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Thkrmotropic liquid crystalline compounds with lateral long-chain substituents. Part VI. Liquid crystalline oxime bmzoates with lateral long-chain substituents
Materials Chemistry and Physics, 1.2 (1985)
461
461-468
THKRMOTROPIC LIC!UIDCRYSTALLINb COPPOUK.0SWITH LATERAL LONG-_----____CHAI&JSUBSTTTUENTS. PART VI. LIQUID CRYSTALLINE OXIME BENZOATES WITH LATERAL IJO~TG-CHAIN -SUBSTITUENTS W. WEISSFLOG VEB Laborchemie Apolda, Betriebsteil SpeziRlchemie Leipzig, DDR-7143 Leipzig-LUtzschena (G.D.R,) A. WIEGELEBEN and D, DEMUS 3lartin-Luther-Universitat Kalle-Wittenberg, Sektion Chemie, mu-4020 Halle (G.D.R.) Received 16 October 1984; accepted 23 October 1984 ABSTRACT The synthesis and liquid crystalline properties of several series of oxime benzoates with long-chain lateral substituents of the general formulae IT
R'm=N-OOC@R2
R
'nH2n+1 CH COO-N+;'&
III
'mH2m+l
R-(+00-N=?&~=N-CCC@R
IV 'nH2n+l
are reported and discussed from the view point of molecular statistical theories. INTRODUCTION The molecules of thermotropic liquid crystals should have more or less rod-like shapes. This rule was originally derived by Vorlander [d and has been confirmed in thousands of examples [g .In systematic studies we proved that there is the possibility of substituting rod-like molecules by lateral long-chain branches 0254-0584/85/$3.30
0 Elsevier Sequoia/Printed
in The Netherlands
462
Surprisingly,
crystalline properties the liquid [3-73. the case of l,4-bis-&subst.-benzoyloxy_7-2-nin
alkylbenzenes
of the general formula
without
losing
n T
the lateral alkyl chain could have up to 16 C-atoms without disappearance
of nematic properties.
The present paper deals
with investigations of similar kinds in substituted oxime benzoates with one (II) or two (III, IV) lateral substituents.
MPERI!WENTAL The transition temperatures were determined by a heating stage microscope. The calorimetric data were obtained by use of a differential scanning calorimeter
(DSC 2, Perkin-Elmer/USA)
which also yielded transition temperatures. The compounds were synthesized by acylation of appropriate oximes or dioximes with substituted benzoylchlorid.es in toluene, catalyzed by triethylamine.
RESULTS The tre.nsltion temperatures of the synthesized compounds are given in Tables 1 to 4. Table 1. Transition Temperatures of 4-B-n-Octyloxybenzoyloxyj'-valerophenoneoxime-4-subst.-benzoates
R
K
N
Is
'gH13'
. 105
*I35
.
K
.
N = nematic Is = isotropic liquid
?I-+5
.
95
. 112
= crystalline solid
463
Table
2.
Tt:ansi tion
Temperatures
of
4-n-Alkanoylbiphenyloxime
oxybenzoates --I_
‘nH2n+1 m
n
K
1
1
.
N
Is
189
.203"
.
2
1
.
165
.208a
.
3
1
.
154
.185&
.
4
1
l
146
.191a
.
5 6
1
.
140
.I84
0
1
.
137
.I80
.
7 8
1
.
132
.l75
.
1
.
136
.I73
.
9 IO
1
.
130
.I68
.
1
.
123
.166
.
6
2
.
107.5
.123.5
.
8
2
.
93
.116
.
1
3
.
108
l.73)
2
3
.
155
(.I081
3
3
.
113
c.87.5)
4
3
.
116.5
l.94.5)
5
3
.
106
(082)
6
3
.
108
(.84.5)
7
3
.
100
l.76.5)
8
3
.
102
t.78.5)
9
3
.
86
C.75)
10
3
l
97
C.75)
8
4
.
111
C.64)
8
5
.
82
8
6
.
85
(.53)
8
7
.
88
C.47.5)
8
9
.
98.5
c.39)
a Decomposition
C.56.5)
above
the
.
.
.
.
.
.
.
.
.
.
0
.
.
.
