Bond angle of nitrous acid

Question

Why are there two possible bond angles for the nitrous acid molecule?

After perusing Wikipedia I found that there are both cis and trans forms of the nitrous acid molecule. I also note that the cis form is sterically hindered. Could this be a reason for the two different bond angles - there are two different geometric isomers and in one case there are larger van der Waals repulsions, which in turn expands the bond angle?

Which bond angles are you referring to? – LDC3 Apr 20 '14 at 04:43 — LDC3, Apr 20 '14 at 04:43
Oops. I am referring to the O-N-O bond angle. – Dissenter Apr 20 '14 at 16:05 — Dissenter, Apr 20 '14 at 16:05

score 1 · Accepted Answer · answered Apr 20 '14 at 01:22

This ism the microwave structure of nitrous acid, 1971. Your mileage may vary condensed phase.

DOI:10.1039/TF9716702179 (1971)
The structure of cis-nitrous acid is found to be: O—H = 0.982, N—O(H)= 1.392, N—O = 1.185 Å, ∠ NOH = 104.0 and ∠ ONO = 113.6°, and for trans-nitrous acid: O—H = 0.958, N—O(H)= 1.432, N—O = 1.170 Å, ∠ NOH = 102.1 and ∠ ONO = 110.7°.

http://nzc.iap.ac.cn/uploadpdf/Wang_et_al._CSB_2007a.pdf
2007 pape with more recent citations.

Also, would you say that hydrogen bonding has to do with the two different structures? I.e. hydrogen bonding between the H and the O in HONO? — Dissenter, May 08 '14 at 01:49

Bond angle of nitrous acid

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