Abstract
Carbon-13 NMR (nuclear magnetic resonance) titration shifts are presented for a number of branched amines, carboxylic and amino acids. It is shown that 13C NMR titration shifts depend on the number of next-nearest-neighbor (β) methyls of the observed 13C nucleus. The magnitude and direction of these β-methyl effects depend on the spatial relationship of the protonated group, the observed carbon and the β methyl, and hence on the molecular conformation and configuration. It is suggested that these effects arise from modification by the β methyl of the intramolecular electric fields produced by protonation. Direct methyl substitution gives rise to similar (α-methyl) effects although these are partially masked by concurrent changes in the electric field shift coefficient of the observed nucleus.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
