In the methanol solvate crystal form of the title diacid diglycol calixarene, C54H72O10·CH4O, two calixarene molecules (in the cone conformation) are dimerized via two methanol molecules hydrogen bonded to the carboxyl groups. An intramolecular bond is also formed between a carboxylic proton and an ether O atom. This result is relevant to the interpretation of the acidic and complexation properties of calixarene carboxylic acids.
Supporting information
CCDC reference: 143250
Compound (I) was synthesized according to the literature method of Barakat et
al. (1998) and was recrystallized from methanol.
The carboxyl and hydroxyl (methanol) protons were found on the difference
Fourier map and introduced as riding atoms with a displacement factor equal to
1.2 times that of the attached O atom. All other H atoms were introduced at
calculated positions as riding atoms with a displacement factor equal to 1.2
(CH, CH2) or 1.5 (CH3) times that of the attached C atom.
Data collection: Kappa-CCD Software (Nonius, 1997); cell refinement: DENZO-SMN (Otwinowski & Minor, 1997); data reduction: DENZO-SMN; program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Sheldrick, 1999); software used to prepare material for publication: SHELXTL (Sheldrick, 1999).
Crystal data top
C54H72O10·CH4O | F(000) = 1976 |
Mr = 913.16 | Dx = 1.146 Mg m−3 |
Monoclinic, P21/c | Mo Kα radiation, λ = 0.71073 Å |
a = 17.7426 (9) Å | Cell parameters from 18139 reflections |
b = 15.5402 (6) Å | θ = 2.6–25.7° |
c = 19.8147 (10) Å | µ = 0.08 mm−1 |
β = 104.279 (2)° | T = 127 K |
V = 5294.6 (4) Å3 | Platelet, colourless |
Z = 4 | 0.45 × 0.28 × 0.25 mm |
Data collection top
Nonius Kappa-CCD diffractometer | 6410 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.050 |
Graphite monochromator | θmax = 25.7°, θmin = 2.6° |
Detector resolution: 18 pixels mm-1 | h = −21→21 |
ϕ scans | k = 0→18 |
18139 measured reflections | l = −24→24 |
9972 independent reflections | |
Refinement top
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.055 | H atoms treated by a mixture of independent and constrained refinement |
wR(F2) = 0.138 | w = 1/[σ2(Fo2) + (0.0543P)2 + 1.7978P] where P = (Fo2 + 2Fc2)/3 |
S = 1.01 | (Δ/σ)max < 0.001 |
9972 reflections | Δρmax = 0.27 e Å−3 |
614 parameters | Δρmin = −0.23 e Å−3 |
0 restraints | Extinction correction: SHELXL97 (Sheldrick, 1997), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.0049 (4) |
Crystal data top
C54H72O10·CH4O | V = 5294.6 (4) Å3 |
Mr = 913.16 | Z = 4 |
Monoclinic, P21/c | Mo Kα radiation |
a = 17.7426 (9) Å | µ = 0.08 mm−1 |
b = 15.5402 (6) Å | T = 127 K |
c = 19.8147 (10) Å | 0.45 × 0.28 × 0.25 mm |
β = 104.279 (2)° | |
Data collection top
Nonius Kappa-CCD diffractometer | 6410 reflections with I > 2σ(I) |
18139 measured reflections | Rint = 0.050 |
9972 independent reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.055 | 0 restraints |
wR(F2) = 0.138 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.01 | Δρmax = 0.27 e Å−3 |
9972 reflections | Δρmin = −0.23 e Å−3 |
614 parameters | |
Special details top
Experimental. A 180° range in ϕ was scanned during data collection, with 2° ϕ steps. The
crystal-to-detector distance was fixed at 28 mm. |
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. Structure solved by direct methods. All non-hydrogen atoms refined
anisotropically. Carboxyl and hydroxyl (methanol) protons found on the Fourier
map and introduced as riding atoms with a displacement factor equal to 1.2
times that of the attached oxygen atom. All other hydrogen atoms introduced at
calculated positions as riding atoms with a displacement factor equal to 1.2
(CH, CH2) or 1.5 (CH3) times that of the attached carbon atom. |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | |
O1 | 0.13968 (9) | 0.29531 (9) | 0.06324 (8) | 0.0259 (4) | |
