Uptake of pyridine

Fig. 13 Set of FTIR spectra of successive states of uptake of pyridine into silicalite-1 (sample No. 4)...

Fig. 21 Uptake of pyridine into H-ZSM-5 as a function of the square root of time monitored by the increase of the absorbance of the typical bands at 1541 cm (pyridine reacted with Bronsted sites to give pyridinium ions, PyB, crosses -H-i-i-i-) and 1453 cm (pyridinium attached to Lewis sites, PyL, crosses x x x x) described by a solution of Pick s second law solid line)...

In the case of dense, surface-grafted polymer brush thin hlms, cross-links are introduced by the simple addition of solutions containing bis(Pd -pincer) compounds 4a or 4b to grafted PVP brushes (Loveless et al. 2006). Because the association constants for pyridine coordination are similar, the uptake of 4a and 4b from equimolar solutions into the PVP brushes (at constant grafting density and molecular weight) is effectively equivalent, producing samples with comparable structure (number and placement of cross-links). 

JV-Nitraminopyridines are reducible both in acid and alkali. In hydrochloric acid the main product from 2-nitraminopyridine was the hydrazino-pyridine, formed in a six-electron reduction, but 2-aminopyridine and 2-chloropyridine were side products, the latter possibly through reaction by an intermediate diazonium compound with chloride. Contrary to nitramines of most primary amines, 2-nitraminopyridine431 is reducible in alkaline solution uptake of the first two electrons forms the 2-pyridyl-N-nitrosamine, which is further reduced to 2-aminopyridine. 

Fig. 1.—Effect105 of Temperature on Uptake of Sulfur, Chlorine, and Nitrogen by Cuprammonium Rayon (on Tosylation in Presence of Pyridine during Four Days). (Taken from K. Hess and N. Ljubitsch, Ann., 507, 62 (1933).)...

Knoth et al. [48] studied the electrochemical behavior of omeprazole with the aid of the direct-current and differential-pulse polarography. Omeprazole was determined in Britton-Robinson buffers pH 7-9 up to a concentration of 10 5 M. The mechanism of the reduction process on the dropping mercury electrode is elucidated. With the consumption of two electrons and two protons, omeprazole will be reduced to 5-methoxy-2-[(3,5-dimethyl-4-methoxypyridin-2-yl)methylthio]-lH-benzimidazole which will be cleaved with the uptake of two further electrons and two protons into 4-methoxy-2,3,5-trimethyl pyridine and 2-mercapto-5-methoxybenz imidazole. 

The four-electron reduction of derivatives of 3-methoxypicolinic acid may follow different routes, depending on the substitution in the ester or amide. Amides may, after uptake of two electrons, lose an amino or a hydroxyl group, and then be further reduced to a pyridinemethanol or an aminomethylpyridine, or the compound may be reduced in the pyridine ring steric crowding favors the formation of aminomethylpyridines or tetra-hydropyridines [452]. 

Although it does not act as selectively as the Pd catalysts, finely divided Ni is sometimes useful for reduction of isolated triple bonds, especially in the presence of nitrogenous bases such as pyridine, ammonia, or piperidine. The heterogeneous catalyst NaH/RONa/Ni(OAc)2 presents practical advantages it is cheap, easily and reproducibly prepared, and can be stored for long periods. By monitoring the uptake of Hj, selective reduction of alkyne to alkene and then to alkane is achieved, particularly in the presence of quinoline. Only mild conditions are required to reduce disubstituted or terminal alkynes to cis-alkenes in high yields ... 

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