Acidity and Basicity of Organic Molecules

Question 1

General facts about acidity?

Answer 1

• 2 acids, higher pKa donate proton to lower pKa
• Higher electronegativity, more acidic
• Electron donating groups reduce electronegativity
• Substituent (atom replacing hydrogen on hydrocarbon chain) position affects acidity
• Resonance does not affect acidity or basicity
• Water has good solvation due to polarity
• Acid = Proton donor or electron acceptor

Question 2

What affects acidity?

Answer 2

• H-A bond
• Electronegativity of A-
  -Solvent nature
• Stabilisation of A-
  SENS (Stinky Education Number Spectacles)

Question 3

How does the strength of the H-A bond affects acidity

Answer 3

• Higher electronegativity, more acidic
• Electronegativity decreases down the column
• Down column, lower bond strength

Question 4

How does electronegativity affects acidity?

Answer 4

• Electronegativity increases
• Increased stabilisation of negative charge of conjugate base
• acidity increases

Question 5

How does a solvent affects acidity?

Answer 5

• Affects the stabilisation of eventual ions and solvation effects
• Good solvation will increase the dissolution of protons, increasing acidity
• Sterically bulky will decrease acidity as it will not be easily dissolute.

Question 6

Induction effects on electron withdrawing and donating groups

Answer 6

Electron withdrawing groups, stabilises anion. Leads to stronger acid (It helps to spread out the electron density) (Distributes through sigma bonds)
Electron donating, stabilises cattion. Stronger base.

Question 7

Hybridisation effects on acidity?

Answer 7

• More S character, closer to the nucleus
• Nucleus is positively charged
• Closer = More stable
• More stable conjugate base = More acidic

Question 8

Resonance effects on acidity?

Answer 8

• Resonance causes the electron density to be more spreaded out. Leading to a distribution through pi bonds