Question

How are chemical bonds represented in the structural formula of a hydrocarbon?

Answer 1

By dashes, `-`; mind you, sometimes the dashes are understood.

Explanation:

Typically, hydrocarbons are represented by zig-zag lines, where each zig and each zag represents a methylene unit, i.e. `CH_2`, unless that carbon is otherwise substituted. The carbon termini are often explicitly drawn as methyls for clarity, i.e. `CH_3` (as per the 1st figure, but not the 2nd).

Given this scheme, `"n-pentane"`, `C_5H_12`, would be drawn as:

Sites of unsaturation along the chain, would be represented by double bonds, and of course `"2-pentene, "C_5H_10`, has the possibility of geometric isomerism:

Could I name this `"3-pentene"`? The olefin bond is at `C3` if I number the right most carbon as `C1`.

I do realize that this seems a lot to take in, and at first acquaintance it might appear insurmountable. Persist with it, and you will rapidly gain a working knowledge. In all examples you find the longest carbon chain before naming the beast.