The linear conjugated polyenes and dienes can be represented by the Free Electron molecular orbital (FEMO). In this p electrons form the pi-bond. Examples of conjugated molecule are: 1, 3- butadiene and 1, 3, hexatriene. The structures of these molecules are given below:
Structure of 1, 3- butadiene: CH 2 = CH ― CH = CH 2
Structure of 1, 3, hexatriene: CH 2 = CH ― CH = CH― CH 2 = CH 2
These move freely in a constant potential along the molecular structure. It is analogous to the motion of a particle moving in a one dimensional box. The box has infinite height. The energy level for this is given as:
En = n 2 h 2 / 8 m e a 2
Where n = 1, 2, 1 …
Here, a represents the length of the linear conjugated chain
me is the mass of the electron.
