A Survey of Large Molecules of Biological Interest toward Selected High‐Mass Star‐forming Regions

We have surveyed the high-mass Galactic star-forming regions G19.61-0.23, G45.47+0.05, and W75N for interstellar methanol (CH 3 OH), formic acid (HCOOH), acetic acid (CH 3 COOH), methyl formate (HCOOCH 3 ), methyl cyanide (CH 3 CN), and ethyl cyanide (CH 3 CH 2 CN) with the Berkeley-Illinois-Maryland Association Array. From our observations, we have detected two new sources of interstellar HCOOH toward the hot core regions G19.61-0.23 and W75N. We have also made the first detections of CH 3 CH 2 CN and HCOOCH 3 toward G19.61-0.23. The relative HCOOH/HCOOCH 3 abundance ratio toward G19.61-0.23 is 0.18, which is comparable to the abundance ratios found by Liu and colleagues toward Sgr B2(N-LMH), Orion, and W51 (~0.10). We have made the first detection of HCOOCH 3 toward W75N. The relative HCOOH/HCOOCH 3 abundance ratio toward W75N is 0.26, which is more than twice as large as the abundance ratios found by Liu and colleagues. Furthermore, the hot core regions around W75N show a chemical differentiation between the O and N cores similar to what is seen toward the Orion Hot Core and Compact Ridge and W3(OH) and W3(H 2 O). It is also apparent from our observations that the high-mass star-forming region G45.47+0.05 does not contain any compact hot molecular core (HMC), and as a consequence its chemistry may be similar to that of cold dark clouds. Finally, the formation of CH 3 COOH appears to favor HMCs with well-mixed N and O, despite the fact that CH 3 COOH does not contain a N atom. If proved to be true, this is an important constraint on CH 3 COOH formation and possibly other structurally similar biomolecules.