Sarcosinium maleate at 123 K

In the crystal structure of the title compound, C₃H₈NO₂⁺·C₄H₃O₄^-, the sarcosine mol­ecule exists in the cationic form, with a positively charged amino group and an uncharged carboxyl­ic acid group. The maleic acid mol­ecule exists in the mono-ionized state. In the semi-maleate ion, the intramolecular hydrogen bond between atoms O5 and O4 is found to be asymmetric. There are no direct hydrogen-bonded interactions between the semi-maleate anions.

Key indicators

• Single-crystal X-ray study
• T = 123 K
• Mean [sigma](C-C) = 0.002 Å
• R factor = 0.039
• wR factor = 0.104
• Data-to-parameter ratio = 14.8

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry

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S1. Comment

The current interest in our laboratory is concerned with the complexes of amino acids with carboxylic acids which are believed to have existed in the prebiotic milieu (Miller & Orgel, 1974). The crystal structures of maleic acid complexes involving glycine (Rajagopal, Krishnakumar, Mostad & Natarajan, 2001), L-alanine (Alagar, Krishnakumar, Subha Nandhini & Natarajan, 2001), β-alanine (Rajagopal, Krishnakumar & Natarajan, 2001), phenylalanine (Alagar, Krishnakumar & Natarajan, 2001), DL-valine (Alagar, Krishnakumar, Mostad & Natarajan, 2001), DL– and L-arginine (Ravishankar et al., 1998), L-histidine and L-lysine (Pratap et al., 2000) have already been reported. The present study reports the crystal structure of a complex of sarcosine with maleic acid. Sarcosine (N-methyl glycine, CH₃NH₂⁺·CH₂COO^-), an α-amino acid, is present in marine animals, such as starfish and sea urchin, and is also a constituent of actinomycin, a peptide antibiotic. The crystal structure of sarcosine itself has been elucidated in our laboratory (Mostad & Natarajan, 1989).

Fig 1. shows the molecular structure with the atom-numbering scheme. The sarcosine moiety exists in the cationic form with a positively charged amino group and a neutral carboxylic acid group. The maleic acid molecule exists in the mono-ionized state. The semi-maleate ion is essentially planar, as observed in the crystal structures of similar complexes. In the semi-maleate ion, an intramolecular hydrogen bond between atoms O5 and O4 is found to be asymmetric, as observed in the crystal structures of many maleic–amino acid complexes. However, in the crystal stuctures of complexes of maleic acid with L-phenylalanine, DL– and L-arginine, L-histidine and L-lysine, this intramolecular hydrogen bond is symmetric, with the H atom shared between the two O atoms.

The packing of molecules of (I) within the unit cell, viewed down the b axis is shown in Fig 2. The sarcosinium and semi-maleate ions which are linked by O—H···O and N—H···O hydrogen bonds, aggregate into alternate columns, extending along the c axis. In these columns, the molecules related by a center of inversion form hydrogen-bonded double layers similar to that of glycinium maleate, L-phenylalaninium maleate and DL-valinium maleate, parallel to the ac plane. No classic hydrogen bonds are observed between these double layers, which are held together by C—H···O and van der Waals interactions. A head-to-tail hydrogen bond between the glide plane-related sarcosinium ions is also present. An interesting feature observed in the structures of amino acid–maleic acid complexes is that compound (I) and glycine maleate crystallize in the same space group and the mode of aggregation of molecules in the crystal structures is also similar.

S2. Experimental

Colorless plate-shaped single crystals of (I) were grown from a saturated aqueous solution containing sarcosine and maleic acid in a stoichiometric ratio of 1:1.

S3. Refinement

All the H atoms were positioned geometrically and were allowed to ride on their respective parent atoms with SHELXL97 (Sheldrick, 1997) defaults for bond lengths and displacement parameters.

Computing details

Data collection: SMART-NT (Bruker, 1999); cell refinement: SMART-NT; data reduction: SAINT-NT (Bruker, 1999); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: PLATON (Spek, 1999); software used to prepare material for publication: SHELXL97.

Figures

	Fig. 1. The molecular structure of (I), with the atom-numbering scheme and 50% probability displacement ellipsoids.
	Fig. 2. Packing of the molecules of (I), viewed down the b axis.

