Nicotinic acid solution

Z. Orekhova, M. Ben-Hamo, E. Manzurola and A. Apelblat, Electrical conductance and volumetric studies in aqueous solutions of nicotinic acid, /. Solution Chem., 2005, 34(6), 687-700. 

At the far-UV end of the spectrum (200-300 nm), nicotinic acid solution in the 0-24mgl range provides a suitable stable reference (Figure 4). 

Figure 4 Absorption spectra produced by a series of acidic nicotinic acid solutions, provided as sealed cell certified reference materials. Measured relative to a solvent blank, at the sample position, in a high-performance reference commercial spectrophotometer.

The total volume of solution is 50 mL (25 mL NaOH solution plus 25 mL of nicotinic acid solution, assuming there is no change in volume on mixing). Dividing the molar amount of nicotinate ion by the volume of solution in Uters gives the molar concentration of nicotinate ion. 

Method 1. Reflux a mixture of pure nicotinic acid (Section V,22), 84 g. (105 ml.) of absolute ethanol and 90 g. (50 ml.) of concentrated sulphuric acid in a flask for 4 hours on a steam bath. Cool the solution and pour it slowly and with stirring on to 200 g. of crushed ice. Add sufficient ammonia solution to render the resulting solution strongly alkaline generally, some ester separates as an oil but most of it remains dissolved in the alkaline solution. Extract the solution with five 25 ml. portions of ether, dry the combined ethereal extracts with anhydrous magnesium sulphate, remove the ether and distil under reduced pressure. The ethyl nicotinate passes over at 117-118°/ 6 mm. the yield is 34 g. The b.p. under normal pressure is 222-224°. 

To a solution of 93.8 g of the monoglycol ester in 500 ml of benzene, there are added 55 g of nicotinic acid chloride and 25 g of trimethylemine dissolved in 200 ml of benzene. The solution is stirred gently at a temperature of 60°C for two hours. After this time, the solution is cooled and washed successively with water, dilute hydrochloric acid, dilute ammonia and water until neutrality, it is dried over anhydrous sodium sulfate, and the sol vent Is evaporated under vacuum In this wey llOg of glycol 2-(p-chlorophenoxy)-2-methylpropionate nico-tlnate Is prepared, which represents a yield of 84%. The product is a sllghly yellow oil having a refraction index of no = 1.5422 and which is distilled with decomposition et 214°C at a pressure of 0.3 mm. 

For purpose of purification, the hot alcoholic solution is mixed with 975 parts by weight of nicotinic acid while being stirred and heated until the nicotinic acid is completely dissolved. 

Nicotinic acid, HC6H402N (JCa = 1.4 X 1CT5) is another name for niacin, an important member of the vitamin B group. Determine [H+] in a solution prepared by dissolving 3.0 g of nicotinic acid (MM = 123.11 g/mol), HNic, in enough water to form 245 mL of solution. 

Nicotinamide and nicotinic acid are both white crystalline substances. Their aqueous solution has a maximal UV absorbance at 263 nm. Both vitamers have the same biological activity as they can be converted into each other. Figure 2 shows the structure of the coenzyme forms NAD+ and NADP+. 

Reviewed here are surface electrochemical studies of organic molecules adsorbed at well-defined Pt(lll) electrode surfaces from aqueous solution. Emphasis is placed upon studies of nicotinic acid (NA), pyridine (PYR), and nine related pyridine carboxylic acids. 

Nicotinic acid and related meta-carboxylic acids display the remarkable characteristic that coordination of the pendant carboxylic acid moieties to the Pt surface is controlled by electrode potential. Oxidative coordination of the carboxylate pendant occurs at positive electrode potentials, resulting in disappearance of the 0-H vibration and loss of surface acidity as judged by absence of reactivity towards KOH. Carboxylate in the 4-position of pyridine (as in INA) is virtually independent of electrode potential, whereas strong coordination of ortho-carboxylates to the Pt surface is present at most electrode potentials. Adsorbed pyridine carboxylic acids are stable in vacuum when returned to solution the adsorbed material displays the same chemical and electrochemical properties as prior to evacuation. 

G9. Gydell, K., Hyperbilirubinemia and hypersideremia following intravenous injection of stored blood, nicotinic acid and hemoglobin solution. Acta Med. Scand. 166, 433 (1960). 

