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What are general trends to determine the strength of a leaving group?

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Final answer:

The strength of a leaving group is determined by its basicity, nucleophilicity, and other factors such as inductive effects and charge delocalization.

Step-by-step explanation:

The strength of a leaving group can be determined by considering its basicity and nucleophilicity.

  1. Basicity: The basicity of a leaving group decreases from top to bottom in a group of the periodic table and from right to left in a row. For example, the base strength of halides follows the order: F¯ > Cl¯ > Br¯ > I¯. However, the leaving group propensity follows the opposite trend, meaning that good leaving groups are weaker bases. Therefore, in a reaction, R-F will have a lower rate than R-I.
  2. Nucleophilicity: Good leaving groups are typically weak bases and poor nucleophiles. Strong bases are poor leaving groups, and weak bases are good leaving groups in nucleophilic reactions.
  3. Other factors, such as inductive effects and charge delocalization, can also influence the acidity or basicity of a compound and the strength of a leaving group.

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