Trimethyl­ammonium bromide at 100 K

The title compound, C₃H₁₀N⁺·Br^-, is composed of hydrogen-bonded (CH₃)₃NH⁺ and Br^- ions. The N, Br and CH of one methyl substituent lie on a mirror plane that relates the two remaining CH₃ groups by symmetry.

Key indicators

• Single-crystal X-ray study
• T = 100 K
• Mean [sigma](N-C) = 0.006 Å
• R factor = 0.048
• wR factor = 0.050
• Data-to-parameter ratio = 17.3

checkCIF/PLATON results

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Alert level C
PLAT125_ALERT_4_C No _symmetry_space_group_name_Hall Given .......          ?
PLAT152_ALERT_1_C Supplied and Calc Volume s.u. Inconsistent .....          ?
PLAT164_ALERT_4_C Nr. of Refined C-H H-Atoms in Heavy-At Struct...          2

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   3 ALERT level C = Check and explain
   0 ALERT level G = General alerts; check

   1 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   0 ALERT type 2 Indicator that the structure model may be wrong or deficient
   0 ALERT type 3 Indicator that the structure quality may be low
   2 ALERT type 4 Improvement, methodology, query or suggestion

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Computing details

Data collection: CrysAlis CCD (Oxford Diffraction, 2002); cell refinement: CrysAlis RED (Oxford Diffraction, 2002); data reduction: CrysAlis RED; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: PLATON2002 (Spek, 2003) and ORTEP-3 (Farrugia, 1997, 2005); software used to prepare material for publication: SHELXL97.

Trimethylammonium bromide

Crystal data

C3H10N^+·Br^−	F(000) = 140
Mr = 140.03	Dx = 1.658 Mg m^−3
Monoclinic, P21/m	Mo Kα radiation, λ = 0.71073 Å
a = 5.349 (3) Å	Cell parameters from 407 reflections
b = 8.023 (4) Å	θ = 3.1–21.2°
c = 6.790 (3) Å	µ = 7.17 mm^−1
β = 105.70 (4)°	T = 100 K
V = 280.5 (2) Å^3	Needle, colourless
Z = 2	0.10 × 0.04 × 0.02 mm

Data collection

Oxford Diffraction Xcalibur diffractometer with Sapphire CCD detector	606 independent reflections
Radiation source: fine-focus sealed tube	449 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.071
Rotation method data acquisition using ω and φ scans	θmax = 26.4°, θmin = 4.3°
Absorption correction: analytical (CrysAlis RED; Oxford Diffraction, 2002)	h = −6→5
Tmin = 0.534, Tmax = 0.870	k = −9→10
2059 measured reflections	l = −6→8

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)] = 0.048	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.050	H atoms treated by a mixture of independent and constrained refinement
S = 0.89	w = 1/[σ^2(Fo^2) + (0.0093P)^2] where P = (Fo^2 + 2Fc^2)/3
606 reflections	(Δ/σ)max < 0.001
35 parameters	Δρmax = 1.24 e Å^−3
0 restraints	Δρmin = −0.68 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
C1	0.2742 (14)	0.2500	0.3723 (12)	0.023 (2)
H1A	0.162 (8)	0.161 (5)	0.339 (6)	0.028*
H1C	0.389 (11)	0.2500	0.500 (9)	0.028*
C2	0.5910 (8)	0.0983 (5)	0.2397 (6)	0.0184 (13)
H2A	0.7170	0.0953	0.3747	0.022*
H2B	0.6834	0.0988	0.1333	0.022*
H2C	0.4788	−0.0002	0.2230	0.022*
Br1	0.03998 (15)	0.7500	0.19962 (11)	0.0199 (2)
N1	0.4311 (10)	0.2500	0.2219 (7)	0.0133 (15)
H1D	0.326 (10)	0.2500	0.091 (8)	0.016*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.012 (5)	0.029 (6)	0.027 (5)	0.000	0.002 (4)	0.000
C2	0.016 (3)	0.017 (3)	0.018 (3)	0.000 (2)	−0.003 (2)	−0.004 (2)
Br1	0.0151 (4)	0.0215 (4)	0.0195 (4)	0.000	−0.0020 (3)	0.000
N1	0.008 (3)	0.019 (4)	0.012 (3)	0.000	−0.001 (3)	0.000

Geometric parameters (Å, º)

C1—N1	1.487 (8)	C2—H2B	0.9800
C1—H1A	0.92 (4)	C2—H2C	0.9800
C1—H1C	0.91 (6)	N1—C2^i	1.474 (4)
C2—N1	1.474 (4)	N1—H1D	0.91 (5)
C2—H2A	0.9800
N1—C1—H1A	107 (3)	H2B—C2—H2C	109.5
N1—C1—H1C	107 (4)	C2^i—N1—C2	111.4 (5)
H1A—C1—H1C	117 (3)	C2^i—N1—C1	111.5 (3)
N1—C2—H2A	109.5	C2—N1—C1	111.5 (3)
N1—C2—H2B	109.5	C2^i—N1—H1D	105.7 (17)
H2A—C2—H2B	109.5	C2—N1—H1D	105.7 (17)
N1—C2—H2C	109.5	C1—N1—H1D	111 (3)
H2A—C2—H2C	109.5

Symmetry code: (i) x, −y+1/2, z.