O2 | −0.00504 (10) | 0.15557 (13) | −0.04012 (11) | 0.0519 (5) | |
H2 | −0.0004 | 0.1049 | −0.0646 | 0.062* | |
O3 | 0.12402 (10) | 0.15310 (11) | −0.02569 (9) | 0.0376 (4) | |
O4 | 0.27890 (9) | 0.16647 (9) | 0.09915 (8) | 0.0255 (4) | |
O5 | 0.26751 (11) | −0.00776 (11) | 0.14700 (10) | 0.0436 (5) | |
O6 | 0.25138 (9) | 0.21671 (9) | 0.24328 (8) | 0.0251 (4) | |
O7 | 0.14253 (10) | 0.14309 (11) | 0.14599 (9) | 0.0390 (4) | |
H7 | 0.1859 | 0.1766 | 0.1422 | 0.047* | |
O8 | 0.10799 (11) | 0.05515 (11) | 0.21930 (9) | 0.0413 (5) | |
O9 | 0.09765 (9) | 0.33020 (10) | 0.22086 (8) | 0.0277 (4) | |
O10 | 0.05528 (10) | 0.20992 (11) | 0.31786 (10) | 0.0433 (5) | |
C1 | 0.06426 (13) | 0.26069 (15) | 0.03285 (13) | 0.0301 (5) | |
H1A | 0.0320 | 0.3053 | 0.0060 | 0.036* | |
H1B | 0.0404 | 0.2432 | 0.0698 | 0.036* | |
C2 | 0.06648 (15) | 0.18467 (16) | −0.01386 (13) | 0.0332 (6) | |
C3 | 0.29886 (15) | 0.09065 (14) | 0.06610 (13) | 0.0319 (6) | |
H3A | 0.3529 | 0.0760 | 0.0861 | 0.038* | |
H3B | 0.2924 | 0.1015 | 0.0168 | 0.038* | |
C4 | 0.24805 (16) | 0.01748 (15) | 0.07583 (13) | 0.0370 (6) | |
H4A | 0.1939 | 0.0349 | 0.0620 | 0.044* | |
H4B | 0.2553 | −0.0306 | 0.0469 | 0.044* | |
C5 | 0.2264 (2) | −0.08277 (18) | 0.15801 (18) | 0.0576 (9) | |
H5A | 0.2384 | −0.0958 | 0.2069 | 0.086* | |
H5B | 0.2414 | −0.1302 | 0.1332 | 0.086* | |
H5C | 0.1715 | −0.0730 | 0.1414 | 0.086* | |
C6 | 0.21804 (14) | 0.14155 (15) | 0.26547 (12) | 0.0301 (5) | |
H6A | 0.1996 | 0.1547 | 0.3065 | 0.036* | |
H6B | 0.2572 | 0.0968 | 0.2776 | 0.036* | |
C7 | 0.15167 (14) | 0.11053 (15) | 0.20826 (12) | 0.0296 (5) | |
C8 | 0.03827 (14) | 0.34339 (16) | 0.25797 (14) | 0.0358 (6) | |
H8A | −0.0011 | 0.3823 | 0.2320 | 0.043* | |
H8B | 0.0609 | 0.3690 | 0.3031 | 0.043* | |
C9 | 0.00186 (15) | 0.25853 (18) | 0.26739 (14) | 0.0410 (7) | |
H9A | −0.0455 | 0.2678 | 0.2826 | 0.049* | |
H9B | −0.0114 | 0.2276 | 0.2235 | 0.049* | |
C10 | 0.02125 (17) | 0.13384 (18) | 0.33664 (16) | 0.0492 (8) | |
H10A | 0.0588 | 0.1037 | 0.3719 | 0.074* | |
H10B | 0.0047 | 0.0977 | 0.2964 | 0.074* | |
H10C | −0.0228 | 0.1487 | 0.3544 | 0.074* | |
C11 | 0.15442 (13) | 0.37274 (14) | 0.03355 (11) | 0.0223 (5) | |
C12 | 0.11685 (13) | 0.44731 (14) | 0.04680 (11) | 0.0244 (5) | |
C13 | 0.12670 (13) | 0.52218 (15) | 0.01092 (12) | 0.0262 (5) | |
H13 | 0.0988 | 0.5711 | 0.0167 | 0.031* | |
C14 | 0.17677 (13) | 0.52616 (14) | −0.03318 (12) | 0.0262 (5) | |
C15 | 0.21850 (13) | 0.45158 (14) | −0.03891 (12) | 0.0261 (5) | |
H15 | 0.2544 | 0.4534 | −0.0660 | 0.031* | |
C16 | 0.20903 (13) | 0.37468 (14) | −0.00608 (11) | 0.0236 (5) | |
C17 | 0.19029 (14) | 0.60923 (15) | −0.07041 (12) | 0.0284 (5) | |
C18 | 0.1972 (2) | 0.58943 (18) | −0.14440 (14) | 0.0492 (8) | |
H18A | 0.2005 | 0.6423 | −0.1685 | 0.074* | |
H18B | 0.1523 | 0.5577 | −0.1688 | 0.074* | |
H18C | 0.2432 | 0.5558 | −0.1422 | 0.074* | |
C19 | 0.26548 (15) | 0.64982 (16) | −0.02867 (14) | 0.0380 (6) | |
H19A | 0.3068 | 0.6084 | −0.0220 | 0.057* | |
H19B | 0.2590 | 0.6681 | 0.0158 | 0.057* | |
H19C | 0.2781 | 0.6986 | −0.0535 | 0.057* | |
C20 | 0.12502 (16) | 0.67481 (17) | −0.07499 (17) | 0.0477 (7) | |
H20A | 0.0766 | 0.6501 | −0.1000 | 0.072* | |
H20B | 0.1358 | 0.7253 | −0.0990 | 0.072* | |
H20C | 0.1217 | 0.6902 | −0.0289 | 0.072* | |
C21 | 0.26041 (13) | 0.29750 (14) | −0.00886 (12) | 0.0250 (5) | |
H21A | 0.2800 | 0.3008 | −0.0504 | 0.030* | |
H21B | 0.2300 | 0.2452 | −0.0115 | 0.030* | |
C22 | 0.32818 (13) | 0.29443 (14) | 0.05510 (11) | 0.0238 (5) | |
C23 | 0.33507 (13) | 0.23104 (14) | 0.10631 (11) | 0.0232 (5) | |
C24 | 0.39594 (13) | 0.23177 (14) | 0.16623 (11) | 0.0242 (5) | |
C25 | 0.45128 (13) | 0.29706 (14) | 0.17371 (12) | 0.0254 (5) | |
H25 | 0.4922 | 0.2978 | 0.2134 | 0.030* | |
C26 | 0.44767 (13) | 0.36092 (14) | 0.12421 (12) | 0.0250 (5) | |
