Steric effects on forming different by-products in the formylation reaction of 2,4-dialkylphenol (dialkyl = t-Bu/t-Bu, t-Bu/Me and Me/Me) proved by their structural and spectral characterizations

Article abstract of DOI:10.1016/j.molstruc.2007.10.035

In the formylation reaction of 2,4-dialkylphenol (2,4-di-tert-butylphenol, 2-tert-butyl-4-methylphenol and 2,4-dimethylphenol) in the presence of hexamethylenetetramine, steric effects of alkyl groups play important roles in forming different types of by-

Full text of DOI:10.1016/j.molstruc.2007.10.035

Available online at www.sciencedirect.com
Journal of Molecular Structure 885 (2008) 154–160
www.elsevier.com/locate/molstruc
Steric effects on forming different by-products in the formylation
reaction of 2,4-dialkylphenol (dialkyl = t-Bu/t-Bu, t-Bu/Me
and Me/Me) proved by their structural and spectral characterizations
Wei Huang *, Zhaolian Chu, Feng Xu
State Key Laboratory of Coordination Chemistry, Coordination Chemistry Institute, School of Chemistry and Chemical Engineering,
Nanjing University, Nanjing 210093, PR China
Received 24 August 2007; received in revised form 6 October 2007; accepted 18 October 2007
Available online 7 November 2007
Abstract
In the formylation reaction of 2,4-dialkylphenol (2,4-di-tert-butylphenol, 2-tert-butyl-4-methylphenol and 2,4-dimethylphenol) in the
presence of hexamethylenetetramine, steric effects of alkyl groups play important roles in forming different types of by-products, namely
2,4-di-tert-butyl-6-[(6,8-di-tert-butyl-2H-1,3-benzoxazin-3(4H)-yl)methyl]phenol (1), 2-tert-butyl-4-methyl-6-[(6-tert-butyl-8-methyl-2H-
1,3-benzoxazin-3(4H)-yl)methyl]phenol (2) and tris(2-hydroxy-3,5-dimethylbenzyl)amine hydrochlorate (3). These three compounds
are fully characterized and single-crystal structures of 1 and 3 are further elucidated.
Ó 2007 Elsevier B.V. All rights reserved.
Keywords: Formylation reaction; Steric effects; Crystal structures; Hydrogen bonding interactions
1. Introduction
phenyl)phosphonate [10] as well as its Fe(III) complex
have been structurally reported previously [11].
Nitrogen-containing benzoheterocycles and their deriva-
tives are important intermediates for organic synthesis and
useful candidates for the studies on biochemistry and medic-
inal chemistry [1–3]. Tris(2-hydroxy-3,5-dialkyl)amines [4]
are typical tripodal ligands and there have been many
related reports in the literature. For instance, Holmes
et al. reported the structures and dynamic NMR behavior
of new classes of silatranes and phosphatranes derived from
the tripodal ligand tris(2-hydroxy-3,5-dialkyl)amine [5].
Gallium(III) and Indium(III) complexes of tris(2-merca-
ptobenzyl)amine and tris(2-hydroxybenzyl)amine [6] and
dimethoxy-(tris(2-oxy-3,5-dimethylbenzyl)amine) tantalum(IV)
salts [7] have also been documented. With regard to
tris(2-hydroxy-3,5-dimethylbenzyl)amine [8], its phen-
ylphosphinate [9] and 2,20-thiobis(4-methyl-6-tert-butyl-
In addition to the conventional preparation methods,
our experimental results show that 2,4-di-tert-butyl-6-
[(6,8-di-tert-butyl-2H-1,3-benzoxazin-3(4H)-yl)methyl]phe-
nol (1), 2-tert-butyl-4-methyl-6-[(6-tert-butyl-8-methyl-2H-
1,3-benzoxazin-3(4H)-yl)methyl]phenol (2) and tris(2-
hydroxy-3,5-dimethylbenzyl)amine hydrochlorate (3) can
also be yielded as the main by-products in the process of
Duff reaction [12] of 2,4-dialkylphenol and hexamethylene-
tetramine (HMT). However, different by-products can be
obtained in different yields due to the use of different
dialkyl ring substituents (dialkyl = t-Bu/t-Bu, t-Bu/Me
and Me/Me), as can be seen in Scheme 1. In addition, we
present herein the single-crystal structures of 1 and 3.
