Alcohols and Phenols (DONE) Flashcards
How can alcohols be prepared from alkaline hydrolysis?
- Reaction mechanism
- Conditions and reagents
- Dilute aqueous sodium hydroxide with halogenoalkane
- Nucleophilic substitution
- Heat under reflux
How can alcohols be prepared from carbonyl compounds and carboxylic acids?
- Type of reaction/mechanism
- Reagents
- Reduction/Nucleophilic addition
- Aldehyde/Ketone and NaBH₄ (sodium borohydride) as a reducing agent or LiAlH₄
- Carboxylic acid with LiAlH₄ only (lithium aluminium hydride)
How can ethanol be prepared from ethene
- Type of reaction/mechanism
- Reagents and conditions
- Why is this method preferred over hydrolysis of halogenoalkanes
- Electrophilic addition
- Ethene, water (steam) as reagents
- Conc phosphoric acid catalyst, 60 atm and 300 degrees
- No by-products, 100% atom economy and heterogenous catalyst
How is a chloroalkane be produced from alcohol? Give other alternatives as well
- Conditions and reagents
- Anhydrous ZnCl₂ catalyst and heat under reflux
- HCl + alcohol
- Other methods include PCl₅, PCl₃ or SOCl₂
How can a bromoalkane be produced from alcohol?
- Conditions and reagents
- Show the additional reactions that must take place (in-situ)
- HBr (made in-situ) + alcohol
- In-situ KBr + conc. H₂SO₄ to form HBr
How can an iodoalkane be produced from alcohol?
- Conditions and reagents
- Show the additional reactions that must take place (in-situ)
(1 additional mark for explaining why the in-situ reaction uses a different chemical than the one used for bromination)
- Concentrated phosphoric (V) acid to make the HI in situ
- Alcohol + HI
- Sul. acid would oxidize the iodide ions to iodine, reducing the yield of HI
How do acid chlorides react with alcohols?
(2 marks)
- They react rapidly to form esters
- Under anhydrous conditions
State the advantages and disadvantages of using acid chlorides to form esters with alcohols instead of carboxylic acids?
(3 ad, 2 dis)
AD
- One way reaction, so higher yield of ester
- No catalyst
- No heating under reflux
DIS
- Produces a toxic gas of HCl
- Acid chlorides are expensive
How do carboxylic acids react with alcohols?
(4 marks)
- Forms an ester
- Concentrated sulfuric acid catalyst must be present, but also acts as a dehydrating agent
- Heat under reflux
- Distill the products and collect the ester at its boiling temperature
How can a pure product of ester be obtained?
(3 marks
- Separating funnel to run off the immiscible ester layer, which is then shaken with NaHCO₃ (aq) to neutralise remaining carboxylic acid
- Ester is dried with anhydrous CaCl₂ to react with any alcohol and water
- Ester can be redistilled to give a pure product
How is phenol acidic (very weakly)
- Name the ion it forms
- Draw an equation to show dissociation
- Provide an explanation (2 marks)
- Phenoxide ion
- Look in book for equation
- One of the lone pairs of the oxygen atom overlaps with the pi electron system of the benzene ring. This makes the C-O bond stronger than in alcohol and causes the proton ion to be lost more easily
- The phenoxide ion is more energetically stable by partial delocalisation of the negative charge and lone pair of electrons
Describe a test to distinguish between carboxylic acids and phenol
(3 marks)
- Add sodium carbonate solution
- Carboxylic acids will react to produce bubbles of Carbon dioxide/fizzing
- Phenols will have no fizzing
Show the reaction of phenol with NaOH (aq) and briefly explain why this is possible given that phenol is a weak acid
(2 marks)
- NaOH is a strong base
- Phenol + NaOH -> Sodium Phenoxide (colourless) + Water
Show the reaction of phenol with bromine (test for bromine) and state the observations
- Phenol + 3Br₂ -> 2,4,6-tribromophenol + 3HBr
- From orange brown to colourless and a white precipitate if formed
How does the phenolic OH group affect the susceptibility of phenol
(2 marks)
- OH group is an activating group, by the partial delocalisation of an oxygen lone pair of electrons around the benzene ring
- More susceptible to electrophilic attack