C27 | 0.38567 (13) | 0.35799 (14) | 0.06540 (12) | 0.0249 (5) | |
H27 | 0.3823 | 0.4001 | 0.0315 | 0.030* | |
C28 | 0.50823 (14) | 0.43319 (15) | 0.13230 (13) | 0.0305 (5) | |
C29 | 0.56483 (17) | 0.43346 (19) | 0.20411 (15) | 0.0525 (8) | |
H29A | 0.6008 | 0.4802 | 0.2070 | 0.079* | |
H29B | 0.5929 | 0.3800 | 0.2113 | 0.079* | |
H29C | 0.5364 | 0.4403 | 0.2392 | 0.079* | |
C30 | 0.55474 (17) | 0.42130 (18) | 0.07746 (16) | 0.0478 (7) | |
H30A | 0.5818 | 0.3673 | 0.0849 | 0.072* | |
H30B | 0.5917 | 0.4673 | 0.0812 | 0.072* | |
H30C | 0.5200 | 0.4219 | 0.0319 | 0.072* | |
C31 | 0.46741 (17) | 0.52074 (16) | 0.12156 (15) | 0.0424 (7) | |
H31A | 0.5056 | 0.5656 | 0.1272 | 0.064* | |
H31B | 0.4372 | 0.5280 | 0.1553 | 0.064* | |
H31C | 0.4338 | 0.5235 | 0.0755 | 0.064* | |
C32 | 0.39989 (13) | 0.16848 (14) | 0.22558 (11) | 0.0257 (5) | |
H32A | 0.3590 | 0.1258 | 0.2123 | 0.031* | |
H32B | 0.4496 | 0.1390 | 0.2364 | 0.031* | |
C33 | 0.39010 (13) | 0.21808 (14) | 0.28834 (11) | 0.0236 (5) | |
C34 | 0.31696 (13) | 0.24513 (14) | 0.29337 (11) | 0.0236 (5) | |
C35 | 0.30700 (13) | 0.30302 (14) | 0.34429 (11) | 0.0242 (5) | |
C36 | 0.37340 (13) | 0.33096 (14) | 0.39223 (11) | 0.0247 (5) | |
H36 | 0.3679 | 0.3692 | 0.4268 | 0.030* | |
C37 | 0.44837 (13) | 0.30408 (14) | 0.39082 (12) | 0.0248 (5) | |
C38 | 0.45481 (13) | 0.24752 (14) | 0.33843 (11) | 0.0253 (5) | |
H38 | 0.5040 | 0.2285 | 0.3366 | 0.030* | |
C39 | 0.51932 (13) | 0.34047 (15) | 0.44373 (12) | 0.0293 (5) | |
C40 | 0.59507 (15) | 0.2969 (2) | 0.43802 (17) | 0.0536 (8) | |
H40A | 0.6377 | 0.3196 | 0.4732 | 0.080* | |
H40B | 0.6036 | 0.3079 | 0.3928 | 0.080* | |
H40C | 0.5912 | 0.2360 | 0.4445 | 0.080* | |
C41 | 0.52603 (16) | 0.43667 (16) | 0.42870 (14) | 0.0392 (6) | |
H41A | 0.4796 | 0.4657 | 0.4327 | 0.059* | |
H41B | 0.5327 | 0.4439 | 0.3824 | 0.059* | |
H41C | 0.5700 | 0.4605 | 0.4616 | 0.059* | |
C42 | 0.51012 (17) | 0.32842 (18) | 0.51796 (13) | 0.0433 (7) | |
H42A | 0.4641 | 0.3577 | 0.5228 | 0.065* | |
H42B | 0.5547 | 0.3519 | 0.5505 | 0.065* | |
H42C | 0.5058 | 0.2682 | 0.5271 | 0.065* | |
C43 | 0.22745 (13) | 0.33977 (14) | 0.34274 (11) | 0.0254 (5) | |
H43A | 0.2274 | 0.3636 | 0.3880 | 0.031* | |
H43B | 0.1887 | 0.2945 | 0.3323 | 0.031* | |
C44 | 0.20756 (13) | 0.40970 (14) | 0.28756 (11) | 0.0241 (5) | |
C45 | 0.14685 (13) | 0.40119 (14) | 0.22739 (11) | 0.0238 (5) | |
C46 | 0.13583 (13) | 0.46252 (13) | 0.17434 (11) | 0.0231 (5) | |
C47 | 0.18408 (13) | 0.53453 (14) | 0.18439 (12) | 0.0269 (5) | |
H47 | 0.1768 | 0.5757 | 0.1493 | 0.032* | |
C48 | 0.24271 (13) | 0.54758 (14) | 0.24474 (12) | 0.0265 (5) | |
C49 | 0.25313 (13) | 0.48331 (14) | 0.29502 (12) | 0.0274 (5) | |
H49 | 0.2924 | 0.4900 | 0.3355 | 0.033* | |
C50 | 0.29342 (15) | 0.62886 (15) | 0.25753 (14) | 0.0355 (6) | |
C51 | 0.2688 (2) | 0.6835 (2) | 0.3123 (2) | 0.0838 (13) | |
H51A | 0.2728 | 0.6500 | 0.3537 | 0.126* | |
H51B | 0.2159 | 0.7019 | 0.2946 | 0.126* | |
H51C | 0.3020 | 0.7329 | 0.3230 | 0.126* | |
C52 | 0.2884 (2) | 0.6791 (2) | 0.1906 (2) | 0.0871 (14) | |
H52A | 0.2986 | 0.6412 | 0.1556 | 0.131* | |
H52B | 0.3262 | 0.7246 | 0.1992 | 0.131* | |
H52C | 0.2373 | 0.7032 | 0.1747 | 0.131* | |
C53 | 0.37896 (16) | 0.60548 (19) | 0.28619 (16) | 0.0487 (7) | |
H53A | 0.3854 | 0.5765 | 0.3300 | 0.073* | |
H53B | 0.4098 | 0.6570 | 0.2926 | 0.073* | |
H53C | 0.3954 | 0.5683 | 0.2539 | 0.073* | |
C54 | 0.07565 (13) | 0.45028 (15) | 0.10551 (11) | 0.0255 (5) | |
H54A | 0.0473 | 0.3971 | 0.1065 | 0.031* | |
H54B | 0.0388 | 0.4975 | 0.0980 | 0.031* | |
O11 | 0.00220 (13) | 0.01632 (14) | −0.11406 (12) | 0.0593 (6) | |
H11 | −0.038 (2) | −0.009 (2) | −0.1493 (18) | 0.071* | |
C55 | 0.0693 (2) | −0.0368 (2) | −0.1036 (2) | 0.0707 (10) | |
H55A | 0.0814 | −0.0474 | −0.1475 | 0.106* | |
H55B | 0.0594 | −0.0905 | −0.0834 | 0.106* | |
