\begin{table}%t6
\par
\caption{\label{tab:observations}Abundances of complex molecules relative to CH$_3$OH.}           %\centerline
 {\begin{tabular}{l c c c c c c c }        % centered columns (4 columns)
\hline\hline                 % inserts double horizontal lines2135.2489
&IRAS 16293-2422/A$^{a,b}$ & Hot cores$^{c}$ & L1157$^{d}$ & MC G-0.02$^{e}$ &Hale-Bopp$^{f}$ & CH$_3$OH$^{g}$& CH$_3$OH:CO$^{g}$\\
\hline                
CH$_3$OH & 1/1& 1 & 1& 1&1& 1 &1\\
CH$_3$CHO &0.038/~$<$~0.0016 &2.9[3.1]~$\times$~$10^{-5}$ &--&0.033 &0.010 &0.01 &$<$0.04\\
CH$_3$CH$_2$OH&--/0.031 &0.019[0.012]&0.007 & 0.040&$<$0.042 &0.1&$<$0.01\\
CH$_3$OCH$_3$&0.20/0.013&0.41[0.51]&--& 0.050&--&0.04 &$<$0.01\\
HCOOCH$_3$& 0.30/0.0084&0.089[0.084]&0.019 &0.037 &0.033 &$<$0.03&$>$0.08\\
HOCH$_2$CHO& --/--& --& --&0.01 &$<$0.017&$<$0.04 & $>$0.04\\
(CH$_2$OH)$_2$&--/-- &-- &--&0.01 &0.10 &0.4&$<$0.01\\
\hline
\end{tabular}
}
\par
\smallskip
$^{a}$ The first value is from single dish data, the second from interferometric studies of the A core. $^{b}$ \citet{Cazaux03,Huang05,Bisschop08} and van Dishoeck \& Herbst (2009).
$^{c}$ Average data and standard deviations towards a sample of seven high-mass hot cores \citep{Bisschop08}. $^{d}$ \citet{Arce08}. $^{e}$ \citet{Requena-Torres06,Requena-Torres08}. 
$^{f}$ \citet{Crovisier04}. $^{g}$ The relative abundance with respect to CH$_3$OH during warm-up of an irradiated 20~K pure CH$_3$OH ice and a CH$_3$OH:CO 1:10 ice mixture.
\end{table}