73743-13-2Relevant academic research and scientific papers
The Experimental Determination of the Conformational Free Energy, Enthalpy, and Enthropy Differences for Alkyl Groups in Alkylcyclohexanes by Low Temperature Carbon-13 Magnetic Resonance Spectroscopy
Booth, Harold,Everett, Jeremy R.
, p. 255 - 259 (2007/10/02)
13C N.m.r. studies at low temperatures of solutions in CFCl3-CDCl3 of methylcyclohexane, -isopropylcyclohexane, cis-1-ethyl-4-methylcyclohexane, cis-1-isoprpyl-4-methylcyclohexane, and cis-1-ethyl-4-isopropylcyclohexane have yielded conformational enthalpy differences and conformational enthropy differences for methyl, ethyl, and isopropyl groups in alkylcyclohexanes.For -ΔH0, the averaged values obtained, in kcal mol-1, were 1.75 (Me), 1.60 Et), and 1.52 (Pri); for ΔS0, the averaged values, in cal mol -1 K-1, were -0.03 (Me), 0.64 (Et), and 2.31 (Pri).The determined values are in good agreement with those calculated by the Allinger group for the gas phase, using a method based on classical mechanics.As a result of the opposing trends for -ΔH0 and ΔS0 values, the sequence of -ΔG0 values at 300 K, namely PriEtMe, is reversed at temperatures below ca. 40 K.
