(R)-(3-Carb­oxy-2-hy­droxy­prop­yl)tri­methyl­aza­nium chloride

Abstract

In the title salt (common name l-carnitine hydro­chloride), C₇H₁₆NO₃ ⁺·Cl⁻, the organic cation features a carb­oxy­lic part (–CO₂H) having unambigous single- and double-bonds [1.336 (2), 1.211 (2) Å]. There is a large N—C—C bond angle [115.9 (1)°] for the C atom connected to the bulky trimethyl­amino substituent. In the crystal, the acid H atom forms a hydrogen bond to the chloride anion, whereas the hydroxyl H atom forms a longer hydrogen bond to the anion, generating a helical chain running along [001].

Related literature  

For racemic carnitine hydro­chloride, see: Tomita et al. (1974 ▶); Yunuskhodzhaev et al. (1991 ▶). For R-carnitine, see: Gandour et al. (1985 ▶).

Experimental  

Crystal data  

• C₇H₁₆NO₃ ⁺·Cl⁻

• M _r = 197.66

• Orthorhombic,

• a = 6.3043 (3) Å

• b = 11.5256 (7) Å

• c = 13.4905 (8) Å

• V = 980.23 (10) ų

• Z = 4

• Mo Kα radiation

• μ = 0.36 mm⁻¹

• T = 100 K

• 0.40 × 0.30 × 0.20 mm

Data collection  

• Agilent Technologies SuperNova Dual diffractometer with Atlas detector

• Absorption correction: multi-scan CrysAlis PRO (Agilent, 2012 ▶) T _min = 0.869, T _max = 0.931

• 6682 measured reflections

• 2251 independent reflections

• 2191 reflections with I > 2σ(I)

• R _int = 0.033

Refinement  

• R[F ² > 2σ(F ²)] = 0.027

• wR(F ²) = 0.072

• S = 1.09

• 2251 reflections

• 117 parameters

• 2 restraints

• H atoms treated by a mixture of independent and constrained refinement

• Δρ_max = 0.28 e Å⁻³

• Δρ_min = −0.19 e Å⁻³

• Absolute structure: Flack (1983 ▶), 926 Friedel pairs

• Flack parameter: 0.01 (5)

Data collection: CrysAlis PRO (Agilent, 2012 ▶); cell refinement: CrysAlis PRO; data reduction: CrysAlis PRO; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: X-SEED (Barbour, 2001 ▶); software used to prepare material for publication: publCIF (Westrip, 2010 ▶).

Supplementary Material

Supplementary material file. DOI: 10.1107/S160053681201598X/xu5512Isup3.cml

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O1—H1⋯Cl1	0.85 (1)	2.18 (1)	3.022 (1)	176 (2)
O3—H3⋯Cl1i	0.83 (1)	2.51 (2)	3.209 (1)	142 (2)

Symmetry code: (i) .

supplementary crystallographic information

Comment

A model for the binding of L-carnitine to the carnitine acetyltransferase enzyme has been proposed on the basis of the crystal structure of L-carnitine (Gandour et al., 1985). L-Carnitine, a zwitterionic compound that is biosynthesized from lysine and methinonine, is the vitamin B_T; it is also avaliable commerically as the hydrochloride salt. The crystal structure of racemic carnitine hydrochloride has been previously reported (Tomita et al., 1974; Yunuskhodzhaev et al., 1991). In the crystal structure of L-carnitine hydrochloride (Scheme I), the carboxyl –CO₂ part carries the acid hydrogen (Fig. 1). This part has unambigous single- and double-bonds [1.336 (2), 1.211 (2) Å]. The three-atom C_carboxyl–C–C_{trimethylamino} unit shows a large angle [115.9 (1) °] for the atom connected to the bulky trimethylamino substituent. The acid hydrogen forms a hydrogen bond to the chloride anion (Table 1). Oddly, the hydroxy group does not engage in any hydrogen bonding interactions.

Experimental

L-Carnithine hydrochloride as supplied by Sigma Chemical Company consists of colorless prismatic crystals, and was used without purification.

Refinement

Carbon-bound H-atoms were placed in calculated positions [C–H 0.98 to 1.00 Å, U_iso(H) 1.2 to 1.5U_eq(C)] and were included in the refinement in the riding model approximation.

The hydroxy and acid H-atoms were located in a difference Fourier map, and were refined with a distance restraint of O–H 0.84±0.01 Å; their temperature factors were refined.

Figures

Fig. 1.

Thermal ellipsoid plot (Barbour, 2001) of C7H16NO3+.Cl- at the 70% probability level; hydrogen atoms are drawn as spheres of arbitrary radius.

