Minds (and memories) can work in wonderful ways. In 1987[1] we were looking at the properties of “stable” tetrahedral intermediates formed in carbonyl group reactions. The reaction involved adding phenylhydroxylamine to acetyl cyanide. NMR signals for two new species were detected, and we surmised one was due to N-attack on the carbonyl and one was due to O-attack, in each case to form a stable tetrahedral intermediate. To try to identify which was which, 15N labelled hydroxylamine was used and then the 15N-13C coupling constants were measured, which could either be 1-bondJ (for N-attack) or 2-bondJ (for O-attack).
References
- A.M. Lobo, M.M. Marques, S. Prabhakar, and H.S. Rzepa, "Tetrahedral intermediates formed by nitrogen and oxygen attack of aromatic hydroxylamines on acetyl cyanide", The Journal of Organic Chemistry, vol. 52, pp. 2925-2927, 1987. http://dx.doi.org/10.1021/jo00389a050