Diketones useful as liquid crystals

Diketones of the formula ##STR1## wherein R.sub.1 is alkyl, perfluoroalkyl or alkoxy, each of 1-18 carbon atoms; R.sub.2 is alkyl or perfluoroalkyl, each of 1-12 carbon atoms; and X is 1,4-trans-cyclohexylene, 1,4-phenylene or 4,4'-cyclohexylphenyl are liquid crystalline compounds.

BACKGROUND OF THE INVENTION 
For liquid crystal display elements, the properties of nematic or 
nematic-cholesteric liquid crystalline materials are utilized to effect a 
significant change in their optical properties, such as light 
transmission, light scattering, double refraction, reflectance or color, 
under the influence of electrical fields. The function of such display 
elements is based, for example, on the phenomenon of dynamic scattering, 
the deformation of aligned phases, the Schadt-Helfrich effect in the 
twisted cell or the nematic-cholesteric phase transition. 
For industrial application of these effects in liquid crystal display 
elements, liquid crystalline materials are needed which have to meet a 
large number of requirements. Particularly important requirements are 
chemical stability towards moisture, air and physical influences, such as 
heat, radiation in the infrared, visible and ultraviolet ranges and steady 
and alternating electrical fields. Furthermore, a liquid crystal mesophase 
in the temperature range from at least 0.degree. C. to +50.degree. C., and 
preferably from -10.degree. C. to +70.degree. C., and a viscosity at room 
temperature of not more than 60 cP are demanded for liquid crystalline 
materials which can be used industrially. Finally, these materials must 
not have any characteristic absorption in the range of visible light, that 
is to say they must be colorless. 
A number of liquid crystalline compounds are already known which meet the 
stability requirements demanded of dielectrics for electronic components 
and which are also colorless. These include, in particular, the 
p,p'-disubstituted phenyl benzoates described in German 
Offenlegungsschrift No. 2,139,628, the p,p-disubstituted biphenyl 
derivatives described in German Offenlegungsschrift No. 2,356,085 or the 
phenylcyclohexane derivatives described in German Offenlegungsschrift No. 
2,636,684. 
These categories of liquid crystalline substances, and also other 
categories of liquid crystalline substances used hitherto in practice, are 
built up from aromatic or hydroaromatic rings which have terminal alkyl 
and/or alkoxy groups and are linked to one another directly or via a 
bridge group. This structure ensures the rigidity of the molecule 
necessary for a liquid crystalline mesophase, and in particular a nematic 
mesophase, to occur. However, many of these compounds have relatively 
little polar character and are therefore frequently not suitable for 
dissolving polar doping agents and/or dichroitic dyes in the 
concentrations which are desired for some types of applications. 
SUMMARY OF THE INVENTION 
Accordingly, it is an object of this invention to provide liquid 
crystalline compounds of polar character in which even strongly polar 
doping agents and/or dichroitic dyes are soluble to a sufficient extent to 
enable color switches based on the guest-host effect to be produced. 
Upon further study of the specification and appended claims, further 
objects and advantages of this invention will become apparent to those 
skilled in the art. 
These objects have been attained, surprisingly, by the discovery that the 
diketones of Formula I 
##STR2## 
wherein R.sub.1 is alkyl, perfluoroalkyl or alkoxy, each of 1-18 carbon 
atoms; R.sub.2 is alkyl or perfluoroalkyl, each of 1-12 carbon atoms; and 
X is 1,4-trans-cyclohexylene, 1,4-phenylene or 4,4'-cyclohexylphenyl, are 
outstandingly suitable as components of polar liquid crystal dielectrics. 
The compounds of Formula I possess liquid crystal mesophases and, because 
of their polar character, are able to dissolve strongly polar doping 
agents and/or dichroitic dyes in concentrations hardly achieved hitherto. 
Furthermore, the compounds of Formula I are able to form salts and complex 
compounds with metal ions. These salts and complexes can be used as doping 
agents effecting the necessary electrical conductivity in liquid crystal 
dielectrics for dynamic scattering. Finally, they possess an outstanding 
stabilizing effect on those liquid crystalline compounds which are 
sensitive to visible light and UV radiation. 
The invention thus relates to the diketones of Formula I, a process for 
their preparation, and their use as components of liquid crystal 
dielectrics. 
The invention also relates to liquid crystal dielectrics which contain at 
least one compound of Formula I and to electro-optical display elements 
which are based on a liquid crystal cell and contain a dielectric of this 
type. 
As can be seen, the diketones of this invention are 
4-cyclohexylacetophenone derivatives of Formula Ia 
##STR3## 
or 4-phenylacetophenone derivatives of Formula Ib 
##STR4## 
or 4-(4-cyclohexylphenyl)-acetophenone derivatives of Formula Ic 
##STR5## 
in which partial Formulae Ia to Ic, the radicals R.sub.1 and R.sub.2 are 
as defined for Formula I. The trans-configuration of the cyclohexane rings 
in Formulae Ia and Ic is shown by the black dot on the right-hand side of 
the respective ring. 
DETAILED DISCUSSION 
In the compounds of this invention, R.sub.1 is alkyl, alkoxy or 
perfluoroalkyl each of 1-18 carbon atoms, which can be straight-chain or 
branched. Among the straight-chain radicals R.sub.1, i.e., methyl, ethyl, 
n-propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, 
n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-pentadecyl, n-hexadecyl, 
n-heptadecyl or n-octadecyl and the analogous alkoxy or perfluoroalkyl 
groups, those with not more than 12 carbon atoms are preferred. 
