4-Hydroxy-2,2,6,6-tetra­methyl­piperidinium trifluoro­acetate

The title compound, C₉H₂₀NO⁺·C₂F₃O₂⁻, is an important inter­mediate in the synthesis of hindered light stabilizers. The piperidinium ring adopts a chair conformation with the hydroxyl group in an equatorial position. The crystal packing is stabilized by O—H...O and N—H...O hydrogen bonds. The CF₃ group is disordered over two positions with almost equal site occupancy factors.

Key indicators

• Single-crystal X-ray study
• T = 113 K
• Mean [sigma](C-C) = 0.004 Å
• Disorder in main residue
• R factor = 0.057
• wR factor = 0.132
• Data-to-parameter ratio = 10.1

checkCIF/PLATON results

No syntax errors found



Alert level B
PLAT230_ALERT_2_B Hirshfeld Test Diff for    F2'    -   F1      ..      10.91 su
PLAT242_ALERT_2_B Check Low       Ueq as Compared to Neighbors for       C11'

Alert level C
PLAT066_ALERT_1_C Predicted and Reported Transmissions Identical .          ?
PLAT125_ALERT_4_C No _symmetry_space_group_name_Hall Given .......          ?
PLAT213_ALERT_2_C Atom F2'     has ADP max/min Ratio .............       3.40 prola
PLAT230_ALERT_2_C Hirshfeld Test Diff for    F1'    -   F1      ..       6.97 su
PLAT230_ALERT_2_C Hirshfeld Test Diff for    F2'    -   F2      ..       6.62 su
PLAT242_ALERT_2_C Check Low       Ueq as Compared to Neighbors for        C11
PLAT250_ALERT_2_C Large U3/U1 Ratio for Average U(i,j) Tensor ....       2.22
PLAT301_ALERT_3_C Main Residue  Disorder .........................      18.00 Perc.

Alert level G
REFLT03_ALERT_4_G Please check that the estimate of the number of Friedel pairs is
            correct. If it is not, please give the correct count in the
            _publ_section_exptl_refinement section of the submitted CIF.
           From the CIF: _diffrn_reflns_theta_max           28.70
           From the CIF: _reflns_number_total               2039
           Count of symmetry unique reflns         2039
           Completeness (_total/calc)            100.00%
           TEST3: Check Friedels for noncentro structure
           Estimate of Friedel pairs measured         0
           Fraction of Friedel pairs measured     0.000
           Are heavy atom types Z>Si present         no
PLAT860_ALERT_3_G Note: Number of Least-Squares Restraints .......         48

   0 ALERT level A = In general: serious problem
   2 ALERT level B = Potentially serious problem
   8 ALERT level C = Check and explain
   2 ALERT level G = General alerts; check

   1 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   7 ALERT type 2 Indicator that the structure model may be wrong or deficient
   2 ALERT type 3 Indicator that the structure quality may be low
   2 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

---

S1. Comment

4-hydroxyl-2,2,6,6-tetramethylpiperidine is a very important intermediate in the synthesis of hindered light stabilizers (Borzatta & Carrozza, 1991; She et al., 2005). The piperidium ring adopts a chair conformation with the hydroxyl group in an equatorial position. The crystal packing is stabilized by O—H···O and N—H···O hydrogen bonds.

Related literature

For general background, see: Borzatta & Carrozza (1991). For related structures, see: Nengfang et al. (2005).

S2. Experimental

An ethanol solution (10 ml) of 2,2,6,6-tetramethylpiperidin-4-ol (3.2 mmol, 0.5 g) was added dropwise to a stirred aqueous solution (6 ml) of trifluoroacetic acid (3.8 mmol, 0.43 g) at 293 K. Then the reaction mixture was filtered and the filtrate stood for about five days until colourless needle shaped crystals were obtained.

