2-Butene (CH3CHCHCH3) is a colorless gas used in the production of various chemicals. It is flammable and has a mild odor. 2-Butene is commonly used in the manufacturing of synthetic rubber and other polymers.
| IUPAC name | But-2-ene |
| Molecular formula | C4H8 or CH3CHCHCH3 |
| CAS number | 624-64-6 |
| Synonyms | 2-Butene, Butylene, Ethylethylene, But-2-ene, B-Butene, Butene-2 |
| InChI | InChI=1S/C4H8/c1-3-4-2/h3-4H,1-2H3 |
2-Butene Properties
2-Butene Formula
The chemical formula for 2-Butene is C4H8. This means that the molecule contains four carbon atoms and eight hydrogen atoms. The formula gives information about the types and number of atoms present in the molecule, but it does not provide information about its structure or properties.
2-Butene Molar Mass
But-2-ene has a molar mass of 56.11 g/mol. Molar mass is the mass of one mole of a substance and is calculated by adding up the atomic masses of all the atoms in the molecule. For but-2-ene, there are four carbon atoms and eight hydrogen atoms, which add up to a total of 56.11 g/mol.
2-Butene Boiling Point
The boiling point of but-2-ene is 0.88 °C. Boiling point is the temperature at which a liquid changes to a gas. In the case of but-2-ene, it is a colorless gas at room temperature, but it can be condensed into a liquid by lowering the temperature. At 0.88 °C, but-2-ene will start to boil and become a gas.
2-Butene Melting Point
But-2-ene does not have a distinct melting point because it exists as a gas at room temperature. However, if it is cooled to a low enough temperature, it can condense into a liquid. At this point, the temperature at which it solidifies will depend on the conditions of the experiment.
2-Butene Density g/mL
The density of but-2-ene is 0.614 g/mL at room temperature and pressure. Density is the amount of mass per unit volume. In the case of but-2-ene, this means that for every milliliter of but-2-ene, there is 0.614 grams of mass.
2-Butene Molecular Weight
The molecular weight of but-2-ene is 56.11 g/mol. Molecular weight is the sum of the atomic weights of all the atoms in a molecule. In the case of but-2-ene, there are four carbon atoms and eight hydrogen atoms, which add up to a total of 56.11 g/mol.
2-Butene Structure
But-2-ene has a linear structure and belongs to the group of alkenes. It has two carbon-carbon double bonds, which give it its characteristic reactivity. The molecule has a central carbon atom with two methyl groups attached to it and two hydrogen atoms attached to each of the carbons at the ends of the molecule.
| Appearance | Colorless gas |
| Specific gravity | 0.614 at 25°C |
| Color | Colorless |
| Odor | Mild |
| Molar mass | 56.11 g/mol |
| Density | 0.614 g/mL at 25°C |
| Melting point | -139.8°C |
| Boiling point | 0.88 °C |
| Flash point | -19°C |
| Water solubility | Insoluble |
| Solubility | Soluble in organic solvents |
| Vapour pressure | 276.8 kPa at 25°C |
| Vapour density | 2.5 (air = 1) |
| pKa | 44 |
| pH | Not applicable |
2-Butene Safety And Hazards
But-2-ene can pose several safety hazards if not handled properly. It is highly flammable and can ignite easily when exposed to heat, flames or sparks. It is also a respiratory and eye irritant and can cause dizziness, headaches and nausea when inhaled. In addition, it is harmful if ingested and can cause damage to internal organs. Proper safety measures such as using protective equipment and ensuring good ventilation should be followed when handling but-2-ene. It is important to have proper training and knowledge of its potential hazards before handling the chemical.
| Hazard symbols | Flammable |
| Safety description | Keep away from heat/sparks/open flames/hot surfaces. Use explosion-proof electrical/ventilating/lighting equipment. Use only non-sparking tools. Take precautionary measures against static discharge. Keep container tightly closed. Store in a well-ventilated place. |
| UN IDs | UN1012 |
| HS code | 290110 |
| Hazard class | 3 |
| Packing group | II |
| Toxicity | Harmful if ingested, respiratory and eye irritant. |
2-Butene Synthesis Methods
Various methods can synthesize but-2-ene, including cracking hydrocarbons, dehydrating 2-butanol, and catalytically dehydrogenating butanes.
The cracking method involves heating hydrocarbons such as naphtha, gas oil, or kerosene to high temperatures, which causes them to break down into smaller molecules, including but-2-ene. One can carry out the process using either thermal or catalytic cracking.
To produce but-2-ene, people use dehydration of 2-butanol as another method. In this method, they heat 2-butanol with a dehydrating agent, such as sulfuric acid or phosphoric acid, to create but-2-ene and water. The reaction is reversible, and they can remove water from the reaction mixture to push the reaction toward forming but-2-ene.
Another method used to synthesize but-2-ene is the catalytic dehydrogenation of butanes. This process involves heating butane over a catalyst such as chromia-alumina or platinum to produce but-2-ene and hydrogen. The reaction exhibits high exothermicity and chemists can conduct it in a fixed bed or fluidized bed reactor.
2-Butene Uses
But-2-ene has a wide range of industrial and commercial applications due to its unique chemical properties. Here are some common uses of but-2-ene:
- Production of butadiene: It is a precursor to butadiene, a chemical used in the production of synthetic rubber and other elastomers.
- Manufacturing of plastics: Used in the production of high-density polyethylene (HDPE) and linear low-density polyethylene (LLDPE) plastics.
- Fuel additive: Used as a fuel additive to increase the octane number of gasoline.
- Solvent: Used as a solvent in various industries such as paints, coatings, and adhesives.
- Chemical intermediate: Used as an intermediate in the production of various chemicals such as butanol, butyraldehyde, and butyric acid.
- Refrigerant: Used as a refrigerant in some applications due to its low boiling point and good heat transfer properties.
- Research and development: Also used in research and development to study the reaction kinetics and thermodynamics of various chemical reactions.
Questions:
Q: Which best describes the structure of 2-butene?
A: but-2-ene is an unsaturated hydrocarbon with a four-carbon chain and a double bond between the second and third carbon atoms.
Q: What is the hybridization at the two central carbon atoms of 2-butene?
A: The two central carbon atoms of but-2-ene are sp² hybridized, meaning they each have three hybrid orbitals and one unhybridized p orbital.
Q: What reagents might be used to convert cis-2-butene into trans-2-butene?
A: Reagents such as bromine or hydrogen gas can be used to convert cis-but-2-ene into trans-but-2-ene through a process called cis-trans isomerization.
Q: Why might it be difficult to visualize the separation of cis- and trans-2-butene by tlc?
A: It might be difficult to visualize the separation of cis- and trans-but-2-ene by thin-layer chromatography (TLC) because the two isomers have very similar physical properties, such as polarity and boiling point, making it hard to differentiate them using TLC.
Q: How many unique stereoisomers result from the reaction involving trans-but-2-ene?
A: The reaction involving trans-but-2-ene results in two unique stereoisomers, as there are only two possible configurations of substituents around the double bond: trans and cis.