Bent Bond - Double and Triple Bonds

Double and Triple Bonds

Two different explanations for the nature of double and triple covalent bonds in organic molecules were proposed in the 1930s. Linus Pauling proposed that the double bond results from two equivalent bonds, which later came to be called banana bonds or tau bonds. Erich Hückel proposed a representation of the double bond as a combination of a sigma bond plus a pi bond. The Hückel representation is the better-known one, and it is the one found in most textbooks since the late-20th century. There is still some debate as to which of the two representations is better, although some theoretical chemists consider both models to be practically equivalent. In a 1996 review, Kenneth B. Wiberg concluded that "although a conclusive statement cannot be made on the basis of the currently available information, it seems likely that we can continue to consider the σ/π and bent-bond descriptions of ethylene to be equivalent." Ian Fleming goes further in a 2010 textbook, noting that "the overall distribution of electrons is exactly the same" in the two models.