Isoprene (C5H8) is a natural organic compound used in the production of rubber, plastics, and other materials. It plays a crucial role in the formation of ozone and air pollution.
| IUPAC Name | 2-methylbuta-1,3-diene |
| Molecular Formula | C₅H₈ |
| CAS Number | 78-79-5 |
| Synonyms | Isoprene, 2-Methyl-1,3-butadiene, β-Isoprene |
| InChI | InChI=1S/C₅H₈/c1-4-5(2)3/h4H,1-2H3 |
Isoprene Properties
Isoprene Formula
The formula of isoprene is C₅H₈. It consists of five carbon atoms and eight hydrogen atoms. The molecular structure of isoprene is characterized by a branched-chain with a double bond between the second and third carbon atoms.
Isoprene Molar Mass
The molar mass of 2-methyl-1,3-butadiene can be calculated by adding the atomic masses of its constituent elements. Carbon has a molar mass of 12.01 g/mol, while hydrogen has a molar mass of 1.01 g/mol. Thus, the molar mass of 2-methyl-1,3-butadiene is approximately 68.12 g/mol.
Isoprene Boiling Point
Isoprene has a boiling point of around 34 °C (93 °F). This relatively low boiling point makes it volatile and prone to evaporation at ambient temperatures.
Isoprene Melting Point
The melting point of 2-methyl-1,3-butadiene is approximately -145 °C (-229 °F). At this temperature, 2-methyl-1,3-butadiene changes from a solid to a liquid state.
Isoprene Density g/mL
The density of 2-methyl-1,3-butadiene is about 0.69 g/mL. This value represents the mass of 2-methyl-1,3-butadiene per unit volume and is influenced by its molecular weight and structural arrangement.
Isoprene Molecular Weight
The molecular weight of 2-methyl-1,3-butadiene is determined by summing the atomic weights of its constituent atoms. With a formula of C₅H₈, the molecular weight of 2-methyl-1,3-butadiene is approximately 68.12 g/mol.
Isoprene Structure
The structure of 2-methyl-1,3-butadiene is characterized by a branched chain of five carbon atoms. It contains a double bond between the second and third carbon atoms. This structure imparts flexibility and reactivity to 2-methyl-1,3-butadiene, making it a key building block in the synthesis of various compounds.
Isoprene Solubility
Isoprene is sparingly soluble in water but readily dissolves in organic solvents like ethanol and acetone. Its solubility characteristics are attributed to the nonpolar nature of its molecular structure.
These notes provide an overview of the key properties of 2-methyl-1,3-butadiene, including its formula, molar mass, boiling point, melting point, density, molecular weight, structure, and solubility. Understanding these properties is essential for studying and utilizing 2-methyl-1,3-butadiene in various industrial applications.
| Appearance | Colorless liquid |
| Specific Gravity | 0.68 – 0.70 g/mL |
| Color | Colorless |
| Odor | Sweet, pungent |
| Molar Mass | 68.12 g/mol |
| Density | 0.68 – 0.70 g/mL |
| Melting Point | -145 °C (-229 °F) |
| Boiling Point | 34 °C (93 °F) |
| Flash Point | -40 °C (-40 °F) |
| Water Solubility | Sparingly soluble |
| Solubility | Soluble in organic solvents |
| Vapour Pressure | 290 mmHg at 25 °C |
| Vapour Density | 2.49 (air = 1) |
| pKa | ~ 40 |
| pH | Neutral |
Isoprene Safety and Hazards
Isoprene or 2-methyl-1,3-butadiene poses certain safety hazards that should be considered. It is highly flammable and can form explosive vapor-air mixtures. Therefore, it should be handled with caution near open flames or heat sources. Isoprene exposure may lead to skin and eye irritation. Prolonged or repeated contact can cause dermatitis. Inhalation of 2-methyl-1,3-butadiene vapors may cause respiratory irritation, dizziness, and headache. It is important to use proper ventilation and personal protective equipment when working with 2-methyl-1,3-butadiene. In case of ingestion, immediate medical attention is necessary. It is advisable to store 2-methyl-1,3-butadiene in a cool, well-ventilated area away from sources of ignition.
| Hazard Symbols | Flammable (F), Irritant (Xi) |
| Safety Description | Keep away from heat/sparks/open flames/hot surfaces. Avoid breathing dust/fume/gas/mist/vapors/spray. Wear protective gloves/eye protection/face protection. Store in a well-ventilated place. |
| UN IDs | UN 1214 |
| HS Code | 2902.41.00 |
| Hazard Class | Class 3 (Flammable liquids) |
| Packing Group | PG II |
| Toxicity | May cause skin and eye irritation. Harmful if ingested. |
Isoprene Synthesis Methods
Various methods can synthesize 2-methyl-1,3-butadiene. One common method involves thermally cracking petroleum-based feedstocks, such as naphtha or light gases, in the presence of catalysts. This process yields a mixture of compounds, including 2-methyl-1,3-butadiene, which we can separate and purify.
