Novel liquid crystal aldoximes and aldoxime ethers: Synthesis, characterization and liquid crystal behavior

Article abstract of DOI:10.1016/j.molliq.2015.04.016

This study describes synthesis and characterization of new liquid crystal aldoximes and aldoxime ethers in detail. Firstly, 4′-(6-bromohexyloxy)biphenyl-4-carbonitrile, 4′-(8-bromooctylox)biphenyl-4-carbonitrile and 4′-(10-bromoodecyloxy)biphenyl-4-carbonitrile derivatives were synthesized, respectively. Then, with this compound, condensation reaction was determined to p-hydroxybenzaldehyde and new aldehyde derivatives were synthesized. This aldehyde derivatives were converted to new oxime derivatives, not found in the literature. Then, these new oxime derivatives were converted to oxime ether derivatives with iodomethane. All of the obtained products were characterized by a combination of FT-IR, ¹H NMR, ¹³C NMR and elemental analysis. Then, the liquid crystal properties of these new compounds were determined by using DSC and POM techniques.

Full text of DOI:10.1016/j.molliq.2015.04.016

MOLLIQ-04769; No of Pages 6
Journal of Molecular Liquids xxx (2015) xxx–xxx
Contents lists available at ScienceDirect
Journal of Molecular Liquids
journal homepage: www.elsevier.com/locate/molliq
Novel liquid crystal aldoximes and aldoxime ethers: Synthesis,
characterization and liquid crystal behavior
⁎
Onder Alici , Ibrahim Karatas
Selcuk University, Science Faculty, Department of Chemistry, 42130 Konya, Turkey
a r t i c l e i n f o
a b s t r a c t
Available online xxxx
This study describes synthesis and characterization of new liquid crystal aldoximes and aldoxime ethers in detail.
Firstly, 4′-(6-bromohexyloxy)biphenyl-4-carbonitrile, 4′-(8-bromooctylox)biphenyl-4-carbonitrile and 4′-(10-
bromoodecyloxy)biphenyl-4-carbonitrile derivatives were synthesized, respectively. Then, with this compound,
condensation reaction was determined to p-hydroxybenzaldehyde and new aldehyde derivatives were synthe-
sized. This aldehyde derivatives were converted to new oxime derivatives, not found in the literature. Then,
these new oxime derivatives were converted to oxime ether derivatives with iodomethane. All of the obtained
products were characterized by a combination of FT-IR, 1H NMR, 13C NMR and elemental analysis. Then, the liquid
crystal properties of these new compounds were determined by using DSC and POM techniques.
© 2015 Elsevier B.V. All rights reserved.
Keywords:
Aldoxime
Aldoxime ethers
Synthesis
Liquid crystal
1. Introduction
whereas the oxime derivatives bearing 4′-(n-bromoalkyloxy) biphenyl-
4-carbonitrile have not been synthesized until now, according to our
Oximes and their derivatives are important intermediates in organic
synthesis. Oximes, compounds with a C_N\\OH group, have provided
a fruitful area of study in recent years. Condensation of aldehydes and
ketones with hydroxylamines is the most commonly used synthetic
route to oximes. Oximes are derived from aldehydes (aldoximes,
RHC_NOH) and ketones (ketoximes, RR′C_NOH, where R and R′ are
not hydrogen). They have remained an important and popular area of
research due to their simple synthesis, versatility and potential applica-
tions in many areas, such as medicine [1], bioorganic systems [2], catal-
ysis [3], electrooptical sensors [4], quartz crystal microbalance (QCM)
sensor [5], liquid crystals [6] and dyes [7]. Research on liquid crystals
has always been interdisciplinary and international since the discovery
of liquid crystals nearly 150 years ago. Research in basic liquid crystal-
line science and technological applications of liquid crystal (LC) mate-
rials have experienced great growth due to their application in the
design of optical and electro-optic devices. Early, it was assumed that
free phenolic or alcoholic groups prevent the formation of mesophase.
