3.2 Ranking Acids and Bases | Organic Chemistry

Chad's Prep・2 minutes read

Understanding the ranking of acids and bases involves evaluating structural features, charge, atom size, electronegativity, resonance, induction, and orbital hybridization to determine stability and strength. The mnemonic "REO" helps compare bases with the same charge, with key factors like charge, atom size, and resonance influencing base strength and stability.

Insights

  • Structural features play a crucial role in comparing acidities and basicities, with factors like charge, atom size, electronegativity, resonance, and induction impacting the stability and strength of acids and bases.
  • Ranking acids and bases involves a systematic approach focusing on conjugate bases, with mnemonic rules like "REO" aiding in evaluating charge, atom, resonance, induction, and orbital differences to determine relative acidity and basicity, essential for understanding organic chemistry reactions.

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Recent questions

  • How are acids and bases ranked?

    By comparing structural features and stability factors.

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Summary

00:00

Comparing Acids and Bases in Chemistry

  • Introduction to ranking acids and bases in the lesson, following an introduction to acids and bases in the previous lesson.
  • Structural features are crucial for comparing acidities and basicities between different acids and bases.
  • New organic chemistry playlist with weekly lessons throughout the school year.
  • Reminder: stronger acid means weaker conjugate base, and vice versa.
  • Stability of a base is linked to lower energy electrons, making it weaker.
  • Lewis definition of base as an electron pair donor; lower energy electrons indicate stability.
  • Mnemonic "REO" used for comparing bases with the same charge.
  • Mnemonic includes charge, atom, resonance, induction, and orbitals.
  • Charge affects the energy of electrons; negative charge leads to stronger base, positive charge to weaker base.
  • Atom rule: basicity increases with smaller size and lower electronegativity; size more important within the same group, electronegativity within the same period.

12:09

Ranking Bases by Charge, Atom, Resonance, Induction

  • The weaker, more stable conjugate base in a comparison was oxygen due to sulfur being larger and oxygen being more electronegative.
  • Resonance rule follows the atom rule in ranking bases, with resonance stabilizing bases.
  • Resonance is assessed after ensuring bases have the same charge and atom, with shared resonance making a base weaker.
  • Quality of resonance structures matters in ranking bases, not just the quantity.
  • Comparing carboxylic acid to phenol can be done using pKa values for easier ranking.
  • Acids are ranked indirectly by assessing their conjugate bases, with stronger acids having weaker conjugate bases.
  • Induction rule focuses on polarity, with electronegative atoms stabilizing bases by pulling electron density away.
  • Induction is about electronegativity, with proximity enhancing its stabilizing impact.
  • Comparing bases involves evaluating charge, atom, resonance, and induction, with electronegativity playing a crucial role.
  • Conjugate acids are compared by first assessing their conjugate bases, with stronger acids having weaker conjugate bases.

25:05

Ranking Conjugate Bases and Acids in Chemistry

  • Conjugate bases were already ranked on the board, but if not, ranking them would be the first step.
  • The last rule in the mnemonic is orbital, focusing on hybridization differences in basic atoms.
  • Comparison of three bases involves checking charge, basic atom, resonance, induction, and finally orbitals.
  • Hybridization differences impact stability, with sp being the most stable, followed by sp2 and sp3.
  • The trend for basicity is determined by the hybridization of the basic atom.
  • Comparing conjugate acids involves following the same rules to determine relative acidity.
  • Three examples are provided for comparing acidity, considering pKa values and applying the mnemonic rules.
  • Understanding relative acidity and basicity is crucial for comprehending chemical reactions in organic chemistry.
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