PROBLEM 3 Draw diagrams to represent the conjugation in these molecules. Draw two ypes of diagram (a) Show curly arrowS linking at least two different ways of representing the molecule (6) Indicate with dotted lines and partial charges (where necessary) the partial double bond (and charge) distribution. H2N N Purpose of the problem 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. H2 1/3(+)NH2 HNNH, 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 difticult to represent this with partial charges but the charges on the oxygens will be nearly a half each. Solutions Manual to accompany Organic Chemistry The third compound is naphthalene. The structure drawn in the questic is the best as both rings are benzene rings. The results of curly arrd 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.