In his off hours, George Casey, a Ukrainian native who came to the U.S. as a law student, teaches cross-border M&A at the University of Pennsylvania. But when The Dow Chemical Co. decided to spin off its chlorine business, it was the teacher who was put to the test. The spinoff “combines almost every existing transaction you can think of as an M&A lawyer,” says Casey, who represented Dow.

The $5 billion deal included a carve-out, equity and debt exchanges and a public company merger. It took eight practice groups more than 18 months and 2,000 pages of documents to complete.