An important principle in chemistry is the isolobal analogy, which states that chemical fragments with similar valence-orbital structures can replace one another in molecules. For example,

are isolobal fragments, each having three electrons with which to form bonds in addition to the bond to H. An isolobal series of molecules would be HCCH, HCSiH, HSiSiH. Similarly, a lone pair of electrons can be used to replace a bond so that

is isolobal with

with the lone pair taking the place of the COH bond. The isolobal set here is HCCH, HCN, NN.

(a) Draw the Lewis structures for the molecules HCCH, HCSiH, HSiSiH, HCN, and NN.

(b) Use the isolobal principle to draw Lewis structures for molecules based on the structure of benzene, C₆H₆, in which one or more CH groups are replaced with N atoms.

Transcribed Image Text:

C-H and Si-H