How can I convert Newman projection for the staggered and eclipsed conformations of 2-methylpentane for rotation about the ##C2-C3## bond to bond line notation?

Here are the six Newman projections for the staggered and eclipsed conformations of 2-methylpentane.

I doesn't matter which one we choose, so let's start with Structure A.

Note that there is a carbon atom at the centre of the "Y" in the middle of the circle, and there is also a "hidden" carbon behind the circle.

We hunt for the longest continuous chain of carbon atoms.

It goes from one of the methyl groups in the front, to C-2 in the middle of the Y, to the hidden C-3, and then to the two carbons of the ethyl group.

That makes a 5-carbon chain.

Now we look for substituents.

One of the methyl groups is part of the main chain, but the other methyl group is a substituent on C-2.

There are no other substituents.

So we have 2-methylpentane.

The bond-line structure consists of a zig-zag line of five carbon atoms with a methyl group attached to C-2.