Hydrogen-bonded networks in 1-(4-methoxyphenyl)-2,2-dimethyl-propan-1-ol

Article abstract of DOI:10.1107/S0108270107046975

The asymmetric unit of the title compound, C12H18O2, contains two independent mol-ecules. They differ only slightly in conformation but form completely different inter-molecular hydrogen-bonded arrays. One molecule exhibits disorder in the hydroxy group r

Full text of DOI:10.1107/S0108270107046975

organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
1981). The title compound, (I), is a further interesting
example, from the point of view of systematization of
hydrogen-bonded networks displayed in mono-alcohols, of a
secondary mono-alcohol with two bulky substituents at the
carbinol C atom.
ISSN 0108-2701
Hydrogen-bonded networks in
1-(4-methoxyphenyl)-2,2-dimethyl-
propan-1-ol
Â
Marek Glinski, Ewa Wilczkowska, Izabela D. Madura and
Janusz Zachara*
Warsaw University of Technology, Faculty of Chemistry, Noakowskiego 3,
00-664 Warsaw, Poland
Since no separation of enantiomers had been undertaken
after synthesis, the crystal examined was obtained from a
racemic mixture. There are two independent molecules in the
asymmetric unit of (I), labelled A and B. The only chiral
centres of the molecules of (I) are at the carbinol C atoms, i.e.
atoms C7 and C27. In the hydroxy group region of molecule B,
disorder was identi®ed and modelled as a superposition of two
fragments, one de®ned by atoms C27, H27, O21 and H21, and
the other by atoms C27A, H27A, O21A and H21A. Depending
on which of the components is considered, the resulting
conformation of molecule B is either S or R. This is re¯ected in
the different values of the appropriate torsion angles (Table 1).
In the following discussion, only the geometric parameters of
the major component, i.e. that with an occupancy factor of
0.787 (3), will be presented.
Correspondence e-mail: janzac@ch.pw.edu.pl
Received 13 August 2007
Accepted 24 September 2007
Online 14 November 2007
The asymmetric unit of the title compound, C12H18O2,
contains two independent molecules. They differ only slightly
in conformation but form completely different intermolecular
hydrogen-bonded arrays. One molecule exhibits disorder in
the hydroxy group region, but this does not in¯uence the
formation of hydrogen bonds. The bulky tert-butyl group on
one side of the carbinol C atom and the benzene ring on the
other side promote the formation of discrete dimeric motifs
via hydrogen-bridged hydroxy groups. Dimers are further
joined by strong hydroxy±methoxy OÐHÁ Á ÁO bonds to form
chains with dangling alcohol groups. Weaker intermolecular
CÐHÁ Á ÁO interactions mediate the formation of a two-
dimensional network.
Comment
Three different basic motifs have been described for the
hydrogen-bonded networks found in crystals of mono-alco-
hols (Brock & Duncan, 1994). Two of the most important
factors on which the formation of hydrogen-bonded systems
depend are the number and size of the groups connected to
the carbinol C atom. Primary mono-alcohols tend to form
extended chain structures which contain Á Á ÁOÐHÁ Á ÁOÐHÁ Á Á
bond sequences (Taylor & Macrae, 2001). Secondary mono-
alcohols tend to form chains or rings, and steric effects
determine which motif is formed. Hence, secondary mono-
alcohols with bulky groups connected to the carbinol C atom
usually exhibit a ®nite motif, i.e. ring structures, instead of
chains (McGregor et al., 2006). As reported by Taylor &
Macrae (2001), tertiary mono-alcohols either form ®nite
motifs via OÐHÁ Á ÁO hydrogen bonds or do not exhibit any
OÐHÁ Á ÁO hydrogen bonding. Furthermore, there is a third
possibility, namely the formation of dimers: Brock & Duncan
(1994) postulate that dimers form when an extended
hydrogen-bonded structure is precluded. Closed dimers are
said to be less likely to form than those with a dangling H atom
and a free acceptor (Jeffrey & Saenger, 1991; Schweizer et al.,
Figure 1
A plot of the two independent molecules of (I), A (right) and B (left),
showing the atom-numbering scheme. Displacement ellipsoids are drawn
at the 50% probability level and H atoms are shown as small spheres of
arbitrary radii. The intermolecular hydrogen bond is indicated by a
dashed line. The minor disorder component of molecule B (see
Comment) has been omitted for clarity.
o720 # 2007 International Union of Crystallography
DOI: 10.1107/S0108270107046975
Acta Cryst. (2007). C63, o720±o722