Occasionally, however, compounds of Formula I which contain branched 
substituents R.sub.1 are also of importance, since these compounds 
sometimes display better solubility characteristics in the customary 
liquid crystal base mixtures. Substituents R.sub.1 of this type which are 
not straight-chain preferably contain not more than one branch in the 
chain. Preferred branched substituents are those in which the carbon chain 
is branched at the carbon atom adjacent to the group X or, in particular, 
at one of the two nearest carbon atoms. Important groups among these 
substituents include those branched groups in which a methyl or ethyl 
group is located in the 1-, 2- or 3-position on a relatively long carbon 
chain, for example, isopropyl, 1-methylpropyl, 2-methylpropyl, 
1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 1-methylpentyl, 
1-ethylpentyl, 2-methylpentyl, 1-methylhexyl, 2-ethylhexyl or 
1-methylheptyl. These selection criteria also apply analogously for the 
corresponding alkoxy groups R.sub.1. 
If R.sub.1 is a perfluoroalkyl group, preferred groups are those which 
contain not more than 8 carbon atoms and, in particular, those with 1-5 
carbon atoms; among such compounds, those in which R.sub.1 is 
trifluoromethyl are particularly easily accessible. For the compounds of 
the partial Formulae Ia and Ic, preferred compounds are those in which 
R.sub.1 is an alkyl group; because the synthesis of the corresponding 
alkoxy and perfluoroalkyl derivatives is more difficult, the use of these 
derivatives in liquid crystal dielectrics is less economical. 
In the compounds of this invention, the radical R.sub.2 is alkyl or 
perfluoroalkyl each of 1-12 carbon atoms. Among such compounds, preferred 
compounds are those in which R.sub.2 is alkyl of 1-8 carbon atoms and in 
particular of 1-4 carbon atoms. Among the analogous perfluoroalkyl 
derivatives, those in which R.sub.2 is of not more than 6 and preferably 
of 1-4 carbon atoms, and in particular is trifluoromethyl, are preferred. 
The compounds of this invention are prepared in the manner customary for 
such substances. Preferably, an acetophenone of Formula II 
##STR6## 
in which R.sub.1 is as defined in Formula I, is reacted in the presence of 
a basic condensing agent with a carboxylic acid ester of Formula III 
EQU R.sub.2 --COO--Z (III) 
in which Z is a lower alkyl group and R.sub.2 is as defined in Formula I, 
and the initially resulting salt of the enol form of the diketone (I) is 
hydrolyzed to the ketone. 
The acetophenones of Formula II are known from the literature in some 
cases, or they can be prepared analogously to the compounds of this type 
which are known from the literature, in particular by acetylation of a 
compound of Formula IV 
##STR7## 
under the conventional conditions of a Friedel-Crafts reaction. In the 
carboxylic acid esters of Formula III, Z is usually an alkyl group of not 
more than 4 carbon atoms, preferably methyl or ethyl. These esters are 
known from the literature. 
The reaction of the acetophenones of Formula II with the esters of Formula 
III is carried out under the conditions generally customary for Claisen 
condensations of this type, the basic condensing agents used being, in 
particular, sodium, potassium, sodium amide, potassium amide, sodium 
hydride or sodium alcoholates or potassium alcoholates. Preferably, the 
reactions are carried out in an anhydrous, inert organic solvent, for 
example, diethyl ether, tetrahydrofuran, benzene, toluene, xylene or 
petroleum ether. In most cases, the alkali metal salt of the enol form of 
the diketone of Formula I is formed, as a solid precipitate, in this 
reaction, which preferably is carried out at a temperature of -20.degree. 
C. to +50.degree. C. This precipitate is filtered off, washed with pure 
solvent and hydrolyzed with water, optionally in the presence of a small 
amount of a mineral acid. If the hydrolysis is carried out in the presence 
of an organic solvent which is immiscible with water, the organic phase 
containing the diketone (I) is subsequently separated off and evaporated. 
The residual diketone is then purified by recrystallization from a 
suitable solvent, for example, methanol, ethanol or ethyl acetate. 
Furthermore, the diketones of this invention of Formula I can be prepared 
by reacting a benzoic acid ester of Formula V 
##STR8## 
in which R.sub.1 and Z are as defined above, with a ketone of the Formula 
VI 
EQU CH.sub.3 --CO--R.sub.2 (VI) 
under conditions which are substantially analogous to those for the 
reaction of the acetophenones II with the carboxylic acid esters III. 
In these preparative reactions, for those products requiring a 
trans-cyclohexyl group as defined above, the corresponding 
cyclohexyl-containing starting material will contain its cyclohexyl ring 
also in the trans-position. That is, configuration of the cyclohexyl ring 
is retained in these preparative reactions. The cyclohexyl configurations 
of the starting materials in each case are commercially available or are 
readily preparable using fully conventional methods, such as those 
disclosed in German Offenlegungsschriften Nos. 26 36 684 and 27 01 591. 
The compounds of Formula I are valuable components of liquid crystal 
dielectrics, which are used to produce electro-optical display elements. 
The fact that the compounds can be used for this purpose is probably due 
to the existence of the tautomeric enol structures VIIa and VIIb 
##STR9## 
This assumption is also supported by the ability of the diketones of this 
invention to form complex salts. 
The liquid crystal dielectrics of this invention consist of two or more 
components, including at least one of Formula I. The other components are 
preferably nematic or nematogenic substances from the categories of the 
azobenzenes, azoxybenzenes, biphenyls, Schiff's bases, in particular 
benzylidene derivatives, phenyl benzoates, phenylcyclohexanes, optionally 
halogenated stilbenes, diphenylacetylene derivatives, diphenylnitrones and 
substituted cinnamic acids. The most important compounds which can be used 
as other components of this type can be characterized by Formula VIII: 
##STR10## 
in which A is 
______________________________________ 
CHCH 
##STR11## 
CX'CH 
##STR12## 
CHCX' 
##STR13## 
CC 
##STR14## 
NN 
##STR15## 
N(O)N 
##STR16## 
NN(O) CHN 
OCO NCH 
COO CHN(O) 
SCO N(O)CH 
COS 
______________________________________ 
or a C--C single bond. Other possible components of the dielectrics of this 
invention are those compounds of Formula VIII in which one or more phenyl 
rings have been replaced by a corresponding number of trans-cyclohexyl 
rings. X' is halogen, preferably Cl. R.sub.3 and R.sub.4 are identical or 
different and can be alkyl, alkoxy, alkanoyl, alkanoyloxy or 
alkoxycarbonyloxy each of not more than 18 and preferably not more than 8 
carbon atoms; furthermore, one of these radicals can also be a cyano, 
nitro or isonitrile group. In most of these compounds, R.sub.3 and R.sub.4 
are preferably different and one of the radicals is usually an alkyl or 
alkoxy group. However, a large number of other variants of the envisaged 
substituents are also customary. Many such substances are available 
commercially. 
