Of 4-methylpyridine

Problem 18.31 Outline the reactions and reagents used to establish the structure of 4-methylpyridine by exhaustive methylation and Hofmann elimination. ... 

Products of 4-methylpyridine and ethoxymethylene cyanoacetate in various ring closure reactions were first described by Antaki,29 but the correct structures (86 R = COOEt, R1 = 4-Me, R2 = H and 87 R1 = 8-Me, R2 = H, X = O) became apparent from the work of Nishigaki eta/.154 and Seidel.28... 

Figure 7.25. Crystal structure of 4-methylpyridine at 4 K. (From Fillaux and Carlile [1990].)...

Boron trihalide adducts of 4-methylpyridine show halogen exchange behavior similar to that of the adducts of trimethylamine 10), and isolation of individual mixed-halogen species is feasible here too. The stability of nitrogen-donor adducts of the mixed boron trihalides parallels the stability of nitrogen-donor adducts of BH2X and BHX2 which have been more extensively studied 19, 153,156). 

The relative rate of alkenylation of 4-alkylpyridines with either butadiene or isoprene is about 8 to 20 times greater than that of 4-methylpyridine, and therefore the alkenylation of 4-methylpyridine is always accompanied by dialkenylation (31). 

Abbreviations used pop, dianion of pyrophosphite (P20,.iH2 ) pep, dianion of /u.-methylenebis(phosphite) im, anion of imidazole 4-mpyt, anion of 4-methylpyridine-2-thioI pyt, anion of pyridine-2-thiol pyms, anion of pyrimidine-2-thione bttz, anion of l,3-benzothiazole-2-thiol form, anion of di-p-tolylformamidine dpb, N,W -diphenylben-zamidine mhp, anion of 6-methyl-2-hydroxypyridine chp, 6-chloro-2-hydroxypyridine and dpt, 1,3-diphenyltriazen. 

Ooi and co-workers adopted an elegant synthetic approach to the mixed-metal complexes of 4-methylpyridine-2-thiolate (4-mpyt). This approach includes the initial preparation of mononuclear complexes [M(4-mpytH)4]Cl2 (M = Pt, Pd), in which all four 4-mpytH ligands coordinate to with sulfur-donor atoms (84,102). The structure of the mononuclear Pd(II) complex with nonsubstituted pyridine-2-thiolate, [Pd(pytH)4]Cl2, is shown in Fig. 16 (84). These mononuclear complexes can be further reacted with the second metal ion to give mixed-metal dinuclear complexes. 

The equilibrium constant for formation of 4-methylpyridine and 4-nitrophenyl acetate from acetyl 4-methylpyridinium ion and... 

These equilibrium equations were used to describe the adsorption properties of 4-methylpyridine on Hg at the potential of zero charge. For simplicity we have assumed a negligible effect from the short-range interactions and the in-plane field. That is, we have adopted the approximations ... 

Fig. 7 shows experimental and calculated adsorption isotherms for 4-methylpyridine adsorption on Hg. Data were taken from [57,58]. The surface concentration of 4-methylpyridine was calculated from ... 

The molecular parameters used in the calculations are those obtained in [17] from the field dependence of the adsorption of 4-methylpyridine. It is seen that the theoretically calculated data are in good agreement with the corresponding experimental data, indicating the validity of the model under consideration. In this case we can use the model to obtain a more detailed picture of the structure of the adsorbed layer. For example, whereas the experimental data give no information about the two states of 4-methylpyridine on Hg [57], this information can be taken from the predictions of the model. This is done in Fig. 7, where the dependence of the partial surface concentration of the two adsorbate states upon the bulk activity of 4-methylpyridine is depicted. 

F. Fillaux, C.J. Carlile G.J. Kearley (1993). Mol. Phys., 80, 671-683. Rotational tunnelling and the rotational potential of CH3-groups in the zinc, manganese and cobalt chloride salts of 4-methylpyridine. 

High selectivity was also reported for the ammoxidation of 4-methylpyridine, e. g. over vanadium-molybdenum oxides [90] highly dispersed vanadia on sili-cated alumina [91] or on vanadium-containing molecular sieves (VSAPO, VAPO [92], also used for the ammoxidation of 3-methylpyridine [93,94]). The ammoxidation of 2-methylpyridine leads to the formation of large amounts of pyridine, by total oxidation of the methyl group and subsequent decarboxylation, in addition to the desired nitrile [95]. Yields in excess of 90% can, nevertheless, be achieved, e. g. over vanadium-tin oxide at ca 670 K [23] or over molybdenum phosphates [96]. When the ammoxidation of 2-, 3- and 4-methylpyridine over vanadium phosphates was compared catalyst activity and the nitrile selectivity reflected the reactivity order 4- > 3- > 2-methylpyridine, probably as a result of different sterie hindranee [41]. 

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