Bis(DL-phenyl­alaninium) sulfate monohydrate

The crystal structure of the title compound, 2C₉H₁₂NO₂⁺·SO₄^2-·H₂O, consists of two protonated phenyl­alaninium cations linked together by hydrogen bonding with the water mol­ecule and the sulfate anion. The aggregation of the hydro­phobic zone is along (10) and of the hydro­philic zone is along (20). The phenyl­alaninium mol­ecules show sterically least favourable g+ or g- conformations.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.004 Å
• R factor = 0.046
• wR factor = 0.119
• Data-to-parameter ratio = 13.1

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry

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S1. Comment

The crystal structures of amino acids and their complexes have provided a wealth of interesting features pertaining to their patterns of aggregation and their ionic interactions (Vijayan, 1988; Prasad & Vijayan, 1993). The crystal structures of L-phenylalanine hydrochloride (Gurskaya & Vainshtein, 1963; Al-Karaghouli & Koetzle, 1975), L-phenylalanine L-phenylalaninium formate (Gorbitz & Etter, 1992), bis(L-phenylalanine) nitrate (Srikrishnan et al., 1984), bis(L-phenylalanine) sulfate monohydrate (Nagashima et al., 1992), L-phenylalanine L-phenylalaninium perchlorate (Srinivasan & Rajaram, 1997) have been reported. In the present study, the structure of DL-phenylalaninium sulfate monohydrate, (I), has been investigated (Fig. 1 and Table 1).

The asymmetric unit of (I) contains two crystallographically independent protonated phenylalaninium units (molecules A and B), one sulfate ion and a water molecule. The two phenylalaninium molecules A and B show sterically least favourable g+ and g- conformation (Benedetti et al., 1983; Suresh et al., 1994) with χ¹ values of 56.2 (3) and -58.1 (3)°, respectively, and has striking similarities with that of L-phenylalnine L-phenylalaninium formate (Gorbitz & Etter, 1992).

A chelated bifurcated hydrogen bond is observed in the case of (i) the amino N atom of molecule A with sulfate O atoms O1 and O4 and (ii) the amino N atom of molecule B with the sulfate O4 atom and the carboxyl O2A atom (Jeffrey & Saenger, 1991). The O4 atom of the sulfate anion acts as acceptor in hydrogen bonded with the water molecule and the amino N atom of molecules A and B. Interestingly, phenylalaninium molecule A forms a hydrogen bond with the sulfate anion only, while molecule B is hydrogen bonded to the sulfate anion, a carboxyl O atom and the water O atom. The sulfate anion links the phenylalaninium molecules into chains running along the b axis through hydrogen bonds with (i) the amino N atom of molecule A and (ii) the amino N and carboxyl O atoms of molecule B. The packing arrangement leads to the formation of a hydrophobic zone by phenyl rings along (101) and a hydrophilic zone along (202) (Fig. 2).

S2. Experimental

The title compound, (I), was crystallized from an aqueous solution of DL-phenylalanine and sulfuric acid by slow evaporation.

S3. Refinement

The H atoms of the water molecule were located and refined using DFIX. All other H atoms were fixed by HFIX and allowed to ride on the parent atom.

Computing details

Data collection: CAD-4 Software (Enraf-Nonius, 1989); cell refinement: CAD-4 Software; data reduction: CAD-4 Software; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); 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) showing the atomic numbering scheme and 50% probability displacement ellipsoids (Johnson, 1976).
	Fig. 2. Packing of the molecules viewed down the b axis.

(I)

Crystal data

2C9H12NO2^+·O4S^2^−·H2O	F(000) = 944
Mr = 446.47	Dx = 1.396 Mg m^−3 Dm = 1.39 Mg m^−3 Dm measured by flotation in a mixture of bromoform and xylene
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71069 Å
a = 14.560 (2) Å	Cell parameters from 25 reflections
b = 6.6000 (12) Å	θ = 8.0–15.8°
c = 22.115 (4) Å	µ = 0.21 mm^−1
β = 90.70 (2)°	T = 293 K
V = 2124.9 (6) Å^3	Needles, colorless
Z = 4	0.4 × 0.2 × 0.1 mm

