Functional Groups
Alcohols
- General Formula: $C_{n}H_{2n+1}OH$
- Structure: –OH
- Nomenclature: -ol
- E.g. Pentan-2-ol
- Intermolecular Forces: Dispersion Forces, Hydrogen Bonding
- Note: Position of hydroxyl group influences properties. Depending on the number of carbon atoms directly attached to the carbon bearing the hydroxyl group, we can classify alcohols by either being primary, secondary, or tertiary (bearing 1, 2, or 3 respectively).
Aldehydes - No position needed
- General Formula: $C_{n}H_{2n}O$
- Structure: –CHO
- Nomenclature: -al
- E.g. Propanal
- Intermolecular Forces: Dispersion Forces, Dipole Dipole
Ketones
- General Formula: $C_{n}H_{2n}O$
- Structure: –CO
- Nomenclature: -one
- E.g. Hexan-2-one
- Intermolecular Forces: Dispersion Forces, Dipole Dipole
Carboxylic Acids - No position needed
- General Formula: $C_{n}H_{2n+1}COOH$
- Structure: –COOH
- Nomenclature: -oic acid
- E.g. Ethanoic Acid! :O… another one -> Nonanoic Acid
- Intermolecular Forces: Dispersion Forces, Dipole Dipole, Hydrogen Bonding
Amines
- General Formula: $C_{n}H_{2n+1}NH_{2}$
- Structure: –NH2
- Nomenclature: -amine
- E.g. Butan-1-amine, Methanamine (Tongue Twister)
- Intermolecular Forces: Dispersion Forces, Hydrogen Bonding (Nitrogen less electronegative than oxygen hence hydrogen bonding is weaker than alcohols)
Amides - No position needed
- General Formula: $C_{n}H_{2n+1}CONH_{2}$
- Structure: –CONH2
- Nomenclature: -amide
- E.g. Propanamide
- Intermolecular Forces: Dispersion Forces, Dipole Dipole, Hydrogen Bonding
Esters - No position needed
- General Formula: $C_{n}H_{2n+2}COO$
- Structure: –COO
- Nomenclature: -yl -oate
- E.g. Methyl Ethanoate, Propyl Decanoate, Hexyl Methanoate
- Intermolecular Forces: Dispersion Forces, Dipole Dipole, Hydrogen Bonding
- Note: Side of the chain with the double bonded oxygen is the main chain (-oate) while the side without the double bonded oxygen is the alkyl group (-yl)
| B.P | Organic Compounds | | | | ——— | —————– | — | — | | Strongest | Amides | | | | | Carboxylic Acids | | | | | Alcohols | | | | | Ketones | | | | | Aldehydes | | | | | Amines | | | | | Esters | | | | | Ethers* | | | | Weakest | Alkanes | | | * Don’t need to know about them but they are normal alkanes but with a cheeky oxygen in the middle to disrupt the carbon chain.
Oxidation of Alcohols and Aldehydes
Common Oxidising Agent used:
- $K_{2}Cr_{2}O_{7}$ - Potassium Dichromate (Focus on Dichromate Ion)
- $H_{2}O_{2}$ - Hydrogen Peroxide
- $KMnO_{4}$ - Potassium Permanganate
Using Acidified Permanganate results in most likely a complete oxidation.
Using Acidified Dichromate results in most likely a incomplete oxidation.
Remember:
- Incomplete oxidation with a 1° alcohol -> Aldehyde
- Always has 2$H^+$ + 2$e^-$ as products in final equation
- Complete oxidation with a 1° alcohol -> Carboxylic Acid
- Always has $H_{2}O$ as reactants and 2$H^+$ + 2$e^-$ as products in final equation
- Oxidation of Aldehydes -> Carboxylic Acid
- Oxidation of 2° alcohol -> Ketone
- 3° Alcohols NEVER oxidized
Reactions with Sodium
Ethanol + Sodium -> Sodium Ethoxide + Hydrogen Gas
Ethanoic Acid + Sodium -> Sodium Ethanoate + Hydrogen Gas
Can be used to differentiate alcohols and carboxylic acids with other organic compounds. e.g. if you have 3 solutions - propanal, methanol, and 2-methylbutan-2-ol
- You can use permanganate ions to tell which one is the tertiary alcohol since it will not react.
- Then you can use sodium to distinguish between the aldehyde and alcohol since aldehydes do not react with sodium.