N-[Tris(hydroxymethyl)methyl]glycine (tricine)

The title compound, C₆H₁₃NO₅, adopts a zwitterionic form where the carboxylic acid H atom is transferred to the amino group. The methyl-glycine backbone is planar. The tris(hydroxy­methyl)­methyl group is rotated as a rigid group around the amino-methyl bond by 22 (1)° and the carboxylic acid plane is rotated by 19.76 (12)° from the plane of the main skeleton. Apart from their H atoms, the three hydroxy­methyl groups adopt a propeller-like conformation around the amino-methyl bond, close to C₃ symmetry.

Computing details

Data collection: CAD-4 Software (Enraf-Nonius, 1989); cell refinement: CAD-4 Software; data reduction: HELENA (Spek, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97; molecular graphics: ORTEPII (Johnson, 1976); software used to prepare material for publication: SHELXL97.

N-[tris(hydroxymethyl)methyl]glycine or N-(2-hydroxy-1,1-bis[hydroxymethyl]ethyl)glycine

Crystal data

C6H13NO5	Dx = 1.523 Mg m^−3
Mr = 179.18	Melting point: 459(2) K
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
a = 6.2806 (16) Å	Cell parameters from 25 reflections
b = 13.5616 (13) Å	θ = 9.7–14.1°
c = 9.6165 (10) Å	µ = 0.13 mm^−1
β = 107.488 (11)°	T = 293 K
V = 781.2 (2) Å^3	Prism, colourless
Z = 4	0.49 × 0.20 × 0.12 mm
F(000) = 384

Data collection

Enraf-Nonius CAD-4 diffractometer	Rint = 0.020
Radiation source: fine-focus sealed tube	θmax = 30.0°, θmin = 3.0°
Graphite monochromator	h = 0→8
profile data from ω–2θ scans	k = 0→19
2434 measured reflections	l = −13→12
2255 independent reflections	3 standard reflections every 180 min
1920 reflections with I > 2σ(I)	intensity decay: 1.1%

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)] = 0.030	Only H-atom coordinates refined
wR(F^2) = 0.089	w = 1/[σ^2(Fo^2) + (0.0479P)^2 + 0.1832P] where P = (Fo^2 + 2Fc^2)/3
S = 1.06	(Δ/σ)max < 0.001
2255 reflections	Δρmax = 0.39 e Å^−3
149 parameters	Δρmin = −0.19 e Å^−3
0 restraints	Extinction correction: SHELXL97 (Sheldrick, 1997), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.069 (6)

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	0.56659 (13)	−0.09470 (6)	0.61101 (8)	0.02764 (18)
O2	0.73866 (14)	−0.11426 (6)	0.84884 (8)	0.02991 (19)
O3	−0.04126 (12)	0.10578 (5)	0.42452 (7)	0.02200 (16)
H3	−0.012 (3)	0.1509 (12)	0.3772 (17)	0.033*
O4	0.08633 (14)	0.07186 (6)	0.86253 (8)	0.0321 (2)
H4	0.128 (3)	0.0723 (13)	0.955 (2)	0.048*
O5	0.52284 (12)	0.25370 (5)	0.73708 (8)	0.02664 (18)
H5	0.601 (3)	0.2944 (12)	0.7037 (17)	0.040*
N1	0.32148 (12)	0.05764 (5)	0.65388 (8)	0.01638 (16)
H1A	0.362 (2)	0.0642 (9)	0.5727 (14)	0.020*
H1B	0.229 (2)	0.0034 (9)	0.6388 (13)	0.020*
C1	0.61573 (15)	−0.06833 (7)	0.74002 (10)	0.01924 (18)
C2	0.52084 (16)	0.02846 (7)	0.77614 (10)	0.0230 (2)
H2A	0.631 (2)	0.0780 (11)	0.7941 (15)	0.028*
H2B	0.472 (2)	0.0191 (10)	0.8634 (15)	0.028*
C3	0.19535 (14)	0.15021 (6)	0.67019 (9)	0.01603 (17)
C4	−0.04097 (15)	0.13842 (7)	0.56471 (10)	0.01931 (18)
H4A	−0.121 (2)	0.2010 (10)	0.5605 (14)	0.023*
H4B	−0.119 (2)	0.0884 (9)	0.6017 (14)	0.023*
C5	0.17907 (17)	0.15926 (7)	0.82451 (10)	0.02172 (19)
H5A	0.083 (2)	0.2180 (10)	0.8285 (15)	0.026*
H5B	0.323 (2)	0.1727 (10)	0.8919 (15)	0.026*
C6	0.31037 (16)	0.24088 (7)	0.63172 (10)	0.02139 (19)
H6A	0.212 (2)	0.2996 (10)	0.6324 (14)	0.026*
H6B	0.329 (2)	0.2318 (10)	0.5356 (15)	0.026*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0325 (4)	0.0312 (4)	0.0196 (3)	0.0082 (3)	0.0084 (3)	−0.0005 (3)
O2	0.0363 (4)	0.0299 (4)	0.0211 (3)	0.0148 (3)	0.0050 (3)	0.0046 (3)
O3	0.0247 (3)	0.0230 (3)	0.0168 (3)	−0.0050 (2)	0.0038 (2)	−0.0011 (2)
O4	0.0386 (4)	0.0375 (4)	0.0213 (4)	−0.0138 (3)	0.0109 (3)	0.0009 (3)
O5	0.0249 (4)	0.0259 (4)	0.0271 (4)	−0.0103 (3)	0.0048 (3)	−0.0002 (3)
N1	0.0169 (3)	0.0154 (3)	0.0154 (3)	0.0010 (2)	0.0027 (3)	−0.0010 (2)
C1	0.0186 (4)	0.0199 (4)	0.0201 (4)	0.0027 (3)	0.0072 (3)	0.0021 (3)
C2	0.0222 (4)	0.0223 (4)	0.0197 (4)	0.0058 (3)	−0.0011 (3)	−0.0020 (3)
C3	0.0174 (4)	0.0142 (3)	0.0160 (3)	0.0003 (3)	0.0042 (3)	−0.0012 (3)
C4	0.0171 (4)	0.0216 (4)	0.0183 (4)	0.0009 (3)	0.0039 (3)	−0.0001 (3)
C5	0.0263 (4)	0.0221 (4)	0.0175 (4)	−0.0010 (3)	0.0077 (3)	−0.0028 (3)
C6	0.0245 (4)	0.0170 (4)	0.0211 (4)	−0.0038 (3)	0.0046 (3)	0.0002 (3)

