Organic Chemistry: Alcohols

These flashcards cover key concepts, definitions, and processes related to the topic of alcohols in organic chemistry.

General formula of Alcohols

CnH(2n+1)OH.

Nomenclature of Alcohols

Follows the pattern of alkan + ol.

Diol

A molecule that contains two -OH groups.

Primary Alcohol

An alcohol where the carbon bonded to the -OH group is attached to one other carbon atom.

Secondary Alcohol

An alcohol where the carbon bonded to the -OH group is attached to two other carbon atoms.

Tertiary Alcohol

An alcohol where the carbon bonded to the -OH group is attached to three other carbon atoms.

Complete Combustion of Alcohols

Alcohols react with oxygen to form carbon dioxide and water.

Halogenation

A reaction where the hydroxyl group in an alcohol is replaced with a halogen atom.

Chlorination of Alcohols

A reaction involving phosphorus(V) chloride added to alcohol, producing phosphoryl chloride and hydrogen chloride.

Bromination

A reaction of alcohol with bromide ions from potassium bromide and sulfuric acid.

Iodination

A reaction using red phosphorus and iodine with an alcohol under heating to form phosphorus(III) iodide.

Dehydration of Alcohols

A reaction where alcohol is heated with concentrated phosphoric acid to form alkenes.

Oxidation of Primary Alcohols

Can be oxidised to form aldehydes and subsequently, carboxylic acids.

Oxidation of Secondary Alcohols

Can be oxidised to form ketones.

Oxidation of Tertiary Alcohols

Do not undergo oxidation.

Oxidising Agent (Primary Alcohols)

Acidified potassium dichromate (K2Cr2O7) is used to oxidise primary alcohols.

Reduction of Dichromate Ions

Orange dichromate ions (Cr2O7^2-) reduce to green Cr^3+ ions during oxidation.

Fehling's Solution

An alkaline solution containing copper(II) ions, used to test for aldehydes.

Tollens' Reagent

An aqueous solution of silver nitrate in excess ammonia, used to identify aldehydes.

Formation of Copper(I) Oxide

Occurs when copper(II) ions are reduced in Fehling’s test.

Formation of Carboxylate Ion

The carboxylic acid formed during oxidation loses a proton, becoming a carboxylate ion.

Diol Definition

Alcohol containing two hydroxyl (-OH) groups.

Alkene Formation

Occurs through dehydration of an alcohol when removed of an -OH and adjacent hydrogen.

Primary Alcohol Test

Can be oxidized to form an aldehyde, which can further oxidize to carboxylic acid.

Ketone Test

Does not oxidize and results in a negative test with both Fehling's and Tollens' reagents.

Silver Mirror Effect

Occurs with Tollens' reagent when an aldehyde is present.

Acidic Medium Requirement

Needed for potassium dichromate to act as an oxidizing agent.

Heating Under Reflux

A technique used for full oxidation, keeping products in the reaction mixture.

Distillation with Addition

Used to obtain aldehyde instead of a carboxylic acid by only heating the oxidizing agent.

Overall Reaction of Alcohols Upon Combustion

Alcohol + Oxygen → Carbon Dioxide + Water.

Formation of Hydrogen Bromide

Occurs when bromine reacts with the alcohol in bromination.

Phosphoric Acid in Dehydration

Concentrated phosphoric acid is used in the dehydration process but does not appear in the final equation.

Alkene Structure

A hydrocarbon with a carbon-carbon double bond.

Aldehyde Structure

Contains a carbonyl group (C=O) at the end of the carbon chain.

Ketone Structure

Contains a carbonyl group (C=O) within the carbon chain.

Role of Ammonia in Tollens' Reagent

Excess ammonia acts as a ligand to stabilize silver ions in solution.

Oxidation Process of Aldehydes

Aldehydes can be oxidised to form carboxylic acids.

Formation of Phosphorus(III) Iodide Equation

2P + 3I → 2PI during iodination reaction.

Hydrolysis of Hydrogen Halide

The resulting hydrogen halide from alcohol reactions can further react with water.

Presence of -OH group Test

Adding phosphorus(V) chloride should produce steamy fumes, indicating presence of alcohol.

Concentration of Acid in Bromination

50% concentrated sulfuric acid used along with potassium bromide during bromination.

Oxidising Agents Examples

Acidified potassium dichromate and other reagents can serve as oxidising agents.

Distillation Purpose

To separate volatile products such as aldehydes during the oxidation process.

Oxidative Reagents in Experiments

Commonly include dichromate, Fehling’s solution, and Tollens’ reagent.

Hydrogen Removal in Dehydration

Involves simultaneous removal of -OH and H- from adjacent carbon atoms.

Evidence of Alcohol Presence in Unknown Liquids

Reactivity with PCl5 is used to indicate the presence of an -OH group.

Boiling Point Relationship

Aldehydes generally have lower boiling points than the corresponding alcohols.

Stability of Ketones

Ketones are stable and do not undergo oxidation under mild conditions.

Mechanism of Aldehyde Oxidation

Involves conversion to a carboxylic acid upon reaction with strong oxidizing agents.

Relationship Between Alcohols and Functional Group

The -OH group provides distinctive properties and reactions of alcohols.

Types of Alcohol Classification

Alcohols can be classified as primary, secondary, and tertiary based on carbon bonding.