To investigate how QI in σ-systems might differ from that in π-systems, we study a model for butane as shown in the Figure (a) as an example. The transport properties of a σ-system can be calculated using the ladder C model. While this model is parameterised for a permethylated silane chain, we use the parameters to represent a generic saturated system that we will refer to butane for simplicity. With this model, the Hamiltonian for butane is written as,