Geometric parameters (Å, º)

O1—C1	1.2379 (11)	C1—C2	1.5241 (13)
O2—C1	1.2623 (11)	C2—H2A	0.944 (15)
O3—C4	1.4184 (11)	C2—H2B	0.985 (14)
O3—H3	0.816 (16)	C3—C5	1.5229 (12)
O4—C5	1.4163 (12)	C3—C6	1.5268 (12)
O4—H4	0.851 (19)	C3—C4	1.5338 (12)
O5—C6	1.4230 (12)	C4—H4A	0.981 (13)
O5—H5	0.862 (17)	C4—H4B	0.966 (13)
N1—C2	1.4906 (11)	C5—H5A	1.005 (14)
N1—C3	1.5175 (11)	C5—H5B	0.960 (14)
N1—H1A	0.896 (13)	C6—H6A	1.009 (14)
N1—H1B	0.923 (13)	C6—H6B	0.974 (13)
C4—O3—H3	111.1 (11)	N1—C3—C4	106.07 (7)
C5—O4—H4	104.1 (12)	C5—C3—C4	108.53 (7)
C6—O5—H5	109.3 (11)	C6—C3—C4	110.98 (7)
C2—N1—C3	118.62 (7)	O3—C4—C3	112.69 (7)
C2—N1—H1A	108.7 (8)	O3—C4—H4A	112.1 (8)
C3—N1—H1A	107.6 (8)	C3—C4—H4A	108.6 (8)
C2—N1—H1B	104.7 (8)	O3—C4—H4B	106.0 (8)
C3—N1—H1B	110.5 (8)	C3—C4—H4B	109.1 (8)
H1A—N1—H1B	106.0 (11)	H4A—C4—H4B	108.2 (11)
O1—C1—O2	126.47 (9)	O4—C5—C3	109.72 (7)
O1—C1—C2	118.71 (8)	O4—C5—H5A	110.9 (8)
O2—C1—C2	114.82 (8)	C3—C5—H5A	108.5 (8)
N1—C2—C1	110.01 (7)	O4—C5—H5B	111.3 (8)
N1—C2—H2A	110.6 (9)	C3—C5—H5B	110.3 (8)
C1—C2—H2A	109.8 (9)	H5A—C5—H5B	106.1 (11)
N1—C2—H2B	107.6 (8)	O5—C6—C3	109.67 (7)
C1—C2—H2B	109.0 (8)	O5—C6—H6A	110.1 (8)
H2A—C2—H2B	109.7 (12)	C3—C6—H6A	107.4 (8)
N1—C3—C5	110.94 (7)	O5—C6—H6B	109.7 (8)
N1—C3—C6	109.97 (7)	C3—C6—H6B	109.2 (8)
C5—C3—C6	110.27 (7)	H6A—C6—H6B	110.8 (11)
C3—N1—C2—C1	177.57 (7)	C6—C3—C4—O3	73.02 (9)
O1—C1—C2—N1	19.76 (12)	N1—C3—C5—O4	−53.88 (10)
O2—C1—C2—N1	−159.87 (9)	C6—C3—C5—O4	−175.96 (8)
C2—N1—C3—C5	−39.57 (11)	C4—C3—C5—O4	62.28 (10)
C2—N1—C3—C6	82.69 (10)	N1—C3—C6—O5	−66.90 (9)
C2—N1—C3—C4	−157.24 (8)	C5—C3—C6—O5	55.75 (10)
N1—C3—C4—O3	−46.39 (9)	C4—C3—C6—O5	176.05 (7)
C5—C3—C4—O3	−165.66 (7)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1A···O1^i	0.896 (13)	1.991 (13)	2.8830 (11)	173.0 (12)
N1—H1B···O3^ii	0.923 (13)	1.876 (13)	2.7894 (11)	170.3 (11)
O3—H3···O5^iii	0.816 (16)	1.928 (16)	2.7347 (11)	170.2 (15)
O4—H4···O2^iv	0.851 (19)	1.904 (19)	2.7220 (11)	160.9 (17)
O5—H5···O2^v	0.862 (17)	1.764 (17)	2.6224 (11)	174.0 (16)
C2—H2A···O5	0.944 (15)	2.494 (14)	3.0781 (13)	120.2 (10)
C2—H2B···O4	0.985 (14)	2.523 (14)	3.1380 (15)	120.4 (10)
C4—H4B···O4	0.966 (13)	2.462 (13)	2.8775 (12)	105.7 (9)
C5—H5B···O5	0.960 (14)	2.473 (13)	2.8460 (13)	103.0 (9)

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