S3. Refinement

In the absence of anomalous scatterers, Friedel pairs had been merged and the absolute structure was arbitrarily assigned. All H atoms were positioned geometrically with C—H ranging from 0.98Å to 1.00Å and refined as riding with U_iso(H)=1.2U_eq(C,N,O) or 1.5_eq(C_methyl). The CF₃ group is disordered over two position with a ratio of occupancy factors of 0.459 (1)/0.541 (1). The atoms of the CF₃ group were restrained to an isotropic behaviour.

Computing details

Data collection: CrystalClear (Rigaku/MSC, 2005); cell refinement: CrystalClear (Rigaku/MSC, 2005); data reduction: CrystalClear (Rigaku/MSC, 2005); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Bruker, 1997); software used to prepare material for publication: CrystalStructure (Rigaku/MSC, 2005).

Figures

Fig. 1. A perspective view of the title compound. Displacement ellipsoids are drawn at the 30% probability level and H atoms are shown as small spheres of arbitrary radii. Only the major occupied site of the disordered CF3 group is shown.

4-Hydroxy-2,2,6,6-tetramethylpiperidinium trifluoroacetate

Crystal data

C9H20NO^+·C2F3O2^−	Dx = 1.320 Mg m^−3
Mr = 271.28	Mo Kα radiation, λ = 0.71070 Å
Orthorhombic, P212121	Cell parameters from 4344 reflections
a = 7.6204 (8) Å	θ = 2.1–28.7°
b = 9.8939 (10) Å	µ = 0.12 mm^−1
c = 18.099 (2) Å	T = 113 K
V = 1364.6 (2) Å^3	Needle, colourless
Z = 4	0.22 × 0.20 × 0.16 mm
F(000) = 576

Data collection

Rigaku Saturn diffractometer	2039 independent reflections
Radiation source: rotating anode	1993 reflections with I > 2σ(I)
Confocal monochromator	Rint = 0.057
Detector resolution: 14.63 pixels mm^-1	θmax = 28.7°, θmin = 2.3°
ω scans	h = −10→10
Absorption correction: multi-scan (CrystalClear; Rigaku/MSC, 2005)	k = −13→13
Tmin = 0.974, Tmax = 0.981	l = −24→24
17989 measured reflections

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)] = 0.057	H-atom parameters constrained
wR(F^2) = 0.132	w = 1/[σ^2(Fo^2) + (0.0506P)^2 + 0.4132P] where P = (Fo^2 + 2Fc^2)/3
S = 1.23	(Δ/σ)max = 0.001
2039 reflections	Δρmax = 0.22 e Å^−3
202 parameters	Δρmin = −0.21 e Å^−3
48 restraints	Extinction correction: SHELXL, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.028 (4)