2. Experimental
2.1. Materials and measurements
*
Melting points were measured without correction in this
Corresponding author. Tel.: +86 25 83686526; fax: +86 25 83314502.
E-mail address: whuang@nuj.edu.cn (W. Huang).
work. 2,4-Di-tert-butylphenol, 2-tert-butyl-4-methylphenol
0022-2860/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2007.10.035

W. Huang et al. / Journal of Molecular Structure 885 (2008) 154–160
155
t-Bu
R1
t-Bu
O
OH
HMT / H3O+
N
R1
CHO
t-Bu
R1
OH
1 R1 = t-Bu
2 R1 = Me
R1 = t-Bu, Me
Me
+
H2
C
OH
Me
NH
_
HMT / H3O+
Cl
CHO
Me
OH
Me
3
3
Scheme 1. Synthetic routes for compounds 1–3.
and 2,4-dimethylphenol were purchased as commercial
chemicals from Aldrich. All other solvents and reagents
were of analytical grade and used without further purifica-
tion. Analyses for carbon, hydrogen and nitrogen were per-
formed on a Perkin-Elmer 1400C analyzer. Infrared
spectra (4000–400 cmꢀ1) were recorded with a Nicolet
(100%). Single crystals suitable for X-ray analysis were
grown from ethanol by slow evaporation at room temper-
ature in air.
2.3. Synthesis of 2-tert-butyl-4-methyl-6-[(6-tert-butyl-8-
methyl-2H-1,3-benzoxazin-3(4H)-yl)methyl]phenol (2)
1
FT-IR 170X spectrophotometer on KBr disks. H NMR
spectra were obtained in a Bruker 500 MHz NMR spec-
trometer. Electrospray ionization mass spectra (ESI-MS)
were recorded on a Finnigan MAT SSQ 710 mass spec-
trometer in a scan range of 100–1200 amu. The samples
were determined by injecting the diluted methanol solu-
tions using 1:1 methanol/water solvent as the mobile phase.
The spray voltage and capillary temperature were set at
4.5 kV and 200 °C, respectively.
The synthesis of 3-tert-butyl-5-methyl-2-hydroxybenzal-
dehyde is the same as 3,5-di-tert-2-hydroxybenzaldehyde
in a yield of ꢁ35% except that CH3COOH was used to
replace CF3COOH. Compound 2 is not isolated because
of the synthetic difficulties (<10% yield) but an ESI-MS
peak at 382.1 corresponding to the cation of
[C25H35NO2+H]+ (100%) verifies the presence of 2 in the
residue.
2.2. Synthesis of 2,4-di-tert-butyl-6-[(6,8-di-tert-butyl-2H-
1,3-benzoxazin-3(4H)-yl)methyl]phenol (1)
2.4. Synthesis of tris(2-hydroxy-3,5-dimethylbenzyl)amine
hydrochlorate (3)
The preparation method of 1 is the same as that of 3,5-
di-tert-2-hydroxybenzaldehyde reported by Larrow et al.
[13]. The crude product (mainly a mixture of 3,5-di-tert-
2-hydroxybenzaldehyde and 1) was suspended in a warm
(55 °C) methanol solution and a white powder was sepa-
rated by vacuum filtration which afforded compound 1 in
a yield of ꢁ35%. 3,5-Di-tert-butyl-2-hydroxybenzaldehyde
could be separated from the filtrate by cooling to 0 °C and
subsequent sucking in a yield of ꢁ45%. Mp 167–168 °C.
