New liquid crystalline tetrahydropyran derivatives

Article abstract of DOI:10.1080/15421400903065705

We synthesized new low polar derivatives of tetrahydropyran with nematic and smectic behaviour. Quantum chemical calculations show, that the most elongated conformers of the cyclohexane and tetrahydropyran derivatives have nearly identical molecular shape

Full text of DOI:10.1080/15421400903065705

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New Liquid Crystalline
Tetrahydropyran Derivatives
Atsuko Fujita a , Tokifumi Masukawa a , Subaru
Kawasaki a & Dietrich Demus b
a Chisso Petrochemical Corporation , Research
Center , Ichihara, Chiba, Japan
b International Scientific Consulting Office , Halle,
Germany
Published online: 05 Oct 2009.
To cite this article: Atsuko Fujita , Tokifumi Masukawa , Subaru Kawasaki & Dietrich
Demus (2009) New Liquid Crystalline Tetrahydropyran Derivatives, Molecular Crystals
and Liquid Crystals, 509:1, 245/[987]-262/[1004], DOI: 10.1080/15421400903065705
To link to this article: http://dx.doi.org/10.1080/15421400903065705
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Mol. Cryst. Liq. Cryst., Vol. 509, pp. 245=[987]–262=[1004], 2009
Copyright # Taylor & Francis Group, LLC
ISSN: 1542-1406 print=1563-5287 online
DOI: 10.1080/15421400903065705
New Liquid Crystalline Tetrahydropyran Derivatives
Atsuko Fujita1, Tokifumi Masukawa1, Subaru Kawasaki1,
and Dietrich Demus2
1Chisso Petrochemical Corporation, Research Center, Ichihara,
Chiba, Japan
2International Scientific Consulting Office, Halle, Germany
We synthesized new low polar derivatives of tetrahydropyran with nematic and
smectic behaviour. Quantum chemical calculations show, that the most elongated
conformers of the cyclohexane and tetrahydropyran derivatives have nearly
identical molecular shape. The different liquid crystalline behaviour can be
explained by different amounts of conformers deviating from the most elongated
shape. The De and Dn have been calculated and compared with the experimental
data obtained by extrapolation from basic mixtures. The two-ring compounds
dissolved in the basic mixture have low order parameters and excellent solubility.
By linear extrapolation, the two-ring compounds possess negative viscosities, but
positive by logarithmic extrapolation.
Keywords: nematics; quantum chemical calculations; synthesis; tetrahydropyrans;
viscosity; De and Dn
1. INTRODUCTION
In order to meet the requirements of the recent powerful development
of Liquid Crystal Display (LCD) devices, liquid crystal materials for
the LCD application are needed which have improved properties [1].
To satisfy these requirements, enormous numbers of liquid crystal
materials are investigated, especially with respect to better properties
of the quality of liquid crystal mixtures, dielectric anisotropy (De), opti-
cal birefringence (Dn), nematic temperature range and viscosity.
Basically, De and Dn of the liquid crystal mixture can be roughly
estimated from the additivity rule of the single compounds, and for
the latter they are predictable from the molecular structure with
quantum chemical calculation methods [2]. On the contrary, it is
Address correspondence to Atsuko Fujita, Chisso Petrochemical Corporation, Goi
Research Centre, Research Center 1, 5-1 Goikaigan, Ichihara, Chiba 290-8551, Japan.
E-mail: afujita@chisso.co.jp
245=[987]