The dielectrics of this invention contain as a rule at least 30, preferably 
50-99 and in particular 60-98 parts by weight of the compounds of the 
Formulae I and, optionally, VIII, per 100 total weight parts of 
dielectric. Of this amount preferably at least 15 parts by weight and 
usually even 20 or more parts by weight are made up by one or more 
compounds of Formula I. However, it is also possible to prepare 
dielectrics of this invention which consist exclusively of two or more 
compounds of Formula I. On the other hand, the invention also comprises 
those liquid crystal dielectrics to which, for example, for doping 
purposes, only less than 15 parts by weight, for example, 0.1 to 3 parts 
by weight, of one or more compounds of Formula I have been added. 
The dielectrics of this invention are prepared in a manner which is in 
itself customary. As a rule, the desired amount of one or more compounds 
of Formula I is dissolved in any additional components which may be 
present, preferably at elevated temperature. If the temperature chosen is 
above the clear point of the base material, it is particularly easy to 
observe when the dissolving process has gone to completion. 
It is, however, also possible to mix solutions of the components of the 
Formulae I and, optionally, VIII, in a suitable organic solvent, for 
example, acetone, chloroform or methanol, and, after thorough mixing, to 
remove the solvent again, for example, by distillation under reduced 
pressure. Of course, with this procedure care must be taken that no 
impurities or undesired doping agents are carried in by the solvent. 
By means of suitable additives, the liquid crystal dielectrics of this 
invention can be so modified that they can be used in all types of liquid 
crystal display elements disclosed hitherto. Such additives are known to 
those skilled in the art and are described in detail in the relevant 
literature. For example, substances for changing the dielectric 
anisotropy, the viscosity, the conductivity and/or the orientation of the 
nematic phases can be added. Such substances are described, for example, 
in German Offenlegungsschriften Nos. 2,209,127, 2,240,864, 2,321,632, 
2,338,281 and 2,450,088. Doping agents and dichroitic dyes include, e.g., 
substituted hydroquinone dibenzoate derivatives, azobenzene derivatives, 
4-alkylcyclohexane carboxylic esters, methine 4-nitroarylidene dyes, 
stilbene derivative dichroic dyes or tris-azo dichroic dyes, respectively 
disclosed in, e.g., U.S. Pat. Nos. 4,099,856, 4,105,654, 4,113,647, 
4,105,299, 4,116,861, or 4,128,497. 
Without further elaboration, it is believed that one skilled in the art 
can, using the preceding description, utilize the present invention to its 
fullest extent. The following preferred specific embodiments are, 
therefore, to be construed as merely illustrative, and not limitative of 
the remainder of the disclosure in any way whatsoever. In the following 
examples, all temperatures are set forth uncorrected in degrees Celsius; 
unless otherwise indicated, all parts and percentages are by weight.

In the examples, m.p. denotes the melting point and Cl. the clear point of 
a liquid crystal substance in degrees centrigrade; boiling points are 
designated b.p. 
EXAMPLE 1 
A solution of 265 g of 4-(4-n-pentylphenyl)-acetophenone in 300 ml of ethyl 
acetate is added to 1 liter of anhydrous diethyl ether which contains 23 g 
of sodium in the form of a wire. The reaction mixture is stirred for 24 
hours at room temperature. The sodium salt which has precipitated is then 
filtered off and washed with diethyl ether and introduced into a shaking 
vessel, with 500 ml of diethyl ether and 500 ml of water. After shaking 
for 1 hour, the organic phase is separated off, dried over sodium sulphate 
and evaporated. The residual 
1-[4-n-pentylbiphenyl-(4')-yl]-butane-1,3-dione is recrystallized from 
ethanol; m.p. 110.degree., Cl. 135.degree.. 
The following compounds are prepared analogously: 
1-[4-(4-methylcyclohexyl)-phenyl]-butane-1,3-dione 
1-[4-(4-ethylcyclohexyl)-phenyl]-butane-1,3-dione 
1-[4-(4-n-propylcyclohexyl)-phenyl]-butane-1,3-dione, m.p. 99.5.degree., 
Cl. 30.degree. 
1-[4-(4-n-butylcyclohexyl)-phenyl]-butane-1,3-dione, m.p. 94.degree., Cl. 
87.degree. 
1-[4-(4-n-pentylcyclohexyl)-phenyl]-butane-1,3-dione, m.p. 81.degree., Cl. 
97.degree. 
1-[4-(4-n-hexylcyclohexyl)-phenyl]-butane-1,3-dione 
1-[4-(4-n-heptylcyclohexyl)-phenyl]-butane-1,3-dione, m.p. 74.degree.. Cl. 
98.degree. 