Anal. Calcd for C31H47NO2: C, 79.95; H, 10.17; N,
3.01%. Found: C, 79.79; H, 9.96; N, 2.82%. IR (KBr disk,
cmꢀ1): 3300 (OH), 2960, 2904, 2869 and 1390 (t-Bu), 1231
The synthesis of 3,5-dimethyl-2-hydroxybenzaldehyde is
the same as above-mentioned two aldehydes. Hydrochl-
orate 3 was obtained as precipitate from the water/ether
mixture. The precipitate was collected and recrystallized
by ethanol/water in a yield of ꢁ40%. Mp 210–211 °C.
Anal. Calcd for C27H34ClNO3: C, 71.11; H, 7.51; N,
3.07%. Found: C, 71.03; H, 7.38; N, 2.97%. IR (KBr disk,
cmꢀ1): 3241 (NAH), 3111, 3011, 2970, 2916, 2862, 1492,
1443, 1422, 1387 (CH3), 1249, 1195 (CAO). 1H NMR
(500 MHz, CDCl3, 298 K, TMS): d 2.24 (s, 18H, CH3),
4.08 (s, 6H, CH2), 6.79 (s, 3H, ArAOH), 7.03 (s, 3H,
ArAH), 7.29 (s, 3H, ArAH), 9.28 (s, 1H, NAH). ESI-
MS: m/z 420.2 [C27H34ClNO3ꢀCl]+ (100%). Single crystals
suitable for X-ray analysis were grown from a mixture of
ethanol and water in a 2:1 (v/v) ratio by slow evaporation
at room temperature in air.
1
(CAO). H NMR (500 MHz, CDCl3, 298 K, TMS): d 1.28
(s, 9H, t-Bu), 1.32 (s, 9H, t-Bu), 1.36 (s, 9H, t-Bu), 1.57 (s,
9H, t-Bu), 4.10 (s, 4H, NACH2AAr), 4.87 (s, 2H,
ArAOACH2AN), 6.84 (s, 1H, ArAOH), 7.23–7.32 (m,
4H, ArAH). ESI-MS: m/z 466.3 [C31H47NO2+H]+

156
W. Huang et al. / Journal of Molecular Structure 885 (2008) 154–160
Table 1
2.5. X-ray data collection and solution
Summary of crystal data, experimental details and refinement results for 1
and 3
Single-crystal samples of 1 and 3 were glue-covered and
mounted on glass fibers and then used for data collection
using graphite mono-chromated MoKa radiation
Compound
1
3
Empirical formula
Formula weight
Crystal system
Space group
Unit cell dimensions
C31H47NO2
465.70
Monoclinic
P21/c
C27H34NClO3
456.00
Orthorhombic
Fdd2
˚
(k = 0.71073 A). Crystallographic data of 1 were collected
at 291(2) K on a Bruker SMART 1 K CCD diffractometer,
while those of 3 were collected at 100(2) K on a Rigaku
Mercury CCD area-detector, using graphite mono-chro-
˚
˚
11.0245(13) A
25.878(5) A
˚
˚
18.770(2) A
46.488(9) A
˚
˚
˚
28.840(4) A
8.485(2) A
mated MoKa radiation (k = 0.71073 A). In the case of
b = 97.247(3)°
5920.3(12)
8
1.045
0.064
b = 90°
10208(4)
16
1.187
0.177
Rigaku system, the original data files generated by CRYS-
TALCLEAR [14] were transformed to SHELXTL97 for-
mat by TEXSAN program [15].