Data collection

Enraf-Nonius sealed tube diffractometer	2806 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.021
Graphite monochromator	θmax = 25.0°, θmin = 2.8°
ω–2θ scans	h = 0→17
Absorption correction: ψ scan (North et al., 1968)	k = 0→7
Tmin = 0.951, Tmax = 0.980	l = −26→26
3825 measured reflections	25 standard reflections every 3 reflections
3671 independent reflections	intensity decay: none

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)] = 0.046	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.119	H atoms treated by a mixture of independent and constrained refinement
S = 1.05	w = 1/[σ^2(Fo^2) + (0.053P)^2 + 1.5922P] where P = (Fo^2 + 2Fc^2)/3
3671 reflections	(Δ/σ)max < 0.001
281 parameters	Δρmax = 0.52 e Å^−3
2 restraints	Δρmin = −0.26 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
S	0.27906 (4)	0.20427 (9)	−0.10666 (3)	0.02978 (17)
O1	0.32429 (11)	0.2919 (3)	−0.05195 (7)	0.0369 (4)
O2	0.19967 (12)	0.0864 (3)	−0.08762 (9)	0.0530 (6)
O3	0.34514 (12)	0.0639 (3)	−0.13478 (8)	0.0468 (5)
O4	0.25546 (17)	0.3665 (3)	−0.14796 (10)	0.0673 (7)
OW	0.57935 (17)	0.4282 (4)	0.18734 (12)	0.0684 (7)
H1	0.628 (2)	0.513 (6)	0.1784 (18)	0.101 (14)*
H2	0.539 (2)	0.445 (6)	0.1566 (13)	0.081 (12)*
O1A	0.50678 (12)	0.3299 (3)	0.04872 (8)	0.0447 (5)
O1B	0.49823 (11)	0.1962 (3)	−0.04434 (8)	0.0433 (5)
H1B	0.4439	0.2278	−0.0425	0.065*
C11	0.54087 (16)	0.2536 (3)	0.00510 (11)	0.0318 (5)
C12	0.64337 (15)	0.2134 (4)	0.00081 (10)	0.0317 (5)
H12	0.6529	0.0672	−0.0037	0.038*
N11	0.68793 (14)	0.2804 (3)	0.05773 (9)	0.0344 (5)
H11A	0.7481	0.2577	0.0559	0.052*
H11B	0.6647	0.2116	0.0886	0.052*
H11C	0.6779	0.4122	0.0630	0.052*
C13	0.68506 (17)	0.3202 (4)	−0.05313 (12)	0.0404 (6)
H13A	0.6562	0.2692	−0.0898	0.048*
H13B	0.6715	0.4638	−0.0505	0.048*
C14	0.78803 (17)	0.2929 (4)	−0.05764 (11)	0.0380 (6)
C15	0.8272 (2)	0.1050 (5)	−0.06414 (16)	0.0612 (9)
H15	0.7900	−0.0095	−0.0660	0.073*
C16	0.9219 (2)	0.0849 (6)	−0.06797 (17)	0.0706 (10)
H16	0.9478	−0.0431	−0.0719	0.085*
C17	0.9768 (2)	0.2511 (6)	−0.06595 (14)	0.0621 (10)
H17	1.0402	0.2369	−0.0686	0.075*
C18	0.9391 (2)	0.4382 (6)	−0.06004 (13)	0.0557 (9)
H18	0.9767	0.5521	−0.0593	0.067*
C19	0.84491 (19)	0.4598 (5)	−0.05507 (12)	0.0451 (7)
H19	0.8198	0.5881	−0.0500	0.054*
O2A	−0.19852 (14)	0.2220 (3)	0.20968 (9)	0.0572 (6)
O2B	−0.10045 (13)	0.1978 (4)	0.13422 (10)	0.0584 (6)
H2B	−0.1328	0.1015	0.1242	0.088*
C21	−0.13276 (16)	0.2795 (4)	0.18392 (11)	0.0352 (6)
C22	−0.07529 (15)	0.4580 (4)	0.20500 (11)	0.0323 (5)
H22	−0.0597	0.5423	0.1701	0.039*
N21	−0.13195 (13)	0.5768 (3)	0.24707 (9)	0.0334 (5)
H21A	−0.1001	0.6834	0.2603	0.050*
H21B	−0.1474	0.4995	0.2783	0.050*
H21C	−0.1826	0.6192	0.2280	0.050*
C23	0.01357 (16)	0.3814 (4)	0.23563 (14)	0.0441 (7)
H23A	−0.0024	0.2894	0.2680	0.053*
H23B	0.0487	0.3056	0.2063	0.053*
