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🥼organic chemistry review

But-

Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025

Definition

The prefix 'but-' is used in the systematic naming of alkenes, which are unsaturated hydrocarbons containing at least one carbon-carbon double bond. This prefix indicates the position of the double bond within the carbon chain of the alkene molecule.

5 Must Know Facts For Your Next Test

  1. The 'but-' prefix is used to indicate the position of the double bond in alkenes with four carbon atoms.
  2. The 'but-' prefix is followed by a number that specifies the position of the double bond, counting from the end of the carbon chain closest to the double bond.
  3. The 'but-' prefix is used in conjunction with the '-ene' suffix to form the complete name of the alkene, such as '2-butene' or '1-butene'.
  4. The position of the double bond can have a significant impact on the physical and chemical properties of the alkene, such as boiling point and reactivity.
  5. Identifying the position of the double bond is crucial for understanding the structure and behavior of alkene molecules in organic chemistry.

Review Questions

  • Explain the purpose of the 'but-' prefix in the systematic naming of alkenes.
    • The 'but-' prefix is used in the systematic naming of alkenes to indicate the position of the carbon-carbon double bond within the carbon chain of the molecule. This is an important piece of information, as the location of the double bond can significantly affect the physical and chemical properties of the alkene, such as its boiling point, reactivity, and stability. By specifying the position of the double bond using the 'but-' prefix, the systematic name of the alkene provides a clear and unambiguous way to identify its structure.
  • Describe how the 'but-' prefix is used in conjunction with the '-ene' suffix to name alkenes.
    • The 'but-' prefix is used in combination with the '-ene' suffix to form the complete systematic name of an alkene. The 'but-' prefix indicates the position of the double bond, while the '-ene' suffix denotes the presence of the carbon-carbon double bond. For example, the alkene with a double bond at the second carbon position in a four-carbon chain would be named '2-butene'. This naming convention allows for the precise identification of the alkene's structure and facilitates clear communication about its properties and reactivity.
  • Analyze the importance of understanding the position of the double bond in alkenes, as indicated by the 'but-' prefix, for predicting their behavior in organic chemistry.
    • The position of the double bond in an alkene, as indicated by the 'but-' prefix, is crucial for predicting its physical and chemical properties, as well as its behavior in organic chemistry reactions. The location of the double bond can influence factors such as boiling point, stability, and reactivity. For example, the position of the double bond can affect the ease of addition reactions, the formation of stereoisomers, and the stability of carbocation intermediates. By understanding the significance of the 'but-' prefix and the position of the double bond, students can more accurately anticipate the properties and reactivity of alkene molecules, which is essential for success in organic chemistry.