3
˚
V/A
Z
D/g cmꢀ3
Absorption coefficient/mmꢀ1
Crystal size [mm]
Temperature [K]
h Range for data collection
Index ranges
The crystal systems of 1 and 3 were determined by laue
symmetry and the space groups were assigned on the basis
of systematic absences using XPREP. Absorption correc-
tions were performed to all data and the structures were
solved by direct methods and refined by full-matrix least-
squares method on F 2obs by using the SHELXTL-PC soft-
ware package [16]. All non-H atoms were anisotropically
refined and all hydrogen atoms were inserted in the calcu-
lated positions assigned fixed isotropic thermal parameters
and allowed to ride on their respective parent atoms. As for
the crystal data of 3, it was difficult to grow good single
crystals especially for smaller ones (samples in large size
and high Rint values were found) and the room temperature
data were not good enough although we have tried many
times. That is why we collected the low temperature data
for 3 at 100 K. Only several ‘‘C alerts” were reported at this
time when checked by Platon, which indicated that the
structure mode of 3 was reliable. The summary of the crys-
tal data, experimental details and refinement results for 1
and 3 is listed in Table 1.
0.20 ꢂ 0.30 ꢂ 0.40 0.20 ꢂ 0.30 ꢂ 0.40
291(2)
100(2)
1.79–26.00
ꢀ13 6 h 6 8
ꢀ22 6 k 6 23
ꢀ35 6 l 6 34
31,324
3.06–25.00
ꢀ30 6 h 6 30
ꢀ49 6 k 6 54
ꢀ10 6 l 6 8
21,282
No. of reflections collected
No. of independent reflections/ 11,639/637
parameters
4334/298
Absorption correction
Observed data [I > 2r(I)]
Goodness-of-fit on F2
F (000)
Multi-scan
8041
1.187
Multi-scan
4076
1.160
2048
3904
Flack parameter
–
0.01(11)
Final R indices [I > 2r(I)]
R1 = 0.0553
wR2 = 0.1452
R1 = 0.0812
wR1 = 0.1503
0.152/ꢀ0.149
R1 = 0.0748
wR2 = 0.1774
R1 = 0.0793
wR1 = 0.1799
0.383/ꢀ0.300
R indices (all data)
Largest diff. peak and hole
ꢀ3
˚
(e A
)
R1 = RkFo| ꢀ |Fck/R|Fo|, wR2 = [R[w(Fo2 ꢀ Fc2)2]/Rw(Fo2)2]1/2
.
3. Results and discussion
and the PhACH2AN@CH2 intermediate (isomerising to
PhACH@NACH3) is formed. At the next reversible step,
one aldehyde group from another 3,5-di-tert-butyl-2-
hydroxybenzaldehyde molecule is added to the imine nitro-
gen atom forming intermediate a, and finally the six-mem-
bered ring contraction occurs and N,O-benzoheterocycle 1
is formed. Because of the strong spatial crowding effects of
two bulky tert-butyl groups, the reaction stops here and 1
is the main by-product in a yield of ꢁ35%. By contrast, for
the starting materials of 2-tert-butyl-4-methylphenol, the
main by-product is also the six-membered N,O-benzohet-
erocycle 2. But the yield is very low (<15%) and it is hard
to isolate from the mixture. As for 2,4-dimethylphenol, the
yielded 3,5-dimethyl-2-hydroxybenzaldehyde can form
intermediate a first, nevertheless it can further react with
another 2,4-dimethylphenol molecule to form 3 in a yield
of ꢁ40%, overwhelming the formation of N,O-benzohet-
erocycle. On considering the ESI-MS peak corresponding
to 1,3-benzoxazine motif is not observed in the case of
compound 3, which is due to the low steric hindrance of
two phenyl-substituted methyl groups. One can conclude
that the steric effects are vital in the formylation reaction
of 2,4-dialkylphenol in forming different by-products.
3.1. Synthesis and spectral characterizations
The structures of 1 and 3 are confirmed by the combina-
tion of the results of EA (ratio of C, H, N), FT-IR, H
1
NMR and ESI-MS (M+1 peak). In our experiments, we
applied Larrow’s method [13] to synthesize 3,5-dialkyl-2-
hydroxybenzaldehydes (dialkyl = t-Bu/t-Bu, t-Bu/Me and
Me/Me), and it is found that the resulting 3,5-dialkyl-2-
hydroxybenzaldehydes can further react with HMT to dif-
ferent extent. In the case of starting material 2,4-di-tert-
butylphenol, 3,5-di-tert-butyl-2-hydroxybenzaldehyde is
the main product whose structure has been reported previ-
ously in our group [17]. However, some of produced 3,5-di-
tert-butyl-2-hydroxybenzaldehyde molecules can further
react with HMT under our experimental condition. The
proposed mechanism for the formation of compound 1 is
shown in Scheme 2. HMT molecule can be decomposed
into CH3ANH2 first by losing NH3 molecule under the
acidic condition, and then CH3ANH2 is added to the
C@O group of 3,5-di-tert-butyl-2-hydroxybenzaldehyde.