C24	0.07292 (15)	0.5482 (4)	0.26114 (12)	0.0366 (6)
C25	0.11920 (18)	0.6813 (5)	0.22420 (12)	0.0465 (7)
H25	0.1133	0.6686	0.1824	0.056*
C26	0.1739 (2)	0.8323 (5)	0.24803 (14)	0.0577 (8)
H26	0.2040	0.9218	0.2225	0.069*
C27	0.1840 (2)	0.8505 (6)	0.31019 (15)	0.0611 (9)
H27	0.2219	0.9502	0.3266	0.073*
C28	0.1380 (2)	0.7217 (5)	0.34712 (13)	0.0555 (8)
H28	0.1438	0.7355	0.3888	0.067*
C29	0.08293 (18)	0.5708 (5)	0.32339 (13)	0.0463 (7)
H29	0.0522	0.4834	0.3492	0.056*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
S	0.0282 (3)	0.0276 (3)	0.0333 (3)	−0.0037 (3)	−0.0074 (2)	−0.0020 (3)
O1	0.0336 (9)	0.0384 (10)	0.0387 (10)	−0.0027 (8)	−0.0090 (7)	−0.0088 (8)
O2	0.0362 (10)	0.0633 (14)	0.0597 (13)	−0.0206 (10)	0.0064 (9)	−0.0188 (11)
O3	0.0380 (10)	0.0588 (13)	0.0439 (11)	0.0020 (9)	0.0019 (8)	−0.0149 (9)
O4	0.0854 (16)	0.0513 (13)	0.0644 (14)	0.0018 (12)	−0.0350 (12)	0.0122 (11)
OW	0.0604 (15)	0.0556 (15)	0.0889 (19)	−0.0116 (12)	−0.0160 (13)	0.0189 (13)
O1A	0.0376 (10)	0.0548 (12)	0.0418 (11)	0.0040 (9)	0.0065 (8)	0.0005 (9)
O1B	0.0291 (9)	0.0482 (11)	0.0523 (11)	0.0011 (9)	−0.0069 (8)	−0.0123 (9)
C11	0.0314 (12)	0.0225 (12)	0.0415 (14)	−0.0014 (10)	0.0002 (11)	0.0022 (11)
C12	0.0298 (12)	0.0311 (12)	0.0340 (12)	−0.0016 (11)	−0.0032 (9)	−0.0026 (10)
N11	0.0346 (11)	0.0331 (11)	0.0353 (11)	−0.0014 (9)	−0.0041 (9)	−0.0002 (9)
C13	0.0345 (13)	0.0487 (17)	0.0379 (14)	0.0009 (12)	0.0001 (11)	0.0058 (12)
C14	0.0337 (13)	0.0482 (16)	0.0322 (13)	0.0026 (13)	0.0024 (10)	0.0021 (12)
C15	0.0512 (18)	0.0501 (19)	0.083 (2)	−0.0004 (16)	0.0156 (16)	0.0005 (17)
C16	0.054 (2)	0.068 (2)	0.090 (3)	0.0240 (19)	0.0210 (18)	0.014 (2)
C17	0.0317 (15)	0.104 (3)	0.0508 (18)	0.0092 (18)	0.0026 (13)	0.0097 (19)
C18	0.0393 (16)	0.085 (3)	0.0431 (17)	−0.0165 (16)	−0.0020 (12)	−0.0015 (16)
C19	0.0449 (15)	0.0493 (17)	0.0412 (15)	−0.0031 (13)	0.0005 (12)	−0.0034 (13)
O2A	0.0453 (11)	0.0670 (14)	0.0597 (12)	−0.0273 (11)	0.0167 (10)	−0.0143 (11)
O2B	0.0465 (12)	0.0628 (14)	0.0664 (14)	−0.0218 (10)	0.0188 (10)	−0.0313 (11)
C21	0.0258 (12)	0.0417 (14)	0.0381 (13)	−0.0018 (11)	−0.0002 (10)	−0.0030 (12)
C22	0.0242 (11)	0.0385 (14)	0.0342 (13)	−0.0021 (10)	0.0015 (9)	−0.0029 (11)
N21	0.0280 (10)	0.0395 (12)	0.0325 (11)	0.0024 (9)	−0.0003 (8)	−0.0006 (9)
C23	0.0266 (13)	0.0415 (15)	0.0641 (18)	0.0007 (11)	−0.0047 (12)	−0.0060 (14)
C24	0.0205 (11)	0.0451 (15)	0.0441 (15)	0.0028 (11)	−0.0005 (10)	−0.0046 (12)
C25	0.0371 (14)	0.066 (2)	0.0359 (14)	−0.0110 (14)	0.0009 (11)	−0.0085 (14)
C26	0.0496 (17)	0.068 (2)	0.0553 (19)	−0.0253 (16)	0.0070 (14)	−0.0048 (16)
C27	0.0469 (17)	0.075 (2)	0.061 (2)	−0.0210 (17)	0.0007 (15)	−0.0251 (18)
C28	0.0464 (16)	0.080 (2)	0.0401 (15)	−0.0041 (16)	−0.0038 (13)	−0.0153 (16)
C29	0.0351 (14)	0.0601 (19)	0.0436 (15)	−0.0010 (13)	0.0005 (11)	0.0047 (14)