Gray [8] clarified this situation by proposing that interactions such as in-
termolecular hydrogen bonding and a non-linear structural arrangement
led to the increment of the melting point above the liquid crystal–isotro-
pic liquid transition temperatures. However additional research showed
that phenolic hydroxyl compounds can give mesophases of high thermal
stabilities [9–11]. Additionally, oximes of alkoxyazobenzenes showing liq-
uid crystal behavior have been prepared [12]. Recently, the synthesis of
different compounds containing 4′-(n-bromoalkyloxy) biphenyl-4-
carbonitrile and their liquid crystal characteristics has been reported,
knowledge [13–16].
We think that they could be interesting as liquid crystal (LC).
Therefore we report the synthesis, characterization and liquid crystal
behavior of the new aldoxime and aldoxime ethers including 4′-(n-
bromoalkyloxy) biphenyl-4-carbonitrile derivatives in the present
study.
2. Experimental
2.1. Materials and methods
Melting points were determined on an Electrothermal 9100 appara-
tus in a sealed capillary and are uncorrected. 1H and 13C NMR spectra
were recorded at room temperature on a Varian 400 MHz spectrometer
in CDCl3 or DMSO-d6. Chemical shifts are expressed in δ units and 1H–1H
coupling constants in Hz. FT-IR spectra were obtained on a Perkin Elmer
Spectrum 100 FT-IR spectrometer. Elemental analyses were determined
on a Leco CHNS 932 instrument. Analytical TLC was performed using
Merck prepared plates (silica gel60 F254 on aluminum). DSC measure-
ments were performed using Seteram DSC 131 under nitrogen against
an indium standard at a heating/cooling rate of 10 °C/min. Transition
temperatures were determined as the onset of the maximum in the en-
dotherm or exotherm. The textures of the liquid-crystalline phase were
observed through polarized optical microscopy, using a Leica DMLM mi-
croscope equipped with a Linkam LTS420 hot stage and a T95 LinkPad
temperature controller, LNP95 liquid nitrogen cooling system, and a
digital camera. All reactions, unless otherwise noted, were conducted
under a nitrogen atmosphere. All starting materials and reagents used
⁎
Corresponding author.
E-mail address: oalici@selcuk.edu.tr (O. Alici).
http://dx.doi.org/10.1016/j.molliq.2015.04.016
0167-7322/© 2015 Elsevier B.V. All rights reserved.
Please cite this article as: O. Alici, I. Karatas, Novel liquid crystal aldoximes and aldoxime ethers: Synthesis, characterization and liquid crystal
behavior, J. Mol. Liq. (2015), http://dx.doi.org/10.1016/j.molliq.2015.04.016

2
O. Alici, I. Karatas / Journal of Molecular Liquids xxx (2015) xxx–xxx
were of standard analytical grade from Fluka, Merck, and Aldrich and
used without further purification.
Ar-CH), 7.68 (d, 2H, J = 8.71 Hz, Ar-CH), 7.63 (d, 2H, J = 8.69 Hz, Ar-
CH), 7.52 (d, 2H, J = 8.89 Hz, Ar-CH), 6.98 (d, 4H, J = 8.49 Hz, Ar-CH),
4.01 (m, 4H, O-CH2), 1.80 (m, 4H, alip. CH2), 1.47 (m, 4H, alip. CH2),
1.34 (m, 8H, alip. CH2). IR (νmax, cm−1): 3065 (arom. C\\H), 2937,
2921, 2853 (alip. C\\H), 2227 (C≡N), 1686 (C_O stretching), 1250,
1183 (C\\O stretching).
2.2. Synthesis
The compounds (1–6) were synthesized according to a previously
known procedure [17–21].
