6. Answer ALL parts of this question: a) Draw all the molecular orbitals of ethene and buta-1,3-diene, indicating where applicable which are the HOMOS and which are the LUMOS in both the ground state and first excited state. b) Use relevant orbitals from those drawn above to explain why buta-1,3- diene reacts with ethene in a [4+2] cycloaddition reaction under thermal conditions, but if two molecules of ethene are to dimerise in a [2+2] cycloaddition reaction, then the reaction must be irradiated with ultraviolet light. c) Identify compound X in the following reaction (Scheme 4) and draw curly arrow mechanisms that lead to it and then lead from it to the final products. CO Me CO₂Me heat heat X CO₂Me CO,Me Scheme 4 d) The reaction shown below (Scheme 5) is another example of a cycloaddition reaction. Identify the number of electrons involved in it, draw a curly arrow mechanism leading to the product and suggest whether this reaction would take place under thermal or photochemical conditions. +

6. Answer ALL parts of this question: a) Draw all the molecular orbitals of ethene and buta-1,3-diene, indicating where applicable which are the HOMOS and which are the LUMOS in both the ground state and first excited state. b) Use relevant orbitals from those drawn above to explain why buta-1,3- diene reacts with ethene in a [4+2] cycloaddition reaction under thermal conditions, but if two molecules of ethene are to dimerise in a [2+2] cycloaddition reaction, then the reaction must be irradiated with ultraviolet light. c) Identify compound X in the following reaction (Scheme 4) and draw curly arrow mechanisms that lead to it and then lead from it to the final products. CO Me CO₂Me heat heat X CO₂Me CO,Me Scheme 4 d) The reaction shown below (Scheme 5) is another example of a cycloaddition reaction. Identify the number of electrons involved in it, draw a curly arrow mechanism leading to the product and suggest whether this reaction would take place under thermal or photochemical conditions. +

Organic Chemistry: A Guided Inquiry

2nd Edition

ISBN:9780618974122

Author:Andrei Straumanis

Publisher:Andrei Straumanis

Chapter15: Radical Reactions

Section: Chapter Questions

Problem 11E

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