246=[988]
A. Fujita et al.
difficult to predict nematic temperature range, viscosity and solubility
properties at lower temperature and these factors are sometimes
deciding the LCD display quality.
Liquid crystalline compounds having a tetrahydropyran structure
are already known [3]. In most cases the tetrahydropyran ring is
directly connected with a benzene ring.
We synthesized new tetrahydropyran derivatives without direct
connection to aromatic rings and found that they have better solubility
and lower melting temperatures in comparison to their carbon analo-
gues, the cyclohexane derivatives.
In this paper, we discuss the differences of the thermal behaviour of
the tetrahydropyran and cyclohexane derivatives from the viewpoint
of conformational differences. Furthermore, the De and Dn have been
calculated and compared with the experimental data obtained from
different basic mixtures. By linear extrapolation from the mixtures
the two-ring compounds show negative viscosities, which are positive,
however, by logarithmic extrapolation. The compounds are valuable
components for mixtures to be used in LCDs.
2. SYNTHESIS AND TRANSITION TEMPERATURES OF
TETRAHYDROPYRAN DERIVATIVES
2.1. Synthesis of 2-Substituted Tetrahydropyran Derivatives
The typical procedure for synthesis of straight carbon chain group sub-
stituted at the 2- position of tetrahydropyran derivatives is shown in
Scheme 1. The desired cyclohexyl tetrahydropyran derivative, P-3,
was synthesized from the cyclohexyl acetaldehyde derivative (A). Con-
densation of Compound A with cyclohexyl amine gave the imine deri-
vative (B). It was reacted with ethyl acrylate under Michael addition
condition to give the formyl ester derivative (C), and the following
selective reduction of the formyl group with NaCNBH3 gave cyclohexyl
lactone (D) which was converted into a hemiacetal through the reac-
tion with trimethyl silyl lithium acetylide. After removal of the tri-
methyl silyl group by the usual method, hydrosilylation reaction of a
hemiacetal and the following selective hydrogenation reaction using
Lindlar catalyst gave vinyl tetrahydropyran derivative (P-4) and pal-
ladium carbon catalyst yielded the saturated compound (P-3).
2.2. Synthesis of 2,5-dicyclohexyl Tetrahydropyran
Derivatives
The typical procedure of synthesis of 2,5-dicyclohexyl tetrahydropyran
derivatives is shown in Scheme 2. A hydroxy ester (I) was obtained

Tetrahydropyran Derivatives
247/[989]
SCHEME 1 Synthesis of 2-alkyl or alkenyl tetrahydropyran a; Cyclohexyl-
amine, Et2O, r.t., b; Ethyl acrylate, reflux, 10 hrs, c; NaCNBH3, pH 3, d;
Trimethylsilylacetylene, n-BuLi, e; Et3SiH, Et2O-BF3, CH2Cl2, f; H2, Lindlar
cat., g; H2, Pd-C=cat.
from the reaction between the oxetane derivative (G) and the lithiated
intermediate of t-butyl cyclohexyl acetate (H) in the presence of the
boron trifluoride etherate complex. Intramolecular esterification of I
under acidic condition gave 2,5-disubstituted lactone (J) in good yield.
Diisobuthylaluminium hydride reduction of lactone (J), and following
hydrosilylation of the hemiacetal finally yielded the desired tetrahy-
dropyran compound (P-10).
2.3. Measurement Conditions and Instruments
1H-NMR: Bruker DRX 500 (500 MHz); d (ppm) ¼ 7.26 for chloroform.
Transition temperature: Perkin Elmer Diamond DSC differential
scanning calorimetry and Nikon Optiphot polarizing microscopy with a
Mettler Toledo FP82HT hot stage. De and elastic constants at 25ꢀC: Hew-
lett Packard 4284A LCR meter. Dn at 25ꢀC: Atago 4 T and 2 T Abbe
refractometer. Rotational viscosity (c1) at 25ꢀC: TOYO Corporation
TCM-1.
SCHEME 2 Synthesis of 2,5-dicyclohexyltetrahydropyran h; LDA, Et2O-BF3,
CH2Cl2, i; TFA, CH2Cl2 j;DIBAL, ꢁ60ꢀC, k; Et3SiH, Et2O-BF3.