2.2.7. The preparation of LC aldoximes: general procedure
2.2.1. 4′-[(6-Bromohexyl)oxy]-1,1′-biphenyl-4-carbonitrile (1)
Compound 1; yield: 8.25 g (90%). Elemental analysis for C19H20BrNO,
found (calculated): C 63.70 (63.90), H 5.63 (5.25), N 3.91 (3.32). 1H NMR
(400 MHz, CDCl3): δ 7.68 (d, 2H, J = 8.67 Hz, Ar-CH), 7.63 (d, 2H, J =
8.66 Hz, Ar-CH), 7.52 (d, 2H, J = 8.86 Hz, Ar-CH), 6.89 (d, 2H, J =
8.86 Hz, Ar-CH), 4.01 (t, 2H, J = 6.40 Hz, \\O-CH2), 3.34 (t, 2H, J =
6.76 Hz, CH2-Br), 1.90 (m, 2H, alip. CH2), 1.83 (m, 2H, alip. CH2), 1.53
(m, 4H, alip. CH2). IR (νmax, cm−1): 3049 (arom. C\\H), 2936, 2922,
2857 (alip. C\\H), 2226 (C≡N), 1599, 1578, 1492 (C_C, arom.), 1240,
1180 (C\\O stretching), 727 (C-Br).
Compounds (4, 5, and 6) (2.5 mmol) was resolved in THF (30 mL).
Another beaker with NH2OH·HCl (0.26 g, 3.75 mmol) and NaOH
(0.25 g, 6.26 mmol) was resolved in water (30 mL). The aqueous solu-
tion was added to the aldehyde solutions and was stirred at reflux for
4 h. After completion of the reaction, the THF was evaporated and the
precipitate was filtered, washed with water and dried in vacuum.
2.2.7.1. 4-(6-[4′-Cyanobiphenyl-4-yloxy]hexyloxy)benzaldoxime (7).
Compound 7; yield: 0.78 g (75%). Elemental analysis for C26H26N2O3,
found (calculated): C 75.34 (74.99), H 6.32 (6.07), N 6.76 (6.23). 1H
NMR (400 MHz, DMSO-d6): δ 10.97 (s, 1H, OH), 8.07 (s, 1H, CH), 7.88
(d, 2H, J = 8.67 Hz, Ar-CH), 7.83 (d, 2H, J = 8.63 Hz, Ar-CH), 7.70 (d,
2H, J = 8.83 Hz, Ar-CH), 7.51 (d, 2H, J = 8.80 Hz, Ar-CH), 7.05 (d, 2H,
J = 8.84 Hz, Ar-CH), 6.95 (d, 2H, J = 8.79 Hz, Ar-CH), 4.01 (m, 4H, O-
CH2), 1.75 (m, 4H, alip. CH2), 1.48 (m, 4H, alip. CH2). IR (νmax, cm−1):
3505 (O\\H stretching), 3064 (arom. C\\H), 2937, 2921, 2853 (alip.
C\\H), 2226 (C≡N), 1686 (C_N stretching), 1251, 1183 (C\\O
stretching), 988 (N\\O stretching).
2.2.2. 4′-[(8-Bromooctyl)oxy]-1,1′-biphenyl-4-carbonitrile (2)
Compound 2; yield: 8.41 g (85%). M.p. 80–81 °C. Elemental analysis
for C21H24BrNO, found (calculated): C 65.29 (64.90), H 6.26 (6.71), N
3.63 (3.42). 1H NMR (400 MHz, CDCl3): δ 7.69 (d, 2H, J = 8.75 Hz, Ar-
CH), 7.64 (d, 2H, J = 8.59 Hz, Ar-CH), 7.53 (d, 2H, J = 8.87 Hz, Ar-CH),
6.99 (d, 2H, J = 8.86 Hz, Ar-CH), 4.02 (t, 2H, J = 6.39 Hz, O-CH2), 3.44
(t, 2H, J = 6.76 Hz, CH2-Br), 1.83 (m, 4H, alip. CH2), 1.47 (m, 4H, alip.