1-[4-(4-n-octylcyclohexyl)-phenyl]-butane-1,3-dione 
1-[4-(4-n-nonylcyclohexyl)-phenyl]-butane-1,3-dione 
1-[4-(4-n-decylcyclohexyl)-phenyl]-butane-1,3-dione 
1-[4-(4-n-undecylcyclohexyl)-phenyl]-butane-1,3-dione 
1-[4-(4-n-dodecylcyclohexyl)-phenyl]-butane-1,3-dione 
1-[4-(4-methylcyclohexyl)-biphenyl-(4')-yl]-butane-1,3-dione 
1-[4-(4-ethylcyclohexyl)-biphenyl-(4')-yl]-butane-1,3-dione 
1-[4-(4-n-propylcyclohexyl)-biphenyl-(4')-yl]-butane-1,3-dione 
1-[4-(4-n-butylcyclohexyl)-biphenyl-(4')-yl]-butane-1,3-dione 
1-[4-(4-n-pentylcyclohexyl)-biphenyl-(4')-yl]-butane-1,3-dione 
1-[4-(4-n-hexylcyclohexyl)-biphenyl-(4')-yl]-butane-1,3-dione 
1-[4-(4-n-heptylcyclohexyl)-biphenyl-(4')-yl]-butane-1,3-dione 
1-[4-(4-n-octylcyclohexyl)-biphenyl-(4')-yl]-butane-1,3-dione 
1-[4-(4-n-nonylcyclohexyl)-biphenyl-(4')-yl]-butane-1,3-dione 
1-[4-(4-n-decylcyclohexyl)-biphenyl-(4')-yl]-butane-1,3-dione 
1-[4-(4-n-undecylcyclohexyl)-biphenyl-(4')-yl]-butane-1,3-dione 
1-[4-(4-n-dodecylcyclohexyl)-biphenyl-(4')-yl]-butane-1,3-dione 
1-[4-(4-methylcyclohexyl)-phenyl]-pentane-1,3-dione 
1-[4-(4-ethylcyclohexyl)-phenyl]-pentane-1,3-dione 
1-[4-(4-n-propylcyclohexyl)-phenyl]-pentane-1,3-dione, m.p. 78.degree., Cl. 
84.degree. 
1-[4-(4-n-butylcyclohexyl)-phenyl]-pentane-1,3-dione 
1-[4-(4-n-pentylcyclohexyl)-phenyl]-pentane-1,3-dione m.p. 59.degree., Cl. 
91.degree. 
1-[4-(4-n-hexylcyclohexyl)-phenyl]-pentane-1,3-dione 
1-[4-(4-n-heptylcyclohexyl)-phenyl]-pentane-1,3-dione 
1-[4-(4-n-octylcyclohexyl)-phenyl]-pentane-1,3-dione 
1-[4-(4-n-nonylcyclohexyl)-phenyl]-pentane-1,3-dione 
1-[4-(4-n-decylcyclohexyl)-phenyl]-pentane-1,3-dione 
1-[4-(4-n-undecylcyclohexyl)-phenyl]-pentane-1,3-dione 
1-[4-(4-n-dodecylcyclohexyl)-phenyl]-pentane-1,3-dione 
1-[4-(4-methylcyclohexyl)-biphenyl-(4')-yl]-pentane-1,3-dione 
1-[4-(4-ethylcyclohexyl)-biphenyl-(4')-yl]-pentane-1,3-dione 
1-[4-(4-n-propylcyclohexyl)-biphenyl-(4')-yl]-pentane-1,3-dione 
1-[4-(4-n-butylcyclohexyl)-biphenyl-(4')-yl]-pentane-1,3-dione 
1-[4-(4-n-pentylcyclohexyl)-biphenyl-(4')-yl]-pentane-1,3-dione 
1-[4-(4-n-hexylcyclohexyl)-biphenyl-(4')-yl]-pentane-1,3-dione 
1-[4-(4-n-heptylcyclohexyl)-biphenyl-(4')-yl]-pentane-1,3-dione 
1-[4-(4-n-octylcyclohexyl)-biphenyl-(4')-yl]-pentane-1,3-dione 
1-[4-(4-n-nonylcyclohexyl)-biphenyl-(4')-yl]-pentane-1,3-dione 
1-[4-(4-n-decylcyclohexyl)-biphenyl-(4')-yl]-pentane-1,3-dione 
1-[4-(4-n-undecylcyclohexyl)-biphenyl-(4')-yl]-pentane-1,3-dione 
1-[4-(4-n-dodecylcyclohexyl)-biphenyl-(4')-yl]-pentane-1,3-dione 
1-[4-(4-methylcyclohexyl)-phenyl]-hexane-1,3-dione 
1-[4-(4-ethylcyclohexyl)-phenyl]-hexane-1,3-dione 
1-[4-(4-n-propylcyclohexyl)-phenyl]-hexane-1,3-dione, m.p. 99.degree., Cl. 
100.degree. 
1-[4-(4-n-butylcyclohexyl)-phenyl]-hexane-1,3-dione 
1-[4-(4-n-pentylcyclohexyl)-phenyl]-hexane-1,3-dione 
1-[4-(4-n-hexylcyclohexyl)-phenyl]-hexane-1,3-dione 
1-[4-(4-n-heptylcyclohexyl)-phenyl]-hexane-1,3-dione 
1-[4-(4-n-octylcyclohexyl)-phenyl]-hexane-1,3-dione 
1-[4-(4-n-nonylcyclohexyl)-phenyl]-hexane-1,3-dione 
1-[4-(4-n-decylcyclohexyl)-phenyl]-hexane-1,3-dione 
1-[4-(4-n-undecylcyclohexyl)-phenyl]-hexane-1,3-dione 
1-[4-(4-n-dodecylcyclohexyl)-phenyl]-hexane-1,3-dione 
1-[4-(4-methylcyclohexyl)-biphenyl-(4')-yl]-hexane-1,3-dione 
1-[4-(4-ethylcyclohexyl)-biphenyl-(4')-yl]-hexane-1,3-dione 
1-[4-(4-n-propylcyclohexyl)-biphenyl-(4')-yl]-hexane-1,3-dione 
1-[4-(4-n-butylcyclohexyl)-biphenyl-(4')-yl]-hexane-1,3-dione 
1-[4-(4-n-pentylcyclohexyl)-biphenyl-(4')-yl]-hexane-1,3-dione 
1-[4-(4-n-hexylcyclohexyl)-biphenyl-(4')-yl]-hexane-1,3-dione 
1-[4-(4-n-heptylcyclohexyl)-biphenyl-(4')-yl]-hexane-1,3-dione 
1-[4-(4-n-octylcyclohexyl)-biphenyl-(4')-yl]-hexane-1,3-dione 
1-[4-(4-n-nonylcyclohexyl)-biphenyl-(4')-hexane-1,3-dione 
1-[4-(4-n-decylcyclohexyl)-biphenyl-(4')-yl]-hexane-1,3-dione 
1-[4-(4-n-undecylcyclohexyl)-biphenyl-(4')-yl]-hexane-1,3-dione 
1-[4-(4-n-dodecylcyclohexyl)-biphenyl-(4')-yl]-hexane-1,3-dione 
1-[4-(4-methylcyclohexyl)-phenyl]-heptane-1,3-dione 
1-[4-(4-ethylcyclohexyl)-phenyl]-heptane-1,3-dione 
1-[4-(4-n-propylcyclohexyl)-phenyl]-heptane-1,3-dione, m.p. 90.degree., Cl. 
