W2.2_Bondings

Question 1

In carbon bonds, describe the bonding nature of single, double, and triple bonds and their bond angles.

Answer 1

• Single bond: tetrahedral (109.5)
• Double bond: planar (120)
• Triple bond: linear (180)

Question 2

Explain resonance in benzenes, which functional groups are involved and its purpose.

Answer 2

• Resonance in benzene: All carbon bonds in same length (1.39Å) vs C-C (1.54Å) vs C=C (1.33Å)
• All 6π electrons are delocalised
• Resonance to acquire stability: all functional groups involving C=X and a highly electronegative atom
  (ex. amide, carboxylic acid, ester, pyrrole)

Question 3

Describe the nature of electrophiles and nucleophiles.

Answer 3

• Electrophiles: accepts lone pair of e-s = Lewis acids/electron-poor/donates proton (ex. -COOH -> -COO-)
• Nucleophiles: availability of lone pair of e-s = Lewis bases/electron-rich/accepts proton (ex. -NH2 -> -NH3+)

Question 4

In nitrogen bonds, describe the bonding nature of amine, amide, and nitrile bonds and their bond angles.

Answer 4

• Amine: tetrahedral (107)
• Amide: planar with resonance (120)
• Nitrile: linear (180)

Question 5

In oxygen bonds, describe the bonding nature of water, alcohol, ether, and carbonyl bonds and their bond angles. What trend can we see in bond angles in tetrahedral shapes?

Answer 5

• Water/alcohol/ether: tetrahedral (104.5)
• Carbonyls: planar (120)
• In tetrahedral shapes, an additional lone pair of electrons decreases bond angle by 2.5