March 2024
Sodium Hydroxide

Sometimes reported detections are disconfirmed by later observations and analysis, as in the prominent case of glycine. But sometimes clained detections fade over time from lack of continued interest or subsequent efforts to confirm them, perhaps because the initial evidence of a molecule's presence was not very strong. This is the case with the linear triatomic molecule sodium hydroxide, NaOH.

Researcher Links
BE Turner
JM Hollis
PJ Rhodes

In 1982, Hollis & Rhodes reported the detection of NaOH toward the OH maser position of Sgr B2 based on a single newly detected rotational transition (J=4-3) and the possible assignment of a second transition (J=3-2) to a previously observed line (U75406) reported by Wilson & Snyder in 1981.

In 1991, Turner reported the results of a search for NaOH and a number of other molecules toward Orion KL. While he tentatively assigned a feature at 226.123 GHz to the J=9-8 transition of NaOH, Turner noted that the line coincides very nearly with a weak transition of methyl formate, a well-established molecule in Orion KL. Furthermore, a search toward IRC +10216, where methyl formate is not present, revealed no evidence of NaOH.

Over 40 years have passed since the reported detection of NaOH by Hollis & Rhodes with no confirmation of these lines or searches for other rotational transitions of NaOH that might be expected to be present toward Sgr B2. Based on this and the very lukewarm evidence for NaOH in Orion KL from Turner, it is difficult to consider NaOH to be a detected species. It is listed with other non-detections and dated 1991, the most recent year any effort to observe NaOH was reported.

In 2021, Owen and co-workers reported a line list for NaOH as a species that might be detectable in exoplanetary atmospheres. As a crystalline solid and solution, sodium hydroxide is very familiar in terrestrial chemistry.

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