Question

How many different staggered conformations are there for 2-methylpropane? How many different eclipsed conformations are there?

Short answer

Answer: There is 1 staggered conformation and 2 eclipsed conformations for 2-methylpropane.

Step-by-step solution

Understand the structure of 2-methylpropane

2-methylpropane, also known as isobutane, is a branched alkane with the molecular formula C4H10. Its structure consists of a chain of three carbon atoms with a methyl group (CH3) attached to the middle carbon atom. To visualize the structure, imagine a carbon chain of three atoms, labeled C1, C2, and C3, and a methyl group connected to C2 as below: C1 - C2 - C3 | CH3 Here, C1 and C3 are the end-carbon atoms, and C2 is the central carbon atom connected to the methyl group (CH3).

Identify the carbon-carbon bond that can rotate

In 2-methylpropane, the carbon-carbon bond that can rotate is the one between C2 and C3. This is because, by rotating around this bond, we can create different conformations by changing the position of the methyl group (CH3) in relation to the end-carbon atom C1.

Determine the possible staggered conformations

A staggered conformation occurs when the bulky groups (in this case, the methyl group and the end-carbon atom C1) are as far apart from each other as possible. In the case of 2-methylpropane, there is only 1 staggered conformation, as follows: - C1 and the methyl group are on opposite sides of the C2-C3 bond. This arrangement maximizes the distance between the bulky groups, reducing steric hindrance (or the repulsion of electron clouds). Below is a Newman projection of the staggered conformation of 2-methylpropane, where C2 (front) is connected to C3 (back), and the bulky groups are far apart. C1 | H -- C2 -- C3 -- H | CH3

Determine the possible eclipsed conformations

An eclipsed conformation occurs when the bulky groups (the methyl group and the end-carbon atom C1) are as close to each other as possible. In the case of 2-methylpropane, there are 2 eclipsed conformations, as follows: 1. C1 and the methyl group are next to each other on the same side of the C2-C3 bond. In this arrangement, the bulky groups are closer together, increasing steric hindrance. Below is a Newman projection of the first eclipsed conformation of 2-methylpropane: C1 | H -- C2 -- C3 -- H | H | CH3 2. C1 and the methyl group are next to each other on different sides of the C2-C3 bond. Similar to the first eclipsed conformation, the bulky groups are close together, increasing steric hindrance. Below is a Newman projection of the second eclipsed conformation of 2-methylpropane: CH3 | H -- C2 -- C3 -- H | H | C1 To summarize, there is 1 staggered conformation and 2 eclipsed conformations for 2-methylpropane.