Related Experiment Video
Updated: Jul 7, 2026

Methods to Identify the NMR Resonances of the 13C-Dimethyl N-terminal Amine on Reductively Methylated Proteins
Published on: December 12, 2013
Preferential protonation and methylation site of thiopyrimidine derivatives in solution: NMR data
Artem V Kozlov1, Vyacheslav E Semenov, Anatoliy S Mikhailov
1Institute of Organic and Physical Chemistry, Arbuzov Str. 8, Kazan, Russian Federation.
Abstract:
Protonation (alkylation) sites of several thiopyrimidine derivatives were directly determined by 1H-15N (1H-13C) heteronuclear single quantum coherence/heteronuclear multiple bond correlation methods, and it was found that in all compounds, protonation (methylation) occurred at the N1 nitrogen. GIAO DFT chemical shifts were in full agreement with the determined tautomeric structures. According to ab initio calculations, the stability of the different protonated forms and methylated derivatives was favored due to thermodynamic control and not kinetic control.
Related Concept Videos
Proton (¹H) NMR: Chemical Shift
Absorption signals of all the protium nuclei in a...
¹H NMR of Labile Protons: Deuterium (²H) Substitution
¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR
NMR Spectroscopy Of Amines
¹H NMR Chemical Shift Equivalence: Homotopic and Heterotopic Protons
Other Nuclides: 31P, 19F, 15N NMR
While fluorine-19 and phosphorous-31 have high natural abundances (100%) and positive gyromagnetic ratios, nitrogen-15 has a low natural abundance and a negative gyromagnetic ratio. However, nitrogen-15 is still preferred over nitrogen-14 (which has a high...

