P-Cyanopyridine

P-Cyanopyridine. Mix 25 g. of powdered nicotinamide with 30g. of phosphoric oxide in a 150 ml. distilling flask by shaking. Immerse the flask in an oil bath and arrange for distillation under a pressure of about 30 mm. Raise the temperature of the oil bath rapidly to 300°, then remove the oil bath and continue the heating with a free flame as long as a distillate is obtained. The nitrile crystallises on cooling to a snow-white solid. Redistil the solid at atmospheric pressure practically all of it passes over at 201° and crystallises completely on cooling. The yield of p-cyanopyridine, m.p. 49°, is 20 g. 

Chapter V. Quinaldine (V,2) 2-methyl-, 2 5-dimethyl- and 2-acetyl-thiophene (V,8-V,10) 2 5-dimethyl- and 2 4-dimethyl-dicarbethoxy-pyrrole (V,12-V,13) 2-amino- and 2 4-dimethyl-thiazole (V,1 V,16) 3 5-dimethyl-pyrazole (V,17) 4-ethylpyridine (from pyridine) (V,19) n-amyl-pyridines from picolines) (V,28) picolinic, nicotinic and isonicotinic acid (V,21-V,22) (ethyl nicotinate and p-cyanopyridine (V,23-V,24) uramil (V,25) 4-methyl-(coumarin (V,28) 2-hyi ox3depidine (V,29). 

Ethyl nicotinate upon treatment with concentrated ammonia solution yields nicotinamide, which gives p-cyanopyridine upon heating with phosphoric oxide ... 

Nicotinic acid is an important intermediate for pharmaceuticals and serves as a provitamin in food additives for animal feeding. It is produced by the Lonza process (involving oxidation of 2-methyl-5-ethyl pyridine using nitric acid) or by the Degussa process.The latter process involved hydrolysis of P-cyanopyridine, which in turn was produced by amminoxidation of P-picoline. A third process involving selective vapour phase oxidation of P-picoline catalysed by vanadium titanium oxide catalyst has also been described. ... 

A major improvement regarding epoxidation of terminal olefins was achieved upon exchanging pyridine for its less basic analogue 3-cyanopyridine (p Krl pyridine = 5.4 pKa 3-cyanopyridine = 1.9) [105]. This improvement turned out to be general for a number of different terminal olefins, irrespective of the existence of steric hindrance at the a-position of the olefin or the presence of other functional groups in the substrate (Scheme 6.13 and Table 6.9). 

A convenient and easily accessible way to quantify hydrophobicity is the determination of the octanolAvater partition coefficient (log P) and we have determined the hydrophobicity of 13 selected ruthenium-arene complexes (71). As expected, hydrophobicity increases with an increase of the size of the coordinated arene ring, but decreases significantly when the chloride is replaced by neutral ligands such as pyridine and 4-cyanopyridine. The latter observation is somewhat counter intuitive at first inspection, but correlates with replacement of anionic chloride to yield a dicationic complex. The hydrophobicity... 

FIGURE 2.30. Redox catalysis induction of Srn1 reactions. Cyclic voltammetry in liquid ammonia + 0.1 M KC1 at —40°C of (a) redox catalyis of the reductive cleavage of 2-chlorobenzonitrile, RX, by 4-cyanopyridine, P. The dotted reversible cyclic voltammogram corresponds to P in the absence of RX. The solid line shows the catalytic increase of the current, (b) Transformation of the voltammogram upon addition of the nucleophile PhS. Adapted from Figure 1 in reference 23, with permisison from the American Chemical Society. 

Fig. 3 Electrochemical and homogeneous standard free energies of activation for self-exchange in the reduction of aromatic hydrocarbons in iV.A -dimethylformamide as a function of their equivalent hard sphere radius, a. 1, Benzonitrile 2, 4-cyanopyridine 3, o-toluonitrile 4, w-toluonitrile 5, p-toluonitrile 6, phthalonitrile 7, terephthalonitrile 8, nitrobenzene 9, w-dinitrobenzene 10, p-dinitrobenzene 11, w-nitrobenzonitrile 12, dibenzofuran 13, dibenzothiophene 14, p-naphthoquinone 15, anthracene 16, perylene 17, naphthalene 18, tra 5-stilbene. Solid lines denote theoretical predictions. (Adapted from Kojima and Bard, 1975.)...

In order to illustrate the application of LSV in mechanistic analysis we can look at the redox behavior of the formazan-tetrazolium salt system which we studied some years ago [17], 1,3,5-Triphenyl formazane was oxidized at controlled potential in CH3CN-Et4NC104 solution to 2,3,5-triphenyl tetrazolium perchlorate which was then isolated in quantitative yield. Coulometry showed that the overall electrode reaction was a two-electron oxidation. It has been shown that the rate of variation of Ep with log v was 30 mV per decade of sweep rate and that there was no variation of the peak potential with the concentration of 1,3,5-triphenylformazan. According to Saveant s diagnostic criteria (Table 1), four mechanistic schemes were possible e-C-e-p-p, e-C-d-p-p, e-c-P-e-p and e-c-P-d-p. If cyclization is the rate-determining step, then the resulting e-C-e-p-p and e-C-d-p-p mechanisms would not imply variation of Ep with the concentration of base. However, we have observed the 35 mV shift of Ep cathodically in the presence of 4-cyanopyridine as a b e. These observations ruled out the first two mechanisms. The remaining possibilities were then e-c-P-e and e-c-P-d, as shown in Scheme 3. 

Two examples of the dehydration of aromatic carboxamides using phosphorus pentoxide (cf. Section 5.13.3, p. 715) are given in Expt 6.169 these are the preparation of benzonitrile and 3-cyanopyridine. 

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