PYRIDINE

CASRN: 110-86-1; DOT: 1282; DOT label: Flammable liquid; molecular formula: C5H5N; FW: 79.10; RTECS: UR8400000; Merck Index: 12, 8153 Physical state, color, and odor: Clear, colorless to pale yellow, flammable liquid with a sharp, penetrating, nauseating fish-like odor. Odor threshold concentrations in water and air were 2 ppm (Buttery et al., 1988) and 21 ppbv (Leonardos et al., 1969), respectively. Detection odor threshold concentrations of 0.74 mg/m3 (2.3 ppmv) and 6 mg/m3 (1.9 ppmv) were experimentally determined by Katz and Talbert (1930) and Dravnieks (1974), respectively. Cometto-Muñiz and Cain (1990) reported an average nasal pungency threshold concentration of 1,275 ppmv. Melting point (°C): -42 (Weast, 1986) Boiling point (°C): 115.25 (Riddick et al., 1986) 115.5 (Weast, 1986) Density (g/cm3): 0.9819 at 20 °C (Weast, 1986) 0.9776 at 25 °C (Jones and Speakman, 1921) Diffusivity in water (x 10-5 cm2/sec): 0.602 (ceff = 60 µM) at 4.0 °C; 1.125 (ceff = 60 µM), 1.951 (ceff = 60 µM), 1.117 (ceff = 120 µM),

and 1.154 (ceff = 310 µM) at 25.0 °C; 1.951 (ceff = 60 µM) at 50.0 °C (Niesner and Heintz, 2000) Dissociation constant, pKa: 5.21 at 25 °C (Gordon and Ford, 1972) Flash point (°C): 20 (NIOSH, 1997) Lower explosive limit (%): 1.8 (NIOSH, 1997) Upper explosive limit (%): 12.4 (NIOSH, 1997) Entropy of fusion (cal/mol⋅K): 8.554 (Parks et al., 1936) Heat of fusion (kcal/mol): 1.977 (Parks et al., 1936)

12 at 25 °C (Hawthorne et al., 1985) 8.83 at 25 °C (Andon et al., 1954) 14.0 at 25 °C (Amoore and Buttery, 1978) 10.0 at 25 °C (static headspace-GC, Welke et al., 1998) 361, 413, 349, 263, and 210 at 2.0, 6.0, 10.0, 18.0, and 25.0 °C, respectively (EPICS-SPME,

Dewulf et al., 1999) 18.4 at 30 °C (headspace-GC, Chaintreau et al., 1995) Ionization potential (eV): 9.32 (Franklin et al., 1969) 9.26 (Lias, 1998) Soil organic carbon/water partition coefficient, log Koc: Unavailable because experimental methods for estimation of this parameter for pyridines are lacking in the documented literature. However, its miscibility in water and low Kow suggest its adsorption to soil will be nominal (Lyman et al., 1982). Octanol/water partition coefficient, log Kow: 0.65 (quoted, Leo et al., 1971) 0.63, 0.68, 0.72 (RP-HPLC, Garst and Wilson, 1984) 0.66 (Mirrlees et al., 1976) 0.70 (Berthod et al., 1988) 1.28 (estimated from HPLC capacity factors, Eadsforth, 1986) Solubility in organics: Soluble in acetone, alcohol, benzene, and ether (Weast, 1986). Miscible with alcohol, ether, petroleum ether, oils, and many other organic liquids (Windholz et al., 1983). Solubility in water: Miscible (Fischer and Ehrenberg, 1948; Amoore and Buttery, 1978; Stephenson, 1993a). A saturated solution in equilibrium with its own vapor had a concentration of 233.4 g/L at 25 °C (Kamlet et al., 1987). Vapor density: 3.23 g/L at 25 °C, 2.73 (air = 1) Vapor pressure (mmHg): 18 at 20 °C (NIOSH, 1987) 14 at 20 °C, 20 at 25 °C, 26 at 30 °C (quoted, Verschueren, 1983) Environmental fate: Biological. Heukelekian and Rand (1955) reported a 5-d BOD value of 1.31 g/g which is 58.7% of the ThOD value of 2.23 g/g. A Nocardia sp. isolated from soil was capable of transforming pyridine, in the presence of semicarbazide, into an intermediate product identified as succinic acid semialdehyde (Shukla and Kaul, 1986). 1,4-Dihydropyridine, glutaric dialdehyde, glutaric acid semialdehyde, and glutaric acid were identified as intermediate products when pyridine was degraded by Nocardia strain Z1 (Watson and Cain, 1975). Photolytic. Irradiation of an aqueous solution at 50 °C for 24 h resulted in a 23.06% yield of carbon dioxide (Knoevenagel and Himmelreich, 1976). A rate constant of 4.9 x 10-13 cm3/molecule⋅sec was reported for the reaction of pyridine and OH

