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Booklet to help with unit 28 P3. Reactions of halogenoalkanes , alcohols and amines. Examples of reactions. Nucleophilic substitution of halogenoalkanes. Description:
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Booklet to help with unit 28 P3 Reactions of halogenoalkanes, alcohols and amines
Nucleophilic substitution of halogenoalkanes Description: The electron-deficient carbon atom of the polar C-Hal bond attracts nucleophiles, allowing a nucleophilic substitution reaction to take place in which the nucleophile replaces the halogen atom Reaction with aqueous hydroxide ions, OH-(aq) produces an alcohol
Nucleophilic substitution of halogenoalkanes Example of a balanced chemical equation: • The hydroxide ion, OH-, behaves as a nucleophile. • The C-Br bond breaks by heterolytic fission losing its electron pair to form a Br- ion.
Elimination reaction of halogenoalkanes Description: When a halogenoalkane is refluxed with hydroxide ions in anhydrous conditions (using NaOH in ethanol as a solvent at 78◦C), an elimination reaction takes place. During the elimination reaction, the halogenoalkane is changed into an alkene, which results in an elimination of a smaller molecule in order to form the alkene
Elimination reaction of halogenoalkanes Example of balanced chemical equation: C2H5Br + OH- C2H4 + Br- + H2O
Nucleophilic substitution of alcohols Description • The electron-deficient carbon atom of the polar C-OH bond of alcohols attracts nucleophiles like Br-. This allows a nucleophilic substitution reaction to take place in which the nucleophile replaces the hydroxyl group in the alcohol. This results in the alcohol changing into a halogenoalkane
Nucleophilic substitution of alcohols Example of balanced chemical equation Displayed representation of reaction
Dehydration of alcohols Description When an alcohol is refluxed with a concentrated acid catalyst such as sulphuric acid H2SO4, or phosphoric acid H3PO4, an elimination reaction takes place: water is eliminated with formation of an alkene NOTE: Dehydration is a type of elimination reaction where water is eliminated from a reactant
Dehydration of alcohols Example of balanced chemical equation Displayed representation of reaction
Acid/Base reactions of amines Description Amines are weak bases so they will react with acids like Hydrochloric acid to form a neutral solution.
Acid/Base reactions of amines • Example of balanced chemical equation • Example of word equation Phenylamine + phenylammonium chloride Hydrochloric acid
Acylation of amines Description These are reactions in which amines act as a nucleophile and a carbonyl group (C=O) replaces a hydrogen in the amine group (-NH2)
Acylation of amines Example of balanced chemical equation Pictures of main reactant and product Product: Phenylethananide Reactant: Phenylamine