Another method entails catalytically dehydrogenating isopentane or isobutane. Under controlled conditions and with the aid of a catalyst, these hydrocarbons undergo a dehydrogenation reaction, resulting in the production of 2-methyl-1,3-butadiene.
We can obtain 2-methyl-1,3-butadiene from renewable sources through bio-based routes as well. By genetically engineering microorganisms like bacteria and yeast, we enable them to produce 2-methyl-1,3-butadiene through metabolic pathways. This approach offers a sustainable and environmentally friendly alternative to traditional synthesis methods.
Furthermore, biomass pyrolysis, a thermochemical process, can generate 2-methyl-1,3-butadiene along with other valuable chemicals. Subjecting biomass materials to high temperatures in the absence of oxygen breaks down the complex organic compounds in biomass, releasing 2-methyl-1,3-butadiene as one of the resulting products.
Overall, 2-methyl-1,3-butadiene synthesis encompasses a range of methods, including thermal cracking, catalytic dehydrogenation, bio-based routes, and biomass pyrolysis. These diverse approaches contribute to the availability of 2-methyl-1,3-butadiene for various industrial applications while considering environmental and sustainability aspects.
Isoprene Uses
Isoprene plays a crucial role in various industries due to its unique properties and reactivity. It finds wide-ranging applications in the following ways:
- Rubber Production: Manufacturers use 2-methyl-1,3-butadiene as a crucial monomer to produce synthetic rubber, including poly2-methyl-1,3-butadiene and styrene-butadiene rubber (SBR). They utilize these rubbers to manufacture tires, conveyor belts, hoses, and various molded rubber products.
- Polymer Production: Isoprene serves as a building block in the production of various polymer resins and elastomers. Industries employ it to synthesize thermoplastic elastomers, adhesives, coatings, and sealants.
- Chemical Intermediates: Isoprene proves versatile as a chemical intermediate in the production of a wide range of chemicals. It aids in the synthesis of pharmaceuticals, fragrances, flavors, antioxidants, and other specialty chemicals.
- Ozone Formation: Isoprene significantly contributes to atmospheric chemistry by reacting with nitrogen oxides (NOx) and sunlight to form ozone. This process affects air quality and contributes to the formation of smog.
- Fuel Additive: Industries utilize 2-methyl-1,3-butadiene as a fuel additive to enhance the combustion efficiency and performance characteristics of gasoline. It improves the octane rating and reduces engine knocking.
- Research and Development: Isoprene plays an extensive role in research and development studies, particularly in chemistry, materials science, and environmental science. Researchers widely employ it as a valuable tool to investigate new reactions, develop innovative materials, and study atmospheric chemistry.
The diverse applications of 2-methyl-1,3-butadiene underscore its significance across multiple industries, ranging from rubber manufacturing to chemical synthesis, while also playing a role in environmental and scientific research.
Questions:
Q: What is the isoprene rule?
A: The 2-methyl-1,3-butadiene rule states that many natural compounds can be derived from 2-methyl-1,3-butadiene, which consists of five carbon atoms and has a branched structure.
Q: How many isoprene units are in alpha-ylangene?
A: Alpha-ylangene contains three 2-methyl-1,3-butadiene units, as it has a linear chain of 15 carbon atoms derived from three 2-methyl-1,3-butadiene building blocks.
Q: How many isoprene units are used to synthesize one molecule of cholesterol?
A: The synthesis of one molecule of cholesterol requires 18 2-methyl-1,3-butadiene units, which are combined and modified through a series of enzymatic reactions.
Q: How many isoprene units are in cholesterol?
A: Cholesterol contains four fused rings and is composed of 30 2-methyl-1,3-butadiene units.
Q: How to identify isoprene units?
A: 2-methyl-1,3-butadiene units can be identified by their characteristic structure, consisting of a branched chain of five carbon atoms with a double bond between the second and third carbon atoms.
Q: What position is the menthyl group on isoprene?
A: The menthyl group is typically located at the fourth carbon atom of a 2-methyl-1,3-butadiene unit.
Q: Is 4-carbon ring isoprene?
A: No, a 4-carbon ring is not a 2-methyl-1,3-butadiene. 2-methyl-1,3-butadiene refers to a specific five-carbon unit with a branched structure and a double bond.
Q: How many isoprene units are in Squalene?
A: Squalene, a triterpene, is composed of six 2-methyl-1,3-butadiene units, resulting in a molecule with 30 carbon atoms.