Difference Between 1 Butyne and 2 Butyne

Main Difference – 1 Butyne vs 2 Butyne

Alkynes are organic compounds having at least one triple bond between two carbon atoms in their chemical structure. Alkynes are hydrocarbon compounds because these compounds are composed only of C and H atoms. Most alkyne compounds are obtained from petroleum oil, and some are made artificially using different chemical reactions. 1-Butyne and 2-butyne are also alkyne compounds. The main difference between 1 Butyne and 2 Butyne is that 1-butyne has the triple bond at the end of the molecule whereas 2-butyne has the triple bond in the middle of the molecule.

Key Areas Covered

1. What is 1 Butyne
      – Definition, Chemical Properties
2. What is 2 Butyne
      – Definition, Chemical Properties
3. Similarities Between 1 Butyne and 2 Butyne
      – Outline of Common Features
4. What is the Difference Between 1 Butyne and 2 Butyne
      – Comparison of Key Differences

Key Terms: Acetylene Group, Alkyne, 1-Butyne. 2-Butyne, Dimethylacetylene, Ethylacetylene, Hydrocarbon

What is 1 Butyne

1-Butyne is an organic compound having a triple bond between two carbon atoms at the end of the molecule. The chemical formula is C₄H₆. This compound falls into the category of alkynes. Compounds in the alkyne group are composed only of C and H atoms bonded via single bonds, and there should be at least one triple bond between two carbon atoms.

Difference Between 1 Butyne and 2 Butyne

Figure 1: Chemical Structure of 1-Butyne

The molar mass of 1-Butyne is about 54.092 g/mol. Generally, Butyne is a compound having a triple bond between two carbon atoms. 1-Butyne is a linear molecule and has its triple bond at the terminal of the molecule. According to the nomenclature of organic compounds, the triple bond is between the 1^st and 2^nd carbon atoms of the molecule.

The common name for this compound is Ethylacetylene since its molecular structure looks like an ethyl group bonded to an acetylene group. At room temperature and pressure, it is a colorless gaseous compound. Its density is higher than the normal air. It is extremely flammable.

What is 2 Butyne

2-Butyne is an organic compound having a triple bond between two carbon atoms in the middle of the molecule. Its chemical formula is C₄H₆. The molar mass of this compound is about 54.092 g/mol. This is also an alkyne.

Figure 2: Linear Chemical Structure of 2-Butyne

The common name for 2-butyne is dimethylacetylene since it looks like two methyl groups attached to an acetylene group. At room temperature, it is a colorless liquid. It has a petroleum-like odor. Since it is a hydrocarbon compound, 2-butyne is immiscible with water. This compound is denser than water. The boiling point of this liquid is about 27 °C. Therefore, it is a volatile compound at room temperature.

Difference Between 1 Butyne and 2 Butyne_Figure 3

Figure 3: Addition of Hydrogen to 2-Butyne

2-Butyne can be converted into 1-butyne from the reaction between 2-butene and H₂. Here, one pi bond of the triple bond is lost, and two hydrogen atoms are attached to the two vinyl carbon atoms (vinyl carbon = carbon atoms that participate in the double bond).

Similarities Between 1 Butyne and 2 Butyne

Both are hydrocarbon compounds.
Both have the similar chemical formula and similar molecular masses.
Both are alkynes.
Both are flammable compounds.
These compounds are position isomers of each other.

Definition

1 Butyne: 1-Butyne is an organic compound having a triple bond between two carbon atoms at the end of the molecule.

2 Butyne: 2-Butyne is an organic compound having a triple bond between two carbon atoms in the middle of the molecule.

Position of the Triple Bond

1 Butyne: The triple bond is in the terminal of 1-butyne.

2 Butyne: The triple bond is in the middle of 1-butyne.

Common Name

1 Butyne: Common name for 1-butyne is Ethylacetylene.

2 Butyne: Common name for 2-butyne is Dimethylacetylene.

Phase at Room Temperature

1 Butyne: 1-Butyne is a colorless gas at room temperature.

2 Butyne: 2-Butyne is a colorless liquid at room temperature.

Boiling Point

1 Butyne: The boiling point of 1-butyne is about 8.08 °C.

2 Butyne: The boiling point of 2-butyne is about 27°C.

Conclusion

1-Butyne and 2-butyne are alkyne compounds. These compounds are composed of a triple bond per molecule. The two compounds are different from each other depending on the position of the triple bond. The main difference between 1 Butyne and 2 Butyne is that 1-butyne has the triple bond in the terminal of the molecule whereas 2-butyne has the triple bond in the middle of the molecule.

References:

1. “1-BUTYNE.” National Center for Biotechnology Information. PubChem Compound Database, U.S. National Library of Medicine, Available here.
2. “2-BUTYNE.” National Center for Biotechnology Information. PubChem Compound Database, U.S. National Library of Medicine, Available here
3. “2-Butyne.” Wikipedia, Wikimedia Foundation, 4 Nov. 2017, Available here.

Image Courtesy:

1. “Ethylacetylene” By Magmar452 – Own work (CC0) via Commons Wikimedia
2. “Dimethylacetylene” By Edgar181 – Own work (Public Domain) via Commons Wikimedia
3. “Addition 2-butyne hydrogen” By Addition 2-Butin Wasserstoff.svg: Prolineserverderivative work: Rhadamante – Addition 2-Butin Wasserstoff.svg (Public Domain) via Commons Wikimedia