Finally, one water molecule is removed by b-elimination

W. Huang et al. / Journal of Molecular Structure 885 (2008) 154–160
157
CH3
CH3
H3C
H
H3C
H3C
H3C
CH3
H3C
N
H
H3C
O
N
N
H
N
(HMT)
O
H
O
CH3COOH
H
H3C
H3C
H
N
H
H
H
H
CH3
O
H
H3C
H3C
H3C
H
NH3
- 1/3
1/3 HMT
H
CH3
CH3
H3C
H3C
CH3
H3C
O
H
N
- H2O
CH2
H3C
H3C
C
H
H
CH3
CH3
CH3
H3C
O
CH3
-OH migration
H3C
H
H
H3C
H
O
H
H
C
3
O
HO
CH2OH
H
C
3
H
H
H
C
3
H
CH
3
N
CH3
CH3
H3C
H3C
H3C
H
C
3
CH
3
H
H
H
H
H
H
H3C
a
Scheme 2. Possible mechanism for the formation of compound 1.
˚
In our experiments, it is no doubt that the nitrogen per-
centage in EA results comes from the HMT molecule.
More importantly, it is deduced that the most intense peaks
in the ES-MS spectra of 1, 2 and 3 demonstrate different
by-products. The isotopic distributions of 1 and 2 are cal-
culated by using the numbers and natural isotopic abun-
0.0011 A), respectively. In addition, two phenol rings in
the same molecule are nearly parallel to their respective
counterparts with the dihedral angles of 19.3(2)° (between
ring C1 to C6 and ring C1A to C6A) and 9.2(2)° (between
ring C18 to C23 and ring C18A to C23A). In each of the
independent molecule, the six-membered N,O-benzohet-
erocycle is not planar, and the related torsion angles are
slightly different from each other. They are
N1AC16AO1AC1, 48.3(2)°; C16AO1AC1AC2, 164.8(3)°;
O1AC1AC2AC15, 176.5(3)°; C1AC2AC15AN1, 165.7(3);
C2AC15AN1AC16, 46.2(3)°; C15AN1AC16AO1, 114.0(3)°;
and N1AAC16AAO1AAC1A, 121.1(2)°; C16AAO1AA
C1AAC2A, 23.2(3)°; O1AAC1AAC2AAC15A, 175.0(3)°;
C1AAC2AAC15AAN1A, 17.3(3)°; C2AAC15AAN1AA
C16A, 135.5(3)°; C15AAN1AAC16AAO1A, 72.1(3)°,
respectively.
dance of atoms in [C31H47NO2+H]+ for
1
and
[C25H35NO2+H]+ for 2 [18]. The fitting results are analo-
gous to the experimental ones, further confirming the exis-
tence of the expected species (Fig. 1). Moreover, single-
crystal structures of 1 and 3 are performed by using X-
ray diffraction method, which will be discussed below.
3.2. Crystal structure of (1)
The atom-numbering scheme of compound 1 is shown
in Fig. 2 where two crystallographically independent mole-
cules are found per asymmetric unit. All the phenolic rings
are essentially coplanar and the dihedral angles of two phe-
nol rings in each molecule are a little bit different, which are
63.2(2)° (between ring C1 to C6 and ring C18 to C23 with
The structure of 1 is further stabilized by intramolecular
hydrogen bonds. Intramolecular O—H. . .N hydrogen
bonding interactions are observed between the phenol oxy-
gen atoms (O2 and O2A) and the nitrogen atoms (N1 and
N1A) (Table 2), forming fused six-membered hydrogen-
bond rings. However, there are no p–p stacking interac-
tions between adjacent molecules in its crystal packing,
mainly due to the steric repulsions of the tert-butyl groups.
