Alcohols
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What two methods are there to produce alcohols?
1.Nucleophilic substituition of halogenoalkanes 2.Reduction of aldehydes, ketones or carboxylic acids.
Describe 3 ways to react chlorine with alcohol
1.Pass HCl through alcohol with dry ZnCl2 catalyst. 2.React with PCl5 to form POCl3 and HCl. (Similar boiling temp between halogenoalkane and POCl3) 3.React with SOCl2 to form SO2 and HCl, which are gases and easily lost/seperated.
What are the conditions required to form alcohols from halogenoalkanes?
Heated under reflux Aqueous alkali such as NaOH or KOH Ethanol helps to dissolve halogenoalkane
What is produced when a alcohol reacts with a hydrogen halide?
Halogenalkane
What conditions are required for the reduction of carbonyl compounds and carboxylic acids to form alcohols?
NaBH4 dissolved in water for aldehydes/ketones LiAlH4 for carboxylic acids(Stronger reducing agent)
Describe how to react iodine with alcohol
Warm iodine with damp red phosphorus forming phosphorus(III) iodide (PI3), which will react with the alcohol to form the halogenoalkane
What is formed when alcohol reacts with ethanoyl chloride, CH3COCl
An ester forms with misty fumes of HCl
Describe how to react bromine with alcohol
Heat the alcohol with potassium bromide(KBr) and sulfuric acid(H2SO4).
What are the pros and cons of the reaction between alcohols and ethanoyl chloride?
Pros: Good yield than if reacted with carboxylic acid as it is not a reversible reaction Cons: Not cost effective in industry as acid chlorides are expensive
Name two ways to produce an ester
1.Alcohol and ethanoyl chloride(acid chlorides) 1.Alcohol and carboxylic acids
Describe the reaction between alcohols and carboxylic acids (Esterification)
An ester is formed by reacting the reactants under reflux, with a H2SO4 catalyst. The insoluble ester layer can be removed using a seperating funnel and the ester can be distilled and collected. An remaining acid is neutralised by NaHCO3
Define phenol
A aromatic alcohol where the OH- group is bonded directly to the benzene ring.
Why does phenol not dissolve readily in water?
Due to the hydrocarbon section.
Why are phenols stronger acids than alcohols?
The H+ ions are more easily lost as the phenoxide ion is formed and is more stable due to the negative charge becoming delocalised around the ring system. Thus because the phenoxide ion is more stable, equilibrium favours its production, making the original compound more acidic as it readily loses H+ to form the phenoxide.
Why are phenols less acidic than carboxylic acids?
Carboxylate ions are more stable than phenoxide ions.
Describe a test that distinguishes phenols and carboxylic acids
Adding sodium carbonate (NaCO3). Carboxylic acids produce CO2, phenols are not acidic enough to.
Describe the reaction between phenols and bromine
Mechanism: Electrophilic substuition, Br is the electrophile The electron density of the phenol polarises the bromine water causing the two to react and produce 2,4,6-tribromophenol (white precipitate) and HBr. The bromine water decolourises
Describe the reaction between phenol and ethanoyl chloride
Slow at room temp so a base is added as a catalyst such as pyridine (C5H5N). The phenol reacts with ethanoyl chloride to produce ethanoic acid.
Describe how to test for phenols with iron(III) chloride
When iron(III) chloride a pale yellow solution reacts with a phenol a purple colour change is observed. *In fact, any compound that has an -OH group bonded directly to a benzene ring will give a positive test with iron(III) chloride. They can be purple, blue or green in colour.
What is observed when iron(III) chloride reacts with carboxylic acid?
Pale yellow to red/brown colour change