5016

Draw a Newman projection for the most stable conformation of propane, as viewed down the carbon-carbon bond, and draw a potential energy diagram illustrating how that energy changes qualitatively as a function of the torsional angle between a hydrogen atom and the methyl group. Use an approximate numerical scale on the energy axis.

5017

(a) Draw the chair conformations of trans-1,2-dimethylcyclohexane and

cis-1,4-dimethylcyclohexane and identify the more stable conformer in each case.

(b) One of the two chair conformations of i–propylcyclohexane is more stable than the other by 3.0 Kcal. m^–1. Would you be able to detect the minor conformer by a spectroscopic method that permitted you to observe a lower limit of 0.1% concentration? (Write a chemical equation, show your reasoning and assume room temperature for the estimation.)

5036

Many substituted cyclobutane and cyclopentane derivatives exist preferentially in the puckered "envelope" conformation. How can this fact be used to rationalize the observation that the cis-isomer of methyl 3-methylcyclobutane carboxylate is more stable than the trans-isomer. Use structures in your expanation.

5100

Given that ∆G (25°) = -0.15 Kcal. mole^–1 for the process

what percent of each conformer will be present at equilibrium at room temperature? Could the minor conformer be detected by ¹H NMR using a routine spectrometer?

5172

Using drawings of chair conformations, show which of the two compounds shown below will exhibit intramolecular hydrogen bonding. Explain your answer. Indicate and explain which molecule is more stable thermodynamically.

5225

Draw the sawhorse (wedge-dash) and Newman projections of one of the conformational energy minima of bromoethane. Draw the same conformation for each representation.

5227

Draw a perspective representation of the most stable conformation of:

(a) trans-1,4-dimethylcyclohexane

(b) cis-1,3-diethylcyclobutane

5285

Draw a potential energy diagram for the conformations which result from 360° rotation about one of the carbon-carbon bonds of propane. Use Newman projection formulas to illustrate the conformation of each maximum or minimum.

5291

Draw sawhorse (wedge and dash) representations for butane in each of the following conformations :

(a) anti-staggered

(b) gauche-staggered