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A double bond in a six-membered ring is usually more stable in an endocyclic position
Chapter 7, Problem 7-48(choose chapter or problem)
A double bond in a six-membered ring is usually more stable in an endocyclic position than in an exocyclic position. Hydrogenation data on two pairs of compounds follow. One pair suggests that the energy difference between endocyclic and exocyclic double bonds is about 9 kJ/mol. The other pair suggests an energy difference of about 5 kJ/mol. Which number do you trust as being more representative of the actual energy difference? Explain your answer. endocyclic exocyclic 107 116 105 110
Questions & Answers
QUESTION:
A double bond in a six-membered ring is usually more stable in an endocyclic position than in an exocyclic position. Hydrogenation data on two pairs of compounds follow. One pair suggests that the energy difference between endocyclic and exocyclic double bonds is about 9 kJ/mol. The other pair suggests an energy difference of about 5 kJ/mol. Which number do you trust as being more representative of the actual energy difference? Explain your answer. endocyclic exocyclic 107 116 105 110
ANSWER:Step 1 of 3
Endocyclic double bond
A covalent double bond in a cyclic system in which both the carbon atoms are part of a ring structure is called an endocyclic double bond. For example, all the three double bonds in benzene are endocyclic.
Exocyclic double bonds
A covalent double bond in a cyclic system in which only one of the carbon atoms is part of the ring is called an exocyclic double bond. One double bond carbon will be a member of the ring, and the other carbon will be outside the ring structure.