75.degree. 
1-[4-(4-n-butylcyclohexyl)-phenyl]-heptane-1,3-dione 
1-[4-(4-n-pentylcyclohexyl)-phenyl]-heptane-1,3-dione 
1-[4-(4-n-hexylcyclohexyl)-phenyl]-heptane-1,3-dione 
1-[4-(4-n-heptylcyclohexyl)-phenyl]-heptane-1,3-dione 
1-[4-(4-n-octylcyclohexyl)-phenyl]-heptane-1,3-dione 
1-[4-(4-n-nonylcyclohexyl)-phenyl]-heptane-1,3-dione 
1-[4-(4-n-decylcyclohexyl)-phenyl]-heptane-1,3-dione 
1-[4-(4-n-undecylcyclohexyl)-phenyl]-heptane-1,3-dione 
1-[4-(4-n-dodecylcyclohexyl)-phenyl]-heptane-1,3-dione 
1-[4-(4-methylcyclohexyl)-biphenyl-(4')-yl]-heptane-1,3-dione 
1-[4-(4-ethylcyclohexyl)-biphenyl-(4')-yl]-heptane-1,3-dione 
1-[4-(4-n-propylcyclohexyl)-biphenyl-(4')-yl]-heptane-1,3-dione 
1-[4-(4-n-butylcyclohexyl)-biphenyl-(4')-yl]-heptane-1,3-dione 
1-[4-(4-n-pentylcyclohexyl)-biphenyl-(4')-yl]-heptane-1,3-dione 
1-[4-(4-n-hexylcyclohexyl)-biphenyl-(4')-yl]-heptane-1,3-dione 
1-[4-(4-n-heptylcyclohexyl)-biphenyl-(4')-yl]-heptane-1,3-dione 
1-[4-(4-n-octylcyclohexyl)-biphenyl-(4')-yl]-heptane-1,3-dione 
1-[4-(4-n-nonylcyclohexyl)-biphenyl-(4')-yl]-heptane-1,3-dione 
1-[4-(4-n-decylcyclohexyl)-biphenyl-(4')-yl]-heptane-1,3-dione 
1-[4-(4-n-undecylcyclohexyl)-biphenyl-(4')-yl]-heptane-1,3-dione 
1-[4-(4-n-dodecylcyclohexyl)-biphenyl-(4')-yl]-heptane-1,3-dione 
1-[4-(4-methylcyclohexyl)-phenyl]-4,4,4-trifluorobutane-1,3-dione 
1-[4-(4-ethylcyclohexyl)-phenyl]-4,4,4-trifluorobutane-1,3-dione 
1-[4-(4-n-propylcyclohexyl)-phenyl]-4,4,4-trifluorobutane-1,3-dione 
1-[4-(4-n-butylcyclohexyl)-phenyl]-4,4,4-trifluorobutane-1,3-dione 
1-[4-(4-n-pentycyclohexyl)-phenyl]-4,4,4-trifluorobutane-1,3-dione, m.p. 
65.degree., Cl. 40.degree. 