Crystal data

C7H16NO3+·Cl−	F(000) = 424
Mr = 197.66	Dx = 1.339 Mg m−3
Orthorhombic, P212121	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2ac 2ab	Cell parameters from 3837 reflections
a = 6.3043 (3) Å	θ = 2.3–27.5°
b = 11.5256 (7) Å	µ = 0.36 mm−1
c = 13.4905 (8) Å	T = 100 K
V = 980.23 (10) Å3	Prism, colorless
Z = 4	0.40 × 0.30 × 0.20 mm

Data collection

Agilent Technologies SuperNova Dual diffractometer with Atlas detector	2251 independent reflections
Radiation source: SuperNova (Mo) X-ray Source	2191 reflections with I > 2σ(I)
Mirror monochromator	Rint = 0.033
Detector resolution: 10.4041 pixels mm-1	θmax = 27.5°, θmin = 2.3°
ω scan	h = −8→8
Absorption correction: multi-scan CrysAlis PRO (Agilent, 2012)	k = −12→15
Tmin = 0.869, Tmax = 0.931	l = −16→17
6682 measured reflections

Refinement

Refinement on F2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.027	H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.072	w = 1/[σ2(Fo2) + (0.0381P)2 + 0.129P] where P = (Fo2 + 2Fc2)/3
S = 1.09	(Δ/σ)max = 0.001
2251 reflections	Δρmax = 0.28 e Å−3
117 parameters	Δρmin = −0.19 e Å−3
2 restraints	Absolute structure: Flack (1983), 926 Friedel pairs
Primary atom site location: structure-invariant direct methods	Flack parameter: 0.01 (5)

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

	x	y	z	Uiso*/Ueq
Cl1	0.16829 (6)	−0.02923 (3)	1.11989 (3)	0.01599 (10)
O1	0.11377 (16)	0.20168 (9)	1.01683 (8)	0.0153 (2)
H1	0.123 (3)	0.1372 (11)	1.0468 (14)	0.032 (6)*
O2	0.09374 (17)	0.09692 (9)	0.87751 (9)	0.0164 (2)
O3	0.03544 (17)	0.23605 (10)	0.69856 (8)	0.0146 (2)
H3	0.066 (4)	0.1658 (10)	0.6948 (18)	0.047 (7)*
N1	0.38932 (18)	0.40990 (10)	0.62406 (10)	0.0107 (2)
C1	0.1083 (2)	0.19013 (12)	0.91830 (11)	0.0113 (3)
C2	0.1258 (2)	0.30406 (12)	0.86490 (11)	0.0120 (3)
H2A	0.2287	0.3542	0.9001	0.014*
H2B	−0.0138	0.3435	0.8659	0.014*
C3	0.1976 (2)	0.28843 (12)	0.75711 (10)	0.0103 (3)
H3A	0.3279	0.2390	0.7552	0.012*
C4	0.2485 (2)	0.40787 (13)	0.71538 (11)	0.0109 (3)
H4A	0.1132	0.4470	0.6989	0.013*
H4B	0.3182	0.4540	0.7680	0.013*
C5	0.6024 (2)	0.35642 (13)	0.64467 (12)	0.0151 (3)
H5A	0.6887	0.3582	0.5843	0.023*
H5B	0.5834	0.2758	0.6661	0.023*
H5C	0.6741	0.4003	0.6971	0.023*
C6	0.2902 (3)	0.35091 (15)	0.53684 (11)	0.0198 (4)
H6A	0.3867	0.3552	0.4800	0.030*
H6B	0.1563	0.3895	0.5203	0.030*
H6C	0.2628	0.2694	0.5531	0.030*
C7	0.4241 (3)	0.53502 (13)	0.59814 (12)	0.0187 (3)
H7A	0.5126	0.5402	0.5386	0.028*
H7B	0.4954	0.5742	0.6533	0.028*
H7C	0.2871	0.5723	0.5856	0.028*

Atomic displacement parameters (Ų)

