Alcohols

• What is the general formula for alcohols?

  $C_{n}H_{2n + 2}O$
• The functional group of alcohols is R-OH
• Alcohols can only be classified as primary, secondary, or tertiary based on their structure.
• Match the classification of alcohols with their corresponding structure:

  Primary alcohol ↔️ $R - CH_{2} - OH$

  Secondary alcohol ↔️ $R - CH(R') - OH$

  Tertiary alcohol ↔️ $R - C(R')(R'') - OH$
• What is the IUPAC name for CH3CH2OH?

  Ethanol
• The IUPAC name for a secondary alcohol with three carbon atoms is propan-2-ol
• What are structural isomers?

  Same formula, different structure
• Ethers are functional group isomers of alcohols.
• Give an example of a functional group isomer of C4H10O.

  1-methoxypropane
• Alcohols have relatively high melting points and boiling points due to the presence of hydrogen bonds.
• Arrange the intermolecular forces in order of increasing strength:

  1️⃣ Van der Waals

  2️⃣ Permanent dipole-dipole

  3️⃣ Hydrogen bonds
• Why does butan-1-ol have a higher boiling point than propan-1-ol?

  Longer carbon chain
• Alcohols with a low Mr are soluble in water due to hydrogen bonding.
• What is the reagent used in the hydration of alkenes to produce alcohols?

  Steam
• The hydration of alkenes requires a phosphoric acid catalyst.
• Match the alkene with the alcohol produced by hydration:

  Ethene ↔️ Ethanol

  Propene ↔️ Propan-2-ol

  Cyclohexene ↔️ Cyclohexanol
• What does a curly arrow in a reaction mechanism show?

  Movement of electron pair
• What are the three important reactions of alcohols?

  Combustion, elimination, oxidation
• Alcohols burn in oxygen to form carbon dioxide and water.
• Why do alcohols combust more efficiently than alkanes?

  Presence of an O atom
• When balancing combustion equations for alcohols, do not forget to include the O in the molecule.
• Match the alcohol with its balanced combustion equation:

  Ethanol ↔️ C₂H₂OH + 3O₂ → 2CO₂ + 3H₂O

  Cyclohexanol ↔️ C₆H₁₂O + 8½O₂ → 6CO₂ + 6H₂O

  Propane-1,3-diol ↔️ CH₂OHCH₂CH₂OH + 4O₂ → 3CO₂ + 4H₂O
• Elimination reactions of alcohols form alkenes.
• What is the key definition of elimination reactions?

  Removal of atoms or groups
• The elimination reactions of alcohols involve dehydration as water is eliminated
• What reagent is used in the elimination reactions of alcohols?

  1. H₂SO₄
• In the elimination reaction of alcohols, the OH group is always removed.
• Outline the mechanism for the elimination reaction of ethanol:

  1️⃣ Protonation of the OH group to form OH₂⁺

  2️⃣ Loss of water to form a carbocation

  3️⃣ Removal of a proton to form ethene
• What are but-1-ene and but-2-ene examples of?

  Structural isomers
• Where are alkenes generally obtained from at present?

  Crude oil
• In the future, it may become more economical to make ethene from ethanol produced by fermentation
• Match the current source of ethene with its end product:

  Crude oil ↔️ Poly(ethene)

  Ethanol ↔️ Ethene
• Alcohols can be oxidised by acidified potassium dichromate(VI).
• When acidified potassium dichromate(VI) acts as an oxidising agent, its colour changes from orange to green
• What is the half equation for the reduction of dichromate(VI) ions?

  Cr₂O₇²⁻ + 14H⁺ + 6e⁻ → 2Cr³⁺ + 7H₂O
• In organic chemistry, what does oxidation involve in terms of bonds?

  Increase in C-O bonds
• Match the type of alcohol with its oxidation product:

  Primary ↔️ Aldehyde or carboxylic acid

  Secondary ↔️ Ketone

  Tertiary ↔️ No oxidation
• Acidified dichromate(VI) can distinguish between tertiary alcohols and other alcohols.
• A primary alcohol is oxidised first to an aldehyde and then to a carboxylic acid.
• What type of apparatus is essential for producing an aldehyde from a primary alcohol?

  Immediate distillation