1. Guanine (1) is commonly represented as a non aromatic, partially saturated heterocycle. However, the common structure of guanine is only one of two possible resonance forms, of whom the second one is clearly aromatic. Knowing that the latter is originated by the delocalisation of one of N6 (nitrogen six) lone pair on the ring, would you be able to predict the structure of the aromatic resonance structure of guanine? Guanine 1 N. NH 3 N- R 1 Why cannot N4 delocalise its lone pair on the ring? What about N3? Is its lone pair delocalised on the pyrimido-imidazole ring? Why?

1. Guanine (1) is commonly represented as a non aromatic, partially saturated heterocycle. However, the common structure of guanine is only one of two possible resonance forms, of whom the second one is clearly aromatic. Knowing that the latter is originated by the delocalisation of one of N6 (nitrogen six) lone pair on the ring, would you be able to predict the structure of the aromatic resonance structure of guanine? Guanine 1 N. NH 3 N- R 1 Why cannot N4 delocalise its lone pair on the ring? What about N3? Is its lone pair delocalised on the pyrimido-imidazole ring? Why?

Organic Chemistry: A Guided Inquiry

2nd Edition

ISBN:9780618974122

Author:Andrei Straumanis

Publisher:Andrei Straumanis

Chapter18: Aromaticity

Section: Chapter Questions

Problem 26CTQ

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