Pyridine or C5H5N is a heterocyclic organic compound with a six-membered ring containing nitrogen. It is a weak base and is used as a precursor to many useful compounds, including pesticides and pharmaceuticals.
| IUPAC Name | Pyridine |
| Molecular Formula | C5H5N |
| CAS Number | 110-86-1 |
| Synonyms | Azabenzene, Azine, Azinoline, Azole, Pyridin, Pyridine base, Pyridinium |
| InChI | InChI=1S/C5H5N/c1-2-4-6-5-3-1/h1-5H |
Pyridine Structure
Pyridine has a six-membered ring with five carbon atoms and one nitrogen atom. The nitrogen atom is located in the ring, giving C5H5N a heterocyclic structure. The structure of C5H5N is important in determining its chemical and physical properties, as well as its reactivity in chemical reactions.
Pyridine formula
The chemical formula for pyridine is C5H5N. This formula represents the number and types of atoms present in a molecule of pyridine. The formula for pyridine is important in determining the stoichiometry of chemical reactions involving pyridine, as well as the amount of pyridine needed for a given reaction.
Pyridine molar mass
Pyridine has a molar mass of approximately 79.1 g/mol. This means that one mole of C5H5N, which contains Avogadro’s number of molecules (6.02 x 10^23), weighs 79.1 grams. The molar mass is an important property of C5H5N, as it is used in calculating the amount of C5H5N needed for a chemical reaction.
Pyridine boiling point
The boiling point of pyridine is 115.2 °C. C5H5N is a volatile liquid at room temperature and pressure, meaning it readily evaporates into the air. The boiling point of C5H5N is important in determining its use in chemical reactions, as it affects the temperature at which C5H5N will evaporate and condense during a reaction.
Pyridine melting point
The melting point of pyridine is -41.6 °C. C5H5N is a colorless liquid at room temperature and pressure, but it can solidify at low temperatures. The melting point of C5H5N is important in determining its use in chemical reactions, as it affects the temperature at which C5H5N will change from a solid to a liquid state.
Pyridine density g/ml
The density of C5H5N is approximately 0.982 g/mL at room temperature and pressure. This means that one milliliter of C5H5N weighs 0.982 grams. The density of C5H5N is important in determining the volume of C5H5N needed for a chemical reaction.
Pyridine molecular weight
The molecular weight of C5H5N is 79.1 g/mol. The molecular weight is the sum of the atomic weights of all atoms in a molecule of C5H5N. The molecular weight is important in determining the amount of C5H5N needed for a chemical reaction.
| Appearance | Colorless liquid |
| Specific Gravity | 0.982 g/mL |
| Color | Colorless |
| Odor | Fishy |
| Molar Mass | 79.1 g/mol |
| Density | 0.982 g/mL |
| Melting Point | -41.6 °C |
| Boiling Point | 115.2 °C |
| Flash Point | 21 °C |
| Water Solubility | Miscible |
| Solubility | Soluble in most organic solvents |
| Vapour Pressure | 12.7 kPa at 20 °C |
| Vapour Density | 2.7 |
| pKa | 5.23 |
| pH | 7 |
Pyridine Safety and Hazards
Pyridine (C5H5N) is a hazardous chemical and must be handled with care. It is toxic by inhalation, ingestion, and skin contact, and can cause irritation to the eyes, skin, and respiratory system. C5H5N is also flammable and can form explosive mixtures with air. Proper protective equipment, including gloves and respiratory protection, should be used when working with C5H5N. C5H5N should be stored in a cool, dry, and well-ventilated area, away from sources of ignition. In case of accidental exposure, seek medical attention immediately. Proper disposal methods should be followed to prevent environmental contamination.
| Hazard Symbols | T, N |
| Safety Description | Toxic, Dangerous for the environment |
| UN IDs | UN1282 (pyridine), UN2312 (pyridine base) |
| HS Code | 2933.39.90 |
| Hazard Class | 6.1 (Toxic substances) |
| Packing Group | II |
| Toxicity | LD50 (oral, rat): 891 mg/kg |
Pyridine Synthesis Methods
There are several methods for synthesizing pyridine (C5H5N), including the Hantzsch Dihydropyridine Synthesis, Chichibabin Synthesis, and Bönnemann Cyclization.
The Hantzsch Dihydropyridine Synthesis involves the reaction of an aldehyde, a β-ketoester, and ammonia or ammonium acetate in the presence of a catalyst such as acetic acid or piperidine. The resulting dihydropyridine is then oxidized to form C5H5N.
The Chichibabin Synthesis involves the reaction of acetylene with ammonia in the presence of a catalyst such as sodium amide. The resulting C5H5N is then purified by distillation.
The Bönnemann Cyclization involves the reaction of an acetylene derivative with a nitro compound in the presence of a palladium or nickel catalyst. The resulting C5H5N is then purified by distillation or chromatography.
Another common method for synthesizing C5H5N is the Smiles rearrangement, which involves the rearrangement of an N-oxide to form C5H5N.
Each of these methods has its own advantages and limitations, and the choice of method will depend on factors such as cost, availability of starting materials and desired purity and yield of the final product. It is important to use appropriate safety precautions and to follow established protocols when working with these methods.
Pyridine Uses
Pyridine (C5H5N) has many uses in various industries, including pharmaceuticals, agrochemicals, and polymer production.
In the pharmaceutical industry, C5H5N is used as a starting material in the synthesis of a variety of drugs, including antihistamines, antibiotics, and anticoagulants. It can also be used as a solvent and as a stabilizer for certain drugs.
In the agrochemical industry, C5H5N is used as a starting material in the synthesis of various herbicides, fungicides, and insecticides. It is also used as a solvent and as an ingredient in some animal feed additives.
C5H5N is also used in the production of polymers and plastics, where it can be used as a solvent, a plasticizer, or a crosslinking agent.
Other uses of C5H5N include its use as a catalyst in certain chemical reactions, as a corrosion inhibitor, and as a laboratory reagent for various analytical and synthetic procedures.
C5H5N’s versatility and a broad range of applications make it a valuable chemical in many industries. However, it is important to handle C5H5N with care and to follow established safety protocols when working with it, due to its toxicity and flammability.
Questions:
Q: Is pyridine aromatic?
A: Yes, C5H5N is considered an aromatic compound due to its planar structure and delocalized pi-electrons.
Q: Pyridine (C5H5N) is a base with a Kb of 1.7 x 10^-9. What is the pH of 0.10 M pyridine?
A: To solve for the pH of 0.10 M pyridine, we can use the Kb expression: Kb = [H+][C5H5N]/[C5H5NH+]. Since C5H5N is a weak base, we can assume that [H+] is negligible compared to [C5H5NH+]. Therefore, we can simplify the expression to Kb = [OH-][C5H5N]/[C5H5NH+]. Plugging in the values, we get Kb = (x^2)/(0.10 – x), where x is the concentration of hydroxide ions. Solving for x, we get x = 1.0 x 10^-6 M. Therefore, the pH of 0.10 M C5H5N is approximately 8.0.
Q: Is pyridine a strong base?
A: No, C5H5N is a weak base with a Kb of 1.7 x 10^-9.
Q: Is pyridine a base?
A: Yes, C5H5N is a base because it can accept protons (H+) from an acid.