4. Alkanes and Cycloalkanes

Choose the conformation in each pair that is most stable. If both are equally stable, then write 'no difference.'

(a)

In Chapter 5, we introduce reaction coordinate diagrams as a plot of potential energy versus the progress of a reaction. Consider the reaction coordinate diagram drawn for the 'reaction' of conformation A becoming conformation B. Which structure is present at the top of the hill?

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Given the following Newman projection of ethane looking down the $C–C$ bond, which of the following wedge and dash structures correctly represents the same conformation?

Which of the following diagrams correctly represents a Newman projection for propane when viewed along the $C_1–C_2$ bond?

Given the following Newman projection of ethane viewed down the $C_1-C_2$ bond, which bond-line structure does it represent? (Front carbon: three hydrogens; back carbon: three hydrogens; all staggered)

Which of the following correctly represents the staggered conformation of ethane in a Newman projection when viewed down the $C–C$ bond?

Which of the following best describes the most stable Newman projection for 2,3-dimethylbutane when viewed down the C$2$-C$3$ bond?

Which of the following best describes the most stable Newman projection for $2_{\text{-methylbutane}}$ when viewed down the $C_2–C_3$ bond?

Draw a graph, similar to Figure 3-9, of the torsional strain of 2-methylpropane as it rotates about the bond between C1 and C2. Show the dihedral angle and draw a Newman projection for each staggered and eclipsed conformation.

Which of the following diagrams represents a Newman projection of butane?

Which of the following best describes a Newman projection in which the front and back substituents are positioned directly in line with each other when viewed along the carbon-carbon bond axis?

Given the following Newman projection looking down the $C_2–C_3$ bond of a straight-chain alkane, where the front carbon ($C_2$) has a methyl group, an ethyl group, and a hydrogen, and the back carbon ($C_3$) has a methyl group, a hydrogen, and an ethyl group, what is the correct IUPAC name of the compound?

Calculate the dihedral angle (θ) for the conformations shown.

(a)

Calculate the dihedral angle (θ) for the conformations shown.

(c)