CH2), 1.38 (m, 4H, alip. CH2). IR (νmax, cm−1): 3045 (arom. C\\H),
2930, 2856 (alip. C\\H), 2222 (C≡N), 1601, 1523 (C_C, arom.), 1248,
1179 (C\\O stretching), 722 (C-Br).
2.2.7.2. 4-(8-[4′-Cyanobiphenyl-4-yloxy]octyloxy)benzaldoxime (8). Com-
pound 8; yield: 0.74 g (71%). M.p. 145–150 °C. Elemental analysis for
C
28H30N2O3, found (calculated): C 75.99 (75.69), H 6.83 (6.77), N 6.33
2.2.3. 4′-[(10-Bromodecyl)oxy]-1,1′-biphenyl-4-carbonitrile (3)
Compound 3; yield: 7.43 g (70%). Elemental analysis for C23H28BrNO,
found (calculated): C 66.67 (66.13), H 6.81 (6.33), N 3.38 (3.45). 1H NMR
(400 MHz, CDCl3): δ 7.68 (d, 2H, J = 8.26 Hz, Ar-CH), 7.63 (d, 2H, J =
8.34 Hz, Ar-CH), 7.52 (d, 2H, J = 8.63 Hz, Ar-CH), 6.99 (d, 2H, J =
8.69 Hz, Ar-CH), 4.00 (t, 2H, J = 6.54 Hz, O-CH2), 3.41 (t, 2H, J =
6.85 Hz, CH2-Br), 1.83 (m, 4H, alip. CH2), 1.45 (m, 4H, alip. CH2), 1.31
(m, 8H, alip. CH2). IR (νmax, cm−1): 3067 (arom. C\\H), 2918, 2852
(alip. C\\H), 2223 (C≡N), 1598, 1493 (C_C, arom.), 1250, 1181 (C\\O
stretching), 726 (C-Br).
(6.53). 1H NMR (400 MHz, DMSO-d6): δ 10.96 (s, 1H, OH), 8.06 (s, 1H,
CH), 7.88 (d, 2H, J = 8.72 Hz, Ar-CH), 7.83 (d, 2H, J = 8.65 Hz, Ar-CH),
7.69 (d, 2H, J = 8.88 Hz, Ar-CH), 7.51 (d, 2H, J = 8.82 Hz, Ar-CH), 7.04
(d, 2H, J = 8.88 Hz, Ar-CH), 6.94 (d, 2H, J = 8.81 Hz, Ar-CH), 3.99 (m,
4H, O-CH2), 1.72 (m, 4H, alip. CH2), 1.42 (m, 4H, alip. CH2), 1.36 (m,
4H, alip. CH2). IR (νmax, cm−1): 3394 (O\\H stretching), 3064 (arom.
C\\H), 2937, 2921, 2854 (alip. C\\H), 2226 (C≡N), 1686 (C_N
stretching), 1250, 1182 (C\\O stretching), 954 (N\\O stretching).
2.2.7.3. 4-(10-[4′-Cyanobiphenyl-4-yloxy]decyloxy)benzaldoxime (9).
Compound 9; yield: 0.72 g (70%). Elemental analysis for C30H34N2O3,
found (calculated): C 76.57 (76.29), H 7.28 (7.57), N 5.95 (5.33). 1H
NMR (400 MHz, DMSO-d6): δ 10.91 (s, 1H, OH), 8.03 (s, 1H, CH), 7.84
(d, 2H, J = 7.96 Hz, Ar-CH), 7.79 (d, 2H, J = 7.98 Hz, Ar-CH), 7.66 (d,
2H, J = 8.34 Hz, Ar-CH), 7.48 (d, 2H, J = 8.27 Hz, Ar-CH), 7.00 (d, 2H,
J = 8.30 Hz, Ar-CH), 6.91 (d, 2H, J = 8.20 Hz, Ar-CH), 3.95 (m, 4H, O-
CH2), 1.67 (m, 4H, alip. CH2), 1.36 (m, 4H, alip. CH2), 1.26 (m, 8H, alip.