Geometric parameters (Å, º)

S—O4	1.446 (2)	C18—C19	1.385 (4)
S—O2	1.4597 (19)	C18—H18	0.93
S—O3	1.4782 (19)	C19—H19	0.93
S—O1	1.4876 (17)	O2A—C21	1.183 (3)
OW—H1	0.92 (2)	O2B—C21	1.316 (3)
OW—H2	0.90 (2)	O2B—H2B	0.82
O1A—C11	1.201 (3)	C21—C22	1.516 (3)
O1B—C11	1.307 (3)	C22—N21	1.476 (3)
O1B—H1B	0.82	C22—C23	1.538 (3)
C11—C12	1.520 (3)	C22—H22	0.98
C12—N11	1.477 (3)	N21—H21A	0.89
C12—C13	1.519 (3)	N21—H21B	0.89
C12—H12	0.98	N21—H21C	0.89
N11—H11A	0.89	C23—C24	1.505 (4)
N11—H11B	0.89	C23—H23A	0.97
N11—H11C	0.89	C23—H23B	0.97
C13—C14	1.515 (3)	C24—C25	1.381 (4)
C13—H13A	0.97	C24—C29	1.391 (4)
C13—H13B	0.97	C25—C26	1.377 (4)
C14—C15	1.373 (4)	C25—H25	0.93
C14—C19	1.379 (4)	C26—C27	1.386 (4)
C15—C16	1.389 (4)	C26—H26	0.93
C15—H15	0.93	C27—C28	1.361 (5)
C16—C17	1.358 (5)	C27—H27	0.93
C16—H16	0.93	C28—C29	1.378 (4)
C17—C18	1.358 (5)	C28—H28	0.93
C17—H17	0.93	C29—H29	0.93
O4—S—O2	113.20 (14)	C14—C19—C18	120.6 (3)
O4—S—O3	110.44 (14)	C14—C19—H19	119.7
O2—S—O3	108.01 (12)	C18—C19—H19	119.7
O4—S—O1	108.98 (12)	C21—O2B—H2B	109.5
O2—S—O1	108.47 (11)	O2A—C21—O2B	124.8 (2)
O3—S—O1	107.57 (10)	O2A—C21—C22	123.3 (2)
H1—OW—H2	105 (4)	O2B—C21—C22	111.9 (2)
C11—O1B—H1B	109.5	N21—C22—C21	107.22 (19)
O1A—C11—O1B	126.7 (2)	N21—C22—C23	111.7 (2)
O1A—C11—C12	122.6 (2)	C21—C22—C23	109.8 (2)
O1B—C11—C12	110.7 (2)	N21—C22—H22	109.4
N11—C12—C13	110.8 (2)	C21—C22—H22	109.4
N11—C12—C11	108.42 (19)	C23—C22—H22	109.4
C13—C12—C11	111.7 (2)	C22—N21—H21A	109.5
N11—C12—H12	108.6	C22—N21—H21B	109.5
C13—C12—H12	108.6	H21A—N21—H21B	109.5
C11—C12—H12	108.6	C22—N21—H21C	109.5
C12—N11—H11A	109.5	H21A—N21—H21C	109.5
C12—N11—H11B	109.5	H21B—N21—H21C	109.5
H11A—N11—H11B	109.5	C24—C23—C22	113.6 (2)
C12—N11—H11C	109.5	C24—C23—H23A	108.8
H11A—N11—H11C	109.5	C22—C23—H23A	108.8
H11B—N11—H11C	109.5	C24—C23—H23B	108.8
C14—C13—C12	113.7 (2)	C22—C23—H23B	108.8
C14—C13—H13A	108.8	H23A—C23—H23B	107.7
C12—C13—H13A	108.8	C25—C24—C29	118.2 (2)
C14—C13—H13B	108.8	C25—C24—C23	121.7 (2)
C12—C13—H13B	108.8	C29—C24—C23	120.1 (3)