H55C | 0.1124 | −0.0084 | −0.0728 | 0.106* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
O1 | 0.0260 (9) | 0.0243 (8) | 0.0268 (8) | −0.0040 (7) | 0.0055 (7) | 0.0014 (7) |
O2 | 0.0339 (10) | 0.0530 (12) | 0.0657 (14) | −0.0123 (9) | 0.0063 (10) | −0.0214 (11) |
O3 | 0.0370 (10) | 0.0364 (10) | 0.0394 (10) | −0.0057 (8) | 0.0093 (8) | −0.0079 (8) |
O4 | 0.0276 (8) | 0.0230 (8) | 0.0266 (8) | −0.0019 (7) | 0.0081 (7) | −0.0031 (7) |
O5 | 0.0542 (12) | 0.0321 (9) | 0.0421 (11) | −0.0054 (9) | 0.0073 (9) | 0.0096 (8) |
O6 | 0.0244 (8) | 0.0265 (8) | 0.0229 (8) | −0.0049 (7) | 0.0028 (7) | 0.0012 (7) |
O7 | 0.0398 (10) | 0.0434 (10) | 0.0294 (10) | −0.0158 (8) | 0.0001 (8) | 0.0060 (8) |
O8 | 0.0451 (11) | 0.0431 (10) | 0.0340 (10) | −0.0213 (9) | 0.0065 (8) | 0.0013 (8) |
O9 | 0.0269 (8) | 0.0282 (8) | 0.0292 (9) | −0.0066 (7) | 0.0090 (7) | 0.0007 (7) |
O10 | 0.0364 (10) | 0.0413 (10) | 0.0503 (12) | −0.0089 (8) | 0.0070 (9) | 0.0153 (9) |
C1 | 0.0250 (12) | 0.0299 (13) | 0.0351 (14) | −0.0056 (10) | 0.0065 (10) | 0.0021 (11) |
C2 | 0.0309 (14) | 0.0352 (14) | 0.0320 (14) | −0.0071 (11) | 0.0052 (11) | 0.0008 (11) |
C3 | 0.0440 (15) | 0.0239 (12) | 0.0299 (13) | 0.0015 (11) | 0.0130 (11) | −0.0049 (10) |
C4 | 0.0470 (16) | 0.0254 (12) | 0.0364 (15) | −0.0037 (12) | 0.0063 (12) | −0.0045 (11) |
C5 | 0.075 (2) | 0.0331 (15) | 0.072 (2) | −0.0061 (15) | 0.0303 (18) | 0.0100 (15) |
C6 | 0.0312 (13) | 0.0292 (12) | 0.0289 (13) | −0.0071 (11) | 0.0053 (10) | 0.0033 (10) |
C7 | 0.0310 (13) | 0.0280 (12) | 0.0301 (13) | −0.0041 (11) | 0.0081 (11) | 0.0000 (10) |
C8 | 0.0264 (13) | 0.0413 (14) | 0.0418 (15) | 0.0003 (11) | 0.0127 (11) | 0.0076 (12) |
C9 | 0.0279 (14) | 0.0503 (16) | 0.0435 (16) | −0.0066 (12) | 0.0061 (12) | 0.0124 (13) |
C10 | 0.0459 (17) | 0.0445 (16) | 0.0595 (19) | −0.0122 (14) | 0.0175 (15) | 0.0169 (14) |
C11 | 0.0226 (11) | 0.0232 (11) | 0.0197 (11) | −0.0007 (9) | 0.0027 (9) | 0.0027 (9) |
C12 | 0.0214 (11) | 0.0270 (12) | 0.0232 (12) | −0.0029 (10) | 0.0025 (9) | −0.0002 (9) |
C13 | 0.0247 (12) | 0.0256 (12) | 0.0271 (12) | 0.0023 (10) | 0.0038 (10) | 0.0002 (10) |
C14 | 0.0242 (12) | 0.0283 (12) | 0.0243 (12) | −0.0027 (10) | 0.0022 (10) | 0.0016 (10) |
C15 | 0.0244 (12) | 0.0325 (12) | 0.0218 (12) | −0.0004 (10) | 0.0063 (10) | 0.0017 (10) |
C16 | 0.0228 (12) | 0.0250 (11) | 0.0219 (11) | 0.0001 (9) | 0.0034 (9) | −0.0009 (9) |
C17 | 0.0288 (13) | 0.0282 (12) | 0.0276 (13) | −0.0021 (10) | 0.0056 (10) | 0.0055 (10) |
C18 | 0.080 (2) | 0.0371 (15) | 0.0311 (14) | −0.0097 (15) | 0.0138 (15) | 0.0055 (12) |
C19 | 0.0382 (15) | 0.0349 (14) | 0.0398 (15) | −0.0067 (12) | 0.0076 (12) | 0.0056 (12) |
C20 | 0.0397 (15) | 0.0372 (15) | 0.067 (2) | 0.0027 (13) | 0.0155 (14) | 0.0235 (14) |
C21 | 0.0270 (12) | 0.0269 (12) | 0.0229 (12) | 0.0004 (10) | 0.0095 (10) | −0.0024 (9) |
C22 | 0.0235 (12) | 0.0256 (11) | 0.0243 (12) | 0.0050 (10) | 0.0095 (10) | −0.0020 (9) |
C23 | 0.0217 (11) | 0.0233 (11) | 0.0265 (12) | 0.0010 (9) | 0.0095 (9) | −0.0038 (9) |
C24 | 0.0281 (12) | 0.0221 (11) | 0.0248 (12) | 0.0040 (10) | 0.0108 (10) | −0.0009 (9) |
C25 | 0.0231 (12) | 0.0304 (12) | 0.0231 (12) | 0.0010 (10) | 0.0065 (10) | −0.0020 (10) |
C26 | 0.0245 (12) | 0.0254 (12) | 0.0262 (12) | 0.0002 (10) | 0.0080 (10) | −0.0038 (10) |
C27 | 0.0279 (12) | 0.0233 (11) | 0.0251 (12) | 0.0015 (10) | 0.0097 (10) | 0.0010 (9) |
C28 | 0.0296 (13) | 0.0274 (12) | 0.0352 (14) | −0.0039 (10) | 0.0094 (11) | −0.0004 (10) |
C29 | 0.0514 (18) | 0.0467 (17) | 0.0508 (18) | −0.0216 (15) | −0.0036 (15) | 0.0027 (14) |
C30 | 0.0418 (16) | 0.0451 (16) | 0.064 (2) | −0.0137 (13) | 0.0284 (15) | −0.0068 (15) |
C31 | 0.0515 (17) | 0.0298 (13) | 0.0475 (17) | −0.0052 (13) | 0.0154 (14) | −0.0069 (12) |
C32 | 0.0272 (12) | 0.0241 (11) | 0.0244 (12) | 0.0017 (10) | 0.0034 (10) | 0.0010 (10) |
