2. Formaldehyde and hydroxymethylene are isomers. Calculate the isomerization energy (formaldehyde → hydroxymethylene) at several levels of theory (HF, MP2, MP4, and CCSD(T)). How do your calculated values compare with the experimental value of 54.9kcal/mol? The most accurate theory was the CCSD(T) it had an error of 3.62%. This theory is known as being the “ Gold Standard ” and it was the most accurate. The MP2 was the least accurate with an error of 11.37%. Theroy WebMo (kcal/mol) Expiremental (kcal/mol) % Error HF 51.81 54.9 5.62 MP2 61.14 54.9 11.37 MP4 58.54 54.9 6.63 CCSD(T) 56.89 54.9 3.62
3. Calculate the proton affinity energy for PH3(PH3 + H + → PH4 + ) using HF, B3LYP, and G2. Compare your results with the experimental value of 187.1 kcal/mol. Use webmo for this, which has G2 built into it. G2 had the highest error of 199.481% but it was the closest in value (186.13 compared to 187.1) to the experimental value. The HF method had the lowest error of 171.324% but the value was the furthest away (133.45 compared to 187.1) Theory Proton Affinity (kcal/mol) Expiremental (kcal/mol) % Error HF -133.45 187.1 171.324 B3LYP -141.02 187.1 175.373 G2 -186.13 187.1 199.481
4. Answer the following questions. a. Why is knowing the charge on atoms useful? Calculating atomic charges is useful to determine the type of bonding, charge transfer reactions and dipole moments. Those all can provide information on the properties and behavior of the molecule.
- Summer '20
- Computational chemistry