Naslov
Comparative ab initio SCF conformational study of phytohormones (auxins) 4-chloro-indole-3-acetic acid and indole-3-acetic acid

Autori
Ramek, Michael ; Tomić, Sanja ; Kojić-Prodić, Biserka

Izvornik
International journal of quantum chemistry (0020-7608) 60 (1996), 8; 1727-1733

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
ab initio calculation ; conformational analysis ; 4-chloro-indole-3-acetic acid ; indole-3-acetic acid

Sažetak
The potential energy surface of 4-chloro-indole-3-acetic acid contains four symmetry unique local minima with a cis-orientation of the COOH group. The 6-31G* optimized positions in T1/T2-space and the relative energies are represented. As in the case of unsubstituted indole-3-acetic acid (IAA), the global minimum (A) is mirror symmetrical and stabilized by a weak C=O· ; · ; · ; H-C2 hydrogen bond. Unlike IAA, the conformers with tilted side chain offer only two different orientations for the COOH group, the torsion angles of which differ by approximately 180° ; these conformers are second and third in energy. The fourth symmetry unique local minimum (D) is not only remarkable because of its high relative energy. It is located at a T1/T2-position, which is close to that of a saddle point in unsubstituted IAA. Furthermore, D is no stable conformer: the lowest potential barrier (in the reaction to A) is only 0.452 kJ/mol, which is lower than the zero point energy of the corresponding vibration mode (that has an unscaled, harmonic frequency of 103.53 cm).

Izvorni jezik
Engleski

Znanstvena područja
Kemija

Napomena
Conference: 36th Annual Sanibel Symposium on the Application of Fundamental Theory to Problems of Biology and Pharmacology Location: ST AUGUSTINE, FL Date: FEB 24-MAR 02, 1996

POVEZANOST RADA