CH2). IR (νmax, cm−1): 3393 (O\\H stretching), 3066 (arom. C\\H),
2936, 2921, 2852 (alip. C\\H), 2236 (C≡N), 1686 (C_N stretching),
1249, 1181 (C\\O stretching), 953 (N\\O stretching).
2.2.4. 4-(6-[4′-Cyanobiphenyl-4-yloxy]hexyloxy)benzaldehyde (4)
Compound 4; yield: 2.25 g (78%). Elemental analysis for C26H25NO3,
found (calculated): C 78.17 (78.94), H 6.31 (6.88), N 3.51 (3.35). 1H
NMR (400 MHz, CDCl3): δ 9.69 (s, 1H, Ald-H), 7.64 (d, 2H, J = 8.82 Hz,
Ar-CH), 7.50 (d, 2H, J = 8.08 Hz, Ar-CH), 7.45 (d, 2H, J = 8.37 Hz, Ar-
CH), 7.34 (d, 2H, J = 8.84 Hz, Ar-CH), 6.80 (d, 4H, J = 8.82 Hz, Ar-CH),
3.86 (m, 4H, O-CH2), 1.68 (m, 4H, alip. CH2), 1.39 (m, 4H, alip. CH2). IR
(νmax, cm−1): 3070 (arom. C\\H), 2943, 2867 (alip. C\\H), 2223
(C≡N), 1686 (C_O stretching), 1249, 1179 (C\\O stretching).
2.2.5. 4-(8-[4′-Cyanobiphenyl-4-yloxy]octyloxy)benzaldehyde (5)
Compound 5; yield: 2.52 g (72%). Elemental analysis for C28H29NO3,
found (calculated): C 78.66 (78.82), H 6.84 (6.13), N 3.28 (3.47). 1H
NMR (400 MHz, CDCl3): δ 9.87 (s, 1H, Ald-H), 7.82 (d, 2H, J = 8.82 Hz,
Ar-CH), 7.68 (d, 2H, J = 8.11 Hz, Ar-CH), 7.64 (d, 2H, J = 8.49 Hz, Ar-
CH), 7.52 (d, 2H, J = 8.80 Hz, Ar-CH), 6.99 (d, 4H, J = 8.76 Hz, Ar-CH),
4.02 (m, 4H, O-CH2), 1.82 (m, 4H, alip. CH2), 1.49 (m, 4H, alip. CH2),
1.41 (m, 4H, alip. CH2). IR (νmax, cm−1): 3064 (arom. C\\H), 2938,
2916, 2853 (alip. C\\H), 2226 (C≡N), 1686 (C_O stretching), 1258,
1183 (C\\O stretching).
2.2.8. The preparation of LC aldoxime ethers: general procedure
Methyl iodide (2.90 mmol) was added to the stirred mixture of com-
pounds (7, 8, and 9) (2.5 mmol), KOH (21 mmol) and 10 mL of DMSO
and stirred at room temperature for 4 h. After completion of the reac-
tion, ethyl acetate (80 mL) was added to the reaction. The mixture
was extracted with brine (3 × 30 mL), and the combined organic layers
were washed with water and dried over Na2SO4. The solvent was re-
moved under reduced pressure, and dried in vacuum.