248/[990]
A. Fujita et al.
2.4. Phase Transitions of the New Compounds
The phase transition temperatures and transition enthalpies are
listed in Table 1. The two-ring tetrahydropyran derivatives, P-1 to
P-4, have mesomorphic temperature ranges at around room tempera-
ture. In particular, compounds having a vinyl side chain, P-2 and P-4,
show wider nematic temperature ranges and lower melting tempera-
tures. From the comparison of compounds P-3 and P-4, P-7 and P-9,
and P-11 and P12, it is obvious that the vinyl substituent in terminal
position of the compounds induces stabilized nematic phases. In order
to compare the properties of the non-polar tetrahydropyran deriva-
tives in Table 1, the phase transitions of analogous cyclohexane deri-
vatives are collected and listed in Table 2. In general, the analogous
cyclohexane derivatives possess higher clearing temperatures and
the substitution of the vinyl group instead of the ethyl group causes
the appearance of the nematic phases. However, in the most cases of
cyclohexane derivatives, the smectic B phase is retained. Compound
R-7 and R-8 having the methoxy group are well known as compounds
which can preserve the nematic phase when they are used in nematic
mixtures [10(b)]. From the above comparison, it is confirmed that the
combination of the tetrahydropyran ring and vinyl groups results in a
strong tendency to exhibit the nematic phase.
The compounds having the tetrahydropyran ring and a linkage
group in the central position of the molecule possess higher melting
temperatures and hardly exhibit mesomorphic properties.
3. MOLECULAR SHAPE AND CONFORMERS OF
TETRAHYDROPYRAN DERIVATIVES
The tetrahydropyran derivatives possess an elongated molecular shape,
suited for formation of liquid crystalline phase. Comparing them with
cyclohexane derivatives, in all cases analogous tetrahydropyran deriva-
tives show lower clearing temperatures. In order to find out the reason
for this behaviour, we calculated the molecular structures optimised by
quantum chemical methods (semi-empirical method, CAChe=PM5 [14]).
Figure 1 shows the optimised molecular shapes of compounds P-3 and
R-4. The molecular length and molecular breadth, which in non-polar
compounds substantially control the clearing temperature, are nearly
identical. The existence of enantiomers arising from the chirality of
the tetrahydropyran ring could be considered as substantial difference.
Generally, optically active substances can have quite different phase
transition temperatures compared with racemates. However, we have
not been able to separate optically pure compounds.

Tetrahydropyran Derivatives
249/[991]
TABLE 1 Phase Transitions of the Tetrahydropyran Derivatives
Phase transition
Enthalpy
(kJ=mol)
Structures
P-1
Temperature (ꢀC)
C -1.9 SmB 56.5 I
C 12.6 SmB 5.4 I
P-2
P-3
P-4
P-5
C 8.2 N 24.6 I
C -14.1 SmB 45.7 I
C 1.5 N 46.0 I
C 197.8 I
C 15.3 N 0.41 I
C 6.1 SmB 4.3 I
C 15.8 N 0.45 I
C 13.4 I
P-6
C 174.6 I
C 15.4 I
P-7
C 206.8 N 221.2 I
C 202.7 N 204.8 I
C 223.2 I
C 9.3 N 0.82 I
C 10.2 N 0.53 I
C 12.9 I
P-8
P-9
P-10
P-11
C 6.8 SmB 199.3 I
C 68.9 N 142.7 I
C 10.8 SmB 11.3 I
C 18.5 N 0.53 I
P-12
C 77.4 N 115.3 I
C 20.1 N 0.4 I
Another difference of the compounds is the right ring, which may
influence the conformation of the right substituent. In order to check
this hypothesis we calculated the relaxed energy map of the rotations

