The Search for a Complex Molecule in a Selected Hot Core Region: A
  Rigorous Attempt to Confirm trans-Ethyl Methyl Ether toward W51 e1/e2
  An extensive search has been conducted to confirm transitions of
\textit{trans}-ethyl methyl ether (tEME, C$_2$H$_5$OCH$_3$), toward the high
mass star forming region W51 e1/e2 using the 12 m Telescope of the Arizona
Radio Observatory (ARO) at wavelengths from 2 mm and 3 mm. In short, we cannot
confirm the detection of tEME toward W51 e1/e2 and our results call into
question the initial identification of this species by \citet{FuchsSpace}.
Additionally, reevaluation of the data from the original detection indicates
that tEME is not present toward W51 e1/e2 in the abundance reported by Fuchs
and colleagues. Typical peak-to-peak noise levels for the present observations
of W51 e1/e2 were between 10 - 30 mK, yielding an upper limit of the tEME
column density of $\leq$ 1.5 $\times$ 10$^{15}$ cm$^{-2}$. This would make tEME
at least a factor 2 times less abundant than dimethyl ether (CH$_3$OCH$_3$)
toward W51 e1/e2. We also performed an extensive search for this species toward
the high mass star forming region Sgr B2(N-LMH) with the NRAO 100 m Green Bank
Telescope (GBT). No transitions of tEME were detected and we were able to set
an upper limit to the tEME column density of $\leq$ 4 $\times$ 10$^{14}$
cm$^{-2}$ toward this source. Thus, we are able to show that tEME is not a new
molecular component of the interstellar medium and that an exacting assessment
must be carried out when assigning transitions of new molecular species to
astronomical spectra to support the identification of large organic
interstellar molecules.
