AQA Chemistry A-level 3.3.11: Amines Detailed Notes PDF
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This document provides AQA Chemistry A-level detailed notes on amines. It covers the preparation of amines, including nucleophilic substitution and reduction reactions, as well as properties, and nucleophilic reactions. Diagrams and examples are included, making it a good resource for studying amines.
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AQA Chemistry A-level 3.3.11: Amines 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 3.3.11: Amines 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 3.3.11.1 - Preparation of Amines Amines are produced when one or more of the hydrogen atoms in ammonia is replaced with an organic group. They can be 1o , 2o or 3o amines depending on how many hydrogen atoms are replaced. Example: Amines can be produced in two ways. Nucleophilic Substitution Amines are produced from the reaction of a halogenoalkane with ammonia in a sealed tube. One mole of halogenoalkane reacts with two moles of ammonia producing a primary amine and an ammonium salt. Example: https://bit.ly/pmt-cc https://bit.ly/pmt-edu https://bit.ly/pmt-cc This substitution reaction can continue until all the hydrogen atoms have been replaced with organic groups. Following this, an additional substitution can occur, producing a quaternary ammonium salt. Example: The multiple number of possible substitutions means that a mixture of products are produced. Therefore the reaction has low efficiency and reaction conditions have to be changed so that only a single substitution occurs. Ammonia can be added in excess in order to achieve only the primary amine, or the mixture of products can be separated using fractional distillation. Reduction of Nitriles Reducing nitriles via hydrogenation can produce amines. This reduction requires LiAlH4, a reducing agent, and acidic conditions or a combination of hydrogen and Nickel (catalytic hydrogenation). Example: https://bit.ly/pmt-cc https://bit.ly/pmt-edu https://bit.ly/pmt-cc Aromatic Amines These can be produced from the reduction of nitrobenzene using concentrated hydrochloric acid (HCl) and a Tin catalyst. Example: Cationic Surfactants These molecules are complexes with a positive and negative end. This makes them good conditioners as the two ends are attracted to different substances, preventing static from building up on surfaces. Cationic surfactants are therefore useful in industry. Example: 3.3.11.2 - Amine Base Properties Amines are weak bases because the lone electron pair on the nitrogen atom can accept protons. The base strength of amines depends on how available the electron pair is on the molecule. The more available the electrons, the more likely it is to accept a proton meaning it is a stronger base. https://bit.ly/pmt-cc https://bit.ly/pmt-edu https://bit.ly/pmt-cc The Inductive Effect In an organic molecule, different functional groups can affect how available a lone electron pair is by changing electron density around the bond. 1. Benzene rings - draw electron density away from the nitrogen making it ‘less available’ Example: Negative inductive effect. 2. Alkyl groups - push electron density towards the nitrogen making it ‘more available’. More alkyl groups means more ‘pushing’. Example: Positive inductive effect. This means aliphatic amines are stronger bases and aromatic amines are weaker. https://bit.ly/pmt-cc https://bit.ly/pmt-edu https://bit.ly/pmt-cc 3.3.11.3 - Nucleophilic Properties Nucleophilic Substitution Amines can act as nucleophiles because the lone electron pair is attracted to ∂+ regions on other molecules. This means amines can substitute halides on halogenoalkanes to form 1o, 2o or 3o amines and quaternary ammonium salts. Nucleophilic Addition-Elimination Amines can also undergo nucleophilic addition-elimination reactions with acyl chlorides to produce amides and N-substituted amides. Mechanism This same reaction mechanism can also occur with acid anhydrides to produce an amide and a carboxylic acid. N-substituted Amides When naming n-substituted amides, they are treated in a similar way to esters. Example: https://bit.ly/pmt-cc https://bit.ly/pmt-edu https://bit.ly/pmt-cc
