![]() ![]() The next diagram shows the sigma bonds formed, but for the moment leaves the p orbitals alone. Each carbon atom uses the sp 2 hybrids to form sigma bonds with two other carbons and one hydrogen atom. The difference in benzene is that each carbon atom is joined to two other similar carbon atoms instead of just one. This is all exactly the same as happens in ethene. The remaining p orbital is at right angles to them.Įach carbon atom now looks like the diagram on the right. The three sp 2 hybrid orbitals arrange themselves as far apart as possible - which is at 120° to each other in a plane. The new orbitals formed are called sp 2 hybrids, because they are made by an s orbital and two p orbitals reorganising themselves. Important! If you have any doubts about this then you should follow the links at the top of the page. They use the 2s electron and two of the 2p electrons, but leave the other 2p electron unchanged. The carbon atom is now said to be in an excited state.īecause each carbon is only joining to three other atoms, when the carbon atoms hybridise their outer orbitals before forming bonds, they only need to hybridise three of the orbitals rather than all four. The extra energy released when these electrons are used for bonding more than compensates for the initial input. ![]() There is only a small energy gap between the 2s and 2p orbitals, and an electron is promoted from the 2s to the empty 2p to give 4 unpaired electrons. That page includes the Kekulé structure for benzene and the reasons that it isn't very satisfactory.Īn orbital model for the benzene structureīenzene is built from hydrogen atoms (1s 1) and carbon atoms (1s 22s 22p x 12p y 1).Įach carbon atom has to join to three other atoms (one hydrogen and two carbons) and doesn't have enough unpaired electrons to form the required number of bonds, so it needs to promote one of the 2s 2 pair into the empty 2p z orbital. You can also read about the evidence which leads to the structure described in this article. You may also find it useful to read the article on orbitals if you aren't sure about simple orbital theory. You will find the current page much easier to understand if you read these other ones first. Important! This article builds on knowledge about the bonding in methane, and the bonding in ethene. Bonding in benzene - sp2 hybridisation and delocalisation ![]()
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