˚
the mean deviation from plane as 0.0021 and 0.0019 A) and
55.1(2)° (between ring C1A to C6A and ring C18A to
C23A with the mean deviation from plane as 0.0013 and

158
W. Huang et al. / Journal of Molecular Structure 885 (2008) 154–160
T: + p FUll ms
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
466.3
100
90
80
70
60
50
467.2
40
30
20
10
468.2
472.1
464.2
465
475.1
475
460.9
460
0
465 466 467 468 469 470 471
m/z
470
m/z
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
T: + p FUll ms
100
382.1
90
80
70
60
50
40
30
383.0
20
10
384.1
375.0
385.1
387.5
372.2
379.9
380
377.1
0
381 382 383 384 385 386 387
m/z
375
385
m/z
Fig. 1. The ESI-MS spectra of compounds 1 and 2 obtained in positive mode around m/z 466.3 [C31H47NO2+H]+ and m/z 382.1 [C25H35NO2+H]+,
together with the corresponding calculated IDPs for comparison.
3.3. Crystal structure of (3)
C6 and ring C19 to C24 with the mean deviation from
plane of 0.0065 A) and 55.0(3)° (between ring C10 to C15
and ring C19 to C24), respectively.
˚
As illustrated in Fig. 3, the X-ray determination results
of 3 reveal that tris(2-hydroxy-3,5-dimethylbenzyl)amine is
in its protonated form, which is countered by a chloride
anion. The chloride anion in 3 is believed to play a key role
in packing the orthorhombic non-centrosymmetric space
group Fdd2 which can be verified by a low Flack parameter
of 0.01(11), since neutral tris(2-hydroxy-3,5-dimethylben-
zyl)amine crystallizes in the monoclinic centrosymmetric
space group P21/c by contrast. All the phenolic rings in 3
are approximately planar and the bond lengths and angles
fall within the normal ranges [9–10]. The dihedral angles
between the three phenyl rings are 56.5(3)° (between ring
C1 to C6 with the mean deviation from plane of
Hydrogen bonding interactions are the most important
feature in 3. The chloride anion links three phenolic oxy-
gen atoms of the same molecule by O—H. . .Cl hydrogen
contacts with similar O. . .Cl separations of 2.35, 2.37 and
˚
2.39 A and O—H. . .Cl angles of 139.0, 146.0 and 142.0°,
respectively. In addition, intramolecular N—H. . .O type
of hydrogen contacts is found between the protonated ter-
tiary nitrogen atom and three phenolic oxygen atoms with
˚
N. . .O separations of 2.16, 2.24 and 2.46 A. However, no
O—H. . .O H-bond is observed in the crystal packing of 3,
which is totally different from neutral tris(2-hydroxy-3,5-
dimethylbenzyl)amine where one of three OH groups
directs outward from the tripodal amino group and links
another neighboring oxygen atom by O—H. . .O hydrogen
˚
0.0143 A and ring C10 to C15 with the mean deviation
˚
from plane of 0.0044 A), 108.9(3)° (between ring C1 to

W. Huang et al. / Journal of Molecular Structure 885 (2008) 154–160
159
Fig. 3. ORTEP diagram (30% thermal probability) of the molecular
structure of 3 with the atom-numbering scheme. H atoms are shown as
small spheres of arbitrary radii and intramolecular hydrogen bonds are
shown as dashed lines.
