Resonance Energy of Benzene: The difference between this experimental and theoretical values of heats of hydrogenation is the amount of stability of benzene. (They are so called after Friedrich August Kekulé, who is commonly credited with having first proposed the hexagonal structure for benzene in 1865; however, a cyclic structure had already been proposed by Joseph Loschmidt four years earlier.)

Kekule subsequently modified his structural formula to one in which oscillation of the double bonds gave two equivalent structures in rapid equilibrium. Real benzene is a lot more stable than the Kekulé structure would give it credit for. In this structure there is a hexagonal ring of carbon atoms distributed in a symmetrical manner, with each carbon atom carrying one hydrogen atom. The problem is that C-C single and double bonds are different lengths. Kekulé’s most famous work was on the structure of benzene. This was a 6 member ring of carbon atoms joined by alternate double and single bonds (as shown) This explained the C 6 H 12 molecular formula; Problems with the Kekulé Model The low reactivity of Benzene. In 1865 Kekulé published a paper in French (for he was then still in Belgium) suggesting that the structure contained a six-membered ring of carbon atoms with alternating single and double bonds.The following year he published a much longer paper in German on the same subject. Real benzene is a perfectly regular hexagon. In real benzene all the bonds are exactly the same - intermediate in length between C-C and C=C at 0.139 nm. The Kekulé structure has p roblems with the shape.

KEKULE STRUCTURE OF BENZENS. Benzene is a planar molecule (all the atoms lie in one plane), and that would also be true of the Kekulé structure. Kekulé's structure of benzene stated that there were 3 double bonds and 3 single bonds. August Kekule von Stradonitz, original name Friedrich August Kekulé, (born Sept. 7, 1829, Darmstadt, Hesse—died July 13, 1896, Bonn, Ger. The contribution of Kekule structure (I) and (II) is 80 % and that of Dewar structures (III), (IV), (V) is 20 % to the actual or real structure of benzene.

Characteristics of benzene In 1865, Kekule proposed the first acceptable ring structure for benzene. Other articles where Kekulé structure is discussed: chemical bonding: Resonant structures: …for each of these so-called Kekulé structures.

Problems with the stability of benzene. In 1931 American chemist Linus Pauling suggested that benzene had a single structure, which was a resonance hybrid of the two Kekule structures.