Propionamide (C2H5CONH2), a complex alkyl amide with 12 atoms is the next member of the amide chemical family after formamide and acetamide. The new laboratory measurements of the propionamide spectrum were carried out in the 9–461GHz range, providing a good opportunity to check directly for the transition frequencies of detected interstellar lines of propionamide. Using these new analyses, based on the six clean lines of propionamide toward Sgr B2(N1E), which are consistent with the LTE synthetic spectrum of propionamide, we reported the tentative detection of propionamide in Sgr B2.

The detection of propionamide in Sgr B2(N) demonstrates that interstellar chemistry can reach sufficient levels of complexity to form relatively large peptide molecules and shows the possible growth of larger amide molecules from smaller ones in a massive star-forming process.