Protonated ethylamine

Potassium borohydride reduction of runanine (17) yielded dihydro-runanine (24), the H-NMR spectrum of which (Table II) exhibited a triplet (64.25), the proton bearing the hydroxyl group coupling with those of C-5 (35). The optical activity of runanine (17), [a]D —400°, was similar to that of hasubanonine (5), [a]D —214° (3) therefore, it was concluded that the ethylamine linkage must have the same configuration as hasubanonine [C-13 (R) and C-14 (S)]. From these results, structure 17 was proposed for runanine (35) however, no application of mass spectral data to the structure elucidation was presented (35). 

Fig. 1. Changes in the chemical shift of protons lining the cleft of 13 (H4) H,) as P-phenyl-ethylamine is added...

A second lithium atom The anion acts as a base and donates an electron to removes a proton from a second the vinylic radical. molecule of ethylamine. 

Another proton transfer studied by the E-jump technique in acetonitrile (42) is that between p-nitrophenol (AH) and tri-ethylamine (B). The extinction coefficients for each of the species in the following equilibrium have been measured by Kree-voy and Liang (3) ... 

There is also a relationship between p a-values of ethanol, phenol and acetic acid on the one hand, and ethylamine, aniline and acetamide on the other (Liler, 1971c, p. 108), which may be presented as a linear free energy relationship (Figure 6) by regarding Et, Ph and CH3 CO as substituents (R). This excellent relationship leaves no doubt that the acidic group in the R—NH3 series remains unchanged, i.e., that acetylammonium ion is formed in the protonation of acetamide in aqueous acid (half-protonation in ca. 19% sulphuric acid). 

Pre-eminent amongst examples is the case of amides, which do not show the typical basicity of amines. Acetamide, for example, has pATa — 1.4, compared with a 10.7 in the case of ethylamine. This reluctance to protonate on nitrogen is caused by delocalization in the neutral amide, in which the nitrogen lone pair is able to overlap into the n system. This type of resonance stabilization would not be possible with nitrogen protonated, since the lone pair is already involved in the protonation process. Indeed, if amides do act as bases, then protonation occurs on oxygen, not on nitrogen. Resonance stabilization is still possible in the D-protonated amide, whereas it is not possible in the A-protonated amide. Note that resonance stabilization makes the D-protonated amide somewhat less acidic than the hydronium ion (pATa — 1.7) the amide oxygen is more basic than water. 

As the distance between the amino groups increases, the effect of the NH2 on the first protonation diminishes, so that pATai values for the 1,3- and 1,4-diamino compounds are very similar to that of ethylamine. Only in 1,2-diaminoethane do we see the electron-withdrawing effects of the second amino group decreasing basicity. However, for the second protonation, it is clear that an ionized... 

The available evidence supports the demethylation scheme and the identity of the initial red product as that of the basic tautomer of trimethylthionine (Azure B), as shown in eqs. 33 and 34. Addition of acid or other weak proton donor protonates the red dye to give the blue form. We have reexamined the reaction of MB or New methylene blue (NMB) in dry acetonitrile with tri-ethylamine (TEA). We have also found that a comparable reaction of NMB occurs with trimethylbenzylstannane (TMBS). Figure 8 shows changes in the visible spectrum of NMB which occur in addition of TEA. Table 12 lists quantitative data. The spectra... 

There is general consensus on the fact that the endogenous agonist histamine, 2-(imidazole-4-yl)ethylamine, binds to the receptor in its monocationic state (protonated at the side chain amine group). The monocationic form is predominantly (96.6%) present at pH 7.4 [11]. In this state, the neutral imidazole ring can exist in two different tautomeric forms, denominated by proximal (it) and tele (x), respectively (Figure 1). 

Ethylamine is therefore easier to protonate (more basic) than 2-chloroethylamine. 

It was envisioned that the addition of an indole derived from a tryptamine to the activated iminium ion, arising from imidazolidinone catalyst 3 and an a,p-unsaturated aldehyde, would generate a C(3)-quaternary carbon-substituted indo-lium ion. As a central feature this intermediate cannot undergo re-aromatization by means of proton loss, in contrast to the analogous 3-H indole addition pathway. As a result, 5-exo-heterocyclization of the pendant ethylamine would provide the corresponding pyrroloindoline compounds. In terms of molecular complexity, this cascade sequence should allow the rapid and enantioenriched formation of stereochemically defined pyrroloindoline architecture from tryptamines and simple a,/i-unsaturated aldehydes. 

Amines and amides are very weak acids and they only react with very strong bases. The pKa values for ethanamide and ethylamine are 15 and 40, respectively, which means that ethanamide has the more acidic proton (Fig.A). This can be explained by making use of resonance and inductive effects (Fig.B). 

A positively charged particle emitted from the nucleus of some radioactive atoms. It is made up of two neutrons and two protons and no electrons. It is shown as the nucleus of a helium atom, 2He2+. An organic compound with similar alkaline properties to ammonia. General formula CnH2n + 1NH2, e.g. ethylamine, when 11 = 2, C2H5 NH2. 

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