2.2.8.1.4-(6-[4′-Cyanobiphenyl-4-yloxy]hexyloxy)benzaldoximemethylether
(10). Compound 10; yield: 0.84 g (81%). Elemental analysis for
2.2.6. 4-(10-[4′-Cyanobiphenyl-4-yloxy]decyloxy)benzaldehyde (6)
Compound 6; yield: 2.61 g (70%). Elemental analysis for C30H33NO3,
found (calculated): C 79.09 (78.97), H 7.30 (7.77), N 3.07 (3.33). 1H
NMR (400 MHz, CDCl3): δ 9.87 (s, 1H, Ald-H), 7.81 (d, 2H, J = 8.83 Hz,
C27H28N2O3, found (calculated): C 75.68 (75.19), H 6.59 (6.71), N 6.54
(6.23). 1H NMR (400 MHz, DMSO-d6): δ 8.10 (s, 1H, CH), 7.84 (d, 2H,
J = 8.72 Hz, Ar-CH), 7.80 (d, 2H, J = 8.64 Hz, Ar-CH), 7.67 (d, 2H,
J = 8.79 Hz, Ar-CH), 7.52 (d, 2H, J = 8.76 Hz, Ar-CH), 7.03 (d, 2H,
Please cite this article as: O. Alici, I. Karatas, Novel liquid crystal aldoximes and aldoxime ethers: Synthesis, characterization and liquid crystal
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O. Alici, I. Karatas / Journal of Molecular Liquids xxx (2015) xxx–xxx
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Scheme 1. Reagents and conditions: (i) K2CO3, KI, 2-butanone, reflux, 24 h; (ii) p-hydroxybenzaldehyde, K2CO3, DMF, reflux, 12 h; (iii) NH2OH·HCl, NaOH, THF, reflux, 2 h; (iv) CH3-I,
NaOH, DMF, room temperature, 4 h.
J = 8.80 Hz, Ar-CH), 6.93 (d, 2H, J = 8.76 Hz, Ar-CH), 4.01 (m, 4H, O-CH2),
3.86 (s, 3H, O-CH3), 1.77 (m, 4H, alip. CH2), 1.50 (m, 4H, alip. CH2). IR
(νmax, cm−1): 3047 (arom. C\\H), 2935, 2857 (alip. C\\H), 2221 (C≡N),
1600 (C_N stretching), 1252, 1182 (C\\O stretching), 1080, 1037
(O\\CH3 stretching), 948 (N\\O stretching).
2.2.8.3. 4-(10-[4′-Cyanobiphenyl-4-yloxy]decyloxy)benzaldoximemethyl
ether (12). Compound 12; yield: 0.77 g (75%). Elemental analysis for
C31H36N2O3, found (calculated): C 76.83 (76.59), H 7.49 (7.69), N 5.78
(5.27). 1H NMR (400 MHz, DMSO-d6): δ 8.00 (s, 1H, CH), 7.69 (d, 2H,
J = 8.63 Hz, Ar-CH), 7.63 (d, 2H, J = 8.51 Hz, Ar-CH), 7.51 (m, 4H, Ar-
CH), 6.99 (d, 2H, J = 8.79 Hz, Ar-CH), 6.87 (d, 2H, J = 8.80 Hz, Ar-CH),
3.98 (m, 4H, O-CH2), 3.94 (s, 3H, O-CH3), 1.79 (m, 4H, alip. CH2), 1.45
(m, 4H, alip. CH2), 1.34 (m, 8H, alip. CH2). IR (νmax, cm−1): 3068, 3040
(arom. C\\H), 2936, 2921, 2852 (alip. C\\H), 2230 (C≡N), 1604 (C_N
stretching), 1249, 1174 (C\\O stretching), 1045, 1017 (O\\CH3
stretching), 950 (N\\O stretching).
2.2.8.2. 4-(8-[4′-Cyanobiphenyl-4-yloxy]octyloxy)benzaldoximemethylether
(11). Compound 11; yield: 0.80 g (78%). Elemental analysis for
C29H32N2O3, found (calculated): C 76.29 (76.69), H 7.06 (7.19), N 6.14
(6.27). 1H NMR (400 MHz, DMSO-d6): δ 8.00 (s, 1H, CH), 7.68 (d, 2H,
J = 8.62 Hz, Ar-CH), 7.63 (d, 2H, J = 8.54 Hz, Ar-CH), 7.51 (m, 4H, Ar-
CH), 6.99 (d, 2H, J = 8.79 Hz, Ar-CH), 6.88 (d, 2H, J = 8.80 Hz, Ar-CH),
3.99 (m, 4H, O-CH2), 3.93 (s, 3H, O-CH3), 1.80 (m, 4H, alip. CH2), 1.48
(m, 4H, alip. CH2), 1.41 (m, 4H, alip. CH2). IR (νmax, cm−1): 3041 (arom.
