4-n-Octyloxybenzoic acid

Measurements have been made with methanol (CH3OH) and acetonitrile (CH3CN) in nematic liquid 4-n-octyloxybenzoic acid (II see Table I) and with acetonitrile and methyl iodide (CH3I) in nematic liquid... 

Figure 1 shows as an example the 60-Mc. per sec. (Mc.p.s.) PMR spectrum of methanol in nematic liquid 4-n-octyloxybenzoic acid. The very stong line belongs to the acidic protons and the OH protons of methanol. The solvent was partially deuterated to suppress this line somewhat. All other lines can be assigned to the protons of the 12CH3 and the 13CH3 groups. 

Figure 1. PMR spectrum (60 Mc.p.s.) of 12CH3OH and nCH3OH in 4-n-octyloxybenzoic acid at 70°C.

Figure 2. Degree of ordert Sc3, of C3 axis of CH3OH dissolved in 4-n-octyloxybenzoic acid...

For a mesophase to obtain, it is generally necessary that the terminal groups of the molecules contain permanent dipoles. For example, the N-I transition of 4-octyloxybenzoic acid is some 40° higher than that of 4-nonylbenzoic acid despite the essentially equivalent size of the two molecules. Similarly, the 4-alkoxy-4 -cyanobiphenyls form substantially more stable mesophases than 4-alkyl-4 -cyanobiphenyls. Polarity of the termini, however, frequently gives rise to very strong intermolecular attractions. In such cases, the melting points of the compound may be raised so high that the mesophase cannot survive. 

C21H20N2O4, 1,4-Bis(acylamido)butadiene, 45B, 69 C21H25NO5, 4 -Nitrophenyl 4-octyloxybenzoate, 46B, 81 C21H2si N20b, 3,3, 5,5 -Tetraiodothyroformic acid N-diethanolamine 1 2 salt, 46B, 81... 

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