organic compounds
The geometric parameters of molecules A and B are very
similar and the most signi®cant differences between the two
unique molecules of (I) are found in the hydroxy and methoxy
group regions (Table 1). For example, in molecule A the C1Ð
dimers are not closed. Each molecule A is linked with two
other symmetry-related A molecules by a strong hydroxy±
methoxy OÐHÁ Á ÁO hydrogen bond (Table 2). These inter-
actions link the dimers into a chain along the c axis (Fig. 2).
This chain can be designated by the ®rst-level graph-set
notation N1 = C(8)[D] (Etter et al., 1990). Another way of
describing this chain is with the p21 rod group characterized by
a 21 screw axis along the c axis (International Tables for
Crystallography, 2002).
Ê
Ê
C7 bond of 1.5138 (19) A is about 0.011 (3) A longer than
C21ÐC27 in molecule B. These differences might be caused
by the disorder. However, the fact that the O atom of the
hydroxy group of molecule A forms two strong OÐHÁ Á ÁO
hydrogen bonds may also be signi®cant. The different strength
of the intermolecular interactions in which atoms O2 and O22
participate (Table 2) may also be a reason for the small
differences between the two unique molecules in the methoxy
group region. Moreover, the anisotropic displacement coef®-
cients of the C atoms which constitute the benzene ring of
molecule B are larger than those of the corresponding atoms
of molecule A.
The chains further self-organize through weak CÐHÁ Á ÁO
interactions to generate a layer. This is indicated by the
geometry of the bond, as well as by the fact that the H atom is
directed towards the O22 lone electron pair (Steiner, 2002).
Within a layer, every B molecule is linked with two other B
molecules to form a chain. The H31CÁ Á ÁO22ii distance is
3
2
1
2
Ê
2.53 A [symmetry code: (ii) x + , y, z + ] and the C31Ð
The title compound exhibits a dimeric structure with graph-
set notation D (Etter, 1990) formed by hydroxy±hydroxy OÐ
HÁ Á ÁO hydrogen bonding (Table 2) which links an A molecule
and a B molecule (Fig. 1). This motif occurs irrespective of
which disorder component is considered. Within each dimer,
the major component of molecule B has the opposite con®g-
uration to that of molecule A. Although two bulky groups
attached to the carbinol C atom hinder the association of more
than two molecules via hydroxy±hydroxy OÐHÁ Á ÁO bonds,
the O atoms from the methoxy groups enable the dimeric
structure to form other more complex supramolecular
networks. The geometric parameters of the hydrogen bonds
which are present in the crystal structure of (I) are shown in
Table 2.
H31CÁ Á ÁO22ii angle is 163ꢀ. The supramolecular structure
which results from these interactions is a layer with pb21a
symmetry (Fig. 2) (International Tables for Crystallography,
2002). These supramolecular layers are parallel to (010), hence
the nonperiodic direction is that parallel to b. The basis
vectors of the layer group, aL and bL, are consistent with the
original a and c basis vectors, respectively. Within a layer, each
chain is related to the adjacent chain by an a-glide plane.
In summary, the bulky tert-butyl group and the benzene ring
on the carbinol C atom of (I) induce steric hindrance which
effectively precludes the formation of a chain-like structure
with hydroxy±hydroxy Á Á ÁOÐHÁ Á ÁO sequences. Instead,
molecules form dimers with a dangling H atom, and their open
structure enables the dimers to arrange themselves into a
hydrogen-bonded chain structure via interactions of methoxy
O atoms with dangling H atoms.
The dimers are assembled into extended chains with
dangling B molecules. This results from the fact that the
Experimental
The title compound was synthesized by the reduction of 1-(4-
methoxyphenyl)-2,2-dimethyl-1-propanone with sodium boro-
hydride. Into a methanol solution of 1-(4-methoxyphenyl)-2,2-di-
methylpropan-1-one (7.7 g), a methanol solution of sodium boro-
hydride was added dropwise at room temperature. The mixture was
stirred for 6 h, hydrolyzed and the product extracted with n-hexane.
The product, (I), was recrystallized from n-hexane (yield 5.8 g, 75%;
m.p. 313±314 K). Prismatic colourless crystals suitable for diffraction
study were obtained by recrystallization from toluene.
Crystal data
3
Ê
C12H18O2
Mr = 194.26
Orthorhombic, Pca21
V = 2175.34 (11) A
Z = 8
Mo Kꢀ radiation
1
Ê
a = 20.8868 (6) A
ꢁ = 0.08 mm
T = 173 (2) K
Ê
b = 6.00175 (18) A
Ê
c = 17.3531 (5) A
0.53 Â 0.37 Â 0.15 mm
Data collection
Oxford Diffraction KM-4 CCD
area-detector diffractometer
Absorption correction: multi-scan
(CrysAlis RED; Oxford
Diffraction, 2005)
Tmin = 0.956, Tmax = 0.988
33345 measured re¯ections
2812 independent re¯ections
2553 re¯ections with I > 2ꢂ(I)
Rint = 0.018
Figure 2
A projection of the crystal structure of (I) along the b axis, showing the
layer of molecules linked by OÐHÁ Á ÁO (dashed lines) and CÐHÁ Á ÁO
(dotted lines) interactions. H atoms not involved in intermolecular
contacts have been omitted for clarity.
ꢁ
Â
Acta Cryst. (2007). C63, o720±o722
Glinski et al. C12H18O2 o721

