Density functional computations of proton affinity and gas-phase basicity of proline.
The proton affinity and gas-phase basicity of proline were evaluated by using density functional theory coupling the B3-LYP hybrid functional with the extended 6--311++G** basis set. Cis and trans conformations of the carboxyl moiety for both exo and endo ring structures were considered for the neutral proline. The results show that the most stable structure of proline has the endo ring conformation with the carboxyl group in the cis position. The structure at the global minimum is stabilized by an intramolecular hydrogen bond. The nitrogen of the ring in the exo form is the preferred protonation site. The calculated proton affinity (924.3 kJ mol(-1)) and gas-phase basicity (894.4 kJ mol(-1)) are in very good agreement with the experimental counterparts.
Marino
T
T
Dipartimento di Chimica, Università della Calabria, I-87030 Arcavacata di Rende (CS), Italy.
Russo
N
N
Tocci
E
E
Toscano
M
M
D005740:Gases; D006860:Hydrogen Bonding; D011338:Probability Theory; D011392:Proline / Q000737:chemistry*; D011487:Protein Conformation; D011522:Protons
D005740:Gases; D011522:Protons; D011392:Proline