Some interesting problems in computational chemistry

Can be solved using Gaussian visualisation software

Problem 1. Model the following reactions(Reactants, products, transition state and reaction pathway) and summarize the results • Tautomerism of Acetone • Diels-Alder reaction between ethylene and butadiene

Problem 2. Calculate and plot the relative energies for the following C11H22 isomers

Isomers

Problem 3. Perform conformational analysis for the following dihedral angles of n-hexane(see figure 1). Choose appropriate step sizes and identify various points of interest(staggered, eclipsed etc).

• Dihedral angle formed by the carbons 1,2,3,4 • Dihedral angle formed by the carbons 3,4,5,6 • 2D scan of the above two dihedral angles

Figure 1: n-hexane

nhexane

Problem 4. Calculate the vibrational spectrum of ethanol. Perform normal mode analysis and assign major peaks in the experimental spectrum(see figure 2) through comparisons.

Figure 2: IR spectrum of ethanol

irspectrum

Problem 5. Read the attached study on ”The intrinsic reaction coordinate”. Perform IRC scans for the reactions described in the paper and draw comparisions.

Problem 6. Formic acid (H-COOH) exists as a dimer in gas phase. (a) Obtain the structure for the dimer and (b) Provide an energetic basis for why it is found as dimers and not as monomers.

Problem 6. Model the Diels-Alder reaction (including the transition state) between cyclopent-1,3-ene and ethene with HF method with STO-3G basis set and provide all important information.