1-Methylpiperidine
1-Methylpiperidine is an organic chemical compound belonging to the group of cyclic compounds and tertiary amines. The compound serves as a starting material for organic syntheses and for the production of catalyst systems.
For the technical production of 1-methylpiperidine, 5-amino-1-pentanol is reacted with methanol at temperatures of 180–230 °C and pressures of 70–120 bar in the presence of copper oxide and sodium oxide catalysts, which are based on aluminum oxide supported on aluminum oxide.
The complete reaction occurs in the liquid phase in a continuous tube or tube bundle reactor. The catalyst is arranged as a fixed bed reactor, through which the reaction mixture can flow from either below or above. The product is purified by multistage distillation in fractionating columns.
Properties
1-Methylpiperidine has a relative density of 3.42 and a relative density of the vapor–air mixture of 1.10. The dynamic viscosity at 20 °C is 5 mPa·s.
Chemical properties
1-Methylpiperidine is a highly flammable, colorless liquid with an amine-like odor. The compound belongs to the class of cyclic, tertiary amines and can also be considered a heterocyclic compound. N-Methylpiperidine is miscible with water and exhibits strong reactivity as an aqueous alkaline solution. At 20 °C, an aqueous solution of the compound has a pH value of 12. Violent reactions may occur with acids and oxidizing agents.
Use
1-Methylpiperidine is used, among other applications, as an intermediate in the production of the growth regulator mepiquat chloride. It is also used as a solvent and in the synthesis of other chemicals. Furthermore, 1-methylpiperidine serves as a reagent for the synthesis of catalyst systems based on ruthenium. It is also employed in the preparation of antibacterial imidazoleium, pyrroleidinium and piperidine salts.
Safety information
The vapors of 1-methylpiperidine form explosive mixtures with air. The substance is primarily absorbed via the respiratory tract. Significant absorption through the skin is also suspected. Ingestion or exposure causes acute irritation of the mucous membrane of the eye, the respiratory tract, and the skin. No chronic data are available for humans. Reproductive toxicity could not be demonstrated in animal studies, but no corresponding human data exist. No detailed information is available on mutagenicity or carcinogenicity. 1-Methylpiperidine has a lower explosion limit of 1.1 % by volume and an upper explosion limit of 9.9 % by volume. The ignition temperature is 205 °C, placing the substance in temperature class T3. With a flash point of 3 °C, 1-methylpiperidine is considered highly flammable. The compound is also classified as highly hazardous to the aquatic environment.