C\\H), 2936, 2858 (alip. C\\H), 2228 (C≡N), 1603 (C_N stretching),
1247, 1173 (C\\O stretching), 1052, 1032 (O\\CH3 stretching), 924
(N\\O stretching).
3. Result and discussion
The synthetic route performed to obtain the LC aldoxime and
aldoxime ethers and their precursors are depicted in Scheme 1.
LC aldoximes (7, 8, and 9) were easily synthesized from the com-
pounds (4, 5, and 6) in the presence of hydroxylamine hydrochloride
Fig. 1. Normalized DSC thermograms of LC aldoxime.
Please cite this article as: O. Alici, I. Karatas, Novel liquid crystal aldoximes and aldoxime ethers: Synthesis, characterization and liquid crystal
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O. Alici, I. Karatas / Journal of Molecular Liquids xxx (2015) xxx–xxx
Fig. 2. Normalized DSC thermograms of LC aldoxime ethers.
and sodium hydroxide in THF. Then, LC aldoximes (7, 8, and 9) were
converted to LC aldoxime ethers (10, 11, and 12) by using iodomethane
and potassium hydroxide in DMF. The LC aldoximes and LC aldoxime
ethers were isolated in good yields by recrystallization without chroma-
tography. The chemical structures of LC aldoximes and aldoxime ethers
were confirmed by combination of 1H NMR, 13C NMR and FT-IR spectra.
From the FT-IR spectra (see Supplementary data, Figs. S18, S21 and
S24), the formation of LC aldoximes 7, 8 and 9 is confirmed by the ap-
pearance of an oxime OH band at 3505, 3394 and 3393 cm−1, respec-
tively. Also, the apparent band at 1686 cm−1 is due to C_N vibration
from oximes. A band at 2225 cm−1 indicates the presence of C≡N func-
tion. LC aldoxime ethers 10, 11 and 12 are confirmed by the appearance
of an oxime ether O\\CH3 band at between 1080 and 1045. Besides, the
apparent band at 945 cm−1 is due to N\\O vibrations. In the 1HNMR
spectra (see Supplementary data, Figs. S7, S10 and S13) of LC aldoximes
(7 and 9) chemical shifts are observed and that the\\OH peak of the
oxime is detected as a singlet at ppm δ 10.96. The \\CH protons are
observed at δ 8.06 ppm. Also, the aromatic protons are detected at the
region of δ 7.88–6.94 ppm as a doublet. The\\O\\CH2\\which is attrib-
uted to a group from the aryl–alkyl ether linkages is detected at the re-
gion of δ 4.01–3.95 ppm. Besides, aliphatic\\CH2 chemical shifts are
observed at the region of δ 1.75–1.26 ppm as a multiplet. In the
1HNMR spectra (see Supplementary data, Figs. S25, S28 and S31) of
LC aldoxime ethers (10, 11 and 12), the oxime \\OH signals at δ
Fig. 3. Polarized optical microscope texture of LC aldoximes (200×). (a) Fan texture of 7 at heating to 78.4 °C. (b) Fan texture of 9 at cooling to 139.1 °C.
Please cite this article as: O. Alici, I. Karatas, Novel liquid crystal aldoximes and aldoxime ethers: Synthesis, characterization and liquid crystal
behavior, J. Mol. Liq. (2015), http://dx.doi.org/10.1016/j.molliq.2015.04.016

O. Alici, I. Karatas / Journal of Molecular Liquids xxx (2015) xxx–xxx
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Fig. 4. Polarized optical microscope texture of LC aldoxime ethers (200×). (a) Droplet texture of 10 at heating to 135.5 °C. (b) Mosaic texture of 11 at cooling to 103 °C. (c) Schlieren texture
of 12 at heating to 84.2 °C. (d) Schlieren texture of 12 at cooling to 104 °C.