C33 | 0.0291 (12) | 0.0201 (11) | 0.0214 (12) | −0.0014 (10) | 0.0057 (10) | 0.0046 (9) |
C34 | 0.0243 (12) | 0.0233 (11) | 0.0208 (11) | −0.0035 (10) | 0.0009 (9) | 0.0022 (9) |
C35 | 0.0268 (12) | 0.0241 (11) | 0.0220 (12) | −0.0029 (10) | 0.0066 (10) | 0.0043 (9) |
C36 | 0.0299 (12) | 0.0251 (11) | 0.0196 (11) | −0.0002 (10) | 0.0070 (10) | −0.0006 (9) |
C37 | 0.0259 (12) | 0.0222 (11) | 0.0243 (12) | −0.0005 (9) | 0.0025 (10) | 0.0032 (9) |
C38 | 0.0244 (12) | 0.0256 (12) | 0.0255 (12) | 0.0013 (10) | 0.0052 (10) | 0.0039 (10) |
C39 | 0.0260 (12) | 0.0305 (12) | 0.0286 (13) | −0.0017 (10) | 0.0014 (10) | 0.0004 (10) |
C40 | 0.0287 (15) | 0.0606 (19) | 0.061 (2) | 0.0088 (13) | −0.0095 (14) | −0.0209 (16) |
C41 | 0.0420 (15) | 0.0356 (14) | 0.0386 (15) | −0.0128 (12) | 0.0074 (12) | −0.0012 (12) |
C42 | 0.0485 (17) | 0.0483 (16) | 0.0259 (14) | −0.0142 (14) | −0.0044 (12) | 0.0048 (12) |
C43 | 0.0269 (12) | 0.0294 (12) | 0.0204 (12) | −0.0017 (10) | 0.0067 (9) | 0.0003 (9) |
C44 | 0.0246 (12) | 0.0254 (11) | 0.0241 (12) | 0.0005 (10) | 0.0095 (10) | −0.0009 (9) |
C45 | 0.0235 (12) | 0.0236 (11) | 0.0261 (12) | −0.0010 (9) | 0.0096 (10) | −0.0014 (9) |
C46 | 0.0248 (12) | 0.0229 (11) | 0.0232 (12) | 0.0034 (9) | 0.0088 (10) | −0.0015 (9) |
C47 | 0.0323 (13) | 0.0236 (12) | 0.0258 (12) | 0.0031 (10) | 0.0095 (10) | 0.0025 (9) |
C48 | 0.0291 (13) | 0.0226 (11) | 0.0285 (12) | 0.0002 (10) | 0.0087 (10) | −0.0012 (10) |
C49 | 0.0255 (12) | 0.0289 (12) | 0.0264 (12) | −0.0006 (10) | 0.0035 (10) | −0.0037 (10) |
C50 | 0.0379 (15) | 0.0272 (13) | 0.0393 (15) | −0.0074 (11) | 0.0056 (12) | −0.0024 (11) |
C51 | 0.075 (2) | 0.0506 (19) | 0.139 (4) | −0.0208 (18) | 0.052 (2) | −0.054 (2) |
C52 | 0.092 (3) | 0.064 (2) | 0.079 (3) | −0.049 (2) | −0.027 (2) | 0.0383 (19) |
C53 | 0.0432 (17) | 0.0489 (17) | 0.0533 (18) | −0.0139 (14) | 0.0104 (14) | −0.0030 (14) |
C54 | 0.0253 (12) | 0.0269 (12) | 0.0246 (12) | 0.0020 (10) | 0.0070 (10) | −0.0006 (10) |
O11 | 0.0527 (14) | 0.0552 (13) | 0.0629 (14) | −0.0109 (11) | 0.0010 (11) | −0.0227 (11) |
C55 | 0.064 (2) | 0.062 (2) | 0.075 (3) | −0.0007 (18) | −0.0038 (19) | −0.0126 (18) |
Geometric parameters (Å, º) top
O1—C11 | 1.392 (3) | C22—C27 | 1.398 (3) |
O1—C1 | 1.430 (3) | C23—C24 | 1.394 (3) |
O2—C2 | 1.326 (3) | C24—C25 | 1.394 (3) |
O2—O11 | 2.634 (3) | C24—C32 | 1.521 (3) |
O3—C2 | 1.207 (3) | C25—C26 | 1.386 (3) |
O4—C23 | 1.397 (3) | C26—C27 | 1.392 (3) |
O4—C3 | 1.434 (3) | C26—C28 | 1.535 (3) |
O4—O7 | 2.820 (2) | C28—C29 | 1.526 (4) |
O5—C5 | 1.421 (3) | C28—C30 | 1.529 (4) |
O5—C4 | 1.422 (3) | C28—C31 | 1.531 (3) |
O6—C34 | 1.402 (2) | C32—C33 | 1.509 (3) |
O6—C6 | 1.427 (3) | C33—C34 | 1.391 (3) |
O7—C7 | 1.306 (3) | C33—C38 | 1.397 (3) |
O8—C7 | 1.214 (3) | C34—C35 | 1.395 (3) |
O9—C45 | 1.393 (3) | C35—C36 | 1.388 (3) |
O9—C8 | 1.440 (3) | C35—C43 | 1.516 (3) |
O10—C9 | 1.415 (3) | C36—C37 | 1.401 (3) |
O10—C10 | 1.418 (3) | C37—C38 | 1.386 (3) |
C1—C2 | 1.507 (3) | C37—C39 | 1.534 (3) |
C3—C4 | 1.493 (3) | C39—C42 | 1.531 (3) |
C6—C7 | 1.499 (3) | C39—C40 | 1.534 (4) |
C8—C9 | 1.500 (3) | C39—C41 | 1.535 (3) |
C11—C16 | 1.390 (3) | C43—C44 | 1.520 (3) |
C11—C12 | 1.394 (3) | C44—C49 | 1.388 (3) |
C12—C13 | 1.397 (3) | C44—C45 | 1.402 (3) |
C12—C54 | 1.520 (3) | C45—C46 | 1.396 (3) |
C13—C14 | 1.393 (3) | C46—C47 | 1.393 (3) |
C14—C15 | 1.395 (3) | C46—C54 | 1.522 (3) |
C14—C17 | 1.535 (3) | C47—C48 | 1.393 (3) |
C15—C16 | 1.390 (3) | C48—C49 | 1.390 (3) |
C16—C21 | 1.516 (3) | C48—C50 | 1.535 (3) |
C17—C19 | 1.522 (3) | C50—C52 | 1.523 (4) |
C17—C20 | 1.528 (3) | C50—C51 | 1.524 (4) |
C17—C18 | 1.532 (4) | C50—C53 | 1.527 (4) |
C21—C22 | 1.517 (3) | O11—C55 | 1.421 (4) |
C22—C23 | 1.398 (3) | O11—O8i | 2.719 (3) |
| | | |
C11—O1—C1 | 113.65 (16) | C27—C26—C28 | 120.0 (2) |
C2—O2—O11 | 108.97 (16) | C26—C27—C22 | 122.9 (2) |
