(2 marks) Each of the calculations above yields a different value for the potential energy of the molecule. Considering the sequence in which C...
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3. (2 marks) Each of the calculations above yields a different value for the
potential energy of the molecule. Considering the sequence in which
C
Excited State
each of the jobs is performed, fill in the boxes on the Jablonski diagram
(SI)
at right with the letters A-D to identify which of the calculations from
B
Question 2 corresponds to each energy level.
4. (1 mark) See the Prelab 2 Video Tutorial on Connect. Given your
answers to Questions 2 and 3, does the job performed in the video
A
Ground State
(So)
request a calculation of benzene's wavelength of maximum absorbance
D
or its wavelength of maximum fluorescence?
(2 marks) Repeat the calculation demonstrated in the Prelab 2 Video Tutorial with each of the three HF-optimized
molecules from Prelab 1. Then fill in the table below. The first line of the table below has been completed for you-
perform the job yourself and confirm that your results are within 1% of the suggested absorbance wavelength before
continuing with the remainder of the calculations.
Molecule
Theory
Basis set
Job number
Absorbance
Calculation time
Wavelength (nm)
Benzene
HF
6-31G(d)
94803
201.27
25.6
Naphthalene
HF
6-31G(d)
184242
243. 12
30.1
Anthracene
HF
6-31G(d)
184245
299. 84
69.2
6.
(2 marks) Repeat the calculation demonstrated in the Prelab 2 Video Tutorial with each of the three B3LYP-optimized
molecules from Prelab ] and fill in the following table. For these calculations, edit the route copied in the Preview pane
to identify B3LYP as the level of theory rather than HF.
Molecule
Theory
Basis set
Job number
Absorbance
Calculation time
B3LYP
Wavelength (nm)
Benzene
6-31G(d)
1 8 4252
223.68
39. 6
Naphthalene
B3LYP
6-31G(d)
129.3
Anthracene
B3LYP
6-31G(d)
184253
27 7 . 94
184254
378. 49
226.9
7. (2 marks) How does the wavelength of maximum absorbance change as the number of aromatic rings increases? Is this
expected? Explain.
8.
(2 marks) In Question 4, you used HF and B3LYP to predict the wavelength of maximum absorbance of a single benzene
molecule in a vacuum. To test these predictions, the absorbance spectrum of benzene will be measured in the gas phase.
Write out a stepwise procedure for testing the accuracy of these predictions in the CHEM 211 laboratory. In addition to the
typical equipment available in your basket, you have access to a stoppered cuvette, benzene, and a scanning
spectrophotometer. (Hint: benzene is a volatile liquid)

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