A ¹³C NMR study of hindered rotation in N¹,N¹‐penta‐ and N¹, N¹‐hexa‐methylene‐N²‐substituted‐phenylformamidines

Abstract

Rates of rotations about the C-N' partial double bond in a series of six N',N' penta-and six N',N'-hexa-methyleneNz-substituted-phenyformamidines were determined from 13C DNMR line shape analysis.Electron accepting substituents at the phenyl ring increase the barrier to rotation, and electron donating substituents decrease the barrier, compared with the nonsubstituted compound. Linear relationships are shown to exist between AG* and the I3C chemical shifts of the functional carbon or the pK, of formamidines.

13C NMR Study of the Interaction of N,N‐Dimethylamides and N,N‐Dimethylamidines with the Nitroxide Radical

“…However, the detected spin density on the amidine carbon nucleus in the acetamidine IV, which may be regarded as some analogue of DMA, is quite unexpected and suggests a remarkable interaction between the TMPN radical and the -N = C group. Thus, the analogy between amidines and amides should be treated with some caution, this also being confirmed by the faster rotation around the C -N(CH 3 h bond in amidines than in amides [17,19,20].…”

13C NMR studies of conformational dynamics in α-tocopherol esters in solution and solid state

“…18 The line shape analysis was carried out using a computer program with an iteration procedure for a classical two-site exchange. 19 Cross polarisation magic angle spinning (CP MAS) solid state 13 C NMR spectra were recorded on a Bruker MSL 300 instrument at 75.5 MHz. The samples were spun at 10 kHz, a contact time of 4 ms, a repetition time of 6 s, and a spectral width of 20 kHz for accumulation of 700-900 scans were used.…”