250/[992]
TABLE 2 Phase Transitions of the Cyclohexane Derivatives
Phase transition
A. Fujita et al.
Temperature
(ꢀC)
Enthalpy
(kJ=mol)
Structures
R-1
Ref.
[4]
C 6.4 N 70.1 I
C 18.0 N 6.2 I
R-2
R-3
[5]
[6]
C ꢁ6.3 SmB
C 13.8 SmB 6.41I
66.8 I
C ꢁ23.9 SmB
C 6.48 SmB
3.29 N 0.46 I
33.9 N 48.6 I
R-4
R-5
[7]
[8]
C -6.28 SmB
77.7 I
C 17.7 SmB 6.86 I
C -7.5 SmB
52.6 N 64.0 I
C 18.3 SmB
3.95 N 0.52 I
R-6
[9]
C 6.1 N 21.1 I
C 18.3 N 0.52 I
R-7
R-8
R-9
[10]
[10]
C 13.8 (SmB
11.2) N 20.8 I
C 17.1 (SmB 2.82)
N 0.45 I
C 12.1 SmB
28.4 N 37.6 I
C 19.8 SmB
3.15 N 0.52 I
[11] C 63.8 N 159.9 I
C 24.0 N 0.67 I
R-10
R-11
R-12
[12]
[13]
[13]
C 64.6 SmB
105.5 N 145.3 I
C 17.35 SmB
4.29 N 0.58 I
C 70.2 SmB
220.1 I
–
C 227.4 SmB
233.4 I
C 10.0 SmB 0.6 I
around the single bond of the right substituent (bond a in Fig. 1). The
result is displayed in Figure 2. We see that the energy maxima and
minima are practically in the same positions. The major differences are
the heights of the maxima at 0 and the minima at ꢁ172ꢀ and ꢁ65ꢀ.

Tetrahydropyran Derivatives
251/[993]
FIGURE 1 Comparison of the molecular structure of a tetrahydropyran and a
cyclohexane derivative.
In the Boltzmann distribution the different conformers exist in
amounts depending on their relative energies.
The Boltzmanndistributionhas been calculated [15] usingthe formula
ꢀ
ꢁ
ꢁHOFi
exp
kBT
ꢀ
ꢁ
xi ¼
ð1Þ
P
ꢁHOFi
i exp
kBT
xi ¼ molar fraction of the conformer i; in the following the existence
probability
EP ¼ 100 xi has been used.
HOFi ¼ Heat of Formation of a conformation
kB ¼ Boltzmann constant
T ¼ temperature, here we used room temperature 298.2 K.

252/[994]
A. Fujita et al.
FIGURE 2 Energy maps of the rotation of the right substituent of compounds
P-3 and R-4 around the single bond. Relaxed energies calculated with PM5.
The molecular breadth in all cases is the breadth of the cyclohexane
˚
ring B ¼ 6.73 A.
Table 3 shows that the most elongated conformer of compound P-3
is not the most stable one. The most stable conformer P-3c is less
elongated, but has the highest existence probability. Contrary to that,
in compound R-4 the most stable conformer R-4 at the same time is
the most elongated and has the highest L=B. Because the clearing
temperatures sensitively depend on L=B, the data of Table 3
TABLE 3 Properties of the Different Conformers of Compounds P3 and R4
Compound=
conformer
HOF
(kcal=mole)
a (ꢀ)
L (A)
L=B
EP (%)
˚
P-3
ꢁ172.94
60.04
ꢁ65.84
ꢁ171.95
ꢁ61.75
62.04
ꢁ127.7065
ꢁ127.4823
ꢁ128.2011
ꢁ100.7215
ꢁ100.1116
ꢁ100.1116
20.06
19.17
19.56
20.20
19.55
19.55
2.98
2.84
2.91
3.00
2.90
2.90
25.07
17.17
57.56
58.33
20.84
20.84
P-3b
P-3c
P-4
P-4b
P-4d
L ¼ molecular length.
B ¼ molecular breadth.

