Details

Autor(en) / Beteiligte

• Juhász, Márta
• Fülöp, Ferenc
• Pihlaja, Kalevi

Titel

Substituent effects on the gas‐phase ring‐chain tautomerism of 3,4,5,6‐tetrahydro‐2 H ‐1,3‐oxazines

Ist Teil von

• Rapid communications in mass spectrometry, 2007-11, Vol.21 (22), p.3701-3710

Erscheinungsjahr

2007

Quelle

Wiley-Blackwell Journals

Beschreibungen/Notizen

• Abstract The electron ionization mass spectra of five series of seven 2‐aryl,4‐R‐substituted (R = Me, Et, i ‐Pr, t ‐Bu or Ph) 3,4,5,6‐tetrahydro‐2 H ‐1,3‐oxazines were recorded at 14 and 70 eV in order to study the ring‐chain tautomeric equilibria in the gas phase. Certain fragment ions were associated with the ring or with the open‐chain forms of the compounds. As in chloroform solution, the electron‐withdrawing effect of the aryl substituent ( p ‐NO 2 , m ‐Br, p ‐Cl, H, p ‐Me, p ‐OMe and p ‐NMe 2 ) shifts the equilibrium towards the ring form. The correlation of ring‐chain equilibria (log K  = [ring]/[chain]) with the Hammett σ + constants of the aryl substituents was in general good or satisfactory although in some cases the p ‐NMe 2 did not fit these correlations. Copyright © 2007 John Wiley & Sons, Ltd.