Estimate the Ionization Potential of benzene

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Reference no: EM132263433

Molecular Orbital Assignment -

This assignment consists of a series of questions based on the material covered in lectures and recommended reading. All answers should show full working, noting any assumptions made. Explain the meaning of symbols used. Where computer generated output is included, your name should appear on the print-out.

Question 1: The 1s and 2p_z hydrogenic wave-functions are of the form:

Ψ_1s = (1/√π)Z^3/2e^-|Z_r|

Ψ_2pz = 1/(4√(2π)) Z^5/2re^-|Z_r/2|cosθ

where the distance r is in atomic units, Z is the nuclear charge. |x| is the modulus (or positive form) of some unknown x.

a) Plot the value of both LCAO-MO's for H₂ along the internuclear axis. Assume that the internuclear distance is 2.5 a.u. Use a spreadsheet and calculate the value of the wave-function in uniform steps of 0.1 a.u. Mark the position of the two nuclei on your graph.

b) Plot the value of the LCAO-MO's arising from the overlap of the H 1s and F 2pz atomic orbitals along the hydrogen fluoride (HF) internuclear axis. Use a spreadsheet and calculate the value of the wave-function in uniform steps of 0.1 a.u. Mark the position of the two nuclei on your graph. Assume that the internuclear distance is 2 a.u. and that the atomic orbital coefficients are those given below:

ψ₊ = 0.19ψ_H + 0.98ψ_F

ψ_- = 0.19ψ_H - 0.98ψ_F

c) Compare the graphs obtained in parts (a) and (b). Comment on where the electron density resides in each molecule.

Question 2: a) The structure of benzene (C₆H₆), optimized using the HF/STO-3G level of theory and basis set in Gaussian09, is given in the standard orientation in Table 1 (in attached file). The optimized MO's from this calculation are listed as atomic orbital coefficients in Table 2. Use these data to identify all MO's with π-symmetry. For each π-MO provide (i) a sketch showing all the localized AO's in the wave-function and (ii) a sketch of the MO. Label your sketches with the MO number and identify and label the HOMO and the LUMO. Be sure to sketch both occupied and unoccupied π MO's and indicate any changes in phase in your sketches. Example sketches for formaldehyde are shown below.

b) Use the data in Table 2 (in attached file) to estimate the Ionization Potential of benzene in units of electron volts. Explain how you derived your answer.

Attachment:- Assignment Files.rar

Reference no: EM132263433

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