Knowledge Bank

Formic acid shares structural elements with the common interstellar molecule methyl formate $(HCOOCH3)$ and the elusive biomolecule acetic acid $(CH3COOH)$. It is the simplest organic acid, but it has only been identified in astronomical sources by fairly weak lines in single-element telescope surveys. In order to study the successive formation of biomolecules in the ISM, we carried out a survey of HCOOH toward galactic hot molecular cores with the Berkeley-Illinois-Maryland Association (BIMA) Array. Up to five transitions with rest frequencies near 87 GHz have been detected simultaneously in three sources: Sgr B2(N), Orion, and W51, HCOOH was found to have an excitation temperature of at least 100 K. The formation of HCOOH is probably related to grain-surface chemistry in hot cores. Abundance comparisons with other molecules such as $HCOOCH3$ and ethyl cyanide $(C2H5CN)$ will be discussed. This work was partially funded by NSF AST96 - 13999 and the University of Illinois.