1-[4-(4-n-hexylcyclohexyl)-phenyl]-4,4,4-trifluorobutane-1,3-dione 
1-[4-(4-n-heptylcyclohexyl)-phenyl]-4,4,4-trifluorobutane-1,3-dione 
1-[4-(4-n-octylcyclohexyl)-phenyl]-4,4,4-trifluorobutane-1,3-dione 
1-[4-(4-n-nonylcyclohexyl)-phenyl]-4,4,4-trifluorobutane-1,3-dione 
1-[4-(4-n-decylcyclohexyl)-phenyl]-4,4,4-trifluorobutane-1,3-dione 
1-[4-(4-n-undecylcyclohexyl)-phenyl]-4,4,4-trifluorobutane-1,3-dione 
1-[4-(4-n-dodecylcyclohexyl)-phenyl]-4,4,4-trifluorobutane-1,3-dione 
1-[4-(4-methylcyclohexyl)-biphenyl-(4')-yl]-4,4,4-trifluorobutane-1,3-dione 
1-[4-(4-ethylcyclohexyl)-biphenyl-(4')-yl]-4,4,4-trifluorobutane-1,3-dione 
1-[4-(4-n-propylcyclohexyl)-biphenyl-(4')-yl]-4,4,4-trifluorobutane-1,3-dio 
ne 
1-[4-(4-n-butylcyclohexyl)-biphenyl-(4')-yl]-4,4,4-trifluorobutane-1,3-dion 
1-[4-(4-n-pentylcyclohexyl)-biphenyl-(4')-yl]-4,4,4-trifluorobutane-1,3-dio 
ne 
1-[4-(4-n-hexylcyclohexyl)-biphenyl-(4')-yl]-4,4,4-trifluorobutane-1,3-dion 
e 
1-[4-(4-n-heptylcyclohexyl)-biphenyl-(4')-yl]-4,4,4-trifluorobutane-1,3-dio 
ne 
1-[4-(4-n-octylcyclohexyl)-biphenyl-(4')-yl]-4,4,4-trifluorobutane-1,3-dion 
e 
1-[4-(4-n-nonylcyclohexyl)-biphenyl-(4')-yl]-4,4,4-trifluorobutane-1,3-dion 
e 
1-[4-(4-n-decylcyclohexyl)-biphenyl-(4')-yl]-4,4,4-trifluorobutane-1,3-dion 
e 
1-[4-(4-n-undecylcyclohexyl)-biphenyl-(4')-yl]-4,4,4-trifluorobutane-1,3-di 
one 
1-[4-(4-n-dodecylcyclohexyl)-biphenyl-(4')-yl]-4,4,4-trifluorobutane-1,3-di 
one 
1-[4-methylbiphenyl-(4')-yl]-butane-1,3-dione 
1-[4-ethylbiphenyl-(4')-yl]-butane-1,3-dione 
1-[4-n-propylbiphenyl-(4')-yl]-butane-1,3-dione 
1-[4-n-butylbiphenyl-(4')-yl]-butane-1,3-dione 
1-[4-n-hexylbiphenyl-(4')-yl]-butane-1,3-dione 
1-[4-n-heptylbiphenyl-(4')-yl]-butane-1,3-dione 
1-[4-n-octylbiphenyl-(4')-yl]-butane-1,3-dione 
1-[4-n-nonylbiphenyl-(4')-yl]-butane-1,3-dione 
1-[4-n-decylbiphenyl-(4')-yl]-butane-1,3-dione 
1-[4-n-undecylbiphenyl-(4')-yl]-butane-1,3-dione 
1-[4-n-dodecylbiphenyl-(4')-yl]-butane-1,3-dione 
1-[4-trifluoromethylbiphenyl-(4')-yl]-butane-1,3-dione 
1-[4-methoxybiphenyl-(4')-yl]-butane-1,3-dione 
1-[4-ethoxybiphenyl-(4')-yl]-butane-1,3-dione 
1-[4-n-propyloxybiphenyl-(4')-yl]-butane-1,3-dione 
1-[4-n-butyloxybiphenyl-(4')-yl]-butane-1,3-dione 
1-[4-n-pentyloxybiphenyl-(4')-yl]-butane-1,3-dione 
1-[4-n-hexyloxybiphenyl-(4')-yl]-butane-1,3-dione 
1-[4-n-heptyloxybiphenyl-(4')-yl]-butane-1,3-dione 
1-[4-n-octyloxybiphenyl-(4')-yl]-butane-1,3-dione 
1-[4-n-nonyloxybiphenyl-(4')-yl]-butane-1,3-dione 
1-[4-n-decyloxybiphenyl-(4')-yl]-butane-1,3-dione 
1-[4-n-undecyloxybiphenyl-(4')-yl]-butane-1,3-dione 
1-[4-n-dodecyloxybiphenyl-(4')-yl]-butane-1,3-dione 
1-[4-methylbiphenyl-(4')-yl]-pentane-1,3-dione 
1-[4-ethylbiphenyl-(4')-yl]-pentane-1,3-dione 
1-[4-n-propylbiphenyl-(4')-yl]-pentane-1,3-dione 
1-[4-n-butylbiphenyl-(4')-yl]-pentane-1,3-dione 
1-[4-n-pentylbiphenyl-(4')-yl]-pentane-1,3-dione 
1-[4-n-hexylbiphenyl-(4')-yl]-pentane-1,3-dione 
1-[4-n-heptylbiphenyl-(4')-yl]-pentane-1,3-dione 
1-[4-n-octylbiphenyl-(4')-yl]-pentane-1,3-dione 
1-[4-n-nonylbiphenyl-(4')-yl]-pentane-1,3-dione 
1-[4-n-decylbiphenyl-(4')-yl]-pentane-1,3-dione 
1-[4-n-undecylbiphenyl-(4')-yl]-pentane-1,3-dione 
1-[4-n-dodecylbiphenyl-(4')-yl]-pentane-1,3-dione 
1-[4-trifluoromethylbiphenyl-(4')-pentane-1,3-dione 
1-[4-methoxybiphenyl-(4')-yl]-pentane-1,3-dione 
1-[4-ethoxybiphenyl-(4')-yl]-pentane-1,3-dione 
1-[4-n-propyloxybiphenyl-(4')-yl]-pentane-1,3-dione 
1-[4-n-butyloxybiphenyl-(4')-yl]-pentane-1,3-dione 
1-[4-n-pentyloxybiphenyl-(4')-yl]-pentane-1,3-dione 
1-[4-n-hexyloxybiphenyl-(4')-yl]-pentane-1,3-dione 
1-[4-n-heptyloxybiphenyl-(4')-yl]-pentane-1,3-dione 
1-[4-n-octyloxybiphenyl-(4')-yl]-pentane-1,3-dione 
1-[4-n-nonyloxybiphenyl-(4')-yl]-pentane-1,3-dione 
1-[4-n-decyloxybiphenyl-(4')-yl]-pentane-1,3-dione 
1-[4-n-undecyloxybiphenyl-(4')-yl]-pentane-1,3-dione 
1-[4-n-dodecyloxybiphenyl-4')-yl]-pentane-1,3-dione 
1-[4-methylbiphenyl-(4')-yl]-hexane-1,3-dione 
1-[4-ethylbiphenyl-(4')-yl]-hexane-1,3-dione 
1-[4-n-propylbiphenyl-(4')-yl]-hexane-1,3-dione 