Tetrahydropyran Derivatives
253/[995]
elucidate why the tetrahydropyran derivatives possess lower clearing
temperatures than analogous cyclohexane derivatives.
4. PHYSICAL PROPERTIES OF THE NEW COMPOUNDS
4.1. Solubility of the Tetrahydropyran Derivatives
Compared with other low polar compounds, the tetrahydropyran deri-
vatives exhibit relatively large solubility in mixtures. As a first
approximation, the solubility can be calculated by the Schroeder-van
Laar equation
ꢂ
ꢃ
DH0i
1
1
ln xi ¼ ꢁ
ꢁ
ð2Þ
R
T
T0i
T ¼ actual temperature
DH0i ¼ melting enthalpy of the pure compound i
T0i ¼ melting temperature of the pure compound i
xi ¼ molar fraction of the compound i
R ¼ universal gas constant
This equation teaches that the solubility of a compound is the
higher, the lower are DH0i and T0i. Comparing the tetrahydropyran
derivatives of Table 1 with the cyclohexane derivatives of Table 2 we
see that the melting temperatures in general are not very different,
but the melting enthalpies of the former are smaller. Melting enthal-
pies of not more than about 15 kJ=mole for three-ring compounds
(Table 1 P-5 to P-10) are unusually small.
4.2. Order Parameters, Dielectric and Optical Data
In order to explain physical data like De and Dn of mixtures, we need the
knowledge of the order parameter of mixtures. Compounds dissolved in
a basic mixture may have the same order parameter as the basic mix-
ture, when the molecules are very similar. However, when the dissolved
molecules are different concerning geometry or chemical nature, their
order parameter can be smaller or larger [16]. Because optical data
can be measured and calculated with higher accuracy than dielectric
data, we use the comparison of measured and calculated optical data
for the determination of the order parameters of selected compounds.
The equation for the dielectric constant e of isotropic media has been
derived by Onsager [17].
e ¼ 1 þ ðNhF=e0Þ½aav þ Fl2=ð3kBTÞꢂ
ð3Þ

254/[996]
A. Fujita et al.
N ¼ NA=Vm ¼ number density
(number of molecules per volume unit)
ð4Þ
NA ¼ 6.02205 ꢃ 1023 molꢁ1 Avogadro constant
Vm ¼ molar volume
h ¼ 3e= 2e þ 1 correction factor considering the internal field
F ¼ (1 ꢁ faav)ꢁ1 correction factor for the reactive field
f ¼ (e ꢁ 1) [2pe0 a3 (2e þ 1)]ꢁ1
aav ¼ average polarizability of a molecule
e0 ¼ 8.854 ꢃ 10ꢁ12 Jꢁ1 C2 mꢁ1 dielectric constant of vacuum
l ¼ electric dipole moment
a ¼ radius of the spherical cavity
For calculating a, we use Onsager’s approximation: 4=3p N a3 ¼ 1.
Maier and Meier [17] derived formulas for the dielectric constants of
nematics:
e ¼ 1 þ ðNhF=e0Þ½aav þ 2=3DaP2 þ Fðl2=3kBTÞð1 ꢁ f1 ꢁ 3 cos2 bgP2Þꢂ
k
ð5Þ
e ¼ 1 þ ðNhF=e0Þ½aav ꢁ 1=3DaP2 þ Fðl2=3kBTÞð1 þ 1=2f1 ꢁ 3cos2 bgP2Þꢂ
?
ð6Þ
Da ¼ a ꢁ a
k
k
?
?
De ¼ e ꢁ e
P2 ¼ order parameter
b ¼ angle between molecule long axis and dipole moment
Da ¼ anisotropy of polarizability
The quantities aav, Da, l and b have been calculated using quantum
chemical methods (CAChe=PM5). The molar volume Vm needed for
calculation of the number density N is obtained by the group contribu-
tion method of Fedors [18].
We derived the empirical relation
P2 ¼ 0:363 log TNI
ð7Þ
between clearing temperature TNI (ꢀC) and P2 at room temperature
(25ꢀC) [20]. The refractive indices have been calculated by setting
l ¼ 0 in Eqs. (3, 5, 6) and by using the approximation
e ¼ n2
ð8Þ