The titanium-mediated photocatalytic oxidation of a pyridine solution was conducted by Low et al. (1991). They proposed that the reaction of OH radicals with pyridine was initiated by the addition of a OH radical forming the 3-hydro-3-hydroxypyridine radical followed by rapid addition of oxygen forming 2,3-dihydro-2-peroxy-3-hydroxypyridine radical. This was followed by the opening of the ring to give N-(formylimino)-2-butenal which decomposes to a dialdehyde and formamide. The dialdehyde is oxidized by OH radicals yielding carbon dioxide and water. Formamide is unstable in water and decomposes to ammonia and formic acid. Final products also included ammonium, carbonate, and nitrate ions. Chemical/Physical. The gas-phase reaction of ozone with pyridine in synthetic air at 23 °C yielded a nitrated salt having the formula: [C6H5NH]+NO3-(Atkinson et al., 1987). Ozonation of pyridine in aqueous solutions at 25 °C was studied with and without the addition of tert-butyl alcohol (20 mM) as a radical scavenger. With tert-butyl alcohol, ozonation of pyridine yielded mainly pyridine N-oxide (80% yield), which was very stable towards ozone. Without tert-butyl alcohol, the heterocyclic ring is rapidly cleaved forming ammonia, nitrate, and the amidic compound N-formyl oxamic acid (Andreozzi et al., 1991). Forms water-soluble salts with strong acids. Pyridine will not hydrolyze because it does not contain a hydrolyzable functional group (Kollig, 1993). At an influent concentration of 1,000 mg/L, treatment with GAC resulted in an effluent concentration of 527 mg/L. The adsorbability of the carbon used was 95 mg/g carbon (Guisti et al., 1974). Exposure limits: NIOSH REL: TWA 5 ppm (15 mg/m3), IDLH 1,000 ppm; OSHA PEL: TWA 5 ppm; ACGIH TLV: TWA 5 ppm (adopted). Symptoms of exposure: Headache, dizziness, nervousness, nausea, insomnia, frequent urination, and abdominal pain (Patnaik, 1992). An irritation concentration of 90.00 mg/m3 in air was reported by Ruth (1986). Toxicity: EC50 (48-h) and EC50 (24-h) values for Spirostomum ambiguum were 989 and 1,226 mg/L, respectively (Nałecz-Jawecki and Sawicki, 1999). LC50 (48-h) and LC50 (24-h) values for Spirostomum ambiguum were 2,547 and 3,117 mg/L, respectively (Nałecz-Jawecki and Sawicki, 1999). LC50 for red killifish 9,330 mg/L (Yoshioka et al., 1986). Acute oral LD50 for mice 1,500 mg/kg, rats 891 mg/kg (quoted, RTECS, 1985). Source: Pyridine occurs naturally in potatoes, anabasis, henbane leaves, peppermint (0 to 1 ppb), tea leaves, and tobacco leaves (Duke, 1992). Identified as one of 140 volatile constituents in used soybean oils collected from a processing plant that fried various beef, chicken, and veal products (Takeoka et al., 1996). Uses: Organic synthesis (vitamins and drugs); analytical chemistry (cyanide analysis); solvent for anhydrous mineral salts; denaturant for alcohol; antifreeze mixtures; textile dyeing; waterproofing; fungicides; rubber chemicals.