`N-methyl-α-aminoetnol maleate'

Crystal data

C3H8NO2^+·C4H3O4^−	F(000) = 864
Mr = 205.17	Dx = 1.478 Mg m^−3 Dm = 1.49 Mg m^−3 Dm measured by flotation in a mixture of xylene and bromoform
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2yc	Cell parameters from 1024 reflections
a = 22.784 (5) Å	θ = 2.0–26.0°
b = 5.9117 (12) Å	µ = 0.13 mm^−1
c = 13.788 (3) Å	T = 123 K
β = 96.69 (3)°	Plate, colorless
V = 1844.5 (6) Å^3	0.50 × 0.30 × 0.20 mm
Z = 8

Data collection

Bruker SMART CCD diffractometer	1897 independent reflections
Radiation source: fine-focus sealed tube	1704 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.032
Detector resolution: 8 pixels mm^-1	θmax = 26.4°, θmin = 1.8°
ω scans	h = −28→27
Absorption correction: multi-scan (SADABS; Bruker, 1998)	k = −7→7
Tmin = 0.937, Tmax = 0.974	l = −17→17
9646 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)] = 0.039	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.104	H-atom parameters constrained
S = 1.14	w = 1/[σ^2(Fo^2) + (0.0422P)^2 + 1.8616P] where P = (Fo^2 + 2Fc^2)/3
1897 reflections	(Δ/σ)max < 0.001
128 parameters	Δρmax = 0.25 e Å^−3
0 restraints	Δρmin = −0.23 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
O1	0.69384 (5)	−0.1708 (2)	0.05525 (8)	0.0328 (3)
H1	0.6756	−0.2883	0.0683	0.049*
O2	0.75395 (5)	−0.26518 (18)	0.19040 (8)	0.0281 (3)
O3	0.64766 (5)	0.4412 (2)	0.08362 (10)	0.0367 (3)
O4	0.56800 (5)	0.63412 (19)	0.10935 (11)	0.0414 (3)
O5	0.46532 (5)	0.56196 (19)	0.12965 (11)	0.0418 (3)
H5	0.5005	0.5887	0.1204	0.063*
O6	0.40758 (5)	0.26790 (19)	0.13922 (9)	0.0332 (3)
N1	0.82562 (5)	0.0953 (2)	0.17753 (9)	0.0239 (3)
H1A	0.8520	−0.0149	0.1642	0.029*
H1B	0.8159	0.0704	0.2395	0.029*
C1	0.73908 (6)	−0.1401 (2)	0.12175 (10)	0.0240 (3)
C2	0.77168 (6)	0.0775 (2)	0.10669 (10)	0.0246 (3)
H2A	0.7827	0.0820	0.0394	0.030*
H2B	0.7455	0.2079	0.1150	0.030*
C3	0.85431 (7)	0.3225 (3)	0.17374 (13)	0.0308 (4)
H3A	0.8897	0.3277	0.2214	0.046*
H3B	0.8265	0.4401	0.1892	0.046*
H3C	0.8654	0.3484	0.1081	0.046*
C4	0.59398 (7)	0.4489 (3)	0.09751 (11)	0.0267 (3)
C5	0.56204 (7)	0.2275 (3)	0.10010 (11)	0.0279 (3)
H5A	0.5852	0.0970	0.0912	0.034*
C6	0.50570 (7)	0.1870 (2)	0.11315 (11)	0.0277 (3)
H6	0.4952	0.0315	0.1126	0.033*
C7	0.45652 (6)	0.3461 (3)	0.12853 (11)	0.0252 (3)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0249 (6)	0.0334 (6)	0.0389 (6)	−0.0048 (5)	−0.0011 (4)	0.0048 (5)
O2	0.0270 (5)	0.0263 (5)	0.0317 (6)	0.0000 (4)	0.0060 (4)	0.0049 (4)
O3	0.0207 (5)	0.0317 (6)	0.0583 (8)	−0.0021 (4)	0.0072 (5)	0.0010 (5)
O4	0.0313 (6)	0.0229 (6)	0.0734 (9)	−0.0062 (5)	0.0199 (6)	−0.0117 (6)
O5	0.0282 (6)	0.0215 (6)	0.0790 (9)	−0.0017 (5)	0.0201 (6)	−0.0072 (6)
O6	0.0215 (5)	0.0260 (6)	0.0530 (7)	−0.0009 (4)	0.0089 (5)	0.0017 (5)
N1	0.0224 (6)	0.0204 (6)	0.0296 (6)	0.0006 (5)	0.0057 (5)	0.0013 (5)
C1	0.0213 (7)	0.0241 (7)	0.0279 (7)	0.0026 (6)	0.0081 (5)	−0.0006 (6)
C2	0.0234 (7)	0.0236 (7)	0.0271 (7)	0.0025 (6)	0.0038 (5)	0.0025 (5)
C3	0.0257 (7)	0.0206 (7)	0.0470 (9)	−0.0008 (6)	0.0083 (6)	−0.0009 (6)
C4	0.0231 (7)	0.0271 (7)	0.0297 (7)	−0.0033 (6)	0.0024 (6)	−0.0021 (6)
C5	0.0243 (7)	0.0216 (7)	0.0379 (8)	0.0025 (6)	0.0038 (6)	−0.0007 (6)
C6	0.0257 (8)	0.0183 (7)	0.0393 (8)	−0.0008 (6)	0.0045 (6)	−0.0004 (6)
C7	0.0235 (7)	0.0229 (7)	0.0293 (7)	−0.0008 (6)	0.0036 (5)	−0.0005 (6)