Tetrahydropyran Derivatives
255/[997]
From blends with mixture A we extrapolated TNI and the anisotro-
pic properties Dn and De. The data are shown in Tables 4 and 5. Table 6
presents the data of the subjected compounds, calculated by quantum
chemistry resp. Fedors’ method. Using these data we can calculate the
optical and dielectric constants, but in addition we need the knowledge
of the order parameter P2 . We do not have direct measurements of P2
for the mixtures including said compounds. But using Eq. (7) it is
possible to calculate P2 at 25ꢀC. This procedure causes difficulties
because for most of the compounds we have directly determined
clearing temperatures of single materials. On the other hand, we have
extrapolated clearing temperatures from the blends with the
Mixture A. Finally, it turns out that using both of the corresponding
P2 the calculated Dn are very different from the extrapolated data.
This is shown in the cases of compounds P-3 (Table 7) and
compound R-4 (Table 8). In both cases the calculated Dn are much
higher than the extrapolated values. In order to reproduce the experi-
mental values by calculation we must use quite low order parameters,
which are much lower than calculated P2 of the Mixture A
(TNI ¼ 72.4ꢀC, P2calc: ¼ 0:674). This behaviour proves that the com-
pounds P-3 and R-4 are not well compatible with the basic mixture.
This is reflected also in the extrapolated De, which are quite different
from the data calculated using the order parameter optimised for Dn.
The calculated data are more positive than the extrapolated values.
Specially, in compound R-4 it is clear from the molecular structure,
TABLE 4 Extrapolated NI Temperature and
Properties of Tetrahydropyrans
Extrapolated from mixture A (15 wt%)
TNI (ꢀC)
Dn
De
P-1
P-2
P-3
P-4
P-5
P-6
P-7
P-8
P-9
P-10
P-11
P-12
17.7
37.7
31.0
0.017
0.044
0.024
0.044
0.070
0.044
0.097
0.084
0.077
0.064
0.124
0.097
0.30
ꢁ0.40
ꢁ0.80
0.30
1.40
ꢁ1.70
2.10
1.40
0.30
0.30
4.73
51.0
174.4
141.0
196.4
182.4
175.0
164.4
137.7
105.7
3.40

256/[998]
A. Fujita et al.
TABLE 5 Extrapolated NI Temperature and
Properties of Bicyclohexanes
Extrapolated from mixture A (15 wt%)
TNI (ꢀC)
Dn
De
R-1
R-2
R-3
R-4
R-5
R-6
R-7
R-8
R-9
R-10
R-11
R-12
20.4
37.0
50.4
51.0
61.0
19.7
12.4
25.0
149.7
133.7
198.7
189.7
0.010
0.010
0.037
0.024
0.044
0.017
0.010
ꢁ0.030
0.117
0.092
0.090
0.087
ꢁ1.3
ꢁ1.3
ꢁ0.6
0.3
ꢁ1.7
ꢁ0.3
ꢁ1.7
0.1
2.3
2.5
3.0
ꢁ1.0
TABLE 6 Data Calculated for R4, P-3, R-12, P-9 and P-10
l (D)
1–3cos2b
ais (a. u.)
Da (a. u.)
Vm (cm3=mol)
R-4
P-3
R-12
P-9
P-10
0.0140
1.7163
0.0134
1.7268
1.5935
0.4206
0.7190
0.2750
0.5370
0.0718
170.69
168.13
205.83
203.30
203.65
46.48
56.11
63.52
72.70
70.08
304.4
292.0
350.5
338.2
338.2
TABLE 7 Compound P-3
Comparison of Calculated and Extrapolated Data
Extrapol. from
mixture A
P2
0.5414
0.6025
0.2200
TNI (ꢀC)
31a
45.7b
2.8012
3.3387
ꢁ0.5375
2.0381
1.8541
0.0660
4.2c
3.032
31
ꢁ0.8
e
k
2.838
3.321
ꢁ0.483
e?
3.229
De
ꢁ0.197
1.9602
1.8930
0.0242
e
(l ¼ 0)
0.024
k
e (l ¼ 0)
?
Dn
aClearing temperature extrapolated from the blend with mixture A.
bClearing temperature of the pure compound.
cCalculated according to Eq. (7).

