0.0081 (13)

Geometric parameters (Å, º)

S—C7	1.739 (3)	C3—C8	1.521 (4)
S—C1	1.773 (3)	C4—C5	1.393 (4)
N1—C1	1.314 (3)	C4—H4	0.9300
N1—C2	1.391 (3)	C7—C6	1.388 (4)
N2—C1	1.347 (3)	C8—H8A	0.9600
N2—H2A	0.8600	C8—H8B	0.9600
N2—H2B	0.8600	C8—H8C	0.9600
C2—C3	1.406 (3)	C6—C5	1.380 (4)
C2—C7	1.408 (3)	C6—H6	0.9300
C3—C4	1.384 (4)	C5—H5	0.9300
C7—S—C1	88.74 (12)	C5—C4—H4	118.9
C1—N1—C2	110.2 (2)	C6—C7—C2	121.9 (2)
C1—N2—H2A	120.0	C6—C7—S	128.5 (2)
C1—N2—H2B	120.0	C2—C7—S	109.61 (19)
H2A—N2—H2B	120.0	C3—C8—H8A	109.5
N1—C1—N2	124.7 (2)	C3—C8—H8B	109.5
N1—C1—S	115.7 (2)	H8A—C8—H8B	109.5
N2—C1—S	119.55 (19)	C3—C8—H8C	109.5
N1—C2—C3	124.6 (2)	H8A—C8—H8C	109.5
N1—C2—C7	115.8 (2)	H8B—C8—H8C	109.5
C3—C2—C7	119.6 (2)	C5—C6—C7	117.9 (3)
C4—C3—C2	117.6 (2)	C5—C6—H6	121.1
C4—C3—C8	123.2 (2)	C7—C6—H6	121.1
C2—C3—C8	119.2 (2)	C6—C5—C4	120.9 (3)
C3—C4—C5	122.1 (3)	C6—C5—H5	119.6
C3—C4—H4	118.9	C4—C5—H5	119.6
C2—N1—C1—N2	−180.0 (2)	C8—C3—C4—C5	−179.6 (2)
C2—N1—C1—S	−0.8 (3)	N1—C2—C7—C6	−179.4 (2)
C7—S—C1—N1	0.6 (2)	C3—C2—C7—C6	−0.8 (4)
C7—S—C1—N2	179.9 (2)	N1—C2—C7—S	−0.1 (3)
C1—N1—C2—C3	−178.0 (2)	C3—C2—C7—S	178.53 (18)
C1—N1—C2—C7	0.6 (3)	C1—S—C7—C6	179.0 (3)
N1—C2—C3—C4	179.1 (2)	C1—S—C7—C2	−0.28 (19)
C7—C2—C3—C4	0.6 (4)	C2—C7—C6—C5	0.4 (4)
N1—C2—C3—C8	−1.4 (4)	S—C7—C6—C5	−178.8 (2)
C7—C2—C3—C8	−179.9 (2)	C7—C6—C5—C4	0.1 (4)
C2—C3—C4—C5	−0.1 (4)	C3—C4—C5—C6	−0.3 (4)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N2—H2A···N1^i	0.86	2.10	2.949 (3)	168
N2—H2B···S^ii	0.86	2.86	3.672 (2)	158

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