C23—O4—C3 | 112.72 (17) | C29—C28—C30 | 108.5 (2) |
C23—O4—O7 | 135.05 (13) | C29—C28—C31 | 107.9 (2) |
C3—O4—O7 | 111.90 (13) | C30—C28—C31 | 109.2 (2) |
C5—O5—C4 | 111.7 (2) | C29—C28—C26 | 112.5 (2) |
C34—O6—C6 | 112.00 (16) | C30—C28—C26 | 108.9 (2) |
C7—O7—O4 | 116.37 (15) | C31—C28—C26 | 109.9 (2) |
C45—O9—C8 | 111.12 (17) | C33—C32—C24 | 108.30 (17) |
C9—O10—C10 | 112.09 (19) | C34—C33—C38 | 117.9 (2) |
O1—C1—C2 | 113.0 (2) | C34—C33—C32 | 120.83 (19) |
O3—C2—O2 | 124.0 (2) | C38—C33—C32 | 120.8 (2) |
O3—C2—C1 | 126.1 (2) | C33—C34—C35 | 122.2 (2) |
O2—C2—C1 | 109.9 (2) | C33—C34—O6 | 118.72 (19) |
O4—C3—C4 | 110.0 (2) | C35—C34—O6 | 118.9 (2) |
O5—C4—C3 | 109.4 (2) | C36—C35—C34 | 117.3 (2) |
O6—C6—C7 | 109.78 (18) | C36—C35—C43 | 121.7 (2) |
O8—C7—O7 | 120.6 (2) | C34—C35—C43 | 120.8 (2) |
O8—C7—C6 | 120.6 (2) | C35—C36—C37 | 122.9 (2) |
O7—C7—C6 | 118.8 (2) | C38—C37—C36 | 117.3 (2) |
O9—C8—C9 | 109.3 (2) | C38—C37—C39 | 122.7 (2) |
O10—C9—C8 | 108.9 (2) | C36—C37—C39 | 120.0 (2) |
C16—C11—O1 | 119.16 (19) | C37—C38—C33 | 122.3 (2) |
C16—C11—C12 | 121.4 (2) | C42—C39—C40 | 108.7 (2) |
O1—C11—C12 | 119.38 (19) | C42—C39—C37 | 110.3 (2) |
C11—C12—C13 | 118.1 (2) | C40—C39—C37 | 111.9 (2) |
C11—C12—C54 | 120.81 (19) | C42—C39—C41 | 109.7 (2) |
C13—C12—C54 | 120.6 (2) | C40—C39—C41 | 107.7 (2) |
C14—C13—C12 | 122.4 (2) | C37—C39—C41 | 108.45 (19) |
C13—C14—C15 | 116.6 (2) | C35—C43—C44 | 109.49 (18) |
C13—C14—C17 | 122.6 (2) | C49—C44—C45 | 118.3 (2) |
C15—C14—C17 | 120.7 (2) | C49—C44—C43 | 119.1 (2) |
C16—C15—C14 | 123.2 (2) | C45—C44—C43 | 122.5 (2) |
C11—C16—C15 | 117.7 (2) | O9—C45—C46 | 120.16 (19) |
C11—C16—C21 | 120.85 (19) | O9—C45—C44 | 119.08 (19) |
C15—C16—C21 | 121.3 (2) | C46—C45—C44 | 120.8 (2) |
C19—C17—C20 | 107.8 (2) | C47—C46—C45 | 118.3 (2) |
C19—C17—C18 | 109.7 (2) | C47—C46—C54 | 119.9 (2) |
C20—C17—C18 | 108.4 (2) | C45—C46—C54 | 121.74 (19) |
C19—C17—C14 | 107.90 (19) | C48—C47—C46 | 122.8 (2) |
C20—C17—C14 | 112.5 (2) | C49—C48—C47 | 116.7 (2) |
C18—C17—C14 | 110.5 (2) | C49—C48—C50 | 120.2 (2) |
C16—C21—C22 | 110.75 (18) | C47—C48—C50 | 123.0 (2) |
C23—C22—C27 | 117.5 (2) | C44—C49—C48 | 123.0 (2) |
C23—C22—C21 | 122.5 (2) | C52—C50—C51 | 111.7 (3) |
C27—C22—C21 | 119.9 (2) | C52—C50—C53 | 106.5 (3) |
C24—C23—O4 | 118.41 (19) | C51—C50—C53 | 107.5 (3) |
C24—C23—C22 | 121.5 (2) | C52—C50—C48 | 111.8 (2) |
O4—C23—C22 | 120.01 (19) | C51—C50—C48 | 108.4 (2) |
C23—C24—C25 | 118.3 (2) | C53—C50—C48 | 110.7 (2) |
C23—C24—C32 | 122.1 (2) | C12—C54—C46 | 109.03 (18) |
C25—C24—C32 | 119.4 (2) | C55—O11—O2 | 123.36 (19) |
C26—C25—C24 | 122.5 (2) | C55—O11—O8i | 107.03 (18) |
C25—C26—C27 | 117.3 (2) | O2—O11—O8i | 129.61 (11) |
C25—C26—C28 | 122.7 (2) | | |
| | | |
C23—O4—O7—C7 | −85.4 (2) | C27—C26—C28—C29 | 171.8 (2) |
C3—O4—O7—C7 | 87.3 (2) | C25—C26—C28—C30 | 112.3 (3) |
C11—O1—C1—C2 | 105.5 (2) | C27—C26—C28—C30 | −68.0 (3) |
O11—O2—C2—O3 | 3.1 (3) | C25—C26—C28—C31 | −128.1 (2) |
O11—O2—C2—C1 | −175.98 (16) | C27—C26—C28—C31 | 51.5 (3) |
O1—C1—C2—O3 | 0.7 (4) | C23—C24—C32—C33 | −113.2 (2) |
O1—C1—C2—O2 | 179.8 (2) | C25—C24—C32—C33 | 61.7 (3) |
C23—O4—C3—C4 | 165.89 (19) | C24—C32—C33—C34 | 78.2 (3) |
O7—O4—C3—C4 | −8.5 (2) | C24—C32—C33—C38 | −93.5 (2) |
C5—O5—C4—C3 | −174.1 (2) | C38—C33—C34—C35 | 3.0 (3) |
O4—C3—C4—O5 | −69.4 (3) | C32—C33—C34—C35 | −168.9 (2) |
C34—O6—C6—C7 | −176.16 (19) | C38—C33—C34—O6 | 179.56 (18) |
O4—O7—C7—O8 | −136.8 (2) | C32—C33—C34—O6 | 7.6 (3) |
O4—O7—C7—C6 | 42.0 (3) | C6—O6—C34—C33 | 94.2 (2) |
O6—C6—C7—O8 | −169.2 (2) | C6—O6—C34—C35 | −89.1 (2) |
O6—C6—C7—O7 | 12.0 (3) | C33—C34—C35—C36 | −2.3 (3) |
C45—O9—C8—C9 | −163.65 (19) | O6—C34—C35—C36 | −178.83 (19) |
C10—O10—C9—C8 | 171.9 (2) | C33—C34—C35—C43 | 172.2 (2) |
O9—C8—C9—O10 | 72.5 (3) | O6—C34—C35—C43 | −4.3 (3) |
C1—O1—C11—C16 | −110.9 (2) | C34—C35—C36—C37 | 0.5 (3) |
