Carbon‐13 NMR studies of nitrogen compounds. I—substituent effects of amino, acetamido, diacetamido, ammonium and trimethylammonium groups

Abstract

C NMR chemical shifts are reported for several alkyl or aryl amines, acetamides, diacetamides and ammonium and trimethylammonium salts. Substituent effects, determined with respect to chemical shifts of amino derivatives, are rationalized in terms of y effects, steric interactions and, for benzene derivatives, in terms of competition between inductive (a,) and resonance (uR) effects. These perturbations can be used to assign chemical shifts of complex structures and to study certain chemical processes. 13

The structure of ammonium pyrazolates in the solid state

“…3 Using all the pyrazole signals and the˛,ˇand C1 0 signals of the amines (12 signals), by interpolating those of the complexes, it is found that phenethylamine (2) there is 29% charged species (25-34% depending on the signal) (71% neutral) and with homoveratrylamine (3) there is 27% charged species (24-33% depending on the signal) (73% neutral) (Scheme 2).…”

A Convenient Method for the Synthesis of Sterically Hindered Aryl Isocyanates

“…Therefore, only shift areas are given for the individual protons; the approxim ate 7-values are: The 13C NM R spectrum of 8, although reported [31], has not been interpreted before. Our assign ments are again based on shift arguments (com pari son with acetanilide, N,N-diacetylaniline [32] and Nphenylm aleim ide), relative intensities and {13C, :H} coupled spectra. Interestingly, the present spectrum (in CDC13) differs from the reported one [31] (in DM SO -d6) in the num ber of signals.…”

Analytical characterization of four new ortho‐methoxybenzylated amphetamine‐type designer drugs

“…Together with the deprotonation came a strong high frequency shift of the carbon atom 2”, the ipso carbon of the o ‐methoxybenzyl group of about 8 ppm, leading to a signal overlap with the signal of carbon atom 5”. This is a typical shift of about 10 ppm for benzyl amines upon deprotonation, independent of the solvent . Also for the proton resonances strong high frequency shifts were observed, namely about 0.5 ppm for H‐1”, about 0.3 ppm for H‐4”, H‐5” and H‐7”, and 0.1 ppm for H‐6”, when only looking at the o ‐methoxybenzyl group (Tables and ).…”

“…This is a typical shift of about 10 ppm for benzyl amines upon deprotonation, independent of the solvent. [15][16][17][18] Also for the proton resonances strong high frequency shifts were observed, namely about 0.5 ppm for H-1", about 0.3 ppm for H-4", H-5" and H-7", and 0.1 ppm for H-6", when only looking at the o-methoxybenzyl group (Tables 3 and 4). For the benzofuran derivative 4·HCl again the typical pattern of the o-methoxybenzyl residue was observed.…”