Molecular orbital calculations based on semi-empirical, ab initio, and DFT methods describe the spectroscopic properties of conjugated molecules a bit better than simple Hckel theory. (a) Using molecular modelling software2 and the computational method of your choice (semi-empirical, ab initio, or density functioncal methods), calculate the energy separation between the HOMO and LUMO of ethene, butadiene, hexatriene, and octatetraene. (b) Plot the HOMOLUMO energy separations against the experimental frequencies for * ultraviolet absorptions for these molecules ( 11.15). Use mathematical software to find the polynomial equation that best fits the data. (c) Use your polynomial fit from part (b) to estimate the frequency of the * ultraviolet absorption of decapentaene from the calculated HOMOLUMO energy separation. (d) Discuss why the calibration procedure of part (b) is necessary.

Chemistry Skills and Reasoning 1 Week 10 Chapter 13: Gases - Gases uniformly ﬁll the container, mixes completely with any other gas, and exerts pressure on its surroundings - Barometer is a device used to measure atmospheric pressure - Boyle”s Law: pressure and volume are inversely related - P1V1 = P2V2 - Charles’ Law: volume and temperature are directly...