title: Differential protonation and dynamic structure of doxylamine succinate in solution using 1H and 13C NMR.
abstract: A protonation and dynamic structural study of doxylamine succinate, a 1:1 salt of succinic acid with dimethyl-[2-(1-phenyl-1-pyridin-2-yl-ethoxy)ethyl]amine, in solution using one- and two-dimensional 1H and 13C NMR experiments at variable temperature and concentration is presented. The two acidic protons of the salt doxylamine succinate are in 'intermediate' exchange at room temperature, as evidenced by the appearance of a broad signal. This signal evolves into two distinct signals below about -30 degrees C. A two-dimensional 1H-1H double quantum filtered correlation experiment carried out at -55 degrees C shows protonation of one of the acidic protons to the dimethylamine nitrogen. A two-dimensional rotating frame 1H-1H NOE experiment at the same temperature reveals that the other proton remains with the succinate moiety. Comparison of the 1H and 13C chemical shifts and the 13C T1 relaxation times of the salt with those of the free base further substantiate the findings.
authors.affiliation: Centre of Biomedical Magnetic Resonance, Sanjay Gandhi Post-graduate Institute of Medical Sciences, Raebareli Road, Lucknow 226 014, India.
authors.forename: B S
authors.initials: BS
authors.lastname: Somashekar
authors.forename: G A
authors.initials: GA
authors.lastname: Nagana Gowda
authors.forename: A R
authors.initials: AR
authors.lastname: Ramesha
authors.forename: C L
authors.initials: CL
authors.lastname: Khetrapal
mesh_terms: D002247:Carbon Isotopes; D004319:Doxylamine / Q000031:analogs & derivatives* / Q000032:analysis* / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008958:Models, Molecular; D008968:Molecular Conformation; D010084:Oxidation-Reduction; D011522:Protons; D012996:Solutions
chemical_list: D002247:Carbon Isotopes; D011522:Protons; D012996:Solutions; D004319:Doxylamine; C035385:doxylamine succinate