  We present results from a time dependent gas phase chemical model of a hot
core based on the physical conditions of G305.2+0.2. While the cyanopolyyne
HC_3N has been observed in hot cores, the longer chained species, HC_5N, HC_7N,
and HC_9N have not been considered typical hot core species. We present results
which show that these species can be formed under hot core conditions. We
discuss the important chemical reactions in this process and, in particular,
show that their abundances are linked to the parent species acetylene which is
evaporated from icy grain mantles. The cyanopolyynes show promise as `chemical
clocks' which may aid future observations in determining the age of hot core
sources. The abundance of the larger cyanopolyynes increase and decrease over
relatively short time scales, ~10^2.5 years. We also discuss several sulphur
bearing species. We present results from a non-LTE statistical equilibrium
excitation model as a series of density, temperature and column density
dependent contour plots which show both the line intensities and several line
ratios. These aid in the interpretation of spectral line data, even when there
is limited line information available.