	U11	U22	U33	U12	U13	U23
Cl1	0.02265 (18)	0.01262 (16)	0.01271 (18)	0.00108 (14)	0.00145 (14)	0.00228 (14)
O1	0.0237 (6)	0.0118 (5)	0.0104 (5)	0.0005 (5)	0.0008 (4)	0.0021 (4)
O2	0.0218 (5)	0.0124 (5)	0.0150 (5)	−0.0037 (4)	−0.0005 (5)	−0.0013 (4)
O3	0.0161 (5)	0.0142 (5)	0.0135 (6)	−0.0021 (5)	−0.0049 (4)	−0.0009 (4)
N1	0.0103 (6)	0.0117 (5)	0.0102 (6)	0.0002 (5)	0.0010 (5)	0.0014 (5)
C1	0.0073 (6)	0.0149 (7)	0.0118 (7)	0.0007 (6)	0.0006 (5)	0.0008 (6)
C2	0.0126 (7)	0.0121 (6)	0.0112 (7)	0.0013 (6)	0.0002 (5)	0.0003 (5)
C3	0.0095 (6)	0.0109 (6)	0.0106 (7)	0.0008 (5)	−0.0011 (5)	0.0004 (6)
C4	0.0114 (6)	0.0115 (6)	0.0099 (7)	0.0010 (6)	0.0024 (5)	0.0004 (6)
C5	0.0118 (7)	0.0180 (7)	0.0155 (8)	0.0044 (6)	0.0011 (6)	0.0008 (6)
C6	0.0210 (8)	0.0305 (9)	0.0081 (8)	−0.0080 (7)	−0.0022 (6)	−0.0002 (6)
C7	0.0167 (7)	0.0134 (7)	0.0260 (9)	−0.0003 (7)	0.0062 (6)	0.0078 (7)

Geometric parameters (Å, º)

O1—C1	1.3363 (18)	C3—C4	1.521 (2)
O1—H1	0.848 (9)	C3—H3A	1.0000
O2—C1	1.2105 (18)	C4—H4A	0.9900
O3—C3	1.4262 (18)	C4—H4B	0.9900
O3—H3	0.833 (9)	C5—H5A	0.9800
N1—C6	1.4956 (19)	C5—H5B	0.9800
N1—C7	1.5000 (19)	C5—H5C	0.9800
N1—C5	1.5042 (18)	C6—H6A	0.9800
N1—C4	1.5188 (18)	C6—H6B	0.9800
C1—C2	1.5018 (19)	C6—H6C	0.9800
C2—C3	1.534 (2)	C7—H7A	0.9800
C2—H2A	0.9900	C7—H7B	0.9800
C2—H2B	0.9900	C7—H7C	0.9800
C1—O1—H1	112.9 (14)	N1—C4—H4A	108.3
C3—O3—H3	106.3 (18)	C3—C4—H4A	108.3
C6—N1—C7	108.35 (12)	N1—C4—H4B	108.3
C6—N1—C5	109.41 (12)	C3—C4—H4B	108.3
C7—N1—C5	107.84 (12)	H4A—C4—H4B	107.4
C6—N1—C4	112.76 (11)	N1—C5—H5A	109.5
C7—N1—C4	106.82 (11)	N1—C5—H5B	109.5
C5—N1—C4	111.47 (11)	H5A—C5—H5B	109.5
O2—C1—O1	122.86 (14)	N1—C5—H5C	109.5
O2—C1—C2	124.29 (14)	H5A—C5—H5C	109.5
O1—C1—C2	112.83 (12)	H5B—C5—H5C	109.5
C1—C2—C3	111.95 (11)	N1—C6—H6A	109.5
C1—C2—H2A	109.2	N1—C6—H6B	109.5
C3—C2—H2A	109.2	H6A—C6—H6B	109.5
C1—C2—H2B	109.2	N1—C6—H6C	109.5
C3—C2—H2B	109.2	H6A—C6—H6C	109.5
H2A—C2—H2B	107.9	H6B—C6—H6C	109.5
O3—C3—C4	109.21 (11)	N1—C7—H7A	109.5
O3—C3—C2	111.29 (11)	N1—C7—H7B	109.5
C4—C3—C2	107.87 (11)	H7A—C7—H7B	109.5
O3—C3—H3A	109.5	N1—C7—H7C	109.5
C4—C3—H3A	109.5	H7A—C7—H7C	109.5
C2—C3—H3A	109.5	H7B—C7—H7C	109.5
N1—C4—C3	115.93 (12)
O2—C1—C2—C3	−19.23 (19)	C7—N1—C4—C3	−178.16 (13)
O1—C1—C2—C3	159.77 (12)	C5—N1—C4—C3	−60.59 (16)
C1—C2—C3—O3	70.19 (14)	O3—C3—C4—N1	−78.63 (15)
C1—C2—C3—C4	−170.02 (12)	C2—C3—C4—N1	160.28 (11)
C6—N1—C4—C3	62.93 (16)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···Cl1	0.85 (1)	2.18 (1)	3.022 (1)	176 (2)
O3—H3···Cl1i	0.83 (1)	2.51 (2)	3.209 (1)	142 (2)

Symmetry code: (i) −x+1/2, −y, z−1/2.