Disrotatory, definition

It would be difficult, at this stage, to present a properly argued preference between schemes A and B in the Introduction as the more faithful representation for the disrotatory electrocyclic ring-opening of cyclohexadiene. Chemical intuition (at least that of the authors) would suggest scheme B, but scheme A is on the textbook pages and, as has been shown by the SC description of the 1,3-dipolar addition of fulminic acid to ethyne, a heterolytic scheme remains a definite possibility. 

As we shall see. Frontier Configuration (FC) theory tells us that stereoselectivity in 4N + 3 electron systems should be qualitatively the same as stereoselectivity in 4N electon systems. Thus, for example, we expect that 1,3-butadiene, allyl anion, and allyl radical will all undergo electrocyclization in a conrotatory fashion. While there is every indication that this is the case in the first two systems, the ring closure of allyl radical-type systems is predicted by computations to be near disrotatory with indicative (but not definitive) experimental results pointing in the same direction. What is Wrong ... 

Figure 15.9 defined suprafacial and antarafacial interactions of a lone pair in a p orbital (called an uj component). Using these definitions, predict if the ring-opening of the cyclopropyl anion shown below will occur in a conrotatory or disrotatory fashion. What will be the stereochemistry of the product ... 

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