Geometric parameters (Å, º)

O1—C1	1.3099 (19)	C1—C2	1.512 (2)
O1—H1	0.8400	C2—H2A	0.9900
O2—C1	1.2178 (18)	C2—H2B	0.9900
O3—C4	1.2607 (19)	C3—H3A	0.9800
O4—C4	1.2640 (19)	C3—H3B	0.9800
O5—C7	1.2913 (19)	C3—H3C	0.9800
O5—H5	0.8400	C4—C5	1.500 (2)
O6—C7	1.2317 (18)	C5—C6	1.338 (2)
N1—C2	1.4818 (19)	C5—H5A	0.9500
N1—C3	1.4973 (19)	C6—C7	1.497 (2)
N1—H1A	0.9200	C6—H6	0.9500
N1—H1B	0.9200
C1—O1—H1	109.5	N1—C3—H3B	109.5
C7—O5—H5	109.5	H3A—C3—H3B	109.5
C2—N1—C3	111.86 (11)	N1—C3—H3C	109.5
C2—N1—H1A	109.2	H3A—C3—H3C	109.5
C3—N1—H1A	109.2	H3B—C3—H3C	109.5
C2—N1—H1B	109.2	O3—C4—O4	121.87 (14)
C3—N1—H1B	109.2	O3—C4—C5	116.99 (13)
H1A—N1—H1B	107.9	O4—C4—C5	121.13 (13)
O2—C1—O1	125.80 (14)	C6—C5—C4	129.39 (14)
O2—C1—C2	121.80 (13)	C6—C5—H5A	115.3
O1—C1—C2	112.39 (12)	C4—C5—H5A	115.3
N1—C2—C1	110.66 (11)	C5—C6—C7	130.71 (14)
N1—C2—H2A	109.5	C5—C6—H6	114.6
C1—C2—H2A	109.5	C7—C6—H6	114.6
N1—C2—H2B	109.5	O6—C7—O5	120.72 (14)
C1—C2—H2B	109.5	O6—C7—C6	118.94 (13)
H2A—C2—H2B	108.1	O5—C7—C6	120.33 (13)
N1—C3—H3A	109.5
C3—N1—C2—C1	−172.10 (12)	O4—C4—C5—C6	0.6 (3)
O2—C1—C2—N1	6.94 (19)	C4—C5—C6—C7	0.5 (3)
O1—C1—C2—N1	−174.65 (12)	C5—C6—C7—O6	−179.84 (16)
O3—C4—C5—C6	−179.78 (16)	C5—C6—C7—O5	0.8 (3)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···O3^i	0.84	1.74	2.5724 (17)	169
O1—H1···O4^i	0.84	2.62	3.2567 (17)	134
O5—H5···O4	0.84	1.59	2.4262 (17)	177
N1—H1B···O2^ii	0.92	2.18	2.8376 (18)	127
N1—H1A···O6^iii	0.92	1.86	2.7826 (17)	178
C2—H2A···O3^iv	0.99	2.46	3.376 (2)	154
C3—H3B···O2^v	0.98	2.40	3.3682 (19)	168

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