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Liquid Crystalline Phases Having Particularly Low Freezing Points.

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cyclic intermediate (8) - after subsequent hydrolysis
with water t o phenylhydrazones (7) o f a-hydroxy aldehydes.
Reactions with alkyl halides designed t o determine t h e
content of benzeneazomethyllithium (see Table) surprisingly led exclusively t o t h e N-alkylation products, i.e. formaldehyde (N-alkyl-N-pheny1)hydrazones(9).
(4), x = Li
(5). X = H
Reactions wlth benzeneazomethyllIthmn ( 2 ) in THF/n-hexane (ca. 9 : I ) a t -60 "C [a]
Reactant(s) [bl
ethyl bromide
n-Hydroxyvaleraldehyde phenylhydrazone
(I-Hydroxycyc1opentyI)formaldehyde phenylhydrazone
Diphenylglycolaldehyde phenylhydrazone
M.P. o r refractive
154 "C
171 'C
59 o c
95 "C
105 "C
oil; .go
oil; ngo
Methyl iodide
Ethyl bromide
[a] Before hydrolysis the reaction mixture was warmed t o 65 "C (alkyl halides), otherwise only t o f 2 0 " C
[bl Equimolar amounts relative t o benzeneazomethane.
[c] Described by H. H. Srroh, Chem. Ber. 91,2660 (1958)
Received: October 15, 1970
cz 299b IEl
German version: Angew. Chem. 82, 987 (1970)
Liquid Crystalline Phases Having Particularly Low
Freezing Points
[*I Prof. Dr. Th. Kauffmann, Dr. D. Berger, B. Scheerer, and
A. Woltermann
Oreanisch-Chemisches Institut der Universitat
44Miinster, Orleansring 23 (Germany)
[**I This work was supported by the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen Industrie.
[I] Organo-lithium and -aluminum Compounds, Part 5 . Part 4: Th. Kauffmann, H . Berg, E. Ludorfl, and A . Waltermann. Aneew. Chem. 82. 986 (1970):
_ _ Aneew.
- Chem. internat.
Edit.9, 960 (1970).
By Huns Kelker, Bruno Scheurle, Rolf Hatz, a n d
Werner Burtsch [*I
I n continuation o f earlier work [1,21 o n t h e synthesis o f lowmelting nematogenic substancessuch a s ( I ) a n d (2) we have
prepared new a z o a n d azoxy c o m p o u n d s (see Table).
F o r optical a n d electro-optical experiments, we chose a z o
c o m p o u n d s in o r d e r t o o b t a i n substances having a low
[21 Th. Kauffmann, H . Berg, and E . Koppelmann, Angew.
Chem. 82. 396 (1970): Aneew. Chem. internat. Edit. 9. 380
[31 A . Schunberg, D . Cernik, and W . Urban, Ber. dtsch. chem.
Ges. 64, 2577 (1931); E . J . Corey and R . A . E. Winter, J. Amer.
Chem. SOC.85, 2677 (1963); for further literature see D . Seebach, Angew. Chem. 81, 698 (1969); Angew. Chem. internat.
Edit. 8, 639 (1969).
[4] R . B . Woodward and R . Hoffmann, Angew. Chem. 81, 797
(1969); Angew. Chem. internat. Edit. 8, 781 (1969).
[5] On cycloaddition of 1,3-diphenyl-2-azaallyllithium to cisand trans-stilbene the configuration is conserved completely,
thus suggesting a concerted cycloaddition process ( E . Koppelm u m , Planned Dissertation, Universitat Munster, probably
[6] T h e instability of formaldehyde phenylhydrazone prohibits
any preparation of (2) from this compound.
[7] The constitution of the reaction products, which, with one
exception (see Table), apparently have not been described
previously, follows from analyses, molecular-weight determinations, and N M R , IR, and mass spectra.
Transition point
( "C), behavior
47-48 (nemat .) [a] [2]
80 (nemat.) [21
42 (nemat.)
8 1 (nemat .)
>71 (nemat.) [b]
>69 (nemat.) [b]
- (isotrop.)
[a] This value is valid for extremely pure (I], e . g . after purification by
electrodialysis 131. The value given in 121 is t o be corrected.
[bl The melting and clearing points of (5) and (6) were obtained with
chromatographically isolated substances (ca. 30 rng in each case). Since
the mixed clearing point of these fractions was determined as 69-70 "C
and the mixture of pure isomers before separation showed an even higher
clearing point (75-76"C), it can be assumed t h a t the clearing points
the pure components o n working u p larger quantities of substances of
could also reach a value of 75-76 "C.
Angew. Chem. internut. Edit.
Vol. 9 (1970) 1 No. 12
detector at 350 nm; initial pressure: 9 at, flow rate: 2 ml/min.
The relative retention was 1.4 with complete separation of both
[l] H . Kelker and B . Scheurle, J . Physique (Suppl. Colloque
C 4) 30, C4 104 (1969).
[2] H . Kelker and B. Scheurle, Angew. Chem. 81, 903 (1969);
Angew. Chem. internat. Edit. 8, 884 (1969)
[3] R . Tobazeon et a/., Lecture S 7, Liquid Crystals Conference,
Berlin 1970; J . Bore/ ef a/., ibid. Lecture S 18.
[4] Houben-Weyl-Miiller: Methoden der Organischen Chemie.
Thieme, Stuttgart 1965, Vol. 10/3, p. 762.
melting point a n d no central dipole, a n d azoxy compounds
so a s t o have available compounds with a relatively high
permanent moment. T h e new azo and azoxy compounds
(31 - (6) listed in t h e T a b l e form nematic phases.
