oxidation of alcohols
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Alcohols can be classified as primary, secondary or tertiary based on how many carbon chains branch off of the carbon atom to which the hydroxyl group is attached.
Primary and secondary alcohols can be oxidised in the presence of an appropriate reducing agent. An acidified dichromate solution is often used to observe the oxidation of alcohols due to an obvious colour change (orange dichromate ions reduced to green chromium (III) ions).
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Oxidation of Aldehydes
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Aldehydes will oxidise under acidic condition (i.e. acidified dichromate) to form a carboxylic acid or under alkaline conditions (i.e. Tollens Reagent) to form a carboxylate ion. In each case a redox reaction occurs (the linked video goes through the Tollens Reagent reaction as an example).
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carboxylic acids and carboxylate ions
As their name suggests carboxylic acids behave as acids. This means they can undergo typical acid-base reactions to form a salt and water, or in the case of a carbonate base salt, water and carbon dioxide. The anion in the resulting salt is a carboxylate ion. Essentially, the carboxyl group has been converted to the carboxylate group through the loss of hydrogen. There is an increase in solubility following the conversion of a carboxylic acid into a carboxylate ion due to the increase in strength of interactions with water molecules. Whilst a carboxyl group is able to hydrogen bond with water molecules the carboxylate group is able to form ion-dipole bonds with water molecules which are even stronger and hence increase the solubility.
esterification
An ester is produced from the reaction between an alcohol and a carboxylic acid. The reaction mixture must be heated under reflux for an extended period of time, and requires a concentrated sulfuric acid catalyst, for the reaction to proceed in a reasonable time period.
There are three key stages to the ester preparation practical you will complete: formation, isolation and purification. It is important that you understand the purpose and process of each stage. Make sure you complete the assigned reading, follow the links on this page to appropriate videos and seek clarification as it is required (and before you are in the lab!).
Follow the links below to relevant information or videos:
Formation
- reflux apparatus
Isolation/Extraction
- separating funnel
- drying with calcium chloride
Purification
- distillation apparatus
There are three key stages to the ester preparation practical you will complete: formation, isolation and purification. It is important that you understand the purpose and process of each stage. Make sure you complete the assigned reading, follow the links on this page to appropriate videos and seek clarification as it is required (and before you are in the lab!).
Follow the links below to relevant information or videos:
Formation
- reflux apparatus
Isolation/Extraction
- separating funnel
- drying with calcium chloride
Purification
- distillation apparatus