organic compounds
Ê
1.5Ueq(O) for the hydroxy group, and with CÐH = 0.95±1.00 A and
Uiso(H) = 1.2Ueq(C) or 1.5Ueq(methyl C).
Re®nement
R[F2 > 2ꢂ(F2)] = 0.027
wR(F2) = 0.073
S = 1.09
2812 re¯ections
278 parameters
9 restraints
H-atom parameters constrained
Data collection: CrysAlis CCD (Oxford Diffraction, 2005); cell
re®nement: CrysAlis RED (Oxford Diffraction, 2005); data reduc-
tion: CrysAlis RED; program(s) used to solve structure: SHELXS97
(Sheldrick, 1990); program(s) used to re®ne structure: SHELXL97
3
Ê
Áꢃmax = 0.20 e A
3
Ê
0.18 e A
Áꢃmin
=
(Sheldrick, 1997); molecular graphics: ORTEPIII (Burnett
&
Table 1
Selected geometric parameters (A, ).
Johnson, 1996) and ORTEP-3 for Windows (Version 1.08; Farrugia,
1997); software used to prepare material for publication: SHELXL97
and PLATON (Spek, 2003).
ꢀ
Ê
O1ÐC7
C1ÐC7
O2ÐC4
O2ÐC12
1.4428 (17) O21ÐC27
1.5138 (19) C21ÐC27
1.3809 (17) O22ÐC24
1.4294 (19) O22ÐC32
1.437 (2)
1.525 (2)
1.3727 (18)
1.4198 (19)
The authors thank the Laboratory of Crystallochemistry at
the Chemistry Department of Warsaw University for the low-
temperature X-ray measurements.
O21ÐC27ÐC21ÐC22
O21ÐC27ÐC21ÐC26
O21ÐC27ÐC28ÐC29
O21ÐC27ÐC28ÐC30
O21ÐC27ÐC28ÐC31
37.5 (2)
O21AÐC27AÐC21ÐC22 146.7 (3)
144.65 (15) O21AÐC27AÐC21ÐC26 37.6 (5)
64.98 (19) O21AÐC27AÐC28ÐC29 167.7 (6)
55.7 (2) O21AÐC27AÐC28ÐC30 54.6 (7)
173.00 (15) O21AÐC27AÐC28ÐC31 72.8 (7)
Supplementary data and an additional ®gure for this paper are available
from the IUCr electronic archives (Reference: BM3037). Services for
accessing these data are described at the back of the journal.
References
Table 2
Hydrogen-bond and short-contact geometry (A, ).
ꢀ
Ê
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DÐH
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DÁ Á ÁA
DÐHÁ Á ÁA
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2.53
2.883 (2)
3.134 (2)
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179
178
163
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Â
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®nding alternative positions from the difference Fourier map, and
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È
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Ê
ride on their parent atoms, with OÐH = 0.84 A and Uiso(H) =
ꢁ
Â
o722 Glinski et al. C12H18O2
Acta Cryst. (2007). C63, o720±o722