HYDROGENATION OF p-(trans-4-ALKYLCYCLOHEXYL) BENZOIC ACIDS IN ALKALINE CONDITIONS.
In a previous work it was shown that reduction of alkylbenzoic acids by sodium in amyl alcohol gives a higher percentage content of the trans isomer than other methods because of subsequent isomerization of the resultant mixture of cis and trans isomers of alkylcyclohexanecarboxylic acids under the influene of soidum alcoholate. In this work this method was used for reduction of p-(trans-4-alkylcyclohexyl)benzoic acids (II), the liquid-crystal properties of which are conclusive evidence of trans-1,4-diequatorial substitution of the cyclohexane group. Experimental evidence shows that reduction of p-(4-trans-butyclohexyl) benzoic acid (II) with Na/C//5H//1//1OH leads to formation of 4-trans-(4-trans-butylcyclohexyl) cyclohexaneacarboxylic left bracket (I)-trans right bracket and 4-cis-(4-trans-butylcyclohexyl) cyclohexanecarboxylic left bracket (I)-cis right bracket acids; in the course of reduction with NaOC//5H//1//1 the latter of these acids undergoes isomerization to (I)-trans to give an equilibrium mixture consisting of 92% (I)-trans and 8% (I)-cis.
Compounds of the formula (I) STR1 wherein X is --R, --OR or --O--CO--R and R is alkyl of 1-12 C-atoms, are useful as liquid crystals or as solvents for measuring n.m.r., u.v. or visible spectra in anisotropic media.
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(2008/06/13)
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