Tetrahydropyran Derivatives
TABLE 8 Compound R-4
257/[999]
Comparison of Calculated and Extrapolated Data
Extrapol. from
P2
0.6848
0.6198
0.300
mixture A
TNI (ꢀC)
77b
51a
6.8c
51
e
1.8919
1.7440
0.1479
1.8919
1.7439
0.0549
1.8825
1.7487
0.1339
1.8825
1.7486
0.0497
1.8365
1.7717
0.0648
1.8364
1.7716
0.0241
k
e?
De
ꢁ1
e
k
(l ¼ 0)
e (l ¼ 0)
?
Dn
0.024
Annotations see Table 7.
that the De should be positive. By shifting the order parameter in Eqs.
(5) and (6) we never can calculate negative De values for this
compound. But when we assume that in addition to the dilution of
Mixture A by adding R-4 De of the basic mixture is diminished, and
negative De may be extrapolated. This explanation should be valid also
for all compounds R-1 to R-8.
In the case of three ring compounds R-9 and R-10, the extrapolated De’s
are positive and thus ‘normal’, because the order parameters of three-
ring compounds are similar to that of the basic mixture (see Table 5).
Tables 9 to 11 show the data calculated for compounds R-12, P-9
and P-10. For the cyclohexane derivative compound R-12 the order
TABLE 9 Compound R-12
Comparison of Calculated and Extrapolated Data
Extrapol. from
P2
0.8504
0.8269
0.920
mixture A
TNI (ꢀC)
220.1b
1.988
1.768
0.221
189.7a
1.984
1.770
0.215
189.7
e
k
2.000
1.762
0.239
e?
De
e
(l ¼ 0)
1.8919
1.7439
0.0549
1.8825
1.7486
0.0497
2.0005
1.7616
0.0871
k
e (l ¼ 0)
?
Dn
0.087
Annotations see Table 7.

258/[1000]
A. Fujita et al.
TABLE 10 Compound P-9
Comparison of Calculated and Extrapolated Data
Extrapol. from
P2
0.8142
0.685
mixture A
TNI (ꢀC)
175a
2.680
77.0
2.713
2.970
ꢁ0.257
2.0084
1.7961
0.0770
175
e
k
e?
2.986
De
ꢁ0.306
2.0351
1.7827
0.0914
e
(l ¼ 0)
k
e (l ¼ 0)
?
Dn
0.077
Annotations see Table 7.
parameter corresponding to the Dn is higher than those corresponding
to the measured and extrapolated clearing temperatures. In the tetra-
hydropyran derivatives P-9 and P-10 it is opposite concerning the
measured clearing temperatures, but concerning the extrapolated
clearing temperatures the value for compound P-10 is slightly larger,
for compound P-9 substantially lower.
TABLE 11 Compound P-10
Comparison of Calculated and Extrapolated Data
Extrapol. from
P2
0.8347
0.8044
0.59
mixture A
TNI (ꢀC)
199.3a
2.865
2.654
0.211
2.0352
1.7856
0.0903
164.4b
2.859
2.656
0.203
2.0291
1.7886
0.0871
42.3
2.823
2.674
0.149
1.9864
1.8100
0.0640
164.4
e
k
e?
De
e
(l ¼ 0)
k
e (l ¼ 0)
0.064
?
Dn
Annotations see Table 7.

