Table 1. Calculated relative energies (DE, kcal/mol) and ester torsion j (degrees, torsional angle C6-C5-C9-O10)
 
basis  method  DE  j(4a)  j(4b) 
3-21G(*)  HF -2.55 0.0  179.9
B3LYP  -2.69 0.0 180.0 
6-31G HF -1.59  0.0 -179.9
B3LYP  -1.66 0.0 180.0 
6-31G* HF -1.32  -8.0 170.3
B3LYP  -1.31 -4.8 172.6 
MP2  -0.97 -10.6 169.2 
6-311G HF -1.47  -1.4 179.0
B3LYP  -1.34 -2.5 177.5 
MP2  -0.75 -8.6 173.6 
6-31+G*  HF -1.07 -10.0  170.2
B3LYP  -1.04 -4.4 174.4 
MP2  -0.75 -12.2 167.9 
6-311G*  HF -1.17 -7.9  171.6
B3LYP  -1.19 -4.3 173.7 
MP2  -0.81 -9.0 171.6 
6-31G**  HF -1.37 -7.3  170.6
B3LYP  -1.34 -4.6 175.0 
MP2  -0.97 -10.2 169.5 
6-31+G**  HF -1.12 -9.3  170.5
B3LYP  -1.04 -5.0 174.8 
MP2  -0.75 -12.2 168.5