Using the Woodward-Hoffmann rules in Table 27.4, predict the stereochemistry of each reaction.

a. a [6 + 4] thermal cycloaddition

b. photochemical electrocyclic ring closure of 1.3.5.7.9-decapentaene

c. a[4i 4] photochemical cycloaddition

d. a thermal [5.5] sigmatropic rearrangement

Table 27.4 Summary of the Stereochemical Rules for Pericyclic Reactions

Reaction conditions Number of electron pairs Thermal Photochemical Even Odd Even Odd Stereochemistry Conrotatory or antaralacial Disrotatory or suprafacial Disrotatory or suprafacial Conrotatory or antarafacial