1-[4-n-butylbiphenyl-(4')-yl]-hexane-1,3-dione 
1-[4-n-pentylbiphenyl-(4')-yl]-hexane-1,3-dione 
1-[4-n-hexylbiphenyl-(4')-yl]-hexane-1,3-dione 
1-[4-n-heptylbiphenyl-(4')-yl]-hexane-1,3-dione 
1-[4-n-octylbiphenyl-(4')-yl]-hexane-1,3-dione 
1-[4-n-nonylbiphenyl-(4')-yl]-hexane-1,3-dione 
1-[4-n-decylbiphenyl-(4')-yl]-hexane-1,3-dione 
1-[4-n-undecylbiphenyl-(4')-yl]-hexane-1,3-dione 
1-[4-n-dodecylbiphenyl-(4')-yl]-hexane-1,3-dione 
1-[4-trifluoromethylbiphenyl-(4')-yl]-hexane-1,3-dione 
1-[4-methoxybiphenyl-(4')-yl]-hexane-1,3-dione 
1-[4-ethoxybiphenyl-(4')-yl]-hexane-1,3-dione 
1-[4-n-propyloxybiphenyl-(4')-yl]-hexane-1,3-dione 
1-[4-n-butyloxybiphenyl-(4')-yl]-hexane-1,3-dione 
1-[4-n-pentyloxybiphenyl-(4')-yl]-hexane-1,3-dione 
1-[4-n-hexyloxybiphenyl-(4')-yl]-hexane-1,3-dione 
1-[4-n-heptyloxybiphenyl-(4')-yl]-hexane-1,3-dione 
1-[4-n-octyloxybiphenyl-(4')-yl]-hexane-1,3-dione 
1-[4-n-nonyloxybiphenyl-(4')-yl]-hexane-1,3-dione 
1-[4-n-decyloxybiphenyl-(4')-yl]-hexane-1,3-dione 
1-[4-n-undecyloxybiphenyl-(4')-yl]-hexane-1,3-dione 
1-[4-n-dodecyloxybiphenyl-(4')-yl]-hexane-1,3-dione 
1-[4-methylbiphenyl-(4')-yl]-heptane-1,3-dione 
1-[4-ethylbiphenyl-(4')-yl]-heptane-1,3-dione 
1-[4-n-propylbiphenyl-(4')-yl]-heptane-1,3-dione 
1-[4-n-butylbiphenyl-(4')-yl]-heptane-1,3-dione 
1-[4-n-pentylbiphenyl-(4')-yl]-heptane-1,3-dione 
1-[4-n-hexylbiphenyl-(4')-yl]-heptane-1,3-dione 
1-[4-n-heptylbiphenyl-(4')-yl]-heptane-1,3-dione 
1-[4-n-octylbiphenyl-(4')-yl]-heptane-1,3-dione 
1-[4-n-nonylbiphenyl-(4')-yl]-heptane-1,3-dione 
1-[4-n-decylbiphenyl-(4')-yl]-heptane-1,3-dione 
1-[4-n-undecylbiphenyl-(4')-yl]-heptane-1,3-dione 
1-[4-n-dodecylbiphenyl-(4')-yl]-heptane-1,3-dione 
1-[4-trifluoromethylbiphenyl-(4')-yl]-heptane-1,3-dione 
1-[4-methoxybiphenyl-(4')-yl]-heptane-1,3-dione 
1-[4-ethoxybiphenyl-(4')-yl]-heptane-1,3-dione 
1-[4-n-propyloxybiphenyl-(4')-yl]-heptane-1,3-dione 
1-[4-n-butyloxybiphenyl-(4')-yl]-heptane-1,3-dione 
1-[4-n-pentyloxybiphenyl-(4')-yl]-heptane-1,3-dione 
1-[4-n-hexyloxybiphenyl-(4')-yl]-heptane-1,3-dione 
1-[4-n-heptyloxybiphenyl-(4')-yl]-heptane-1,3-dione 
1-[4-n-octyloxybiphenyl-(4')-yl]-heptane-1,3-dione 
1-[4-n-nonyloxybiphenyl-(4')-yl]-heptane-1,3-dione 
1-[4-n-decyloxybiphenyl-(4')-yl]-heptane-1,3-dione 
1-[4-n-undecyloxybiphenyl-(4')-yl]-heptane-1,3-dione 
1-[4-n-dodecyloxybiphenyl-(4')-yl]-heptane-1,3-dione 
1-[4-methylbiphenyl-(4')-yl]-4,4,4-trifluorobutane-1,3-dione 
1-[4-ethylbiphenyl-(4')-yl]-4,4,4-trifluorobutane-1,3-dione 
1-[4-n-propylbiphenyl-(4')-yl]-4,4,4-trifluorobutane-1,3-dione 
1-[4-n-butylbiphenyl-(4')-yl]-4,4,4-trifluorobutane-1,3-dione 
1-[4-n-pentylbiphenyl-(4')-yl]-4,4,4-trifluorobutane-1,3-dione 
1-[4-n-hexylbiphenyl-(4')-yl]-4,4,4-trifluorobutane-1,3-dione 
1-[4-n-heptylbiphenyl-(4')-yl]-4,4,4-trifluorobutane-1,3-dione 
1-[4-n-octylbiphenyl-(4')-yl]-4,4,4-trifluorobutane-1,3-dione 
1-[4-n-nonylbiphenyl-(4')-yl]-4,4,4-trifluorobutane-1,3-dione 
1-[4-n-decylbiphenyl-(4')-yl]-4,4,4-trifluorobutane-1,3-dione 
1-[4-n-undecylbiphenyl-(4')-yl]-4,4,4-trifluorobutane-1,3-dione 
1-[4-n-dodecylbiphenyl-(4')-yl]-4,4,4-trifluorobutane-1,3-dione 
1-[4-trifluoromethylbiphenyl-(4')-yl]-4,4,4-trifluorobutane-1,3-dione 
1-[4-methoxybiphenyl-(4')-yl]-4,4,4-trifluorobutane-1,3-dione 
1-[4-ethoxybiphenyl-(4')-yl]-4,4,4-trifluorobutane-1,3-dione 
1-[4-n-propyloxybiphenyl-(4')-yl]-4,4,4-trifluorobutane-1,3-dione 
1-[4-n-butyloxybiphenyl-(4')-yl]-4,4,4-trifluorobutane-1,3-dione 
1-[4-n-pentyloxybiphenyl-(4')-yl]-4,4,4-trifluorobutane-1,3-dione 
1-[4-n-hexyloxybiphenyl-(4')-yl]-4,4,4-trifluorobutane-1,3-dione 
1-[4-n-heptyloxybiphenyl-(4')-yl]-4,4,4-trifluorobutane-1,3-dione 
1-[4-n-octyloxybiphenyl-(4')-yl]-4,4,4-trifluorobutane-1,3-dione 
1-[4-n-nonyloxybiphenyl-(4')-yl]-4,4,4-trifluorobutane-1,3-dione 
1-[4-n-decyloxybiphenyl-(4')-yl]-4,4,4-trifluorobutane-1,3-dione 
1-[4-n-undecyloxybiphenyl-(4')-yl]-4,4,4-trifluorobutane-1,3-dione and 
1-[4-n-dodecyloxybiphenyl-(4')-yl]-4,4,4-trifluorobutane-1,3-dione. 
