Fig. 1
From: Reaction rebalancing: a novel approach to curating reaction databases
In this example two fragments (shown in red) remain unmatched: \(\hbox {Br}\) with a single bond as cut, and an ethyl group also with a single bond. The cut edges of the fragments are shown as dashed red lines. A merge rule inserts a single bond (dashed green) connecting the end-points of the cut edges