Draw the most stable conformation of 2-methylhexane as a Newman projection down the C2-C3 bond.

Draw the most stable conformation of 2-methylhexane as a Newman projection down the C2-C3 bond.

The Correct Answer and Explanation is:

To draw the most stable conformation of 2-methylhexane as a Newman projection down the C2-C3 bond, we first need to understand the structure and the possible conformations of the molecule.

Step 1: Drawing the Molecular Structure

2-methylhexane is a chain of six carbon atoms, with a methyl group (-CH3) attached to the second carbon (C2). The carbon-carbon backbone can be numbered from left to right as follows:

• C1: The first carbon in the chain
• C2: The second carbon in the chain (the point of substitution)
• C3: The third carbon in the chain (the other carbon involved in the bond we’re focusing on)
• C4: The fourth carbon in the chain
• C5: The fifth carbon in the chain
• C6: The sixth carbon in the chain

The molecule can be visualized as:

    CH3-CH2-CH(CH3)-CH2-CH2-CH3

Step 2: Understanding the Newman Projection

The Newman projection represents the molecule as viewed down a specific bond—in this case, the C2-C3 bond. This bond is a central point of focus, with the atoms on either side of the bond being depicted in a circular format.

• The front carbon (C2) is represented as a dot.
• The back carbon (C3) is represented as a circle.

We need to consider the different groups attached to these carbons:

• C2 has a hydrogen (H), a methyl group (-CH3), and an ethyl group (-CH2CH3) attached to it.
• C3 has two hydrogens (H) and an ethyl group (-CH2CH3) attached to it.

Step 3: Identifying the Most Stable Conformation

In a Newman projection, the most stable conformation occurs when the substituents on the front and back carbons are as far apart as possible (minimizing steric hindrance). This is typically a staggered conformation, where the groups are positioned in a way that minimizes repulsion.

• The staggered conformation minimizes the 1,3-diaxial interactions and steric hindrance between the substituents.
• The eclipsed conformation has all the substituents aligned, which leads to higher energy due to steric strain.

Step 4: Drawing the Staggered Conformation

In the staggered conformation of 2-methylhexane down the C2-C3 bond:

1. C2 has three substituents:
   • A hydrogen (on a vertical line).
   • A methyl group (-CH3) (on a line at a 120-degree angle).
   • An ethyl group (-CH2CH3) (on a line at a 240-degree angle).
2. C3 has two substituents:
   • Two hydrogens (one on each of the horizontal lines).
   • An ethyl group (-CH2CH3) (on a line at a 120-degree angle).

In the most stable conformation (the staggered conformation), the substituents are arranged so that the ethyl groups (-CH2CH3) on C2 and C3 are as far apart as possible, avoiding steric strain. The methyl group on C2 is placed in a position where it does not clash with the substituents on C3.

Final Newman Projection

cssCopyEdit          H         H
           \       /
            C2----C3
           /       \
      CH3-CH2       CH2-CH3

This is the most stable conformation of 2-methylhexane down the C2-C3 bond, where the groups are staggered and there is minimal steric repulsion.