DL-Piperidine-2-carboxyl­ic acid

A chair conformation is found for zwitterionic DL-piperidinium-2-carboxyl­ate, C₆H₁₁NO₂. Hydro­gen-bonding interactions involving the carboxyl­ate groups and ammonium H atoms give rise to a two-dimensional structure comprised of interconnected 12-membered rings.

Key indicators

• Single-crystal X-ray study
• T = 173 K
• Mean [sigma](C-C) = 0.002 Å
• R factor = 0.035
• wR factor = 0.128
• Data-to-parameter ratio = 18.2

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry


 Alert Level C:



ABSMU_01  Alert C The ratio of given/expected absorption coefficient lies
          outside the range 0.99 <> 1.01
          Calculated value of mu =     0.098
          Value of mu given      =     0.100


 0 Alert Level A = Potentially serious problem

 0 Alert Level B = Potential problem

 1 Alert Level C = Please check

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S1. Comment

The title molecule, (I), exists as a zwitterion [C21—O21 = 1.2508 (15) Å and C21—O22 = 1.2468 (15) Å] and adopts a chair conformation with the carboxylate occupying an equatorial position. The molecular structure is consistent with that found for the tetrahydrate (Bhattacharjee & Chacko, 1979) but features a different packing arrangement.

As shown in Fig. 1, two centrosymmetrically related carboxylate residues are linked by two ammonium cations, leading to the formation of 12-membered rings. As each molecule is involved in two donor and two acceptor hydrogen–bonding interactions that extend in the b and c directions, a two-dimensional network is formed. Layers stack along the a axis via hydrophobic interactions.

S2. Experimental

Crystals were obtained by the vapour diffusion of diethyl ether into an ethanol/benzene (5:1 v/v) solution of commercial dl-piperidine-2-carboxylic acid (Sigma).

Computing details

Data collection: MSC/AFC Diffractometer Control Software (Molecular Structure Corporation, 1996); cell refinement: MSC/AFC Diffractometer Control Software; data reduction: TEXSAN (Molecular Structure Corporation, 1997); program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEPII (Johnson, 1976); software used to prepare material for publication: TEXSAN.

Figures

Fig. 1. MThe mlecular structure, crystallographic numbering scheme and hydrogen-bonding scheme for (I). Displacement ellipsoids are shown at the 50% probability level.

(I)

Crystal data

C6H11NO2	F(000) = 280
Mr = 129.16	Dx = 1.304 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71069 Å
a = 11.148 (3) Å	Cell parameters from 14 reflections
b = 5.822 (2) Å	θ = 7.4–12.1°
c = 10.813 (4) Å	µ = 0.10 mm^−1
β = 110.39 (2)°	T = 173 K
V = 657.8 (4) Å^3	Block, colourless
Z = 4	0.30 × 0.20 × 0.10 mm

Data collection

Rigaku AFC-7R diffractometer	Rint = 0.018
Radiation source: rotating anode	θmax = 27.5°, θmin = 3.8°
Graphite monochromator	h = −14→14
ω–2θ scans	k = −7→0
3323 measured reflections	l = −14→13
1513 independent reflections	3 standard reflections every 400 reflections
1191 reflections with I > 2σ(I)	intensity decay: 0.7%

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)] = 0.035	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.128	H-atom parameters not refined
S = 0.98	w = 1/[σ^2(Fo^2) + (0.1P)^2] where P = (Fo^2 + 2Fc^2)/3
1513 reflections	(Δ/σ)max < 0.001
83 parameters	Δρmax = 0.24 e Å^−3
0 restraints	Δρmin = −0.19 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
O21	0.09484 (8)	0.37073 (16)	0.30718 (9)	0.0275 (3)
O22	0.18325 (10)	0.20556 (18)	0.50530 (9)	0.0359 (3)
N1	0.13411 (9)	−0.00698 (16)	0.17974 (9)	0.0175 (3)
H1	0.1467	0.1219	0.1366	0.0342 (13)*
H2	0.0481	−0.0174	0.1663	0.0342 (13)*
C2	0.20693 (11)	0.01657 (19)	0.32359 (10)	0.0180 (3)
H3	0.1955	−0.1282	0.3680	0.0342 (13)*
C3	0.34878 (11)	0.0429 (2)	0.34526 (12)	0.0253 (3)
H4	0.3978	0.0585	0.4407	0.0342 (13)*
H5	0.3624	0.1835	0.3004	0.0342 (13)*
C4	0.39645 (11)	−0.1668 (3)	0.29050 (13)	0.0315 (3)
H6	0.4874	−0.1445	0.3004	0.0342 (13)*
H7	0.3905	−0.3051	0.3413	0.0342 (13)*
C5	0.31718 (12)	−0.2021 (2)	0.14553 (13)	0.0283 (3)
H8	0.3442	−0.3461	0.1141	0.0342 (13)*
H9	0.3331	−0.0735	0.0933	0.0342 (13)*
C6	0.17490 (11)	−0.2146 (2)	0.12337 (11)	0.0227 (3)
H10	0.1256	−0.2242	0.0276	0.0342 (13)*
H11	0.1568	−0.3544	0.1660	0.0342 (13)*
C21	0.15627 (11)	0.2162 (2)	0.38344 (11)	0.0204 (3)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O21	0.0283 (4)	0.0240 (5)	0.0351 (5)	0.0079 (4)	0.0170 (4)	0.0049 (4)
O22	0.0577 (7)	0.0307 (6)	0.0238 (5)	0.0092 (4)	0.0196 (4)	−0.0037 (4)
N1	0.0182 (5)	0.0180 (5)	0.0171 (5)	−0.0004 (3)	0.0069 (4)	0.0001 (3)
C2	0.0199 (5)	0.0196 (6)	0.0156 (5)	0.0022 (4)	0.0075 (4)	0.0004 (4)
C3	0.0181 (6)	0.0320 (7)	0.0251 (6)	0.0014 (5)	0.0067 (4)	−0.0073 (5)
C4	0.0222 (6)	0.0398 (8)	0.0320 (7)	0.0099 (5)	0.0088 (5)	−0.0073 (6)
C5	0.0279 (6)	0.0325 (7)	0.0287 (7)	0.0041 (5)	0.0151 (5)	−0.0059 (5)
C6	0.0262 (6)	0.0214 (6)	0.0218 (6)	0.0001 (5)	0.0100 (5)	−0.0045 (4)
C21	0.0217 (5)	0.0178 (6)	0.0254 (6)	−0.0009 (4)	0.0128 (4)	−0.0021 (4)

Geometric parameters (Å, º)

O21—C21	1.2508 (15)	C2—C21	1.5309 (15)
O22—C21	1.2468 (15)	C3—C4	1.5305 (18)
N1—C2	1.4891 (15)	C4—C5	1.5216 (18)
N1—C6	1.4943 (15)	C5—C6	1.5210 (16)
C2—C3	1.5234 (16)
C2—N1—C6	111.59 (9)	C6—C5—C4	111.61 (10)
N1—C2—C3	109.20 (9)	N1—C6—C5	110.22 (9)
N1—C2—C21	111.37 (9)	O22—C21—O21	127.42 (11)
C3—C2—C21	112.00 (10)	O22—C21—C2	114.85 (10)
C2—C3—C4	110.00 (10)	O21—C21—C2	117.72 (10)
C5—C4—C3	110.54 (10)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···O22^i	0.92	1.90	2.7672 (17)	157
N1—H2···O21^ii	0.92	1.83	2.7005 (17)	156

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