Ethene

Definition

Ethene, also known as ethylene, is a simple unsaturated hydrocarbon with the chemical formula C₂H₄. It is the simplest alkene and plays a crucial role in various topics within organic chemistry, including calculating the degree of unsaturation, naming alkenes, understanding cis-trans isomerism, and evaluating the stability of alkenes.

5 Must Know Facts For Your Next Test

1. Ethene is the simplest alkene, containing a carbon-carbon double bond.
2. The presence of the carbon-carbon double bond in ethene contributes to its degree of unsaturation, which is calculated using the formula: Degree of Unsaturation = (2C + 2 - H + N) / 2.
3. Ethene is named according to the IUPAC rules for naming alkenes, where the longest carbon chain containing the double bond is identified, and the position of the double bond is indicated using a numerical prefix.
4. Ethene can exist in cis and trans isomeric forms, where the hydrogen atoms attached to the carbon-carbon double bond are on the same side (cis) or opposite sides (trans).
5. The stability of ethene is influenced by factors such as the presence of electron-donating or electron-withdrawing substituents, as well as the steric effects of the substituents around the double bond.

Review Questions

• Explain how the presence of the carbon-carbon double bond in ethene contributes to its degree of unsaturation.
  • The carbon-carbon double bond in ethene is considered a single degree of unsaturation, as it reduces the number of hydrogen atoms in the molecule compared to a saturated hydrocarbon. The degree of unsaturation is calculated using the formula: Degree of Unsaturation = (2C + 2 - H + N) / 2. For ethene, with the formula C₂H₄, the degree of unsaturation is 1, as the molecule has two carbon atoms, four hydrogen atoms, and one carbon-carbon double bond.
• Describe the cis-trans isomerism observed in ethene and how it affects the stability of the molecule.
  • Ethene can exist in two different stereoisomeric forms, cis and trans, based on the orientation of the hydrogen atoms around the carbon-carbon double bond. In the cis isomer, the hydrogen atoms are on the same side of the double bond, while in the trans isomer, the hydrogen atoms are on opposite sides. The trans isomer of ethene is more stable than the cis isomer due to reduced steric interactions between the hydrogen atoms. This difference in stability can impact the reactivity and properties of ethene in various organic reactions.
• Evaluate how the stability of ethene is influenced by the presence of electron-donating or electron-withdrawing substituents on the carbon-carbon double bond.
  • The stability of ethene can be affected by the presence of substituents on the carbon-carbon double bond. Electron-donating substituents, such as alkyl groups, can increase the stability of the alkene by stabilizing the double bond through hyperconjugation. Conversely, electron-withdrawing substituents, such as halogens or carbonyl groups, can decrease the stability of the alkene by destabilizing the double bond through inductive effects. These factors must be considered when predicting the reactivity and behavior of ethene and other alkenes in organic chemistry reactions.

Related terms

Degree of Unsaturation: A calculation that determines the number of carbon-carbon double or triple bonds in a molecule, providing information about its saturation level and potential reactivity.

Cis-Trans Isomerism: A type of stereoisomerism in alkenes where the substituents on the carbon-carbon double bond are either on the same side (cis) or on opposite sides (trans).

Alkene Stability: The relative stability of alkenes, which is influenced by factors such as substitution patterns, steric effects, and the presence of electron-donating or electron-withdrawing groups.