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Piperidine is a clear, colorless liquid. Pepper, ammonia or amine odor.

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Piperidine occurs at low levels in a variety of food products (Neurath et al 1977), including baked ham (0.2 p.p.m.), milk (0.11 p.p.m.) coffee (1 p.p.m. dry) (Singer and Lijinsky 1976) and canned fish (Tanikawa and Motohiro 1960). It is also found in black pepper (Windholz 1983), hemp (Obata and Ishikawa 1960), hemlock (Cromwell 1956) and tobacco (Furia and Bellanca 1975). Piperidine is a natural constituent of skin (Sax and Lewis 1987), human urine (Von Euler 1944), brain (Honegger and Honegger 1960) and cerebrospinal fluid (Perry et al 1964). Humans excrete about 3-20 mg/d in the urine (Reinhardt and Britelli 1981).

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Piperidine is an organic heterocyclic amine widely used as building block and reagent in the synthesis of organic compounds including pharmaceuticals.

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The secondary amine piperidine is highly reactive and is therefore frequently employed as an intermediate for pharmaceuticals and for plant protection agents. It is also used as a vulcanization accelerator in rubber manufacture and as an oil or fuel additive. Piperidine and, in many cases, piperidine acetate are useful catalysts for condensation reactions, e.g., the Knoevenagel reaction, aldol condensation, and the condensation of a nitroparaffin with an aldehyde. However, for the last of these reactions, diethylamine is the preferred catalyst. The use of piperidine is particularly advisable where the reactants or products are unstable in the presence of stronger bases.

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Piperidine is usually prepared by the electrolytic reduction of pyridine. It may also be obtained by heating piperidine with alcoholic KOH or by the cyclization of 1,5-diaminopentane hydrochloride (Windholz 1983). U.S. production in 1983 was approximately 606,000 pounds (HSDB 1988). Commercial piperidine is supplied in two grades, 95 and 98 percent pure (Sax and Lewis 1987).

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Usually prepared by electrolytic reduction of pyridine.

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piperidine: A saturated heterocycliccompound having a nitrogen atom ina six-membered ring, C₅H₁₁N; r.d.0.86; m.p. –7°C; b.p. 106°C. The structureis present in many alkaloids

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A clear colorless liquid with a pepper-like odor. Less dense than water, but miscible in water. Will float on water. Flash point 37°F. Melting point -15.8°F (-9°C). Boiling point 222.8°F (106°C). May severely irritate skin and eyes. May be toxic by ingestion and inhalation. Vapors heavier than air. Used to make rubber and as a solvent.

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Highly flammable. Miscible in water.

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1-Oxa-4-azacyclohexane neutralizes acids in exothermic reactions to form salts plus water. May be incompatible with isocyanates, halogenated organics, peroxides, phenols (acidic), epoxides, anhydrides, and acid halides. Flammable gaseous hydrogen may be generated in combination with strong reducing agents, such as hydrides.

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An irritation threshold of 26 p.p.m. has been reported from studies on human volunteers (Bazarova and Migukina 1975). Levels of 2 to 5 p.p.m. in air have been recorded during the transfer of piperidine from drums in a semi-closed system. At this level, the vapors were intolerable but no irritation was observed (ANON 1982). In an accidental case of skin exposure, third-degree burns developed after only 3 min of skin contact (Linch 1965). Piperidine has a pronounced emetic effect in humans. When administered to schizophrenic patients at doses of 1 to 6 g/d, it was shown to cause nausea and a subjective sense of well being (Giacobini 1976; Tasher et al 1960). The primary, but low-level, means of human exposure, however, is from the natural piperidine content of foods (HSDB 1988).

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1-Oxa-4-azacyclohexane evolves explosive concentrations of vapor at normal room temperatures. When heated to decomposition, 1-Oxa-4-azacyclohexane emits highly toxic fumes of nitrogen oxides. Dangerous, when exposed to heat, flame, or oxidizers. Avoid 1-Perchloryl1-Oxa-4-azacyclohexane and oxidizing materials. 1-Oxa-4-azacyclohexane is a reactive compound and forms complexes with the salts of heavy metals. 1-Oxa-4-azacyclohexane evolves explosive concentrations of vapor at normal room temperatures. Keep away from igniting sources and heat.

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Piperidine is used as a solvent, a curing agent for rubber and epoxy resins, a catalyst in silicone esters, an intermediate in organic synthesis and as a complexing agent (HSDB 1988; Reinhardt and Britelli 1981). It is a trace constituent in oils and fuels (Sax and Lewis 1987). It is used in the manufacture of local anesthetics, analgesics and other pharmaceuticals, and also for wetting agents and germicides (Gehring 1983). It is also used as a flavor additive in soups, meats, condiments, baked goods, candy and non-alcoholic beverages at 0.05-5.0 p.p.m. (Furia and Bellanca 1975).

