Conformation of cationic N,N-di­methyl­glycine in di­methyl­glycinium tri­fluoro­acetate

In the title compound, C₄H₁₀NO₂⁺·C₂F₃O₂^-, the main N-C-COOH skeleton of the protonated amino acid is nearly planar. The C=O/C-N and C=O/O-H bonds are syn and the two methyl groups are gauche to the methyl­ene H atoms. The conformation of the cation in the crystal is compared to that given by ab initio calculations (Hartree-Fock, self-consistent field molecular-orbital theory). The tri­fluoro­acetate anion has the typical staggered conformation with usual bond distances and angles. The cation and anion form dimers through a strong O-H...O hydrogen bond which are further interconnected in infinite zigzag chains running parallel to the a axis by N-H...O bonds. Weaker C-H...O interactions involving the methyl groups and the carboxy O atoms of the cation occur between the chains.

Computing details

Data collection: CAD-4 Software (Enraf-Nonius, 1989); cell refinement: CAD-4 Software; data reduction: PLATON (Spek, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEPII (Johnson, 1976); software used to prepare material for publication: SHELXL97.

1-Carboxy-N,N-dimethylmethanaminium trifluoroacetate

Crystal data

C4H10NO2^+·C2F3O2^−	F(000) = 896
Mr = 217.15	Dx = 1.560 Mg m^−3
Orthorhombic, Pbca	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ac 2ab	Cell parameters from 25 reflections
a = 10.4286 (5) Å	θ = 7.6–15.2°
b = 12.1213 (12) Å	µ = 0.16 mm^−1
c = 14.6271 (18) Å	T = 293 K
V = 1849.0 (3) Å^3	Block, colourless
Z = 8	0.36 × 0.28 × 0.26 mm

Data collection

Enraf-Nonius CAD-4r diffractometer	Rint = 0.026
Radiation source: fine-focus sealed tube	θmax = 25.0°, θmin = 3.4°
Graphite monochromator	h = 0→12
profile data from ω–2θ scans	k = 0→14
2039 measured reflections	l = −17→17
1631 independent reflections	3 standard reflections every 180 min
1313 reflections with I > 2σ(I)	intensity decay: 6%

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.037	Only H-atom coordinates refined
wR(F^2) = 0.105	w = 1/[σ^2(Fo^2) + (0.0432P)^2 + 1.220P] where P = (Fo^2 + 2Fc^2)/3
S = 1.04	(Δ/σ)max < 0.001
1631 reflections	Δρmax = 0.32 e Å^−3
158 parameters	Δρmin = −0.22 e Å^−3
0 restraints	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0037 (8)

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	0.37422 (18)	0.75622 (16)	0.38316 (13)	0.0371 (4)
O1	0.47604 (14)	0.75224 (14)	0.33191 (10)	0.0510 (4)
H1	0.535 (3)	0.709 (2)	0.3570 (16)	0.061*
O2	0.36058 (14)	0.70971 (14)	0.45480 (10)	0.0553 (4)
C2	0.27260 (19)	0.83002 (17)	0.34297 (13)	0.0398 (5)
H2	0.307 (2)	0.9068 (19)	0.3403 (14)	0.048*
H3	0.249 (2)	0.8045 (17)	0.2844 (15)	0.048*
N	0.15551 (15)	0.83082 (13)	0.40050 (11)	0.0363 (4)
H4	0.177 (2)	0.8348 (17)	0.4561 (16)	0.044*
C3	0.0812 (2)	0.7265 (2)	0.39215 (16)	0.0493 (6)
H5	0.008 (3)	0.732 (2)	0.4314 (18)	0.074*
H6	0.139 (3)	0.665 (2)	0.4037 (18)	0.074*
H7	0.056 (3)	0.720 (2)	0.3287 (19)	0.074*
C4	0.0727 (3)	0.9279 (2)	0.3801 (2)	0.0608 (7)
H8	0.120 (3)	0.996 (3)	0.388 (2)	0.091*
H9	0.000 (3)	0.926 (3)	0.421 (2)	0.091*
H10	0.047 (3)	0.926 (3)	0.316 (2)	0.091*
C5	0.22586 (19)	0.91437 (16)	0.64755 (13)	0.0408 (5)
O3	0.2249 (2)	0.91227 (19)	0.73024 (11)	0.0897 (7)
O4	0.15583 (14)	0.86397 (13)	0.59241 (9)	0.0490 (4)
C6	0.3225 (2)	0.99420 (16)	0.60486 (13)	0.0435 (5)
F1	0.28285 (16)	1.09729 (11)	0.61338 (11)	0.0744 (5)
F2	0.34261 (17)	0.97713 (15)	0.51651 (9)	0.0856 (6)
F3	0.43645 (12)	0.99013 (13)	0.64460 (11)	0.0755 (5)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0375 (10)	0.0395 (10)	0.0344 (10)	−0.0002 (8)	−0.0015 (8)	−0.0020 (8)
O1	0.0397 (8)	0.0646 (10)	0.0487 (8)	0.0127 (7)	0.0076 (7)	0.0124 (7)
O2	0.0486 (9)	0.0751 (11)	0.0422 (8)	0.0115 (8)	0.0013 (7)	0.0188 (8)
C2	0.0396 (11)	0.0435 (11)	0.0363 (10)	0.0041 (9)	0.0041 (8)	0.0049 (8)
N	0.0389 (9)	0.0404 (9)	0.0297 (8)	0.0053 (7)	−0.0006 (7)	−0.0017 (7)
C3	0.0447 (12)	0.0551 (14)	0.0480 (12)	−0.0073 (10)	0.0037 (10)	−0.0074 (11)
C4	0.0564 (15)	0.0597 (15)	0.0664 (16)	0.0235 (13)	0.0065 (13)	0.0085 (13)
C5	0.0429 (11)	0.0414 (10)	0.0380 (10)	−0.0036 (9)	−0.0006 (9)	0.0013 (8)
O3	0.1116 (17)	0.1152 (16)	0.0422 (10)	−0.0578 (14)	−0.0038 (10)	0.0100 (9)
O4	0.0461 (8)	0.0570 (9)	0.0437 (8)	−0.0154 (7)	0.0035 (6)	−0.0059 (7)
C6	0.0465 (11)	0.0407 (11)	0.0433 (11)	−0.0056 (9)	−0.0006 (9)	−0.0032 (9)
F1	0.0865 (11)	0.0398 (7)	0.0970 (11)	0.0004 (7)	−0.0003 (9)	0.0074 (7)
F2	0.1044 (13)	0.0999 (12)	0.0526 (8)	−0.0531 (10)	0.0272 (8)	−0.0138 (8)
F3	0.0431 (8)	0.0829 (11)	0.1004 (11)	−0.0104 (7)	−0.0082 (8)	0.0027 (9)

