1 (124)

Prévia do material em texto

Chapter 16 Suggested solutions for Chapter 16 121 planar but the combination of a double bond and a tetrahedral centre at the other ring removes all possibility of a plane of symmetry. This too is chiral. Me Me Me H Me N N N N P PF₆ P N The third molecule tries to look chiral but it is almost planar because of conjugation, and the NO drogen atom above the plane reflects the hydrogen atom below it. The plane of the ring is a plane and the molecule is not chiral. The fourth molecule is an allene with the two alkenes gonal to each other. It needs to be drawn more realistically to show that there is a plane of cutting the cyclohexane ring at right angles and passing through the methyl group on the end of the allene. Not chiral either. H H 0 H H 0 NH₂ NH₂ Me H N ON Me Me The last two molecules are more straightforward. The tricyclic compound has a plane of vertically down the middle and is not chiral. The sulfoxide is a simple example of a genic atom other than carbon. Sulfoxides are tetrahedral with the oxygen atom and the lone above and below the plane as drawn. This one is chiral. 0 0 HN NH S S Ph Ph H H 0 Problem 6 Discuss the stereochemistry of these compounds. (Hint. This means saying how many astereoisomers there are, drawing clear diagrams of each, and saying whether they are hiral or not.) Purpose of the problem am- sure that you can handle this important approach to the stereochemistry of molecules. gested solution follow the hint given in the question! Diastereoisomers are different compounds so they must with stinguished first. Then it is easy to say if each diastereoisomer is chiral or not. The first two are e of You the one compound one compound no diastereoisomers 0 no diastereoisomers hiral plane of symmetry no plane of symmetry ale is not chiral chiral H