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The Hückel method or Hückel molecular orbital theory, proposed by Erich Hückel in 1930, is a simple method for calculating molecular orbitals as linear combinations of atomic orbitals. The theory predicts the molecular orbitals for π-electrons in π-delocalized molecules , such as ethylene , benzene , butadiene , and pyridine .
Möbius (left) and Hückel (right) orbital arrays. The two orbital arrays in Figure 3 are just examples and do not correspond to real systems. In inspecting the Möbius one on the left, plus–minus overlaps are seen between orbital pairs 2-3, 3-4, 4-5, 5-6, and 6-1, corresponding to an odd number (5), as required by a Möbius system.
He is mainly known for the Debye–Hückel theory of electrolytic solutions and the Hückel method of approximate molecular orbital (MO) calculations on π electron systems. Hückel was born in the Charlottenburg suburb of Berlin. He studied physics and mathematics from 1914 to 1921 at the University of Göttingen.
A program for the extended Hückel method is YAeHMOP which stands for "yet another extended Hückel molecular orbital package". [10] YAeHMOP has also been merged with the Avogadro open-source molecular editor and visualizer to enable calculations directly from the Avogadro graphical user interface for materials that are periodic in one, two, or ...
Hückel or Huckel may refer to: Erich Hückel (1896-1980), German physicist and chemist Debye–Hückel equation (named after Peter Debye and Erich Hückel), in chemistry, a method of calculating activity coefficients; Hückel method (named after Erich Hückel), a method for the determination of energies of molecular orbitals
As predicted by Hückel molecular orbital theory, the lowest π orbital in such molecules is non-degenerate and the higher orbitals form degenerate pairs. Benzene's lowest π orbital is non-degenerate and can hold 2 electrons, and its next 2 π orbitals form a degenerate pair which can hold 4 electrons.
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