Concept explainers
(a)
Interpretation:
Without consulting tables or figures, answer the following questions: a thermal disrotatory electrocyclic reaction involving 12 electrons allowed or forbidden-the statement is to be verified.
Concept introduction:
Electrocyclic reactions are a pericyclic reaction which occur intramolecularly. These reactions will result in the formation of ring compounds under the influence of heat or light. Notably, in this process one new sigma bond is formed and one old π-bond is consumed. Intriguingly, the reverse ring opening electrocyclic reaction can also be possible to occur under the same reaction mechanism but in reverse manner. According to molecular orbital concepts, systems having 4n π electrons undergoes conrotatory ring closure is allowed and this ring closure is forbidden for systems having 4n + 2 π systems. Similarly, disrotatory closing of rings is forbidden for 4n π electrons and allowed for 4n + 2 π electron systems.
(b)
Interpretation:
a [8s + 4s] photochemical cycloaddition is allowed-the statement is to be verified.
Concept introduction:
The reactions in which the formation of cyclic product observed by combining two or more unsaturated molecules is called cyclo addition reaction. Besides, the net reduction of bond multiplicity is observed. Molecules having 4n π electrons is allowed under photochemical conditions and 4n +2 π electrons is allowed under thermal conditions.
(c)
Interpretation:
the HOMO of (Z)-3, 4-dimethyl-1, 3, 5-hexatriene symmetric or antisymmetric-the statement is to be verified.
Concept introduction:
The reactions in which the formation of cyclic product observed by combining two or more unsaturated molecules is called cyclo addition reaction. Besides, the net reduction of bond multiplicity is observed. Molecules having 4n π electrons is allowed under photochemical conditions and 4n +2 π electrons is allowed under thermal conditions.
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Chapter 28 Solutions
Organic Chemistry Study Guide and Solutions
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