Naslov
Quantum chemical conformational analysis of the auxin phytohormone 4-methyl-3-indole acetic acid

Autori
Ramek, Michael ; Tomić, Sanja

Izvornik
International journal of quantum chemistry (0020-7608) 75 (1999), 6; 1003-1008

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

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

Sažetak
The potential energy surface of 4-methyl-indole-3-acetic acid (4-Me-IAA) contains five symmetry unique minima. Similar to 4-Et-IAA, the global minimum is not mirror-symmetrical but has a tilted acetic acid side chain. The carbonyl oxygen atom comes close enough to one of the methyl group hydrogen atoms (distance: 2.575 Å) to form a weak hydrogen bond (bond order: 0.018), which is weaker than the corresponding H-bond in the global minimum of 4-Et-IAA. The mirror symmetrical local minimum contains a different C-H···O=C hydrogen bond of similar strength (distance: 2.329 Å, bond order: 0.018), but also two repulsive H···H interactions between the methyl and the acetic acid side chain (distances: 2.405 Å). The reaction paths of 4-Me-IAA show characteristic elements of both, IAA and 4-Cl-IAA. In a qualitative sense, 4-Me-IAA thus is inbetween IAA and 4-Cl-IAA, which has a fascinating equivalence in the biological activity data: Rescher et al. studied the correlation between binding affinity and maximum growth rate of meize coleoptil section at the optimum concentration of 10 mol/l for several compounds and determined the following order: naphthalene-1-acetic acid > 4-Cl-IAA > 4-Me-IAA > IAA > 4-Et-IAA > 2-Me-IAA. In this order, 4-Me-IAA also takes a position between IAA and 4-Cl-IAA, although this could be explained in part by the higher lipophilicity of the chlorinated compounds.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

POVEZANOST RADA