Discuss the various bonding and antibonding orbital of butadiene. Place them in order of increasing energy. What is the electronic configuration of butadiene in both the ground and the excited state.

First, we need to draw the structure of butadiene. The molecular formula of butadiene is C4H6, and its structural formula is CH2=CH-CH=CH2. The double bonds between carbon atoms create a conjugated π system, which is essential for understanding its molecular orbitals and electronic configurations.

In butadiene, we will focus on the π-system. We have four available p orbitals (one p orbital from each carbon atom) to create the molecular orbitals. The number of molecular orbitals generated will be equal to the number of atomic orbitals combined (in this case, 4). Since butadiene is a linear molecule, we focus on the symmetry of the p orbitals. We can construct four molecular orbitals (MOs) based on their symmetries: 1. The lowest energy (bonding) MO, called π1, results from the constructive interaction of all four p orbitals. 2. The second-lowest energy MO, called π2, results from the constructive interaction of two adjacent p orbitals and destructive interaction of the other two. 3. The next MO, called π3*, is an antibonding MO resulting from the constructive interaction between two carbon atoms and destructive interaction with the other two. 4. The highest energy (antibonding) MO, called π4*, results from the destructive interaction of all four p orbitals. Therefore, the energy order of molecular orbitals from lowest to highest is: π1 < π2 < π3* < π4*.

Now that we have the molecular orbitals, we should distribute the π-electrons among these orbitals. Butadiene has four π-electrons, one from each double bond between carbon atoms. According to the Aufbau principle, electrons occupy the lower energy orbitals first. Two electrons will occupy π1 and the other two electrons will occupy π2. So, the ground state electronic configuration of butadiene is: π1^2π2^2π3*^0π4*^0

For the excited state electronic configuration, we assume that one electron is promoted from the highest occupied molecular orbital (HOMO) to the lowest unoccupied molecular orbital (LUMO). In this case, one electron from π2 will move to π3*. Thus, the electronic configuration of butadiene in the excited state will be: π1^2π2^1π3*^1π4*^0 In conclusion, we have analyzed the bonding and antibonding molecular orbitals of butadiene, determined their energy order, and found the electronic configurations for both the ground and excited states.