10.96 ppm which belongs to 7, 8 and 9 disappeared and the OCH3
protons appeared at δ 3.94 ppm as a singlet.
The polarized optic microscope (POM) texture of LC aldoximes and
aldoxime ethers are presented in Figs. 3 and 4. For aldoximes (7 and
9), POM textures were observed as a fan texture (Fig. 3) [22]. For
aldoxime ethers (10, 11 and 12) different textures were observed
(Fig. 4). In the POM texture evaluation of aldoxime ethers, in compound
10 the LC structure was observed as a droplet texture while compound
11 was observed as a mosaic texture. Also, for compound 12 the LC
structure was determined as a Schlieren texture [22]. In addition, POM
and DSC results are in compliance.
The LC properties of aldoximes and aldoxime ethers were investigat-
ed by polarizing optical microscopy (POM) and differential scanning
calorimetry (DSC). The DSC thermograms of LC aldoximes (7 and 9)
and aldoxime ethers (10, 11 and 12) are presented in Figs. 1 and 2.
Also, the POM textures of LC aldoxime (7 and 9) and aldoxime ethers
(10, 11 and 12) are presented in Figs. 3 and 4.
The thermal behavior of LC aldoximes and aldoxime ethers are pre-
sented in Table 1 and the representative DSC thermograms in Figs. 1 and
2. In the DSC evaluation of compound 7, the nematic phase was ob-
served during heating at 78.4 °C and the isotropic phase was observed
at 112 °C. But, in compound 9 the transition from isotropic to liquid
crystalline phase is not observed on the heating stage while it was ob-
served at 139.1 °C on the cooling stage (Fig. 1). Also, in compounds 10
and 11, the liquid crystal phase transitions were shown on the cooling
stage. For compound 10, the transition from isotropic to liquid crystal-
line phase was shown at 135.5 °C. But, in compound 11 the liquid crystal
phase transition was shown at 103 °C (Fig. 2). In addition, for compound
12 the liquid crystal phase transitions on both the heating stage and
cooling stage were observed. For compound 12, during the heating
stage the nematic phase was shown at 84.2 °C and the isotropic phase
at 112.2 °C and during the cooling stage the nematic phase was shown
at 104 °C (Fig. 2).
4. Conclusion
In conclusion, novel LC aldoximes and aldoxime ethers have been re-
ported. These aldoximes and aldoxime ethers present enantiotropic
liquid-crystalline properties, with nematic type textures. Some of
them show a wide mesophase range. These aldoximes and aldoxime
ethers can flash on future liquid crystal oxime compounds with conve-
nient material features for some applications.
Acknowledgment
We thank the Scientific Research Projects Foundation of Selcuk, Uni-
versity (SUBAP-Grant Number 09101038) for financial support of this
work produced from a part of Onder Alici's PhD Thesis. Also we thank
Advanced Technology Research and Application Centre of Selcuk Uni-
versity for POM measurements.
Table 1
Phase transition temperatures of LC aldoxime and aldoxime ethers.
Appendix A. Supplementary data
a
b
Compd.
n
Transition temperature (°C) (corresponding entropy
ΔT1 ΔT2
changes, ΔS/R) heating/cooling
Supplementary data to this article can be found online at http://dx.
doi.org/10.1016/j.molliq.2015.04.016.
7
9
10
11
12
6
Cr 78.4 (5.08) N 112 (0.73) I
33.6
–
–
10 I 139.1 (−1.39) N 94.5 (−5.89) Cr
44.6
42.2
28.9
28
6
8
I 135.5 (−0.90) N 93.3 (−8.35) Cr
I 103 (−0.24) N 74.1 (−3.96) Cr
–
References
–
10 Cr 84.2 (3.24) N 112.2 (6.48) I/I 104 (−0.91) N 76
(−7.03) Cr
28
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behavior, J. Mol. Liq. (2015), http://dx.doi.org/10.1016/j.molliq.2015.04.016

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