  The Galaxy is in continuous elemental evolution. Since new elements produced
by dying stars are delivered to the interstellar medium, the formation of new
enerations of stars and planetary systems is influenced by this metal
enrichment. We aim to study the role of the metallicity on the gas phase
chemistry of the interstellar medium. Using a system of coupled-ordinary
differential equations to model the chemical reactions, we simulate the
evolution of the abundance of molecules in the gas phase for different initial
interstellar elemental compositions. These varying initial elemental
compositions consider the change in the "elemental abundances" predicted by a
self-consistent model of the elemental evolution of the Galaxy. As far as we
are aware, this is the first attempt to combine elemental evolution of the
Galaxy and chemical evolution of molecular clouds. The metallicity was found to
have a strong effect on the overall gas phase composition. With decreasing
metallicity, the number of long carbon chains was found to increase, the
time-scale on which small molecular species are increases, and the main form of
oxygen changed from O and CO to O2. These effects were found to be mainly due
to the change in electron, H3+, and atomic oxygen abundance.
