(a)
Interpretation: The product formed by the thermal electrocyclic ring opening or ring closure to the given compound is to be predicted. The process has to be labeled as conrotatory and disrotatory and the stereochemistry around stereogenic center and double bond is to be indicated.
Concept introduction: Electrocyclic reactions involve ring opening or ring closure in a conjugated polyene. According to Woodward-Hoffmann rules, the polyene containing even number of bonds in photochemical conditions undergoes reaction in disrotatory fashion and polyene containing odd number of bonds undergo reaction in conrotatory fashion.
(b)
Interpretation: The product formed by the thermal electrocyclic ring opening or ring closure to the given compound is to be predicted. The process has to be labeled as conrotatory and disrotatory and the stereochemistry around stereogenic center and double bond is to be indicated.
Concept introduction: Electrocyclic reactions involve ring opening or ring closure in a conjugated polyene. According to Woodward-Hoffmann rules, the polyene containing even number of bonds in photochemical conditions undergoes reaction in disrotatory fashion and polyene containing odd number of bonds undergo reaction in conrotatory fashion.
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