Aromatic amines absorption spectra

Formation of an amide is also indicated in the reaction of PCTFE with Cr(CO)6 and the primary amine, benzylamine. The infrared absorption spectrum shows an N-H stretch centered at 3400 cm, aromatic C-H stretches at 3063 and 3030 cm1, aliphatic C-H stretches at 2933 and 2876 cm1, a broad amide I/amide II band ranging from 1680-1580 cm1, and a C-N stretch at 1454 cm1. The C-Cl stretch at 970 cm1 also shows a significant decrease in... 

Excited-state complexes between two dissimilar entities, called exciplexes, are also frequently formed. The most thoroughly studied exciplexes are those between an aromatic compound and either an amine or a conjugated olefin or diene. Compound 12, for example, has an absorption spectrum identical with... 

The formulation of enamines of quinuclidine in a mesomeric form would break Bredt s rule. No mesomerism occurs in 2,3-benzo-quinuclidine between the nitrogen atom and the aromatic ring thus, the compound does not exhibit the characteristic ultraviolet absorption of aromatic amines.43 Dehydroquinuclidine may only be formulated as l-azabicyclo[2.2.2]oct-2-ene the overlap of the olefinic ir-orbital and the lone pair orbital on nitrogen is precluded. Its ultraviolet spectrum exhibits merely end-absorption the compound is... 

For many molecules, due to extensive redistribution of electron densities, acid-base property in the excited state differs considerably from that in the ground state [33 For instance, aromatic amines are weakly basic in the ground state. But many of them become acidic in the excited state and readily donate a proton to a proton acceptor to produce the anion in the excited state. Such a molecule, which behaves as an acid in the excited state, is called a photoacid similarly, photobases are those that display basic properties in the excited state. In many cases, excited state proton transfer (ESPT) results in dual emission bands. One of these emission bands arises om the neutral excited state and bears mirror image relation with the absorption spectrum. The other emission band is due to the excited deprotonated (anion) or protonated species and exhibits a large Stokes shift. 

With aromatic acids the presence of the aromatic ring absorptions in the 1600—1500 cm region complicates the spectrum a good deal, but nevertheless j3-phenylalanine, tyrosine and similar products appear to be essentially normal [13, 17]. Anthranilic acid, on the other hand, shows normal carboxyl and amine absorptions shghtly modified by the internal hydrogen bond, and so does not behave as a typical amino-acid. The absence of the zwitterion form in this case may be associated with the hydrogen bond effect. 

Derivatives of rifamycins S and SV of the quinonimine type (Fig. 18), formed by condensation of rifamycin O with aromatic amines (34), hydrazides (35), amidrazones (36) and aminoguanidines (37) 37), showed high in vitro activity against Gram-positive bacteria but poor in vivo absorption 37, 126). The unsubstituted aminoguanidine derivative (38, Fig. 18) displayed especially good broad-spectrum antibiotic properties but was not suitable for oral or parenteral use. 

Only the alkyl groups and the aromatic ring can be detected in the spectrum of this tertiary amine.The absorptions due to the aromatic ring skeletal vibrations are stronger than usual, suggesting that the ring is substituted with a polar substituent. 

Infrared spectrum The IR shows a sharp peak around 3400 cm-1, possibly the N—H of an amine or the =C—H of a terminal alkyne. Because the MS suggests a nitrogen atom, and there is no other evidence for an alkyne (no C=C stretch around 2200 cm-1), the 3400 cm-1 absorption is probably an N — H bond. The unsaturated =C—H absorptions above 3000 cm-1, combined with an aromatic C = C stretch around 1600 cm-1, indicate an aromatic ring. 

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