The detection of the trans (anti) conformer of nitrous acid (t-HONO) was reported in 2019 by
Coutens and coworkers toward the
protostellar source IRAS 16293-2422 B.
The cis (syn) conformer was not detected.
The detection was made through the
survey, which is probably the only astronomical survey that has been used to generate its own
orchestral composition (although there is
another short piece based on ALMA data).
The primary coverage of the survey is 329 to 363 GHz, where the rotational transitions of
numerous complex organic molecules can also be found.
Nitrous acid is the smallest acid that contains
nitrogen. When deprotonated, the NO–
nitrite anion is
obtained. Nitrous acid is less stable that
nitric acid, HNO3, which has an
additional oxygen atom datively bonded to the nitrogen 2s2 pair.