The Influence of the Position of Oxygen on the Phase Behaviour of Benzylidene Anilines

Abstract

Synthesis and Characterization of N (p-n-alkyl benzylidene)-p-n-alkoxy anilines (n.Om), N (p-nalkoxy benzylidene)-p-n-alkoxy anilines (nO.Om) and N (p-n-alkyl benzylidene)-p-n-alkyl anilines (n.m), where n = m = either 4 or 5, has been carried out using thermal microscopy (TM) and differential scanning calorimetry (DSC). The results are discussed in the light of other experimental observations on N (p-n-alkoxy benzylidene)-p-n alkyl anilines (nO.m). It has been observed that the position of oxygen on either side of the rigid core of the benzylidene moiety plays an important role in the manifestation of different phase variants.

Influence of Oxygen on Phase Behavior of N(p-n-Octyloxy Benzylidene)p-n-Alkoxy Anilines: A Comparative Study

“…The compounds are prepared by condensation of the corresponding benzaldehyde (0.1 mole) and aniline (0.1 mole) on refluxing with absolute ethanol in the presence of few drops of glacial acetic acid [8]. After refluxing the reactants for four hours, solvent is removed by distillation under reduced pressure, and the pure compound is recrystalized from absolute ethanol at low temperature.…”

Influence of oxygen in lower homologues of Schiff-base compounds: a comparative study

“…The benzylidene aniline compounds were prepared [5] by the condensation of respective benzaldehydes (0.1 mol) and anilines (0.1 mol) by refluxing the ingredients in absolute ethanol in the presence of a few drops of glacial acetic acid. The reactants were refluxed for four hours and the solvent was removed by distillation under reduced pressure.…”

“…An overview of the results of mesogenity exhibited by the present case of the homologues of Schiff's base 1O.5, 1.O5, 1O.O5, 1.5, 2O.5, 2.O5, 2O.O5 and 2.5 compounds suggests an interesting trend in the following way: the reversal of central linkage (studied through 1.O5 and 2.O5) is found to quench the liquid-crystalline nature. It may be compared with the reversal in higher homologues [5] for n ¼ m ¼ 5, through N( p-n-Pentyloxy benzylidene)p-n-Pentyl aniline (5O.5) and N( p-n-Pentylbenzylidene)p-n-Pentyloxy aniline (5.O5) compounds, as it is found to produce a null effect even at LC clearing temperature. However, the variety of LC phases they exhibit is found to be drastically reduced.…”

Role of Oxygen on Phase Behaviour of Benzylidene Aniline – A Comparative Study

“…However, the change in position of oxygen from aldehyde side to the aniline side N (p-n-Octyl benzylidene) p-n−Pentyloxy aniline (8.O5) causes the compound to become a room temperature liquid. But the effect is less prominent in the case of middle homology (5O.5 and 5.O5) because both are exhibiting liquid crystalline nature at above room temperature level [13]. Furthermore, in lower homologous series like 1O.5, 1.O5, 2O.5, and 2.O5, there is no pronounced effect observed on melting/clearing temperature, but quenching of liquid crystallinity is observed in case of 1.O5 and 2.O5 [14].…”

“…In both cases of lower and higher homologous series (1.5, 2.5 and 8.5), the effect is merely the same; the thermal stability of the compound went below room temperature. However, in middle homologue n = m = 5, 5.5, compound, the existence of liquid crystallinity is at and above room temperature [13]. It is well known that physical and chemical properties of the liquid crystal molecules change with the length of alkyl chains.…”