C1—O1—C11—C12 | 72.1 (2) | C43—C35—C36—C37 | −173.9 (2) |
C16—C11—C12—C13 | 9.3 (3) | C35—C36—C37—C38 | 0.4 (3) |
O1—C11—C12—C13 | −173.72 (19) | C35—C36—C37—C39 | 177.5 (2) |
C16—C11—C12—C54 | −162.5 (2) | C36—C37—C38—C33 | 0.3 (3) |
O1—C11—C12—C54 | 14.5 (3) | C39—C37—C38—C33 | −176.7 (2) |
C11—C12—C13—C14 | −4.8 (3) | C34—C33—C38—C37 | −2.0 (3) |
C54—C12—C13—C14 | 166.9 (2) | C32—C33—C38—C37 | 169.9 (2) |
C12—C13—C14—C15 | −1.3 (3) | C38—C37—C39—C42 | −129.5 (2) |
C12—C13—C14—C17 | −177.5 (2) | C36—C37—C39—C42 | 53.5 (3) |
C13—C14—C15—C16 | 3.4 (3) | C38—C37—C39—C40 | −8.4 (3) |
C17—C14—C15—C16 | 179.6 (2) | C36—C37—C39—C40 | 174.6 (2) |
O1—C11—C16—C15 | 175.68 (19) | C38—C37—C39—C41 | 110.3 (2) |
C12—C11—C16—C15 | −7.3 (3) | C36—C37—C39—C41 | −66.7 (3) |
O1—C11—C16—C21 | −8.7 (3) | C36—C35—C43—C44 | 97.2 (2) |
C12—C11—C16—C21 | 168.3 (2) | C34—C35—C43—C44 | −77.0 (2) |
C14—C15—C16—C11 | 0.8 (3) | C35—C43—C44—C49 | −63.4 (3) |
C14—C15—C16—C21 | −174.8 (2) | C35—C43—C44—C45 | 113.6 (2) |
C13—C14—C17—C19 | 98.7 (3) | C8—O9—C45—C46 | −98.7 (2) |
C15—C14—C17—C19 | −77.3 (3) | C8—O9—C45—C44 | 81.7 (2) |
C13—C14—C17—C20 | −20.1 (3) | C49—C44—C45—O9 | −176.3 (2) |
C15—C14—C17—C20 | 163.9 (2) | C43—C44—C45—O9 | 6.7 (3) |
C13—C14—C17—C18 | −141.4 (2) | C49—C44—C45—C46 | 4.1 (3) |
C15—C14—C17—C18 | 42.6 (3) | C43—C44—C45—C46 | −172.9 (2) |
C11—C16—C21—C22 | −80.3 (3) | O9—C45—C46—C47 | 177.1 (2) |
C15—C16—C21—C22 | 95.1 (2) | C44—C45—C46—C47 | −3.3 (3) |
C16—C21—C22—C23 | 111.3 (2) | O9—C45—C46—C54 | −5.8 (3) |
C16—C21—C22—C27 | −66.9 (3) | C44—C45—C46—C54 | 173.7 (2) |
C3—O4—C23—C24 | −88.9 (2) | C45—C46—C47—C48 | 0.3 (3) |
O7—O4—C23—C24 | 83.7 (2) | C54—C46—C47—C48 | −176.9 (2) |
C3—O4—C23—C22 | 93.0 (2) | C46—C47—C48—C49 | 1.9 (3) |
O7—O4—C23—C22 | −94.4 (2) | C46—C47—C48—C50 | −177.0 (2) |
C27—C22—C23—C24 | 1.3 (3) | C45—C44—C49—C48 | −1.9 (3) |
C21—C22—C23—C24 | −177.0 (2) | C43—C44—C49—C48 | 175.2 (2) |
C27—C22—C23—O4 | 179.31 (19) | C47—C48—C49—C44 | −1.0 (4) |
C21—C22—C23—O4 | 1.0 (3) | C50—C48—C49—C44 | 177.8 (2) |
O4—C23—C24—C25 | −179.05 (19) | C49—C48—C50—C52 | 164.8 (3) |
C22—C23—C24—C25 | −1.0 (3) | C47—C48—C50—C52 | −16.4 (4) |
O4—C23—C24—C32 | −4.1 (3) | C49—C48—C50—C51 | −71.6 (3) |
C22—C23—C24—C32 | 173.9 (2) | C47—C48—C50—C51 | 107.2 (3) |
C23—C24—C25—C26 | 0.3 (3) | C49—C48—C50—C53 | 46.1 (3) |
C32—C24—C25—C26 | −174.7 (2) | C47—C48—C50—C53 | −135.1 (2) |
C24—C25—C26—C27 | 0.0 (3) | C11—C12—C54—C46 | 78.9 (3) |
C24—C25—C26—C28 | 179.7 (2) | C13—C12—C54—C46 | −92.7 (2) |
C25—C26—C27—C22 | 0.3 (3) | C47—C46—C54—C12 | 58.9 (3) |
C28—C26—C27—C22 | −179.4 (2) | C45—C46—C54—C12 | −118.2 (2) |
C23—C22—C27—C26 | −0.9 (3) | C2—O2—O11—C55 | 23.6 (3) |
C21—C22—C27—C26 | 177.4 (2) | C2—O2—O11—O8i | −156.90 (17) |
C25—C26—C28—C29 | −7.9 (3) | | |
Symmetry code: (i) −x, −y, −z. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O7—H7···O4 | 0.95 | 2.04 | 2.820 (2) | 138 |
O7—H7···O6 | 0.95 | 2.14 | 2.630 (2) | 111 |
O2—H2···O11 | 0.94 | 1.70 | 2.634 (3) | 176 |
O11—H11···O8i | 0.95 (3) | 1.77 (3) | 2.719 (3) | 176 (3) |
Symmetry code: (i) −x, −y, −z. |
Experimental details
Crystal data |
Chemical formula | C54H72O10·CH4O |
Mr | 913.16 |
Crystal system, space group | Monoclinic, P21/c |
Temperature (K) | 127 |
a, b, c (Å) | 17.7426 (9), 15.5402 (6), 19.8147 (10) |
β (°) | 104.279 (2) |
V (Å3) | 5294.6 (4) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.08 |
Crystal size (mm) | 0.45 × 0.28 × 0.25 |
|
Data collection |
Diffractometer | Nonius Kappa-CCD diffractometer |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 18139, 9972, 6410 |
Rint | 0.050 |
(sin θ/λ)max (Å−1) | 0.610 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.055, 0.138, 1.01 |
No. of reflections | 9972 |
