Question

Consider 1-bromo-2-methylpropane and draw the following. (a) The staggered conformation(s) of lowest energy (b) The staggered conformation(s) of highest energy

Short answer

Answer: The lowest energy staggered conformation of 1-bromo-2-methylpropane is the anti-periplanar arrangement, where Br and CH3 are 180 degrees apart in the Newman projection. The highest energy staggered conformations of 1-bromo-2-methylpropane are the gauche arrangements, where Br and CH3 are either 60 degrees or 300 degrees apart in the Newman projection.

Step-by-step solution

Understand the molecule: 1-bromo-2-methylpropane

1-bromo-2-methylpropane is an organic molecule containing a bromine atom attached to the first carbon atom and a methyl group attached to the second carbon atom. To better visualize this molecule, we can represent it as follows: Br-CH2-CH(CH3)-CH3.

Understanding staggered conformations

Staggered conformations are the conformations in which the hydrogens and substituents (in this case, the methyl and bromine) on adjacent carbon atoms are as far apart as possible, minimizing steric hindrance and strain (Newman projections will be useful here).

Draw the staggered conformations

In order to draw the staggered conformations, we will start by drawing Newman projections along the C2-C3 bond (where C1 is bromine-substituted and C2 is methyl-substituted). For each conformation, we will maintain the three hydrogen atoms on C1 and the two hydrogen atoms on C2. Then, we will rotate the C2 methyl group and bromine atom by 60 degrees in both directions, giving us a total of three conformations.

Identify lowest energy staggered conformation

The lowest energy staggered conformation is the one with the least steric hindrance. This occurs when the bulky bromine and methyl groups are as far apart as possible, or in an anti-periplanar arrangement. In the Newman projection, Br and CH3 will be opposite each other (180 degrees apart).

Identify highest energy staggered conformation

The highest energy staggered conformation is the one with the most steric hindrance. This occurs when the bulky bromine and methyl groups are as close together as possible while still being staggered, or in a gauche arrangement. In the Newman projection, Br and CH3 will be 60 degrees or 300 degrees apart.

Draw the staggered conformation of lowest energy (answer to part a)

The lowest energy staggered conformation of 1-bromo-2-methylpropane is the anti-periplanar arrangement, where Br and CH3 are 180 degrees apart in the Newman projection. Here is the Newman projection representation of the lowest energy staggered conformation: ``` H Br H \ | / C2--C3 / | \ H H CH3 ```

Draw the staggered conformation of highest energy (answer to part b)

The highest energy staggered conformation of 1-bromo-2-methylpropane is the gauche arrangement, where Br and CH3 are 60 degrees or 300 degrees apart in the Newman projection. Here is the Newman projection representation of the highest energy staggered conformation: ``` H Br H \ | / C2--C3 / | \ H CH3 H ``` And the other highest energy staggered conformation with Br and CH3 300 degrees apart: ``` CH3 H H \ | / C2--C3 / | \ H H Br ```