Week #6 (Due Sunday, Feb. 22)

 

 

1.     Construct the Huckel matrix for ethylene. Calculate the energies.(Assume a=0 and b=-1)

To find two values of E find determinant and set equal to zero:

Quadratic equation has solutions:

2.     For benzene how many atomic basis functions are necessary according to Huckel theory? 6 How many molecular orbitals should result? 6 (#MOs=#AOs) Construct the Huckel matrix for benzene in terms of a=0 and b.

Only nearest neighbors interact. Note: the upper right and lower left correspond to the first carbon interacting with the sixth due to the ring nature of the system.

 

 

 

 

 

 

 

 

 

 

 

3.     Complete the Spartan tutorial ‘Benzene Chromium Tricarbonyl’ in Chapter 7 of the Spartan Tutorial and Users Guide. If a hardback copy is not available you can access the guide by opening Spartan and choosing Help à On Line Help.

NOTE: Make sure in part 4. you select ‘New Molecule’ and NOT simply ‘New’ under the File menu.

 

The presence of the Cr(CO)₃ group withdraws electron density from the benzyl ring which makes it more “positive” and hence more/less susceptible to electrophilic/nucelophilic attack.

 

 

 

 

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