The examples which follow relate to the use, according to this invention, 
of the diketones (I) as components of liquid crystal dielectrics: 
EXAMPLE 2 
A mixture of 46.7 parts by weight of 4-n-pentylphenyl anisate, 23.3 parts 
by weight of 4'-n-pentylphenyl 4-n-hexyloxybenzoate, 15.0 parts by weight 
of 1-[4-(4-n-pentylcyclohexyl)-phenyl]-pentane-1,3-dione, 7.5 parts by 
weight of 1-[4-(4-n-pentylcyclohexyl)-phenyl]-butane-1,3-dione and 7.5 
parts by weight of 1-[4-(4-n-butylcyclohexyl)phenyl]-butane-1,3-dione has 
a melting point of 5.degree. and a clear point of 64.degree.. 5 parts by 
weight of the dichroitic dye 
1-hydroxy-4-N-(p-n-nonyloxyphenyl)-amino-anthraquinone can be dissolved in 
this mixture at 25.degree. without difficulty. 
EXAMPLE 3 
A mixture of 58.0 parts by weight of 4-n-butyl-4'-methoxyazoxybenzene, 29.0 
parts by weight of 4-ethyl-4'-methoxyazoxybenzene, 8.0 parts by weight of 
2'-cyano-4'-n-heptylphenyl 4-n-heptylbiphenyl-(1)-carboxylate and 5.0 
parts by weight of 1-[4-(4-n-pentylcyclohexyl)-phenyl]-butane-1,3-dione 
has a melting point of -4.degree. and a clear point of 78.degree.. 
Ethyl-dodecyl-dimethyl-ammonium 4-(4-n-hexyloxybenzene)-benzoate is 
readily soluble in the mixture; the dielectric thus obtained is 
outstandingly suitable for liquid crystal display elements based on the 
dynamic scattering effect. The dichroitic dye 
1-hydroxy-4-N-(p-n-nonyloxyphenyl)-amino-anthraquinone is also readily 
soluble in this mixture in amounts of up to 5%; these dye-containing 
dielectrics are particularly well suited for the preparation of colored 
display elements which operate on the basis of the deformation of aligned 
phases (DAP effect). 
EXAMPLE 4 
A mixture of 26.1 parts by weight of 4-(4-n-propylcyclohexyl)-benzonitrile, 
36.9 parts by weight of 4-(4-n-pentylcyclohexyl)-benzonitrile, 27.0 parts 
by weight of 4-(4-n-heptylcyclohexyl)-benzonitrile, 5.0 parts by weight of 
1-[4-(4-n-propylcyclohexyl)-phenyl]-4,4,4-trifluorobutane-1,3-dione and 
5.0 parts by weight of 
1-[4-(4-n-pentylcyclohexyl)-phenyl]-4,4,4-trifluorobutane-1,3-dione has a 
melting point of 0.degree. and a clear point of 50.degree.. Dichroitic 
dyes such as, for example, 
1-hydroxy-4-N-(p-n-nonyloxyphenyl)-aminoanthraquinone, are readily soluble 
in this mixture; after customary doping with a chiral substance, the 
dielectrics obtained in this way make it possible to prepare a liquid 
crystal color switch with good contrast. 
EXAMPLE 5 
A mixture of 14 parts by weight of 
1-[4-(4-n-butylcyclohexyl)-phenyl]-butane-1,3-dione, 14 parts by weight of 
1-[4-(4-n-pentylcyclohexyl)-phenyl]-butane-1,3-dione, 14 parts by weight 
of 1-[4-(4-n-heptylcyclohexyl)-phenyl]butane-1,3-dione, 29 parts by weight 
of 1-[4-(4-n-pentylcyclohexyl)-phenyl]-pentane-1,3-dione and 29 parts by 
weight of 1-(4-heptylphenyl)-butane-1,3-dione has a melting point of 
20.degree. and a clear point of 49.degree.. The mixture possesses a 
negative dielectric anisotropy and a good dissolving power for dichroitic 
dyes or acetylacetonate complexes of polyvalent metal ions; such solutions 
possess an electrical conductivity which is carried, on the other hand, by 
the metal cations and, on the other hand, by the keto-enolate anions 
contained in the liquid crystal matrix. 
The preceding examples can be repeated with similar success by substituting 
the generically or specifically described reactants and/or operating 
conditions of this invention for those used in the preceding examples. 
From the foregoing description, one skilled in the art can easily ascertain 
the essential characteristics of this invention, and without departing 
from the spirit and scope thereof, can make various changes and 
modifications of the invention to adapt it to various usages and 
conditions.