DL 2646 then AA 3748 at Boston
Chicago O'Hare → Boston → Washington National
Timetable, Boston time
23:08DL 2646 from Chicago O'Hare at the gate
21:15AA 3748 to Washington National leaves the gate
22 h 07 apart on the timetable, overnight
AA 3748 leaves 22 h 07 after DL 2646 arrives on the timetable: more than half a day, so not a connection we count.