.
clearing
temperatures
4-n-alkyl-
464 Table
3. Temper,2 tures
Tri~.nsitian 0xybenzoatesJ
o:F I.lkandioned-ioxime-Sis-~-n-nlkgl-
-~-___.-_---p___p_I_ 1
-o-
$’
CmH2m+l-o 0
COO-B=C-C=U-OOC A2
m
R2
R'
K
N
19
. 224 . 234 . 208
*
1
CH3
2 3
" 7,
. 224 201 . 207
4
11
l
5 6
II
. 175
. 181.5
II
. 155
. 177
.
7 8
(I II
l
151
. 170
I
l
146
. 167,5
.
9 IO
11
l
141
. 160
.
n
l
140
t 159
*
‘2*5
l
146
. 128
,I
. 124
11
l
(.
203 )
(.
. 136.5
114
. 118
13:: I
(.
77 >
*
I,
.
86 89
(. 76) (. 78.51
. 105
(.
64 >
. -100.5
(.
69 1
.
(.
65 1
1,
. 104
(.
67 1
3
II 11
11
,t
II
: Y$
(.
If
,139
.
.
l
l
.
l
.
.
l
122 > -
.
.
* 135
(.
85)
.
(.
72)
99
l
.
11 iso-E3H7
l
l
C.82)
CH3 II
l
‘
88
1 2
.
. 128
.
93.5
.
w 127.5
11 t,
y7
5
204
If
c5Hl 1
4
l
.
.
(mntinu~
on fachw page)
465 ?E?zlle 3. (cont. 1 __l_---_---_PP-1 R2 R m 6
iso-C
CH3
K i7
3’-7
l
B
:r s
104
(.
75)
.
(.
69)
.
72)
.
7
”
”
.
94
8
II
17
.
97.5(.
g
11
11
.
81
(.
70)
.
,t
,I
.
86
(.
72)
.
10
Table& Tranoition Teqer-Lires bjs-L-subst
.
CH30 b
-
151
b a
c7”1 5O
l
a . 97 b 32
C4H90
C6”l3o
(.
143)
. 160 b" -
c+1110
S---M--^__-
; a
b
ca.o.5 y”-y5
l
73 23.5
a . 82
b
23
I,43
'%
. 123
35
. 142 1.1
. .
l
‘% 10IC 40
.
.
99 34.5
.
.
94 30.5
.
c81-1,70 a . 68 b 43.5 C9'I190 a . 70-80 . 100 b ca.005 47 . 107
C10H210
51
b" 1 C5Hll
a
-
. 127
(.
109)
.
C6H,3 C7H15
d a
-
:
(.
108)
.
(.
110)
.
.I’,:
a Trar,sition temperatures in oC b
. .
z .
.
42
c2x50 C3H70
of $, 4 '-3i-n-decr^nojrlbi~he~~l~~o~~me-
.-benzoate7 -~
Traxdt ion $nthalpies in kJ.mole'
' Double peak pointing to two solid :nodipications
466 DISCUSSION As already found in the case of substituted phenyl benzoates o-71 , also in derivatives of oxime benzoates lateral branches do not prevent liquid crystalline properties. Generally it was found that the smectic properties are strongly suppressed by lateral branches. Fig. 1 displays the transition temperatures of 4-n-alkanoylbiphenyloxime 4-n-al!eratures,however, show a continuously decreasing t.rendwith :increasinglength of lateral substitv.e:lt, pointing to a saturation value at long alkyl chains. This saturation effect was proved in the case of laterally brenched phenyl benzoates b,.g and interpreted in terms of conformation that the lateral alkyl chain is nearly parallel to the molecular long axis [5,6]. Therefore we assume that also in the branched oxime benzoates the lateral alkyl chains have en orientation nearly parallel to the molecular long axis.
A9Pc
.
-F-N-OOC
@OCBH,7
150-
50-
X\.__
1
__
--,b,,
I
3
5
7
9 n
Fig. 1. Melting (4,) and clearing temperatures (fiNI> of the 4-n-alkanoyl-biphenyloxime4-n-octyloxybenzoates
467
As the compounds lj.sted in Teble 3 show, also two lateral. substituents are possible in nematogenic depTessj_on
of
the
clearing
teaper,aturen
subs-kances. But the is
remarkable in these
two-ring compounds, especially in the case of bulky subst.i_tuents like iso propyl (Pig, 2). Nevertheless, two
also
>nolecnl.es
!mving
a greeter
rigid
core
md
long-chain s~tbs~;ituents(Table 4) may be nematogenic.
lateral
The clearing enthalpies .i_nthis series seem to alternate weakly but they do not show the strong i.ncrease wh'l.chis always found in homologous
series with stnectosenic properties
[8]. Compared
with the high melting enthal.pies, the clearing enthalpies are which is compatible w-i-tha molecular structure broadened smaY!.J., by the two lateral branches. The existence of nemati_c phases, hint of the orlen%ation however, may be considered as a strong _~ of the lateral branches being nearly parallel to the long molecuJ_e axis.
