2- Picoline VOLUME

If much liquid ammonia is lost during the preparation of the sodamide, the volume should be m e up to 500-600 ml. before adding the y picoline. 

The standard synthesis method features side-chain chlorination of a methylpyridine (picoline), followed by exchange-fluoriaation with hydrogen fluoride or antimony fluorides (432,433). The fluoriaation of pyridinecarboxyHc acids by sulfur tetrafluoride (434) or molybdenum hexafluoride (435) is of limited value for high volume production operations due to high cost of fluorinating agent. 

The relative production volumes of pyridine compounds can be ranked in the following order pyridine (1) > P-picoline (3) > a-picoline (2)> niacin (27) or niacinamide (26)> 2-vinylpyridine (23)> piperidine (18). U.S. and Japanese production was consumed internally as well as being exported, mainly to Europe. European production is mosdy consumed internally. Growth in production of total pyridine bases is expected to be small through the year 2000. 

The separation of mixtures involving N-methyl-JLtetrahydropyridines into their pure components by means of gas-liquid chromatography was discussed in a report by Holik et al. (87). They found that, using tris(/3-cyanoethoxymethyl)-y-picoline as the stationary phase, the primary factors involved in the specific retention volumes of these enamines is the electronic effect of a methyl substituent and the nitrogen atom on the carbon-carbon double bond. It was observed that 1,3-dimethyl-Zl -tetrahydropyridine (141) has a smaller specific retention volume and, hence, is eluted before... 

Isothermal a—time curves for the decomposition at 363—464 K of the pseudo octahedral compounds NiL2(NCS)2 (L = py, 3-picoline or quinoline) to NiL(NCS)2 and volatilized L, obeyed the contracting volume equation [eqn. (7), n = 3]. E values decreased in the sequence L = py > 3-picoline > quinoline and this order was ascribed to the effect of increasing ligand volumes [1128]. 

Synthetic Methods of Manufacture. Due to rising demand, production of the pyridine bases by large-scale synthesis passed the volume of tar bases extracted from coal tar in the 1960s. By the early 1970s. capacity in the United States for the synthetic manufacture of pyridine, the picolines, and 2-methyl-5-ethylpyridine (MEP) was in the tens of millions of pounds. All of these products can be made by condensation reactions of aldehydes and ammonia, MEP is no lunger made in the United Stales,... 

However, the zwitterion mechanism appears attractive for picolinic and related acids. The volumes of activation for decarboxylation of picolinic are large and positive. This is consistent with release of solvent in going to the transition state as is indicated in reaction (4) of the zwitterion mechanism. The rate data for the decarboxylation of quinaldinic acids fits attractively into the zwitterion mechanism. The ratio of rate coefficients for the decarboxylation of zwitteron ion (I) to that of quinaldinic acid (II) shows a minimum value of 57 in quinoline solvent at 145.8 The anion of quinaldinic acid shows no detectable decomposition in... 

Ring systems containing two heteroatoms tend to feature less in the vapor-phase literature. This is partly because of the greater reactivity (i. e. reduced aromaticity) of these heterocyclic compounds. In addition, there has been less commercial incentive to develop catalyzed processes for these smaller-volume niche products. As an example, both pyrimidine (26) [51] and pyrazine (27) [52] can be made by catalyzed vapor-phase methods they can also be recovered from the pyri-dine- ff-picoline reaction. In principle, pyrimidine and pyrazine could then serve as platforms-much like pyridine does-for preparing a wide range of derivatives. The market for these derivatives is, however, best met by traditional convergent syntheses in the liquid phase. 

Preparation. This chromium complex is usually prepared by the reaction of benzene with chromium hexacarbonyl under high pressure. Rausch has recently published a simple synthesis based on a patent procedure in which equi-volume amounts of benzene and 2-picoline are refluxed for an extended period under nitrogen. Carbon monoxide is evolved, and little sublimation of chromium hexacarbonyl occurs. Yields are 90-94% for reactions conducted for 96 hr. or more. The method is presumably successful because of formation of the 2-picoline complex (A), which reacts with benzene to form (1). 

Cupric acetate and dil. HCl added to an aq. suspension of ethyl N-(a-picolinoyl)-glycylalaninate, allowed to stand 2hrs. at room temp, with occasional shaking, coned, to half its volume, and the precipitated picolinic acid Cu(II)-complex removed by filtration crude glycylalanine. Y 75%. - Also quinoline-a-carboxylic acids form stable Cu(II)-complexes. F. e. s. A. K. Koul et al., Synth. Commun. 2, 383 (1972) anthranilyl as protective group cf. Tetrahedron 29, 625 (1973). 

CHaCOCeHs 2 equivalents of 3-picoline in an equal volume of benzene added at 5° to 2 equivalents of a suspension of Na-diisopropyl-amide in benzene, stirred 30 min. at 5°, 1 equivalent of ethyl benzoate in an equal volume of benzene added, and stirred an additional hr. at 5° 3-phenacylpyridine. Y 78%.—Similarly, alkyl 3-picolyl ketones have been prepared, for the first time. F. e., also with other pyridine derivatives... 

Activation and reaction volumes (Table 8.4) and pressure dependences of quantum yields for isomerization and substitution reactions of cis- and frani-[Rh(NH3)4XY]", with X and Y variously from Cl, Br, OH2, are, as for [Rh(NH3)5X] complexes (Table 8.3), consistent with dissociative activation. The excited state is square-pyramidal [Rh(NH3)4X]" with X apical. Quantum yields have been determined for (stereoretentive) photoaquation of a series of complexes trans-[RhL4Cl2], where L = a heterocyclic amine, such as pyrazine (8) or a picoline. The relative quantum yields for chloride loss and for heterocyclic ligand (L) loss vary with the nature of L, with, a marked correlation with ligand pKa values. Relatively little of the aquation goes by chloride loss here, in contrast to ammine analogues. ... 

FIGURE 21 Separation of meta ions by ion chromatography. (A) Aikaii metais using Ion-200 cation exchange column eluent 2.0 mM picolinic acid, pH 2.0 flow rate 2.6 ml/min sample volume 5 ij, 2-6 ppm each ion conductivity detection. (B) Inorganic anions using Ion-100 anion exchange column 1.5 mM phthalate, pH 5.0 flow rate, 1.5 ml/min sample volume 10 jtd 30-80 ppm each ion conductivity detection. [Reprinted with permission from Interactions Chemicals, Inc.]... 

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