Safety Profile

Poison by ingestion, skin contact, and intraperitoneal routes. Moderately toxic by subcutaneous route. Mildly toxic by inhalation. An experimental teratogen. Experimental reproductive effects by inhalation. A skin irritant. Mutation data reported. A very dangerous fire hazard when exposed to heat, flame, or oxidizers. Can react vigorously with oxidzing materials. To fight fire, use alcohol foam, CO2, dry chemical. Explodes on contact with 1- perchloryl-piperidme, dqanofurazan, N- nitrosoacetadde. When heated to decomposition it emits highly toxic fumes of NOx. Used in agriculture and pharmaceuticals, and as an intermediate for rubber accelerators. Used in production of drugs of abuse.

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Piperidine is used in agriculture and pharmaceuticals; intermediate for rubber accelerators; as a solvent; as a curing agent for rubber and epoxy resins; catalyst for condensation reactions; as an ingredient in oils and fuels; complexing agent; manufacture of local anesthetics; in analgesics; pharmaceuticals, wetting agents; and germicides; synthetic flavoring. Not registered as a pesticide in the Unied States.

Carcinogenicity

No tumors were produced in rats given piperidine (0.09%) in drinking water for 1 year. Mice receiving 19 doses of 50 mg/kg by intraperitoneal injection within 61 weeks followed by an 18-week observation period showed no increase in cancer incidences (251). Piperidine and sodium nitrite given together also failed to produce tumors. The failure of this treatment was surprising because nitrosopiperidine induced a high incidence of lung and esophageal tumors. The authors suggest that the relative strong basicity of piperidine reduced the rate of reaction with nitrite to such an extent that an ineffective amount of nitrosopiperidine was formed. In mice that had cholesterol pellets containing piperidine implanted in their bladders and were given sodium nitrite in their drinking water, an increase in bladder cancers was produced. Piperidine given as a series of 24 injections in groups of mice failed to produce lung tumors in the strain A mouse cancer screen. When piperidine and sodium nitrite were incubated in the isolated rat urinary bladder, nitrosopiperidine was detected in the bladder contents. No studies designed to evaluate the carcinogenic potential of piperidine alone following lifetime exposures have been reported.

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Piperidine is readily absorbed through the gastrointestinal tract, skin and lungs (HSDB 1988). In hens, 35 to 70% of an injected dose is rapidly excreted unchanged in the urine (Williams 1959; Sperber 1949). Rabbits also excrete piperidine unchanged (Hildebrandt 1900). When injected intraventricularly into rats, piperidine disappeared exponentially with a half-life of 20 min (Meek 1973). In a more recent study, Okano et al (1978) found that in rats most of an i.p. dose of [3H]-piperidine was excreted unchanged. Two major metabolites were identified as 3- and 4-hydroxypiperidine. Both compounds were also found in untreated animals and thus are probably metabolites of piperidine of exogenous or endogenous origin. These metabolites represent a detoxification mechanism, since they lack the potent pharmacological activities of the parent compound. Two unidentified metabolites were assumed to be conjugates. In a much earlier study, Novello et al (1926) claimed that piperidine was excreted as the ethereal sulfate. Metabolic studies of analgesics and anesthetics containing the piperidine ring have demonstrated the occurrence of N-hydroxylation, formation of a 6-oxo-derivative, and C-oxidative ring cleavage (Oelschlager and Al Shaik 1985). N-nitrosopiperidine has been synthesized from piperidine and sodium nitrite in the gastric contents,R.L. Reed isolated stomach and isolated small intestine of rats (Alam et al 1971; Epstein 1972).

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UN2401 Piperidine, Hazard Class: 8; Labels: 8-Corrosive material, 3-Flammable liquid.

Purification Methods

Dry piperidine with BaO, KOH, CaH2, or sodium, and fractionally distil (optionally from sodium, CaH2, or P2O5). Purify from pyridine by zone melting. [Beilstein 22 H 6, 22

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Piperidine is a highly flammable liquid. Vapor may form explosive mixture with air (at room temperature). A medium-strong base. Reacts violently with oxidizers (chlorates, nitrates, peroxides, permanganates, perchlorates, chlorine, bromine, fluorine, etc.); contact may cause fires or explosions. Keep away from alkaline materials, strong bases, strong acids, oxoacids, epoxides. Piperidine neutralizes acids in exothermic reactions to form salts plus water. May be incompatible with isocyanates, halogenated organics, peroxides, phenols (acidic), epoxides, anhydrides, and acid halides. Flammable gaseous hydrogen may be generated in combination with strong reducing agents, such as hydrides.

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