Question

How can I convert 2-methylhexane `C2-C3` bond from Newman projection to bond line notation?

Answer 1

Start with the two most stable staggered Newman projection conformers for 2-methylhexane viewed along the `C_2 - C_3` bond.

In order to determine the bond line notation for 2-methylhexane you can pick either of the two projections shown above. I'll show you the one on the left.

The first thing to do is determine the groups attached to the two carbonds that form the `C_2 - C_3` bond. Let `C_2` be the front carbon, represented in the diagram by the intersection of the three in the center of the circle.

The front carbon will have a methyl group attached in the plane of the paper, another methyl group attached to the right of the circle - this methyl group will be coming out of the plan of the paper - and a hydrogen atom attached to the left of the circle - this atom will be going into the plane of the paper.

Now for the back carbon, `C_3`. The back carbon is represented by the circle. Notice it has a propyl group attached in the plane of the paper, a hydrogen atom attached to the right of the circle, and another hydrogen atom attached to the left of the circle.

Now that you've determined what groups are present, you must draw the hexane parent chain. I've labeled the `C_2` and `C_3` carbons to make the conversion easier

Notice that the two groups that are drawn in the plane of the page are already there - the methyl group attached to `C_2` and the propyl group - `CH_2CH_2CH_3` - attached to `C_3`.

Now it's time to place the groups that were not in the plane of the page. The trick here is to know that hydrogen atoms attached to carbon atoms are not shown in bond line notation.

This means that the final bond line notation representation for 2-methylhexane will differ from the that of hexane by just one methyl group - `CH_3` placed on `C_2`