Tetrahydropyran Derivatives
259/[1001]
TABLE 12 Extrapolated Viscosities of Tetrahydropyran Derivatives based on
Mixtures A, B and C
Extrapolated from
mixture A (15%)
Extrapolated from
mixture B
Extrapolated from
mixture C
a
a
glin
glog
glin
glog
conc. (wt%) c1lin
c1log
conc. (wt%)
P-1
P-2
P-3
P-4
P-5
P-6
P-7
P-8
P-9
P-10
P-11
P-12
ꢁ0.9
ꢁ9.7
3.3
ꢁ2.8
34.3
36.5
40.2
–
45.5
35.5
35.1
39.8
9.0
6.1
10.5
8.0
35.1
37.9
43.1
–
51.9
36.6
36.1
42.5
10.7
ꢁ0.80
10.2
6.50
42.6
36.8
30.0
–
12.1
6.1
11.7
15
15
15
15
15
10
10
–
–
–
–
ꢁ96.7
36.8
ꢁ13.3
–
21.8
67.8
45.5
–
20
20
20
–
9.40
60.0
46.6
33.5
–
–
–
–
265.0 301.0
215.0 226.0
268.9 315.0
195.1 200.0
242.6 264.0
203.1 209.0
20
15
10
10
20
20
72.2
–
–
228
10
–
–
–
–
–
–
–
aMeasured by transient current method [21].
b Units of g and c1 are mPaꢄs.
4.3. Viscosity of the New Compounds
The viscosity of the target compounds usually is calculated using a
linear relation between viscosity and concentration:
gblend ¼ xMi gMi þ xtgt
ð9Þ
TABLE 13 Extrapolated Viscosities of Tetrahydropyran Derivatives based on
Mixtures A, B and C
Extrapolated. from
Extrapolated
Extrpolated from
mixture A (15%)
from mixture B (15%)
mixture C (20%)
a
a
glin
glog
glin
glog
c1lin
c1log
R-1
R-2
R-3
R-4
R-5
R-6
R-7
R-8
R-9
R-10
ꢁ9.3
ꢁ19.1
ꢁ25
ꢁ11
ꢁ16
ꢁ1.7
ꢁ3.5
1.2
6.2
3.9
2.9
5.7
4.5
8.7
8.0
9.6
25.1
21.7
–
–
–
–
6.4
ꢁ9.0
ꢁ18.0
ꢁ4.3
ꢁ8.6
–
3.5
1.9
4.8
3.6
–
5.6
9.2
12.3
18.3
ꢁ208.1
ꢁ199.9
ꢁ120.0
ꢁ99.1
ꢁ82.5
ꢁ78.2
ꢁ18.7
122.9
–
7.0
16.9
20.8
24.4
25.4
43
ꢁ1.4
6.0
25.9
21
11.0
18.3
125.2
–
aMeasured by transient current method [21].
bUnits of g and c1 are mPaꢄs.

260/[1002]
A. Fujita et al.
FIGURE 3 Base mixtures.
xMi, gMi ¼ concentration and viscosity of the basis mixture
xt,gt ¼ concentration and viscosity of the target compound
gblend ¼ viscosity of the blend of basis mixture and target compound
Equation (9) yields negative values for gt, when the target compound
has viscosity reducing effect of the total mixture and the deviation is
larger. Kneppe et al. recommended a logarithmic dependence of the
viscosity from the concentration for calculation of viscosities of mixtures,
Eqs. (10) [19]. Equation (10) is better founded than Eq. (9) from the
theoretical standpoint, but Eq. (9) is easier to handle in the practice.

Tetrahydropyran Derivatives
261/[1003]
log gblend ¼ xMi log gMi þ xt log gt
ð10Þ
In Tables 12 and 13 we have compiled the linearly and logarithmi-
cally extrapolated viscosities of subjected compounds from three types
of base mixture (Figure 3). Most of the two-ring compounds possess
negative viscosities by linear extrapolation. Comparing the data
extrapolated from the polar mixture A and those from the low polar
mixture B, we find that the data from the polar mixture are lower
than the latter. However, when we compare the logarithmically
extrapolated data, there is no substantial difference. Especially, all
logarithmically extrapolated viscosities for two-ring compounds are
positive with reasonable values.
The three-ring compounds generally possess higher viscosities, and
in most cases there is no large difference between linear and logarith-
mic extrapolation. Irrespective of the mathematical treatment of the
experimental data we can notice that the low polar compounds listed
in Tables 4 and 5 possess low viscosities, which make the materials
interesting for mixtures with faster response times suitable for appli-
cations in displays.
5. CONCLUSIONS
We have synthesized new derivatives of tetrahydropyran and
cyclohexane with two and three rings. Due to their elongated molecu-
lar shape most of the compounds exhibit liquid crystalline phases,
especially nematic phases. The differences in the clearing tempera-
tures of the tetrahydropyran and cyclohexane derivatives can be
explained by different amounts of most elongated conformers. Due to
their small melting enthalpies the tetrahydropyran derivatives show
large solubility in liquid crystal mixtures. We have compared
calculated and measured De and Dn and found that the two-ring
compounds have quite low order parameters when they are solved in
basic mixtures. Especially the two-ring compounds possess unusually
small viscosities. The new materials are useful components in
mixtures for practical application.
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