Liquid crystalline properties of dissymmetric molecules IV. The substituent effect on thermal properties of nematic and smectic A phases in three aromatic ring systems with ester linkages
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This paper describes the effect of substituent and ester linkage on smectic properties for some derivatives of 4-R -phenyl 4-(4-octyloxybenzoyloxy)benzoates (1), 4-octyloxyphenyl 4-(4-R-benzyloxy)benzoates (2), 4-(4-octyloxybenzoyloxy)phenyl 4- R -benzoates (3), and 4-R-phenyl 4-octyloxyphenyl terephthalates (4) where R = OCH3, CH3, OC8H17, C8H17, halogens, CF3, OCF3, CN, NO2, etc. The thermal properties are discussed in terms of the electrostatic nature of the substituents and the relative orientation of the ester groups with respect to both terminal substituents. The substituent effect on the layer structure of the smectic A phase is also examined by means of a small angle X-ray analysis.Keywords:
Benzoates
Abstract The thermal properties of 4-cyanophenyl 4-(4-alkyloxybenzoyloxy)benzoates having a lateral substituent have been examined. Commencing with the nonyloxy homologue the hydrogen derivative shows a smectic A phase having a partially bilayered arrangement (SAAd). When the substituents are introduced at position X, the SAd phase commences from the octyloxy homologue, and the chlorine and bromine derivatives show an additional SAd phase in the low temperature region. When the substituents are introduced at position Y, the SAd phase commences either from the undecyloxy or the dodecyloxy homologue, and the nitro derivative shows two tilted phases in the low temperature region. Compounds having a methoxy group at position Z have difficulty in forming the SAd phase. The effect of the substituent on the thermal properties of the smectic phases has been discussed in terms of the electrostatic and structural properties of the substituents. A driving force for the formation of the partially bilayered arrangement is also discussed.
Benzoates
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Acceptor
Position (finance)
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Abstract Ring and ester proton chemical shifts in six series of substituted methyl pyridinecarboxylates have been measured. Results for ring protons ortho and para to the substituent can generally be accounted for by additive substituent, ester and nitrogen effects. Shifts for protons meta to the substituent, when compared with analogous shifts in monosubstituted benzenes, provide evidence of substituent–nitrogen interactions. In particular, a special effect is noted for series where both the proton and substituent are adjacent to the nitrogen. The origin of this effect is discussed. The ester proton results lead to essentially the same conclusions. Although this probe is much less sensitive to substituent effects, the same special effect is evident for the methyl 6‐X‐picolinate series.
Chemical shift
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Abstract In our continued effort to synthesize materials which exhibit nematic behavior at room temperature, homologous p-alkylcarbonato-p-'-alkoxyphenyl benzoates were prepared. Of the 48 compounds that were synthesized, 27 exhibited enantiotropic and 14 monotropic nematic properties while only 7 were not liquid crystalline. One binary mixture of enantiotropic derivatives had a nematic range of 27–73°C while a ternary mixture exhibited nematic behavior between 24 and 76°C. In addition, seven other mixtures had crystal nematic transition temperatures below 30°C.
Benzoates
Homologous series
Biaxial nematic
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Like ethyl benzoates, the alkaline hydrolysis of 2-methyl substituted ethyl benzoates in 85% ethanol-water at 25°C followed the Hammett rule, though the ρ value increased from 2.50 to 2.76 due to the presence of the ortho-methyl group . Under the same conditions, the ρ value for the ionizations of substituted anilines was 3.34, which is considerably higher than 2.77 observed in water . The 4- or 5-substituent effects on the ortho effect in the alkaline hydrolysis of ethyl 2-methylbenzoates have been discussed based on the substituent effects in the original systems as well as in the product systems . Though marked differences were noted between the ortho effect in the dissociation of various benzoic acids and that in the hydrolysis of their esters, the substituent effects on the ortho effect were alike. If the ester group in the transition state is treated as a substituent, the .D value (-0.09--0. 17) is found to be on the considerably negative side from σm-CO2θ. The carbonyl character may thus be masked to a considerable extent in the transition state.
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Hammett equation
Alkaline hydrolysis
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ABSTRACT Vacciniin (6‐benzoyl‐D‐glucose) and benzoic acid were the only benzoates detected in extracts of the Stevens cultivar of cranberry. Vacciniin represents 75% of the total and was not inhibitory to the yeasts, Gram positive, or Gram negative bacteria tested.
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Benzoic acid
Gram
Gram-Negative Bacteria
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A series of nine co-crystals formed from acridine and benzoic acids have been synthesized and structurally characterized and the influence of the halogen substituent on the formation of halogen and hydrogen bonding in the co-crystals of the title compounds has been investigated.
Halogen bond
Acridine
Benzoic acid
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