Acetanilide resonance

Acetanilide, electrophilic aromatic substitution of, 939-940 Acetate ion, bond lengths in, 43 electrostatic potential map of, 43, 53, 56, 757 resonance in, 43 Acetk acid, bond angles in, 755 bond lengths in, 755 dimer of, 755 dipole moment of, 39 electrostatic potential map of, 53, 55... 

De la Mare and Hassan254 obtained second-order rate coefficients (in parenthesis) for the following 4-methylacetanilide (1.53), 2-methylacetanilide (0.193), 2,6-dimethylacetanilide (0.0118), acetanilide (0.93), 4-acetamidodiphenyl (0.248) and 1,4-diacetamidobenzene (0.231) the results for the acetanilides demonstrated the effect of steric hindrance to coplanarity thereby inhibiting resonance of the nitrogen lone pair with the aromatic ring. The rate coefficients for chlorination of 3-chloroacetanilide (0.215), 4-chloroacetanilide (0.010) 3-nitroacetanilide (6.7 x 10 5) and phenyl benzoate (3.2 x 10-6) have also been measured258,261. 

The lone pair of electrons on nitrogen of acetanilide Interacts with ojQTgen atom due to resonance as shown below ... 

Forbes and co-workers9 have extensively studied the ultra-violet absorption spectra of several series of disubstituted benzene derivatives acetophenones, benzoic adds, benzaldehydes, phenylbenzoates, acetanilides- nitrobenzenes, anilines, fluorobenzenes, chlorobenzenes, phenols and anisoles. They have collected valuable data and interpreted them in terms of the resonance and steric interactions of substituents. Baliab. and co-workers27 have studied the absorption spectra of aryl sulphones and sulphoxides. The absorption spectra of substituted phenylazides28 and phenyl isothiocyanates29 have been discussed by Rao et al. 

Hi) High sensitivity to conjugative -polar effects. The great positional and substrate selectivity of biphenyl and naphtalene may be in principle due to two separate causes either to conjugative polar effects as for electrophilic reactions (Scheme 3) or to resonance stabilization of the intermediate radicals (Scheme 4). The first effect was considered much more important for two reasons the high selectivity shown by aromatic compounds such as phenol, anisole, acetanilide and the fact that, in the absence of marked polar effects, as in homolytic phenylation of biphenyl, the partial rate factor of the para position has a rather low value (2.5), not differing greatly from those of the ortho (2.1) and meta (1.0) positions 2). 

EthynyIphenyl-6-(trimethylsilylethynyl)aniline. A 100 mL round bottom flask equipped with a magnetic stirbar was charged with 3-ethynylphenyl-6-(trimethylsilylethynyl)acetanilide (0.25 g, 0.75 mmol), HCl (15 mL, 1.5 M), and THF (15 mL). The reaction mixture was heated to reflux for 2.5 h. The reaction progress was monitored by TLC. The reaction was quenched and extracted with water (3x) and diluted with CH2CI2. The organic layers were combined and dried over MgS04. Volatiles were removed in vacuo. Crude H NMR and TLC showed two inseparable products with similar amine and aromatic resonances. Therefore, the crude reaction mixture was reacted further without purification. 

Table 8.9 also records the pKa values of diphenylamine, acetanilide, the naphthylamines, and a small selection of hetcroaromatic bases. It will be noted that a second ring-nitrogen atom depresses basic strength (by a (- I) effect) except in a few cases where a base-strengthening resonance counteracts this effect (e.g. pyrazole, imidazole). 

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