AQA Chemistry A-level 3.3.8 Aldehydes and Ketones Detailed Notes PDF
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These detail notes from PMT education cover aldehydes and ketones, oxidation, reduction, and naming conventions in organic chemistry. The notes are suitable for A-level chemistry students.
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AQA Chemistry A-level 3.3.8: Aldehydes and Ketones Detailed Notes This work by PMT Education is licensed under https://bit.ly/pmt-cc https://bit.ly/pmt-edu-cc CC BY-NC-ND 4.0...
AQA Chemistry A-level 3.3.8: Aldehydes and Ketones Detailed Notes This work by PMT Education is licensed under https://bit.ly/pmt-cc https://bit.ly/pmt-edu-cc CC BY-NC-ND 4.0 https://bit.ly/pmt-cc https://bit.ly/pmt-edu https://bit.ly/pmt-cc 3.3.8.1 - Aldehydes and Ketones Aldehydes These organic compounds are recognised by the functional group -CHO containing a carbonyl group (C=O). They are produced from the initial oxidation and distillation of 1o alcohols. Aldehydes will readily oxidise further, in the presence of acidified potassium dichromate to produce carboxylic acids. Example: Aldehydes are tested for using Tollen’s reagent or Fehling’s solution as they produce a positive result in both tests if present. Ketones These organic compounds are recognised by the functional group -C=O, a carbonyl group. They are produced from the oxidation of 2o alcohols with acidified potassium dichromate. Example: There is no further oxidation of ketones and they produce no visible change with both Tollen’s reagent and Fehling’s solution. https://bit.ly/pmt-cc https://bit.ly/pmt-edu https://bit.ly/pmt-cc Reduction All of the oxidation reactions involved in the production of the species above can be reversed via reduction reactions. In these reactions, a reducing agent of NaBH4 is used and it is an example of nucleophilic addition. Mechanism The reducing agent NaBH4 provides the H:- nucleophile. However, a H+ ion is also required so the reaction takes place under aqueous conditions. Hydroxynitriles Nucleophilic addition reactions can also take place with the :CN- nucleophile. This is a form of synthesis as it causes the carbon chain to be extended by one carbon atom. The product of the reaction is a hydroxy-nitrile. Mechanism KCN (potassium cyanide) is often used as the reagent to provide the nucleophile instead of HCN (hydrogen cyanide). This is because HCN is hard to store as a gas and reacts to produce dangerous byproducts. https://bit.ly/pmt-cc https://bit.ly/pmt-edu https://bit.ly/pmt-cc Hydroxy-nitriles commonly contain a chiral carbon centre meaning optical isomers of the product exist. The :CN- nucleophile can attack from either above or below the double bond, causing different enantiomers to be produced. Naming Hydroxynitriles When naming these compounds, the carbon on the nitrile group is included in the carbon chain and is taken to be carbon number one. Example: The following compound is 2-hydroxypropanenitrile. https://bit.ly/pmt-cc https://bit.ly/pmt-edu https://bit.ly/pmt-cc