R2 C,HZ,,,O@COO-N=&C=N-OOC@OCnHz,l AY N,PC
I
A3
180-
*-x x-X
L
5
‘.-x
6
7
8
RZ= CH,;
R3
qCH,
R2= CH,;
R3
q
C2H5
9n
'g. 2. Clearing temperatures of alkandionedioxime-bis>-n-alkyloxybenzoateg,
468
COXCLUSION The introduction of one or two lateral branches offers a lot of possibilities
for the synthesis of new nematogenic
compounds. We are conducting further work in this direction.
REFERENCES 1
Che:lische Kristal_lo~ra&ie der Fli.issi~~keit;en D. Vorl#nder, -_l-----_-~-. _-___._,f Akadem. VerlR~sgesellschqft, Leipzig, 1924.
2
Kristslle in D. Demus, H. Demus and il. Zaschke, Pliissige --_Ifur Grundsto-C-Cirldus.trie, Tabellen, VEB Deutsche.t-Verl_a,?: Leipzig, 1974, 2nd edition
4 5
3
Vi. Weissflog and D. Demus, Cryst.------_ Res. Technol. 18 (1983jK21. lies. WV. Weissflog and 1). Demus, Cryst. -_---_--Technol. -19 (1984) 55. D. Demus, A. Hauser, A. Isenberg, M. Pohl, Ch. Selbmann,
6
W. Weissflog and S. Wieczorek, Cryst. Res. Technol -_-._.---_--_.L, in press. D. Demus, S. Diele, A. Hauser, I. Lati-f, Ch. Selhmann and
7
W. Weissflog, Cry_st. _-- Res. Technol., in press. W, bieissflog and D. Demus, Mol. Crgst. Liq. Cryst., in press.
8
D. Demus, S. Diele, S. Grande and 9. Sackmann, in G. B. Brown (ed.), Advances in Liquid Crystals, Vol. 6, Academic Press, New York - London,
1983, PO I.
461
461-468
THKRMOTROPIC LIC!UIDCRYSTALLINb COPPOUK.0SWITH LATERAL LONG-_----____CHAI&JSUBSTTTUENTS. PART VI. LIQUID CRYSTALLINE OXIME BENZOATES WITH LATERAL IJO~TG-CHAIN -SUBSTITUENTS W. WEISSFLOG VEB Laborchemie Apolda, Betriebsteil SpeziRlchemie Leipzig, DDR-7143 Leipzig-LUtzschena (G.D.R,) A. WIEGELEBEN and D, DEMUS 3lartin-Luther-Universitat Kalle-Wittenberg, Sektion Chemie, mu-4020 Halle (G.D.R.) Received 16 October 1984; accepted 23 October 1984 ABSTRACT The synthesis and liquid crystalline properties of several series of oxime benzoates with long-chain lateral substituents of the general formulae IT
R'm=N-OOC@R2
R
'nH2n+1 CH COO-N+;'&
III
'mH2m+l
R-(+00-N=?&~=N-CCC@R
IV 'nH2n+l
are reported and discussed from the view point of molecular statistical theories. INTRODUCTION The molecules of thermotropic liquid crystals should have more or less rod-like shapes. This rule was originally derived by Vorlander [d and has been confirmed in thousands of examples [g .In systematic studies we proved that there is the possibility of substituting rod-like molecules by lateral long-chain branches 0254-0584/85/$3.30
0 Elsevier Sequoia/Printed
in The Netherlands
462
Surprisingly,
crystalline properties the liquid [3-73. the case of l,4-bis-&subst.-benzoyloxy_7-2-nin
alkylbenzenes
of the general formula
without
losing
n T
the lateral alkyl chain could have up to 16 C-atoms without disappearance
of nematic properties.
