We know where General Electric plans to build its headquarters: On a 2.5-acre property along Fort Point Channel, near the Summer Street Bridge. But where is Jeff Immelt, the company’s CEO, going to live? The answer, we’re told, is 36 Commonwealth Ave., a four-bedroom condo with three fireplaces and a deck overlooking the Public Garden. The purchase was first reported by the Boston Business Journal. The 3,565-square-foot condo, listed for $7.9 million, has a large gourmet kitchen, a wood-paneled library on the second floor, and access to two enclosed parking spaces, which are much coveted in Back Bay. Immelt (inset), who succeeded Jack Welch as chairman of GE, is married with one daughter.