C o m p o u n d s ( 3 ) a n d ( 4 ) were prepared by coupling of diazotized p-n-butylaniline with phenol; c o m p o u n d (7) is
formed first a n d this is reacted either with diazomethane o r
- better -~ with dimethyl sulfate t o give t h e methyl ether
( 3 ) or with ethyl iodideisodium ethoxide t o give t h e ethyl
ether ( 4 ) . T h e reaction with dimethyl sulfate affords very
pure ( 3 ) after two recrystallizations from petroleum ether.
C o m p o u n d s ( 5 ) a n d (6) were obtained by t h e known141
method of oxidation of (31 with 3 0 % hydrogen peroxide in
acetic acid; a mixture of isomers is formed (m.p. 19’C,
N,’I transition point 75-76’C)
that can be separated
chromatographically r* *I.
a-Diimine-Metal Chelates: Cyclic Delocalization of
x-Electrons and 13C Chemical Shifts [***I
Remarkably, uniaxially oriented layers exhibit clearly defined dichroism in t h e I R spectra of substances ( I ) , ( 3 ) ,
(S), a n d (6). Thus, for example, in t h e case of (3) t h e extinction coefficient €(isotropic) for t h e wave numbers 1292
a n d 1178 cm-1 is considerably higher t h a n that of t h e uniaxially oriented phase €1.T h e order of t h e €-values is reversed a t 1100 cm-1, i.e. €1> E(isotropic). Similar effects
occur in t h e case of t h e o t h e r substances. Investigations on
this anisotropic effect a r e still in progress.
By Christian Tanzer, Roger Price, Eberhard Breitmaier,
Gunther Jung, a n d Wolfgang Voelter [*I
I R spectroscopic determination of t h e M O x-bonding
order1‘1, a s well a s 1 H - N M R studies121, indicate cyclic
delocalization of x-electrons in a-diimine-metal chelates
(1)-(3). Since 13C chemical shifts depend characteristically
o n t h e x-electron density a t each C a t o m 131, a comparison
of t h e chemical shifts of 13C-NMR signals of s o m e nonbenzenoid aromatic c o m p o u n d s of known x-electron
distribution with t h e corresponding shifts for s o m e a-diimine-metal chelates should provide further evidence a b o u t
t h e so-called aromaticity 11,41 of these chelates.
T h e position of t h e 0 a t o m s i n ( 5 ) a n d ( 6 ) was determined
by mass spectrometry. Whereas in t h e oxidation mixture
i- a n d
t h e fragmentation masses 137 (CH30-CsH4-NO)
163 (C4Hg-C6H4-NO)+
occur i n t h e ratio of a b o u t 3:1,
the component more strongly absorbed o n silica gel (later
eluted with methylene chloride) [(5)] showed t h e m a s s 137
but n o t M = 163, t h e o t h e r isomer [ / 6 ) ]showed mass 163,
while M = 137 was absent. Since each isomer forms i t s own
nematic phase i t follows t h a t t h e trans c o m p o u n d is involved in each case. T h e ratio of t h e isomers occurring in
t h e oxidation is ca. 6 0 % ( 5 ) a n d 4 0 % (6).
Received: October 15, 1970
[ Z 300 IE]
German version: Angew. Chem. 82, 984 (1970)
[*I Dr. H. Kelker, Dr. B. Scheurle, Dr. R. Hatz, and
T h e 13C signals in N M R spectra a r e shifted upfield by 29.9
a n d 46.6 p p m when, respectively, cyclopentadiene a n d
cyclooctatetraene a r e converted i n t o t h e aromatic cyclopentadienyl a n d cyclooctatetraenyl anions 131: t h e opposite
effect is, however, observed o n conversion of cycloheptatriene i n t o t h e cycloheptatrienyl cation, namely, a downfield shift of t h e three olefinic 13C signals by 24.7, 28.9, a n d
35.2 p p m [31.
Dr. W. Bartsch
Farbwerke Hoechst AG
623 FrankfurtiMain 80 (Germany)
[**I A good separation was obtained o n an S I F thin-layer
chromatography plate (Riedel-de Haen) after a previous two
hours’ activation of the plate at 150°C o r - better - in a
column under the following conditions: 25 cm V4A tube; iai:
9 mm; stationary phase: silica gel Camag D - 0 , air-classified
fraction 5-10 p n , dried at 150 “ C and packed dry in the column; elution medium: methylene cloride dried over silica gel;
apparatus: Siemens chromatograph S 200 with PM-IV UV
Comparison of t h e Fourier transform 13C-NMR spectra of
some cc-diimine-metal chelates with those of t h e free di-
Table I .
13C shifts 8 of diimines and a-diimine chelates (TMS as external standard).
a-Diimine chelate
6 (ppm)
- 150.8
HzNN- C(CH,)--C(CH3)= NNHZ
[HzNN= C(CH3)-C(CH3)=NNHz]FeClz
[(CH&CN- C H - C H = N C ( C H ~ ) J I J M O ( C O ) ~
- 162.4
a,a’-Bipyridyl [bl
- 10.6
- 17.0
- 60.5
- 59.7
\ -158.4
{ 1128.4
o-Phenanthroline lbl
1 -150.75
{ I130.85
c 1::;s
{ 13.75
\ -133.2
- 31.15
{ 7154.05
[z,a’-Bipyridyll3FeClz [bl
t -3.35
1 -2.85
( -1.2
\ --134.35
la1 T M S as internal standard
Ibl The entries in the Table refer lo the signals of the magnetically nonequivalent ring carbon atoms in the z.8, or y positions relative t o the nitrogen.
Angew. Chem. internat. Edit.
Vol. 9 (1970)
1 No.
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