Question

Note on alternant and non alternant hydrocarbons

Answer 1

Non-alternant hydrocarbons: These hydrocarbons have invariably feature at least one ring constructed with an odd number of carbon atoms.

Alternant hydrocarbon : It is any conjugated hydrocarbon system which does not possess an odd-membered ring. 

Answer 2

Answer:

One of the most important distinctions made at the Hückel level is that between alternant (e.g. 1) and non-alternant hydrocarbons (e.g. 2). Non-alternant hydrocarbons invariably feature at least one ring constructed with an odd number of carbon atoms, whereas alternant hydrocarbons have no such rings2-4.