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	Occ. (<1)
O1	0.9028 (3)	−0.20835 (18)	0.73102 (11)	0.0271 (5)
H1	0.8683	−0.2769	0.7078	0.041*
O2	0.6874 (3)	0.4099 (2)	0.58896 (13)	0.0394 (6)
O3	0.7885 (3)	0.5590 (2)	0.67201 (12)	0.0398 (6)
N1	0.8175 (3)	0.1997 (2)	0.67551 (12)	0.0226 (5)
H1A	0.9012	0.2378	0.7056	0.027*
H1B	0.7631	0.2695	0.6510	0.027*
C1	0.6801 (4)	0.1339 (3)	0.72563 (15)	0.0244 (5)
C2	0.7571 (4)	0.0022 (3)	0.75609 (14)	0.0241 (5)
H2A	0.8503	0.0245	0.7922	0.029*
H2B	0.6639	−0.0475	0.7827	0.029*
C3	0.8336 (4)	−0.0893 (3)	0.69685 (14)	0.0233 (5)
H3	0.7392	−0.1152	0.6612	0.028*
C4	0.9789 (4)	−0.0143 (3)	0.65571 (15)	0.0234 (5)
H4A	1.0300	−0.0753	0.6181	0.028*
H4B	1.0729	0.0095	0.6911	0.028*
C5	0.9142 (4)	0.1151 (3)	0.61754 (14)	0.0241 (6)
C6	0.6475 (4)	0.2352 (3)	0.78794 (18)	0.0326 (7)
H6A	0.7557	0.2477	0.8164	0.049*
H6B	0.5549	0.2009	0.8205	0.049*
H6C	0.6110	0.3220	0.7668	0.049*
C7	0.5089 (4)	0.1126 (3)	0.68236 (19)	0.0335 (7)
H7A	0.4141	0.0899	0.7168	0.050*
H7B	0.5244	0.0387	0.6469	0.050*
H7C	0.4789	0.1958	0.6558	0.050*
C8	1.0678 (4)	0.2025 (3)	0.59214 (16)	0.0302 (6)
H8A	1.0229	0.2852	0.5691	0.045*
H8B	1.1384	0.1522	0.5562	0.045*
H8C	1.1408	0.2262	0.6348	0.045*
C9	0.7963 (4)	0.0851 (3)	0.55106 (16)	0.0331 (7)
H9A	0.7112	0.0149	0.5643	0.050*
H9B	0.8685	0.0536	0.5097	0.050*
H9C	0.7338	0.1675	0.5366	0.050*
C10	0.7562 (4)	0.5187 (3)	0.60881 (16)	0.0281 (6)
C11	0.8356 (12)	0.6096 (9)	0.5496 (5)	0.037 (3)	0.459 (14)
F1	0.7559 (17)	0.7299 (6)	0.5473 (4)	0.067 (3)	0.459 (14)
F2	1.0045 (10)	0.6341 (15)	0.5611 (4)	0.086 (4)	0.459 (14)
F3	0.8194 (18)	0.5655 (13)	0.4799 (6)	0.070 (4)	0.459 (14)
C11'	0.7828 (13)	0.6165 (8)	0.5453 (4)	0.042 (3)	0.541 (14)
F1'	0.6352 (15)	0.6809 (12)	0.5291 (5)	0.126 (4)	0.541 (14)
