Question

b) Benzene and ar Please fint mPle in the Picte: ter ange) fxoni low Estimating the delocalization energy within the Hückel appr tonian matrix Example 10E.2 Use the Hickel approxination to find the energies of the π s of cyclobutadiene, and estimate the delocalization αβ000 energy Method Set for butadiene, but note that atoms A and D are also now neigh bours Then solve for the roots of the secular equation and assess the total π-bond energy. For the delocalization energy, subtract from the total π-bond energy the energy of two π-bonds. Answer The hamiltonian matrix is up the secular determinant using the same basis as 0βαβο 00βαβ 000βα 0 100 βαβο H-10 βαβ βοβα 0 01 0 0 0 0 1 10 0 0 2 0 0 0 1010 The MO energies, th Disgonalize 00 0 0 1010 000 -2 Digonalization gives the energesofth orbital as Four electrons must be accommodated. Two occupy the lowest orbital (ofenergy α+24), and two occupy the doubly degener. ate orbitals (of en ergy α). The total energy is therefore 40+4. Two isolated π bonds would have an energy 4α+4, therefore, in this case, the delocalization energy is zero.

Answer 1