10. Suggest a PM3 level QM calculation (as implemented in Argus Lab) to estimate

Question

10. Suggest a PM3 level QM calculation (as implemented in Argus Lab) to estimate the vacuum phase change in enthalpy (H) for the synthesis of di-alanine from alanine,

Be sure to briefly explain and justify all of your calculation steps.

a. Predicted heat of formation for alanine (Hf (ala)) = ____________ kcal/mol

b. Predicted heat of formation for di-alanine (Hf (di-ala)) = ____________ kcal/mol

c. Predicted heat of formation for water (Hf (water)) = ____________ kcal/mol

d. Predicted change in enthalpy (H) for the synthesis of di-alanine from alanine ________ kcal/mol

Explanation / Answer

Outline to approach the problem:

Predicted heat of formation for alanine (Hf (ala)) = -560 KJ/mol = -560*0.239 Kcal/mol = -133.84 Kcal/mol

Predicted heat of formation for di-alanine (Hf (di-ala)) = -467.86 KJ/mol = -111.82 Kcal/mol

Predicted heat of formation for water (Hf (water)) = -285.83 KJ/mol = -68.32 Kcal/mol

Predicted change in enthalpy (H) for the synthesis of di-alanine from alanine = {Hf (di - ala) + Hf (water)} - 2*Hf (ala) = -111.82 + (-68.32) - 2*(-133.84) = 87.54 Kcal/mol

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