The present paper deals
with investigations of similar kinds in substituted oxime benzoates with one (II) or two (III, IV) lateral substituents.
MPERI!WENTAL The transition temperatures were determined by a heating stage microscope. The calorimetric data were obtained by use of a differential scanning calorimeter
(DSC 2, Perkin-Elmer/USA)
which also yielded transition temperatures. The compounds were synthesized by acylation of appropriate oximes or dioximes with substituted benzoylchlorid.es in toluene, catalyzed by triethylamine.
RESULTS The tre.nsltion temperatures of the synthesized compounds are given in Tables 1 to 4. Table 1. Transition Temperatures of 4-B-n-Octyloxybenzoyloxyj'-valerophenoneoxime-4-subst.-benzoates
R
K
N
Is
'gH13'
. 105
*I35
.
K
.
N = nematic Is = isotropic liquid
?I-+5
.
95
. 112
= crystalline solid
463
Table
2.
Tt:ansi tion
Temperatures
of
4-n-Alkanoylbiphenyloxime
oxybenzoates --I_
‘nH2n+1 m
n
K
1
1
.
N
Is
189
.203"
.
2
1
.
165
.208a
.
3
1
.
154
.185&
.
4
1
l
146
.191a
.
5 6
1
.
140
.I84
0
1
.
137
.I80
.
7 8
1
.
132
.l75
.
1
.
136
.I73
.
9 IO
1
.
130
.I68
.
1
.
123
.166
.
6
2
.
107.5
.123.5
.
8
2
.
93
.116
.
1
3
.
108
l.73)
2
3
.
155
(.I081
3
3
.
113
c.87.5)
4
3
.
116.5
l.94.5)
5
3
.
106
(082)
6
3
.
108
(.84.5)
7
3
.
100
l.76.5)
8
3
.
102
t.78.5)
9
3
.
86
C.75)
10
3
l
97
C.75)
8
4
.
111
C.64)
8
5
.
82
8
6
.
85
(.53)
8
7
.
88
C.47.5)
8
9
.
98.5
c.39)
a Decomposition
C.56.5)
above
the
.
.
.
.
.
.
.
.
.
.
0
.
.
.
.
clearing
temperatures
4-n-alkyl-
464 Table
3. Temper,2 tures
Tri~.nsitian 0xybenzoatesJ
o:F I.lkandioned-ioxime-Sis-~-n-nlkgl-
-~-___.-_---p___p_I_ 1
-o-
$’
CmH2m+l-o 0
COO-B=C-C=U-OOC A2
m
R2
R'
K
N
19
. 224 . 234 . 208
*
1
CH3
2 3
" 7,
. 224 201 . 207
4
11
l
5 6
II
. 175
. 181.5
II
. 155
. 177
.
7 8
(I II
l
151
. 170
I
l
146
. 167,5
.
9 IO
11
l
141
. 160
.
n
l
140
t 159
*
‘2*5
l
146
. 128
,I
. 124
11
l
(.
203 )
(.
. 136.5
114
. 118
13:: I
(.
77 >
*
I,
.
86 89
(. 76) (. 78.51
. 105
(.
64 >
. -100.5
(.
69 1
.
(.
65 1
1,
. 104
(.
67 1
3
II 11
11
,t
II
: Y$
(.
If
,139
.
.
l
l
.
l
.
.
l
122 > -
.
.
* 135
(.
85)
.
(.
72)
99
l
.
11 iso-E3H7
l
l
C.82)
CH3 II
l
‘
88
1 2
.
. 128
.
93.5
.
w 127.5
11 t,
y7
5
204
If
c5Hl 1
4
l
.
.
(mntinu~
on fachw page)
465 ?E?zlle 3. (cont. 1 __l_---_---_PP-1 R2 R m 6
iso-C
CH3
K i7
3’-7
l
B
:r s
104
(.
75)
.
(.
69)
.
72)
.
7
”
”
.
94
8
II
17
.
97.5(.
g
11
11
.
81
(.
70)
.
,t
,I
.
86
(.
72)
.
10
Table& Tranoition Teqer-Lires bjs-L-subst
.
CH30 b
-
151
b a
c7”1 5O
l
a . 97 b 32
C4H90
C6”l3o
(.
143)
. 160 b" -
c+1110
S---M--^__-
; a
b
ca.o.5 y”-y5
l
73 23.5
a . 82
b
23
I,43
'%
. 123
35
. 142 1.1
. .
l
‘% 10IC 40
.
