Pyridine-formic acid

SIS 1 silica stationary phase, eluent ethyl acetate-formic acid-water (6 1 1, v/v) S1S2 silica stationary phase, eluent toluene-ethyl formate-formic acid (4 4 1, v/v) S1S3 C18 stationary phase, eluent methanol-water-acetic acid (25 25 3, v/v) S1S4 silica stationary phase, eluent toluene-pyridine-formic acid (100 20 7, v/v) S1S5 cellulose stationary phase, eluent acetic acid-water (1 1, v/v) S1S6 C18 stationary phase, eluent methanol-water-acetic acid (78 25 3, v/v). Reprinted with permission from A. Pieroni et al. [124]. 

A few common volative buffer mixtures, along with their respective pH range are pyridine-formic acid (2.3-3.5) trimethylamine-formic acid (or acetic acid) (3.0-6.0) triethanolamine-HCl (6.8-8.8) ammonia-formic acid (or acetic acid) (7.0-10.0). See Buffers... 

Figure 18.4. Separation and quantification of cationic As species by HPLC-ICP-MS using a Supelcosil LC-SCX cation exchange column, 20 mM pyridine-formic acid, 1.5 mL min-1, 40°C. (a) pH 2.6 and (b) pH 2.2.

The dicarboxymethyl derivative has been characterized in electrophoretic and chromatographic systems, and all three derivatives were separated by ion exchange chromatography in pyridine-formic acid buffer at pH 3.25 (Banaszak and Gurd 1964). 

Mobile phase Gradient. Pyridine formic acid n-propanol water from 8 8 0 84 to 8 8 40 44 over 1 h. 

PHYSICOCHEMICAL STUDY OF PYRIDINE-FORMIC ACID SYSTEM. 

Methyl ethyl ketone-2-methyl-pyridine-formic acid-water,... 

Pungent odour. Formic acid, acetic acid, acetyl chloride, acetic anhydride, benzoyl chloride, benzyl chloride, pyridine. Benzoquinone (when warmed with water). 

The desired pyridylamine was obtained in 69 % overall yield by monomethylation of 2-(aminomethyl)pyridine following a literature procedure (Scheme 4.14). First amine 4.48 was converted into formamide 4.49, through reaction with the in situ prepared mixed anhydride of acetic acid and formic acid. Reduction of 4.49 with borane dimethyl sulfide complex produced diamine 4.50. This compound could be used successfully in the Mannich reaction with 4.39, affording crude 4.51 in 92 % yield (Scheme 4.15). Analogous to 4.44, 4.51 also coordinates to copper(II) in water, as indicated by a shift of the UV-absorption maximum from 296 nm to 308 nm. 

Although less common, azeotropic mixtures are known which have higher boiling points than their components. These include water with most of the mineral acids (hydrofluoric, hydrochloric, hydrobromic, perchloric, nitric and sulfuric) and formic acid. Other examples are acetic acid-pyridine, acetone-chloroform, aniline-phenol, and chloroform-methyl acetate. 

Dihydro- and 1,4-dihydro derivatives are formed as intermediates in the reduction of quaternary pyridine salts and their homologues with sodium borohydride or formic acid. A proton is added to the present enamine grouping and the formed immonium salts are reduced to the l-methyl-l,2,5,6-tetrahydropyridine derivatives (157) and to completely saturated compounds (158) (254) (Scheme 14). 

The scope of this reaction is similar to that of 10-21. Though anhydrides are somewhat less reactive than acyl halides, they are often used to prepare carboxylic esters. Acids, Lewis acids, and bases are often used as catalysts—most often, pyridine. Catalysis by pyridine is of the nucleophilic type (see 10-9). 4-(A,A-Dimethylamino)pyridine is a better catalyst than pyridine and can be used in cases where pyridine fails. " Nonbasic catalysts are cobalt(II) chloride " and TaCls—Si02. " Formic anhydride is not a stable compound but esters of formic acid can be prepared by treating alcohols " or phenols " with acetic-formic anhydride. Cyclic anhydrides give monoesterified dicarboxylic acids, for example,... 

Fig. 4.1. Potential ranges of solvents, (a) h.n.p.s of acids. I, Acetic acid II, benzoic acid III, formic acid IV, salicylic acid V, sulphuric acid VI, p-toluenesulphonic acid, (b) h.n.p.s of conjugate acids of I, n-butylamine II, piperidine III, ethylenediamine (1) IV, ammonia V, ethylenediamine (2) VI, pyridine.

---