  We propose a method for controlling a class of low temperature chemical
reactions. Specifically, we show the hydrogen abstraction channel in the
reaction of formaldehyde (H$_{2}$CO) and the hydroxyl radical (OH) can be
controlled through either the molecular state or an external electric field. We
also outline experiments for investigating and demonstrating control over this
important reaction. To this end, we report the first Stark deceleration of the
H$_{2}$CO molecule. We have decelerated a molecular beam of H$_{2}$CO
essentially to rest, producing cold molecule packets at a temperature of 100 mK
with a few million molecules in the packet at a density of $\sim10^{6}$
cm$^{-3}$.
