Draw a Newman projection for the molecule below from the perspective indicated. Which of the groups (letters A-H) are methyl groups? CH3 H H H A H B ☑ >> H. ABCDEFG I H -H CH3 G D CH F E Numeric 4 points How many gauche interactions exist in the conformation shown in the previous problem? 1

Consider the molecule 1-bromo-2-methylbutane. C3 and C4 should be drawn as Et as in theexample. This group is called an ethyl group and can be considered a sphere about twice the sizeof a methyl group. Draw the following Newman projections sighting down the C1C2 bond... a. The lowest potential energy conformation. b. The highest potential energy staggered conformation.

Using your model of butane (CH3CH2CH2CH3) , complete the following graph of the anglebetween the two Me groups vs. potential energy. a. Label each Newman projection of butane on the graph with the words staggered, eclipsed, gauche, and anti, as appropriate. (Note that some structures will have more than one label.) b. Draw a wedge and dash bond representation of butane in its lowest P.E. conformation.

In the next chapter we'll look at cycloalkanes—saturated cyclic hydrocarbons—and we’ll see that the molecules generally adopt puckered, nonplanar conformations. Cyclohexane, for instance, has a puckered shape like a lounge chair rather than a flat shape. Why?