11. Protonation is also an essential step in certain analytical procedures such as electrospray mass spectrometry.12. The site of protonation can be very important, for example, for biological activity. 13. The halogen decreases the basicity of the carbonyl oxygen, thus making protonation less favorable. 14. Protonation occurs onto the sp?hybridized nitrogen.15. Birch did not accept this conclusion and continued suggesting meta protonation of the radical anion. 16. Acid catalysis involves protonation of the bromide, converting it to a better leaving group. 17. Other hydrocarbon oxonium ions are formed by protonation or alkylation of alcohols or ethers ( ). 18. The coordination of the metal cation to the glutamate residue stabilizes the carbiocation intermediate after protonation . 19. Other investigators have thought the protonation is meta ( 1, 3 ) to the substituent. 20. Subsequently, in 1992 and 1996 Birch published twice still suggesting that meta protonation was preferred.
