lab reports
CHM 3411 – Problem Set 6
Due date: Wednesday, March 23rd.
Do all of the following problems. Show your work.
1) Consider the cyclic molecule C8H8, the eight carbon analogue to benzene. a) Write the secular detrerminant corresponding to the pi-bonding in C8H8. b) Using the secular determinant, the following energies are found for the pi-bonding molecular orbitals:
1 = + 2
2 = + 1.41 (two states)
3 = (two states)
4 = - 1.41 (two states)
5 = - 2
Give the electron configuration for the pi-bonding for the ground state of C8H8. c) What is value for S (total spin quantum number) for the ground state of C8H8. d) What is E, the pi-bonding energy, for the ground state of C8H8. e) Ed, the dlocalization energy, is defined as
Ed = E - N ( + )
where E is the pi-bonding energy, N is the number of pi-electrons, and ( + ) is the energy expected if the pi-bonding consisted entirely of two centered pi bonds (like the pi bond in ethene, C2H4). Ed is thus a measure of the additional lower in energy due to multicentered pi-bonding. What is Ed for the ground state of C8H8?
2) For each of the following molecules list all of the elements of symmetry. a) CH3Cl (chloromethane) b) NH3 (ammonia) c) C6H4F2 (1,3-difluorobenzene)
3) The absorbance of a 0.0816 M solution of a molecule is measured using a 1.000 cm pathlength cuvette. Two peaks are observed in the spectrum, one at = 317 nm (A = 0.1286), the other at = 284 nm (A = 0.7215). Assuming Beer’s law holds
A = ac (3.1)
what are the values for %T (percent transmission) and a (absorption coefficient, in units of L/mol.cm) for the molecule at the above two wavelengths?
Also do the following from Atkins.
Exercise 9.16b Estimate the lifetime of a state that gives rise to a line of width a) 200. MHz, b) 2.45 cm-1. (Note that lifetime broadening is discussed in Section 9.6 of Atkins, pp 350-352. The key equation is E = /, where E is
Due date: Wednesday, March 23rd.
Do all of the following problems. Show your work.
1) Consider the cyclic molecule C8H8, the eight carbon analogue to benzene. a) Write the secular detrerminant corresponding to the pi-bonding in C8H8. b) Using the secular determinant, the following energies are found for the pi-bonding molecular orbitals:
1 = + 2
2 = + 1.41 (two states)
3 = (two states)
4 = - 1.41 (two states)
5 = - 2
Give the electron configuration for the pi-bonding for the ground state of C8H8. c) What is value for S (total spin quantum number) for the ground state of C8H8. d) What is E, the pi-bonding energy, for the ground state of C8H8. e) Ed, the dlocalization energy, is defined as
Ed = E - N ( + )
where E is the pi-bonding energy, N is the number of pi-electrons, and ( + ) is the energy expected if the pi-bonding consisted entirely of two centered pi bonds (like the pi bond in ethene, C2H4). Ed is thus a measure of the additional lower in energy due to multicentered pi-bonding. What is Ed for the ground state of C8H8?
2) For each of the following molecules list all of the elements of symmetry. a) CH3Cl (chloromethane) b) NH3 (ammonia) c) C6H4F2 (1,3-difluorobenzene)
3) The absorbance of a 0.0816 M solution of a molecule is measured using a 1.000 cm pathlength cuvette. Two peaks are observed in the spectrum, one at = 317 nm (A = 0.1286), the other at = 284 nm (A = 0.7215). Assuming Beer’s law holds
A = ac (3.1)
what are the values for %T (percent transmission) and a (absorption coefficient, in units of L/mol.cm) for the molecule at the above two wavelengths?
Also do the following from Atkins.
Exercise 9.16b Estimate the lifetime of a state that gives rise to a line of width a) 200. MHz, b) 2.45 cm-1. (Note that lifetime broadening is discussed in Section 9.6 of Atkins, pp 350-352. The key equation is E = /, where E is