F2'	0.900 (2)	0.7116 (8)	0.5599 (3)	0.099 (5)	0.541 (14)
F3'	0.8406 (14)	0.5571 (12)	0.4839 (5)	0.070 (4)	0.541 (14)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0347 (11)	0.0164 (8)	0.0303 (10)	0.0008 (8)	−0.0069 (9)	0.0017 (8)
O2	0.0504 (13)	0.0219 (10)	0.0458 (12)	−0.0013 (10)	−0.0187 (11)	−0.0011 (9)
O3	0.0615 (15)	0.0274 (10)	0.0306 (11)	−0.0091 (11)	−0.0059 (11)	−0.0024 (9)
N1	0.0236 (11)	0.0177 (10)	0.0266 (10)	−0.0003 (9)	−0.0010 (9)	−0.0003 (9)
C1	0.0212 (12)	0.0193 (11)	0.0327 (14)	−0.0006 (10)	0.0012 (11)	0.0002 (10)
C2	0.0220 (12)	0.0239 (12)	0.0266 (12)	−0.0010 (11)	0.0014 (10)	0.0015 (10)
C3	0.0260 (13)	0.0189 (11)	0.0251 (12)	0.0016 (10)	−0.0050 (10)	0.0015 (10)
C4	0.0242 (12)	0.0226 (12)	0.0235 (12)	0.0017 (11)	−0.0001 (10)	−0.0021 (10)
C5	0.0278 (13)	0.0202 (12)	0.0244 (12)	0.0020 (11)	−0.0004 (11)	−0.0008 (10)
C6	0.0298 (15)	0.0269 (14)	0.0412 (16)	0.0004 (12)	0.0098 (13)	−0.0047 (13)
C7	0.0242 (13)	0.0266 (13)	0.0498 (18)	0.0009 (11)	−0.0036 (13)	0.0032 (14)
C8	0.0356 (16)	0.0263 (14)	0.0286 (14)	−0.0029 (13)	0.0046 (12)	0.0016 (12)
C9	0.0434 (18)	0.0272 (14)	0.0287 (14)	0.0013 (13)	−0.0109 (13)	0.0016 (11)
C10	0.0292 (13)	0.0200 (12)	0.0351 (14)	0.0032 (11)	−0.0061 (12)	−0.0015 (11)
C11	0.048 (5)	0.030 (5)	0.033 (5)	−0.009 (4)	−0.006 (4)	−0.004 (4)
F1	0.132 (8)	0.020 (3)	0.049 (4)	0.017 (4)	0.014 (4)	0.011 (2)
F2	0.064 (5)	0.129 (9)	0.065 (4)	−0.058 (5)	0.007 (3)	0.005 (5)
F3	0.136 (10)	0.043 (6)	0.030 (5)	−0.037 (6)	−0.025 (5)	0.002 (4)
C11'	0.063 (6)	0.037 (4)	0.026 (4)	0.000 (4)	−0.010 (3)	−0.001 (3)
F1'	0.123 (7)	0.136 (7)	0.120 (6)	0.051 (6)	−0.004 (5)	0.080 (5)
F2'	0.198 (13)	0.060 (5)	0.039 (3)	−0.082 (7)	0.013 (6)	−0.012 (3)
F3'	0.105 (7)	0.063 (7)	0.042 (5)	−0.025 (5)	0.042 (4)	−0.024 (4)

