Butylcyclohexane

A tert butyl group is so large that tert butylcyclohexane exists almost entirely in the conformation m which the tert butyl group is equatorial The amount of axial tert butylcyclohexane present is too small to measure... 

The reactions of the cis and irons isomers of 4-/-butylcyclohexyltrimethylammonium chloride with potassium t-butoxide in r-butanol have been compared. The cis isomer gives 90% 4-r-butylcyclohexane and 10% AyV-dimethyl-4-r-butylcyclohexylamine, while the irons isomer gives only the latter product in quantitative yield. Explain the different behavior of the two isomers. 

The rates of removal of axial and equatorial protons from 4-t-butylcyclohexane in NaOD/dioxan have been measured by an NMR technique. The rate of removal of an axial proton is 5.5 times faster than for an equatorial proton. What explanation can you offer for this difference ... 

Compare energies for equatorial and axial chair conformers for methylcyclohexane, R = Me, and tert-butylcyclohexane, R = CMe3. Which is more stable in each molecule Use equation (1) to calculate the ratio of major to minor conformers for each system at 298 K. Which molecule shows a larger preference Why (Hint Compare nonbonded interactions and/or geometrical distortions in the higher-energy conformers that are absent in the lower-energy conformers.)... 

Which is more stable, the equatorial or axial chair conformer of i-propylcyclohexane, R=CHMe2 Calculate the ratio of major to minor conformers at 298 K. Is it more like that found for tert-butylcyclohexane or for methylcyclohexane Why ... 

Problem 11.19 Which isomer would you expect to undergo E2 elimination faster, f/uus-l-bromo-4-fr7t-butyJcyclohexane or ds-l-bromo-4-tert-butylcyclohexane Draw each mole-, cule in its more stable chair conformation, and explain your answer. 

Coleman, Kobylecki, and Utley studied the electrochemical reduction of the conformationally fixed ketones 4-tert-butylcyclohexanone and 3,3,5-tri-methylcyclohexanone 82>. Stereochemically, the cleanest reductions took place at a platinum cathode in a mixture of hexamethylphosphoramide and ethanol containing lithium chloride. Under these conditions the equatorial alcohol predominated heavily (95% from 4-fer/-butylcyclohexane and 91% from 3,3,5-trimethylcyclohexanone).In acidic media roughly equal quantities of axial and equatorial alcohol were produced. It was suggested that organo-lead intermediates are involved in the reductions in aqueous media. This is reasonable, based upon the probable mechanism of reduction in acid 83F Reductions in acid at mercury cathodes in fact do result in the formation of... 

The conformation of tert-butylcyclohexane with tert-butyl group equatorial is more than 21 kJ mol-1 more stable than the axial form. 

At room temperature, 99.99% of the molecules of /ert-butylcyclohexane have the tert-butyl group in the equatorial position due to the large energy difference between the two conformations. 

Kessler and co-workers (136) reported that the barrier to rotation in cis-di-ferf-butylcyclohexane (92) was 16.3 kcal/mol at 298 K. This relatively low... 

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