Topic 13: Alcohols and amines

Question 1

What role does the electronegativity of O play in the chemistry of alcohol? What effect does it have on the properties of alcohol (polarity and boiling point)?

Answer 1

O is very electronegative -> electron deficient on H and C
The OH and CO groups are polar, so the alcohol is polar molecule.

The polar groups allow alcohols to do H bonding
–> high boiling point

Question 2

Is alcohol basic or acidic? How do they react with acids and bases?

Answer 2

Alcohols are neither too acidic nor too basic.
- Acid: not readily accepts H+ –> favours deprotonating OH2

• Base: very strong base to deprotonate OH

Question 3

Why is phenol more acidic than alcohol?

Answer 3

The ability of phenoxide ion after being deprotonated to delocalize the (-) charge by resonance structure and stabilize makes phenols more likely to lose H+, thus more acidic.

Question 4

What is called a conjugated molecule?

Answer 4

Conjugated molecules have alternating single and double bonds, thus resulting in an extended electron cloud in which pi electrons can be shared.

Question 5

Explain the mechanism in which the unhybridized pi orbitals share electrons

Answer 5

Alternating single and double bonds allow the unhybridized pi orbitals above and below the plane, thus share the electrons that they have.

Question 6

List and explain the features of aromaticity

Answer 6

• Conjugated: ability to share cloud of electrons, thus result in resonance structure and more stable ions
• Conjugated system is cyclic
• Contain 4n+2 pi electrons

Question 7

How to determine primary, secondary and tertiary amines?

Answer 7

Depends on the number of alkyl groups being attached to the nitrogen

Question 8

Differentiate aliphatic and aromatic amines

Answer 8

• Aliphatic: not in aromatic rings or not directly attached to an aromatic ring
• Aromatic: the N atom is directly attached to an aromatic ring

Question 9

Why is amine polar? What is the effect on amine’s properties?

Answer 9

N has a lone pair in 1 sp3 orbital and also higher electronegativity than H
–> intermolecular H bonding –> able to form H bonds with other molecules and with water
–> high boiling point and water-soluble

Question 10

Compare the H bonds between amines and alcohols
Mention an affect of such difference

Answer 10

• The difference in electronegativity between O-H is larger than N-H, so the H bonds between O-H is stronger.
• Thus, for an amine and alcohol with the same number of electrons, alcohol has higher boiling point.

Question 11

Are amines acidic or basic? Are aliphatic amines stronger or weaker in the (acidity/basicity)?

Answer 11

Amines are basic, with the lone pair, it readily accepts H+
Aliphatic amines are more basic than aromatic because the aromatic ring and resonance structure reduces the electron density on N atom –> poorer eletron acceptor

Question 12

How do amines react in aqueous solution and how do they form water-soluable salts?

Answer 12

• Amines are basic –> react as weak bases in aqueous solution –> accept H+
• Amines can react with acid to form water-soluable salts

Question 13

What is the product of alcohol being oxidized?

Answer 13

Alcohol can be oxidized to become aldehyde, then carboxylic acid based on conditions.

Question 14

Do phenols react with strong base?

Answer 14

Phenols, even though being more acidic than alcohol, are still weak acid. They react with strong base like NaOH to yield salts.