No. of parameters | 614 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.27, −0.23 |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O7—H7···O4 | 0.947 | 2.042 | 2.820 (2) | 138.2 |
O7—H7···O6 | 0.947 | 2.144 | 2.630 (2) | 110.5 |
O2—H2···O11 | 0.939 | 1.698 | 2.634 (3) | 175.5 |
O11—H11···O8i | 0.95 (3) | 1.77 (3) | 2.719 (3) | 176 (3) |
Symmetry code: (i) −x, −y, −z. |
Calixarenes are macrocyclic molecules made up of p-substituted phenolic units linked by methylene bridges ortho to the OH functions (Gutsche, 1989; Vicens & Böhmer, 1991; Böhmer, 1995). The ability of parent phenolic calixarenes, as well as of their chemically modified derivatives obtained by the substitution of the phenolic H atoms with various types of ligating groups, to bind metal ions is well established (Böhmer, 1995).
With calix[4]arenes, the substituents frequently immobilize the molecule in a single conformation: cone, partial cone, 1,2- or 1,3-alternate. Calixarene carboxylic acids, in which the carboxylic groups are attached to the phenolic O atoms, display interesting complexation properties towards alkali and alkali earth metal cations (McKervey et al., 1996), as well as towards the lanthanides and Th (Arnaud-Neu et al., 1997). The tetra(carboxymethoxy) derivative of p-tert-butylcalix[4]arene has been shown recently to display a high selectivity for AcIII cations (Chen et al., 1998). The systematic study of the acid-base and complexation properties towards alkali metal cations of a series of calixarene carboxylic acids has been reported by McKervey et al. (1996). The determination of pKa values in methanol showed that, whatever the number of carboxylic acid functions (except for one mono-acid compound), the p-tert-butylcalix[4]arene carboxylic acid derivatives in the cone conformation are less acidic than phenoxyacetic acid. This observation was interpreted in terms of stabilization of the protonated form by intramolecular hydrogen bonding. The structure of the title methanol solvate, (I), reported herein indicates that, in solution in methanol, intermolecular hydrogen bonds leading to dimerization are also to be taken into account. \scheme
The asymmetric unit of (I) comprises one calixarene and one methanol molecule. The calixarene is in a distorted cone conformation, in which the dihedral angles between the four aromatic rings and the mean plane defined by the four methylenic bridges are 49.62 (7), 84.69 (5), 48.42 (6) and 88.05 (5)°. The two rings bonded to the glycolic chains are more vertical than the other two rings. Such a pseudo-C2 geometry is rather frequent in calix[4]arenes bearing different bulky substituents and the resulting pinching of the cone has been thought to prevent solvent inclusion in the calixarene cavity (Drew et al., 1997), which is confirmed in the present case. This geometry enables one of the carboxylic O atoms (O7) to be directed towards the inside of the molecule and to form hydrogen bonds with the ether atoms O4 and O6 (see Table 1).
The methanol molecule forms two hydrogen bonds, one with the carboxylic atom O2, pertaining to the acid group directed outwards, and the other with the atom O8(-x, -y, -z) from another calixarene molecule, related to the first one by the symmetry centre. This leads to the formation of dimers, including two head-to-head calixarene molecules, with their main axis parallel to each other, interconnected by two methanol molecules. Obviously, such a dimerization would not be possible if both carboxylic groups were involved in intramolecular hydrogen bonds. On the other hand, a dimerization by direct bonding of the carboxylic groups of the two molecules would probably be hampered by the steric hindrance of the glycolic chains. The present bonding pattern must be taken into consideration when complexation equilibria in methanol, during cation transportation, are considered.