The B-group vitamin, nicotinic acid (259), was irradiated with low-intensity light at 254 nm. In aqueous solution without buffer, the bi-aryl (260) was obtained, presumably via decarboxylation to give the pyridyl anion which would attack position 6 of nicotinic acid. In aqueous acid, the substrate was photo-hydroxylated to give 2-hydroxynicotinic acid (40%). Clearly, only the cationic form was sufficiently activated for position 2 to be attacked by the solvent. Nicotinamide under the same conditions was also converted to the 2-hydroxy derivative, but the reaction was slower [161]. 

Prepare a solution of 5 m 3-cyanopyridine (320 mL) to be used as substrate for nicotinic acid preparation in 0.1 m potassium phosphate buffer pH 8.0. 

Keep the solution overnight at 0 °C and allow the nicotinic acid crystals to settle down to the bottom of the container. Separate the crystals and dissolve in distilled water, adjust the pH to 4—5 and cool to 0-4 °C. Decant the liquid and dry the crystals in vacuum evaporator or at 50 °C in an oven (90% yield). 

Stock solution 4. 100 x stock solution of vitamins was prepared by dissolving biotin (20 mg), folic acid (20 mg), pyrodoxine hydrochloride (100 mg), riboflavin (50 mg), thiamine hydrochloride (50 mg), nicotinic acid (50 mg), pantothenic acid (50 mg), vitamin B12 (1 mg), 4-aminobenzoic acid (50 mg) and thioctic acid (50 mg) in deionized water. The volume was adjusted to 1.0 L. The solution was filtered, sterilized and stored as 10 mL aliquots at —20 °C. 

Adsorbate Molecular Orientation at Electrode Surface. Adsorption of some molecules from solution produces an oriented adsorbed layer. For example, nicotinic acid (NA, or 3-pyridinecarboxylic acid, niacin, or vitamin B3) is attached to a Pt(lll) surface primarily or even exclusively through the N atom with the ring in a (nearly) vertical orientation (12) (Fig. 10.5a). 

Aldehydes are obtained in 86% and 75% yields, respectively, from benzoic acid on refluxing for 6 hours and from nicotinic acid on standing at room temperature for 24 hours with bis(N-methylpiperazino)alane in tetrahydro-furan [963]. Reduction of 3-fluorosalicylic acid with 2% sodium amalgam in aqueous solution containing sodium chloride, boric acid and p-toluidine gave, at 13-15°, a Schiff base which on hydrolysis with hydrochloric acid and steam distillation afforded 3-fluorosalicylaldehyde in 57% yield [136. The purpose of p-toluidine is to react with the aldehyde as it is formed and protect it from further reduction. 

A number of syntheses of substituted 2,3 -bipyridines are worthy of note. Tetracyclone heated at 215°C with nicotinonitrile affords 3,4,5,6-tetraphenyl-2,3 -bipyridine, whereas 3,4-di(2-pyridyl)pyridine is obtained by an oxidative degradation of the corresponding 6,7-disubstituted thiazolo[3,2-a]-pyridinium salt. Nicotinic acid on UV irradiation in aqueous solution at pH 4-6 gives 2,3 -bipyridine-5-carboxylic acid, whereas irradiation of picolinic acid in the same pH range in the absence of metal ions gives some 2,3 -bipyridine. 6,6 -Diphenyl-2,3 -bipyridine is thought to be formed from... 

After the evaporation of most of the liquid, the nicotinic acid nitrate from two runs is transferred to a 1.5-I. beaker, 400 cc. of distilled water is added (Note 4) and the mixture is heated unlil complete solution results. On cooling, the nicotinic acid nitrate separates as yellow granular crystals and is... 

Niacin is one of the more stable water-soluble vitamins. Both nicotinic acid and nicotinamide are stable in air at ambient temperature (93,96). Aqueous solutions of nicotinic acid or nicotinamide can be autoclaved for short periods, e.g., 10 minutes at 120°C, without degradation. Nicotinic acid s stability in solution is independent of pH, but nicotinamide is stable only at neutral pH. Heating nicotinamide in 1 N acid or alkali at 100°C will induce its conversion to nicotinic acid. 

The availability of commercial bench-top mass spectrometry detectors for HPLC is facilitating the development of HPLC-MS methods for many analytes. This is more common in pharmaceutical than food applications. As is generally the case, mass spectrometry is first being applied to standard solutions and relatively simple samples before being applied to more complex food matrices. A standard mixture of ten vitamers, AA, DHAA, PN, PL, PM, thiamine, nicotinic acid, nicotinamide, pantothenic acid and biotin, were recently determined by HPLC-particle beam... 

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