H13A—C13—H13B	107.7	C26—C25—C24	121.2 (3)
C15—C14—C19	118.4 (2)	C26—C25—H25	119.4
C15—C14—C13	121.8 (3)	C24—C25—H25	119.4
C19—C14—C13	119.8 (3)	C25—C26—C27	119.7 (3)
C14—C15—C16	120.4 (3)	C25—C26—H26	120.1
C14—C15—H15	119.8	C27—C26—H26	120.1
C16—C15—H15	119.8	C28—C27—C26	119.6 (3)
C17—C16—C15	120.4 (3)	C28—C27—H27	120.2
C17—C16—H16	119.8	C26—C27—H27	120.2
C15—C16—H16	119.8	C27—C28—C29	120.8 (3)
C18—C17—C16	119.9 (3)	C27—C28—H28	119.6
C18—C17—H17	120.0	C29—C28—H28	119.6
C16—C17—H17	120.0	C28—C29—C24	120.5 (3)
C17—C18—C19	120.2 (3)	C28—C29—H29	119.7
C17—C18—H18	119.9	C24—C29—H29	119.7
C19—C18—H18	119.9
O1A—C11—C12—N11	0.8 (3)	O2A—C21—C22—N21	−18.5 (4)
O1B—C11—C12—N11	−179.8 (2)	O2B—C21—C22—N21	161.7 (2)
O1A—C11—C12—C13	−121.6 (3)	O2A—C21—C22—C23	103.1 (3)
O1B—C11—C12—C13	57.8 (3)	O2B—C21—C22—C23	−76.7 (3)
N11—C12—C13—C14	56.2 (3)	N21—C22—C23—C24	−58.1 (3)
C11—C12—C13—C14	177.2 (2)	C21—C22—C23—C24	−176.9 (2)
C12—C13—C14—C15	60.9 (4)	C22—C23—C24—C25	−70.0 (3)
C12—C13—C14—C19	−119.0 (3)	C22—C23—C24—C29	110.5 (3)
C19—C14—C15—C16	0.1 (5)	C29—C24—C25—C26	0.1 (4)
C13—C14—C15—C16	−179.8 (3)	C23—C24—C25—C26	−179.5 (3)
C14—C15—C16—C17	−0.7 (6)	C24—C25—C26—C27	0.8 (5)
C15—C16—C17—C18	0.1 (5)	C25—C26—C27—C28	−1.5 (5)
C16—C17—C18—C19	1.0 (5)	C26—C27—C28—C29	1.2 (5)
C15—C14—C19—C18	1.1 (4)	C27—C28—C29—C24	−0.4 (5)
C13—C14—C19—C18	−179.0 (2)	C25—C24—C29—C28	−0.3 (4)
C17—C18—C19—C14	−1.7 (4)	C23—C24—C29—C28	179.2 (3)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1B—H1B···O1	0.82	1.80	2.614 (2)	170
O2B—H2B···O2^i	0.82	1.77	2.575 (3)	168
N11—H11A···O2^ii	0.89	2.49	2.992 (3)	116
N11—H11B···O3^ii	0.89	2.09	2.884 (3)	148
N11—H11C···O1^iii	0.89	1.97	2.831 (3)	163
N11—H11C···O4^iii	0.89	2.56	3.170 (3)	126
N21—H21A···OW^iv	0.89	2.01	2.836 (3)	154
N21—H21C···O4^v	0.89	2.05	2.843 (3)	147
N21—H21C···O2A^vi	0.89	2.33	2.826 (3)	115
N21—H21B···O3^vii	0.89	1.97	2.797 (3)	154
OW—H1···O4^iii	0.92 (2)	2.00 (2)	2.904 (3)	165 (4)
OW—H2···O1A	0.90 (2)	2.54 (3)	3.295 (3)	142 (3)

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