Fig. 2. The molecular structure of the asymmetric unit of 1, showing 30%
thermal probability displacement ellipsoids and the atom-numbering
scheme. Hydrogen atoms are omitted for clarity.
expected 3,5-dialkyl-2-hydroxybenzaldehydes are discussed
in this paper. In the case of starting materials 2,4-di-tert-
butylphenol and 2-tert-butyl-4-methylphenol, the resulted
aldehydes can further react with HMT under our experi-
mental condition and the main by-products 1 and 2 are
formed with different yields. In contrast, for the starting
material 2,4-dimethylphenol, the yielded intermediate a
can further react with one 2,4-dimethylphenol molecule
to form 3 due to the relatively low steric hindrance of
two phenyl-substituted methyl groups. This work supplies
Table 2
˚
Hydrogen bonding interactions (A, °) in compounds 1 and 3
D—H. . .A
D—H H. . .A D—A
\DHA Symmetry
code
1
O2—H2A. . .N1
O2A—H2B. . .N1A 0.96
0.96
2.10
1.81
2.705(2) 120.0
2.552(2) 132.0
3
a
practical method to synthesize 3,5-di-tert-butyl-2-
O1—H1. . .Cl1
O2—H2. . .Cl1
O3—H3. . .Cl1
N1—H1A. . .O1
N1—H1A. . .O2
N1—H1A. . .O3
C16—H16B. . .Cl1
C25—H25A. . .Cl1
0.82
0.82
0.82
0.90
0.90
0.90
0.97
0.97
2.35
2.39
2.37
2.16
2.24
2.46
2.72
2.77
3.019(4) 139.0
3.071(3) 142.0
3.089(4) 146.0
2.816(4) 129.0
2.864(4) 127.0
3.035(4) 123.0
3.586(4) 149.0
3.548(4) 138.0
hydroxybenzaldehyde and 1 as well as 3,5-dimethyl-2-
hydroxybenzaldehyde and 3 in medium yields at the same
time, where two new single-crystal structures of 1 and 3
are included.
x, y, ꢀ1 + z
x, y, ꢀ1 + z
5. Supplementary material
contact and no C3 symmetry is observed. So one can con-
clude that the presence of Clꢀ counterion in 3 results in
the formation of a packing structure with higher symme-
try where every OH group is bonded toward the chloride
anion and the hydrogen atom boned to tertiary nitrogen
atom at both ends via three O—H. . .Cl and O—H. . .O
hydrogen bonds. Furthermore, weak C—H. . .Cl hydrogen
bonds can be observed in compound 3 between the two of
three methylene groups (C16 and C25) and the chloride
anion.
CCDC reference numbers 643316 and 643317 for com-
pounds 1 and 3 contain the supplementary crystallographic
data for this paper. These data can be obtained free of charge
at http://www.ccdc.cam.ac.uk/conts/retrieving.html [or
from the Cambridge Crystallographic Data Centre, 12,
Union Road, Cambridge CB2 1EZ, UK; Fax: (Interna-
tional) +44 1223/336 033; E-mail: deposit@ccdc.cam.ac.uk].
Acknowledgements
W.H. acknowledges the Major State Basic Research
Development Programs (Nos. 2007CB925101 and
2006CB806104), the Scientific Research Foundation for
the Returned Overseas Chinese Scholars, State Education
Ministry and the National Natural Science Foundation
of China (No. 20301009) for financial aid.
4. Conclusion
In summary, steric effects on forming different by-prod-
ucts in the formylation reaction of 2,4-dialkylphenol (dial-
kyl = t-Bu/t-Bu, t-Bu/Me and Me/Me) in addition to the

160
W. Huang et al. / Journal of Molecular Structure 885 (2008) 154–160
(b) S. Groysman, S. Segal, M. Shamis, I. Goldberg, M. Kol, Z.
Appendix A. Supplementary data
Goldschmidt, E. Hayut-Salant, J. Chem. Soc., Dalton Trans. (2002)
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Am. Chem. Soc. 124 (2002) 7035.
Supplementary data associated with this article can be
found, in the online version, at doi:10.1016/j.molstruc.
2007.10.035.
[10] A. Chandrasekaran, P. Sood, R.O. Day, R.R. Holmes, Inorg. Chem.
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