PROBLEM3 Draw diagrams to represent the conjugation in these molecules. Draw two types of diagram: (a) Show curly arrows linking at least two diferent ways of representing the molecule (6) Indicate with dotted lines and partial charges (where necessary) the partial double bond (and charge) distribution. HN NH2 Purpose of the problemn Amore exacting exploration of the precise details of conjugation. Suggested solution Treating each compound separately in the styles demanded by the question, the first (the guanidinium ion) is a very stable cation because of conjugation. The charge is delocalized onto all three nitrogen atoms as the first three structures show. Each nitrogen has an equal positive charge so our fourth diagram shows one third + on each. NH2 1/3(+) NH2 HNNH H NH HNNH 1/3(+) J/3(+) HN NH2 The second compound is what you will learn to call an enolate anion. The negative charge is delocalized throughout the molecule, mostly on the oxygens but some on carbon. It is difficult to represent this with partial charges but the charges on the oxygens will be nearly a half each. 4 Solutions Manual to accompany Organic Chemistry The third compound is naphthalene. The structure drawn in the questid is the best as both rings are bezene rings. The results ot curly arr diagrams show how naphthalene is delocalized all round the outer ring fact these diagrams show the ten electrons in the outer ring- this is a 4n + number and all three diagrams show that naphthalene is aromatic.