Geometric parameters (Å, º)

C1—O2	1.198 (2)	C3—H6	0.97 (3)
C1—O1	1.301 (2)	C3—H7	0.97 (3)
C1—C2	1.506 (3)	C4—H8	0.97 (3)
O1—H1	0.89 (3)	C4—H9	0.97 (3)
C2—N	1.483 (2)	C4—H10	0.97 (3)
C2—H2	1.00 (2)	C5—O3	1.210 (2)
C2—H3	0.94 (2)	C5—O4	1.248 (2)
N—C3	1.488 (3)	C5—C6	1.530 (3)
N—C4	1.490 (3)	C6—F1	1.322 (2)
N—H4	0.84 (2)	C6—F3	1.324 (2)
C3—H5	0.96 (3)	C6—F2	1.325 (2)
O2—C1—O1	125.69 (19)	N—C3—H7	106.8 (16)
O2—C1—C2	122.49 (18)	H5—C3—H7	111 (2)
O1—C1—C2	111.81 (16)	H6—C3—H7	106 (2)
C1—O1—H1	110.4 (16)	N—C4—H8	110.4 (19)
N—C2—C1	111.21 (15)	N—C4—H9	108.1 (19)
N—C2—H2	108.3 (12)	H8—C4—H9	110 (3)
C1—C2—H2	108.4 (13)	N—C4—H10	109.1 (18)
N—C2—H3	107.8 (14)	H8—C4—H10	107 (3)
C1—C2—H3	109.9 (13)	H9—C4—H10	113 (3)
H2—C2—H3	111.3 (18)	O3—C5—O4	129.1 (2)
C2—N—C3	112.13 (16)	O3—C5—C6	115.25 (19)
C2—N—C4	111.63 (17)	O4—C5—C6	115.54 (17)
C3—N—C4	110.66 (19)	F1—C6—F3	105.93 (17)
C2—N—H4	109.3 (15)	F1—C6—F2	106.80 (18)
C3—N—H4	105.4 (15)	F3—C6—F2	106.26 (18)
C4—N—H4	107.5 (15)	F1—C6—C5	110.69 (18)
N—C3—H5	108.0 (17)	F3—C6—C5	112.85 (17)
N—C3—H6	108.7 (16)	F2—C6—C5	113.79 (16)
H5—C3—H6	116 (2)
O2—C1—C2—N	−3.2 (3)	O4—C5—C6—F1	102.9 (2)
O1—C1—C2—N	178.09 (16)	O3—C5—C6—F3	44.1 (3)
C1—C2—N—C3	−73.7 (2)	O4—C5—C6—F3	−138.58 (19)
C1—C2—N—C4	161.49 (19)	O3—C5—C6—F2	165.3 (2)
O3—C5—C6—F1	−74.4 (3)	O4—C5—C6—F2	−17.4 (3)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···O4^i	0.89 (3)	1.71 (3)	2.593 (2)	175 (3)
N—H4···O4	0.84 (2)	2.04 (2)	2.836 (2)	158 (2)
C3—H5···O2^ii	0.96 (3)	2.37 (3)	3.302 (3)	163 (2)
C3—H7···O1^iii	0.97 (3)	2.52 (3)	3.470 (3)	166 (2)

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