4-Ethylpyridine, oxidation

The kinetics of the coherent synchronous reactions of HP decomposition and oxidation of pyridine derivatives has been reported. Regioselective oxidation of the pyridine derivatives were studied and conditions have been optimized for the production of 4-vinylpyridine, 4-vinylpyridine oxide, 2,2 -dipyridyl, and pyridine. A probable synchronized reaction mechanism has been suggested for the decomposition of HP and the free radical chain oxidation of pyridine derivatives. It is suggested that the hydroperoxy radical (H02-radical) plays a key role in this reaction mechanism. The activation energy has been calculated for the elementary steps of the dehydrogenation of 4-ethylpyridine. Oxidation of formamidine disulfide with HP in acidic medium results in the formation... 

The alkyl pyridines (6) and (7) can be transformed either to nicotinic acid or nicotinonitrile. In the case of nicotinic acid, these transformations can occur by either chemical or biological means. From an industrial standpoint, the majority of nicotinic acid is produced by the nitric acid oxidation of 2-meth5i-5-ethylpyridine. Although not of industrial significance, the air oxidation has also been reported. Isocinchomeronic acid (10) (Fig. 2) is formed as an intermediate. 

Although an inherently more efficient process, the direct chemical oxidation of 3-methylpyridine does not have the same commercial significance as the oxidation of 2-methyl-5-ethylpyridine. Liquid-phase oxidation procedures are typically used (5). A Japanese patent describes a procedure that uses no solvent and avoids the use of acetic acid (6). In this procedure, 3-methylpyridine is combined with cobalt acetate, manganese acetate and aqueous hydrobromic acid in an autoclave. The mixture is pressurized to 101.3 kPa (100 atm) with air and allowed to react at 210°C. At a 32% conversion of the picoline, 19% of the acid was obtained. Electrochemical methods have also been described (7). 

Ethylpyridine-l-oxide [14906-55-9] M 123.1, m 109-110 , pKEst l l- Crystd from acetone/ether. 

Bis(alkyldithio-/selenocarbamates) of Zn(ID and Cd(II) have previously been used in many applications including the rubber industry 1 and in analysis,382 as well as for single-molecular precursors in the growth of II VI thin films by CVD, as described earlier.181,383 They have also been shown to be good precursors for the preparation of II VI nanoparticles, in a process that involves their decomposition in a high-boiling donor solvent such as tri-n-octylphosphine oxide or 4-ethylpyridine (Figure 47). 

Nicotinic acid Nicotinic acid, pyridine-3-carboxylic acid (20.2.9) is synthesized industrially by heating a paraldehyde trimer of acetaldehyde, under pressure with ammonia, which leads to the formation of 2-methyl-5-ethylpyridine, followed by oxidation with nitric acid which gives the desired product [22-25]. 

Ethylpyridine [536-75-4] M 107.2, h 168.2-168.3 , d 0.942. Dried with BaO, and fractionally distd. Purified by conversion to the picrate, recrystn and regeneration of the free base followed by distn. 4-Ethylpyridine-l-oxide [14906-55-9] M 123.1, m 109-110 . Crystd from acetone/ether. 

Ethylpyridine N-oxide, AK98 N-Ethylpyridinium bromide, AK98 Ethyl 2-(4-pyridy1)acrylate, AR63... 

Isonicotinic acid (128) has been prepared from 4-picoline (19)192,193 or from 4-ethylpyridine (132).194-197 Using 4-ethylpyridine and a Pt anode resulted in higher yields.193 Platinum was slightly better for oxidizing 4-methylpyridine (19) but 132 was oxidized in good yield at a Pb02 anode.192,195 The conclusions reached in each of these separate reports seem to be unclear as to... 

A recent patent describes selective oxidations on certain alkylpyridines.206 For instance, oxidation of the isomeric ethylpyridines gave the isomeric acetylpyridines (137) in reasonable yields (Scheme 45). The carboxylic acid was always a co-product. Certain of the dimethylpyridines (138,20) were oxidized... 

For production of niacinamide in the past, methylethylpyridine was oxidized with nitric acid to yield niacin, and P-picoline was treated with air and ammonia to produce the nitrile that was then hydrolyzed to niacinamide. A more modern process can produce both niacin and niacinamide from a single feedstock, either P-picoline or 2-methyl-5-ethylpyridine by oxidative ammonolysis, a combination of oxidation and animation. 

Because PBI is expensive, other thermostable polymers were explored and tested as catalysts (246). A cross-linked version of a polyimide (PI) support with incorporated triazole rings (12b) gave better results than PBI for the epoxidation of cyclohexene. Moreover, it can be reused in the cyclohexene epoxidation at least 10 times without any loss of activity (247). Even less expensive, but thermooxidatively stable materials include polysiloxane-based resins, which have also been used for incorporation of Ti (see Section II,A). In this case, the synthesis comprises the polymerization of TEOS and an oligomeric dimethyl silanol with the addition of functional trialkoxysilanes such as trimethoxysilyl-2-ethylpyridine instead of Ti(OiPr)4 (248). Preliminary results show that the activity per Mo atom is higher than that of PBI-Mo. Furthermore, the degree of leaching of Mo is very low. Thus, it is expected that the polysiloxane-based systems may soon find wide application in oxidation chemistry. 

Subsequent oxidation in acetic acid with chloranil yielded XXVIIIa whose spectra resemble very closely those of sempervirine. A parallel procedure via the phenylhydrazone of XXVIIb which was obtained by a known series of reactions from 2-cyano-5-ethylpyridine gave first XXVIb and finally XXVIIIb isolated as perchlorate. The last was identical with fiavopereirine perchlorate of natural origin. 

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