Geometric parameters (Å, º)

O1—C3	1.431 (3)	C6—H6A	0.9800
O1—H1	0.8400	C6—H6B	0.9800
O2—C10	1.250 (3)	C6—H6C	0.9800
O3—C10	1.236 (3)	C7—H7A	0.9800
N1—C1	1.531 (3)	C7—H7B	0.9800
N1—C5	1.531 (3)	C7—H7C	0.9800
N1—H1A	0.9200	C8—H8A	0.9800
N1—H1B	0.9200	C8—H8B	0.9800
C1—C6	1.529 (4)	C8—H8C	0.9800
C1—C2	1.531 (4)	C9—H9A	0.9800
C1—C7	1.537 (4)	C9—H9B	0.9800
C2—C3	1.519 (4)	C9—H9C	0.9800
C2—H2A	0.9900	C10—C11'	1.516 (7)
C2—H2B	0.9900	C10—C11	1.525 (8)
C3—C4	1.526 (4)	C11—F2	1.326 (9)
C3—H3	1.0000	C11—F1	1.337 (8)
C4—C5	1.536 (4)	C11—F3	1.339 (8)
C4—H4A	0.9900	C11'—F2'	1.324 (8)
C4—H4B	0.9900	C11'—F1'	1.325 (8)
C5—C8	1.527 (4)	C11'—F3'	1.333 (8)
C5—C9	1.530 (4)
C3—O1—H1	109.5	H6A—C6—H6B	109.5
C1—N1—C5	120.2 (2)	C1—C6—H6C	109.5
C1—N1—H1A	107.3	H6A—C6—H6C	109.5
C5—N1—H1A	107.3	H6B—C6—H6C	109.5
C1—N1—H1B	107.3	C1—C7—H7A	109.5
C5—N1—H1B	107.3	C1—C7—H7B	109.5
H1A—N1—H1B	106.9	H7A—C7—H7B	109.5
C6—C1—N1	105.6 (2)	C1—C7—H7C	109.5
C6—C1—C2	110.8 (2)	H7A—C7—H7C	109.5
N1—C1—C2	108.2 (2)	H7B—C7—H7C	109.5
C6—C1—C7	109.1 (2)	C5—C8—H8A	109.5
N1—C1—C7	109.7 (2)	C5—C8—H8B	109.5
C2—C1—C7	113.1 (2)	H8A—C8—H8B	109.5
C3—C2—C1	113.6 (2)	C5—C8—H8C	109.5
C3—C2—H2A	108.9	H8A—C8—H8C	109.5
C1—C2—H2A	108.9	H8B—C8—H8C	109.5
C3—C2—H2B	108.9	C5—C9—H9A	109.5
C1—C2—H2B	108.9	C5—C9—H9B	109.5
H2A—C2—H2B	107.7	H9A—C9—H9B	109.5
O1—C3—C2	109.1 (2)	C5—C9—H9C	109.5
O1—C3—C4	110.1 (2)	H9A—C9—H9C	109.5
C2—C3—C4	109.5 (2)	H9B—C9—H9C	109.5
O1—C3—H3	109.4	O3—C10—O2	128.9 (3)
C2—C3—H3	109.4	O3—C10—C11'	117.9 (4)
C4—C3—H3	109.4	O2—C10—C11'	112.8 (4)
C3—C4—C5	113.1 (2)	O3—C10—C11	112.4 (4)
C3—C4—H4A	109.0	O2—C10—C11	118.2 (4)
C5—C4—H4A	109.0	F2—C11—F1	106.4 (8)
C3—C4—H4B	109.0	F2—C11—F3	107.3 (8)
C5—C4—H4B	109.0	F1—C11—F3	102.6 (8)
H4A—C4—H4B	107.8	F2—C11—C10	112.5 (7)
C8—C5—C9	108.9 (2)	F1—C11—C10	111.5 (7)
C8—C5—N1	105.4 (2)	F3—C11—C10	115.7 (9)
C9—C5—N1	111.2 (2)	F2'—C11'—F1'	106.0 (8)
C8—C5—C4	111.2 (2)	F2'—C11'—F3'	104.8 (8)
C9—C5—C4	112.4 (2)	F1'—C11'—F3'	107.9 (8)
N1—C5—C4	107.6 (2)	F2'—C11'—C10	113.2 (6)
C1—C6—H6A	109.5	F1'—C11'—C10	111.2 (6)
C1—C6—H6B	109.5	F3'—C11'—C10	113.3 (8)
C5—N1—C1—C6	165.7 (2)	O2—C10—C11—F2	−121.8 (8)
C5—N1—C1—C2	47.0 (3)	C11'—C10—C11—F2	164 (3)
C5—N1—C1—C7	−76.9 (3)	O3—C10—C11—F1	−69.1 (8)
C6—C1—C2—C3	−166.0 (2)	O2—C10—C11—F1	118.7 (8)
N1—C1—C2—C3	−50.6 (3)	C11'—C10—C11—F1	45 (2)
C7—C1—C2—C3	71.2 (3)	O3—C10—C11—F3	174.2 (8)
C1—C2—C3—O1	179.6 (2)	O2—C10—C11—F3	2.0 (11)
C1—C2—C3—C4	59.1 (3)	C11'—C10—C11—F3	−72 (2)
O1—C3—C4—C5	−180.0 (2)	O3—C10—C11'—F2'	25.7 (9)
C2—C3—C4—C5	−60.1 (3)	O2—C10—C11'—F2'	−160.6 (8)
C1—N1—C5—C8	−166.6 (2)	C11—C10—C11'—F2'	−47 (2)
C1—N1—C5—C9	75.6 (3)	O3—C10—C11'—F1'	−93.5 (8)
C1—N1—C5—C4	−47.8 (3)	O2—C10—C11'—F1'	80.2 (9)
C3—C4—C5—C8	167.3 (2)	C11—C10—C11'—F1'	−167 (3)
C3—C4—C5—C9	−70.4 (3)	O3—C10—C11'—F3'	144.8 (8)
C3—C4—C5—N1	52.4 (3)	O2—C10—C11'—F3'	−41.5 (10)
O3—C10—C11—F2	50.4 (9)	C11—C10—C11'—F3'	72 (2)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1B···O2	0.92	1.88	2.786 (3)	169
N1—H1A···O1^i	0.92	1.96	2.869 (3)	171
O1—H1···O3^ii	0.84	1.85	2.682 (3)	171

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