pyridine Basic information

pyridine Numbering system

pyridine Physical and Chemical Properties

Appearance and characteristics:

Transparent and clean liquid with a unique odor

Density:

0.983 g/mL at 20 °C

Boiling point:

96-98 °C(lit.)

Melting point:

-42 °C

Freezing point:

-42℃

Flash point:

68 °F

Refractive index:

n20/D 1.509(lit.)

Water solubility:

Miscible

Stability:

Stable. Flammable. Incompatible with strong oxidizing agents, strong acids.

Storage conditions:

The warehouse is ventilated, low-temperature and dry, and stored separately from oxidants and acids

Steam density:

2.72 (vs air)

Steam pressure:

23.8 mm Hg ( 25 °C)

security information

• RTECS：

• UR8400000

Safety instructions:

S36/37/39-S38-S45-S61-S28A-S26-S28-S24/25-S22-S36/37-S16-S7

WGK Germany：

two

Hazard category code:

R11; R20/21/22

Dangerous goods transportation code:

UN 1282 3/PG 2

Customs code:

two billion nine hundred and thirty-three million nine hundred and ninety thousand and ninety

Hazard category:

three

Packaging grade:

II

Dangerous goods signs:

F; Xn

Hazard description:

H225; H302 + H312 + H332; H315; H319

Danger signs:

GHS02, GHS07

Signal words:

Danger

Hazard prevention instructions:

P210; P261; P280; P305 + P351 + P338; P370 + P378; P403 + P235

Production method and purpose

Production method

A mixture of acetaldehyde (1.648mol), 37% formaldehyde (1.665mol), and ammonia (3.096mol) was reacted at 432 ℃ using SiO2-Al2O3-Bi2O3 as the catalyst, with a pyridine yield of 48.4%. At the same time, β - methylpyridine is also generated. By changing the operating conditions, the yields of pyridine, methylpyridine, and methylpyridine can be adjusted. In addition, 1,5-pentanediamine hydrochloride can also be synthesized into pyridine by heating cyclization and dehydrogenation in the presence of Pt catalyst. Refining method: The main impurities are water and its homologues. Water can be distilled off by refluxing potassium hydroxide, sodium hydroxide, barium oxide, calcium oxide, or metallic sodium. 4A type molecular sieves, calcium hydride, and lithium aluminum hydride can also be used for dehydration. In industry, azeotropic mixtures composed of benzene or toluene are commonly used for azeotropic distillation dehydration. The separation of homologous compounds can be refined by forming addition compounds with zinc chloride or mercuric chloride, in addition to fractional distillation. For example, a solution of 424g of zinc chloride and 365mL of water is mixed with 173mL of concentrated hydrochloric acid and 345mL of 95.6% ethanol, and 500mL of freshly distilled pyridine is added. After a period of time, the product composed of 2C5H5N · ZnCl2 crystallizes and precipitates from the solution. After filtration, recrystallize twice with anhydrous ethanol. Decompose this crystal with concentrated sodium hydroxide solution (26.7g of sodium hydroxide per 100g of crystal). Filter and dry the obtained free pyridine with solid potassium hydroxide or barium oxide before fractionation. To separate the homologues of pyridine, pyridine can also be added to an acetone solution of oxalic acid while stirring. Pyridine forms oxalate precipitate, which is filtered and washed with cold acetone, followed by alkaline regeneration of pyridine. The non alkaline impurities contained in pyridine can be removed by steam distillation in acidic solutions. In addition, there are refining methods using oxidants for treatment. For example, stir 135mL of pyridine, 2.5L of water, and 90g of potassium permanganate at 100 ℃ for 2 hours, let it stand for 15 hours, and then filter. Add about 500g of sodium hydroxide to the filtrate to separate the pyridine. Pour out pyridine, reflux with calcium oxide for 3 hours, and then distill.

2. Recovery and treatment of pyridine alkali from coke oven gas generated during coking process to obtain pyridine. Alternatively, pyridine can be obtained by reacting a mixture of acetaldehyde, formaldehyde, and ammonia. Alternatively, 1,5-pentanediamine hydrochloride can be heated and cyclized, and then dehydrogenated in the presence of platinum catalyst to produce pyridine.

3. Take industrial pyridine as the raw material, collect its 114-116 ℃ fraction through atmospheric distillation, and put it into a brown glass bottle to obtain the finished product. To prepare chromatographically pure pyridine, nitrogen can be used as the carrier gas. Industrial pyridine can be injected into the preparative gas chromatograph, and its main peak components can be separated and collected. Then, they can be sealed in glass ampoules.

The most common industrial synthesis method for pyridines is to react various inexpensive and readily available aldehydes or ketones with ammonia to obtain various pyridines. The reaction between saturated fatty aldehydes and ammonia forms a pyridine ring with 3 mol of saturated fatty aldehydes and 1 mol of ammonia. In theory, the amount of ammonia used is 1/2 or 1/3 of that of aldehydes or ketones, but to prevent a decrease in yield and catalyst activity, it is usually excessive by 0.9 to 9 times. The reaction conditions are a mixed gas velocity of 500-1000/h and a reaction temperature of 400-500 ℃. Usually, alumina silica catalysts are used, and various metals are added to improve yield, prolong catalyst life, and facilitate regeneration. The reaction equation is as follows:

use to

Used for manufacturing vitamins, sulfonamides, insecticides, plastics, etc. In addition to being used as a raw material for pharmaceuticals and various pyridine compounds, it is also used as an alkaline solvent in the chemical industry and laboratories. It is also an excellent solvent for deacidification agents and acylation reactions, as pyridine can combine with acylating agents to form N-acylpyridine complexes. A pyridine solution composed of pyridine and metal salts or organometallic compounds, used as a catalyst in the form of a complex for polymerization reactions, oxidation reactions, carbonylation reactions of acrylonitrile, etc. It can also be used as a stabilizer for silicone rubber and as a raw material for anion exchange membranes. As a corrosion inhibitor, pyridine has a corrosion inhibition effect on metals and can be directly added to acid washing solutions to achieve corrosion inhibition through its adsorption effect. Used as an analytical reagent, widely used as a solvent, and eluent for liquid chromatography. It is also used in organic synthesis.

toxicity