.
99 34.5
.
.
94 30.5
.
c81-1,70 a . 68 b 43.5 C9'I190 a . 70-80 . 100 b ca.005 47 . 107
C10H210
51
b" 1 C5Hll
a
-
. 127
(.
109)
.
C6H,3 C7H15
d a
-
:
(.
108)
.
(.
110)
.
.I’,:
a Trar,sition temperatures in oC b
. .
z .
.
42
c2x50 C3H70
of $, 4 '-3i-n-decr^nojrlbi~he~~l~~o~~me-
.-benzoate7 -~
Traxdt ion $nthalpies in kJ.mole'
' Double peak pointing to two solid :nodipications
466 DISCUSSION As already found in the case of substituted phenyl benzoates o-71 , also in derivatives of oxime benzoates lateral branches do not prevent liquid crystalline properties. Generally it was found that the smectic properties are strongly suppressed by lateral branches. Fig. 1 displays the transition temperatures of 4-n-alkanoylbiphenyloxime 4-n-al!
A9Pc
.
-F-N-OOC
@OCBH,7
150-
50-
X\.__
1
__
--,b,,
I
3
5
7
9 n
Fig. 1. Melting (4,) and clearing temperatures (fiNI> of the 4-n-alkanoyl-biphenyloxime4-n-octyloxybenzoates
467
As the compounds lj.sted in Teble 3 show, also two lateral. substituents are possible in nematogenic depTessj_on
of
the
clearing
teaper,aturen
subs-kances. But the is
remarkable in these
two-ring compounds, especially in the case of bulky subst.i_tuents like iso propyl (Pig, 2). Nevertheless, two
also
>nolecnl.es
!mving
a greeter
rigid
core
md
long-chain s~tbs~;ituents(Table 4) may be nematogenic.
lateral
The clearing enthalpies .i_nthis series seem to alternate weakly but they do not show the strong i.ncrease wh'l.chis always found in homologous
series with stnectosenic properties
[8]. Compared
with the high melting enthal.pies, the clearing enthalpies are which is compatible w-i-tha molecular structure broadened smaY!.J., by the two lateral branches. The existence of nemati_c phases, hint of the orlen%ation however, may be considered as a strong _~ of the lateral branches being nearly parallel to the long molecuJ_e axis.
R2 C,HZ,,,O@COO-N=&C=N-OOC@OCnHz,l AY N,PC
I
A3
180-
*-x x-X
L
5
‘.-x
6
7
8
RZ= CH,;
R3
qCH,
R2= CH,;
R3
q
C2H5
9n
'g. 2. Clearing temperatures of alkandionedioxime-bis>-n-alkyloxybenzoateg,
468
COXCLUSION The introduction of one or two lateral branches offers a lot of possibilities
for the synthesis of new nematogenic
compounds. We are conducting further work in this direction.
REFERENCES 1
Che:lische Kristal_lo~ra&ie der Fli.issi~~keit;en D. Vorl#nder, -_l-----_-~-. _-___._,f Akadem. VerlR~sgesellschqft, Leipzig, 1924.
2
Kristslle in D. Demus, H. Demus and il. Zaschke, Pliissige --_Ifur Grundsto-C-Cirldus.trie, Tabellen, VEB Deutsche.t-Verl_a,?: Leipzig, 1974, 2nd edition
4 5
3
Vi. Weissflog and D. Demus, Cryst.------_ Res. Technol. 18 (1983jK21. lies. WV. Weissflog and 1). Demus, Cryst. -_---_--Technol. -19 (1984) 55. D. Demus, A. Hauser, A. Isenberg, M. Pohl, Ch. Selbmann,
6
W. Weissflog and S. Wieczorek, Cryst. Res. Technol -_-._.---_--_.L, in press. D. Demus, S. Diele, A. Hauser, I. Lati-f, Ch. Selhmann and
7
W. Weissflog, Cry_st. _-- Res. Technol., in press. W, bieissflog and D. Demus, Mol. Crgst. Liq. Cryst., in press.
8
D. Demus, S. Diele, S. Grande and 9. Sackmann, in G. B. Brown (ed.), Advances in Liquid Crystals, Vol. 6, Academic Press, New York - London,
1983, PO I.