4.3 Alcohols & Phenols Flashcards
Draw a phenol
Explain the reactivity of phenol (diagram too)
- lone pair on the oxygen is drawn to the ring
- increases electron density of the ring, activating it
- ring is able to induce dipoles
Describe the test for phenols
- Ferric chloride test, FeCl3
- lead to deep purple solution
- add bromine give white ppt
Explain the reactivity of phenol
- phenol is highly reactive due to the overlap of p-orbitals of the oxygen from the hydroxyl group and the p-orbitals of the carbons on the benzene ring of phenol
- overlapping causes lone pair on oxygen to be drawn to the ring
- increases electron density of the ring, activating it and making it able to induce dipoles
Explain the reactivity of benzene
- not very reactive
- 3 double bonds
- double bonds must be broken
- molecules reacting with it must be +ve to attract electrons in the bond and break them
Explain the reactivity of cyclohexene
- very reactive
- only one double bonds must be broken
- can easily induce dipoles due to high delocalisation
Primary alcohol
One carbon bonded to the C-OH group
Secondary alcohol
Two carbon atoms bonded to the C-OH group
What are the methods of forming alcohols?
- halogenoalkanes by a substitution reaction
- reducing aldehydes, ketones or carboxylic acids
Draw the nucleophilic substitution of a halogenoalkane
What is used in carbonyl reduction to produce alcohols?
- sodium tetrahydridiborate / NaBH4 (aldehyde and ketones)
- lithium aluminium hydride (carboxylic acids)
Primary alcohol mechanism
Primary —> aldehyde —> carboxylic acid
- H+/Cr2O7 at each stage
- distillation in first stage
- reflux to go alcohol to carboxylic acid
Secondary alcohol mechanism
Secondary —> ketone
- H+/Cr2O7
Tertiary alcohol mechanism
No change occurs
Why is the boiling temperature of methanol higher than that of chloromethane?
- methanol has hydrogen bonding
- chloromethane has VdW
- hydrogen bonds stronger than VdW
Reagents and conditions for conversion of alcohol to carboxylic acid
- acidified potassium dichromate
- heat
What is meant by heterolytic bond fission?
- bond breaks and both electrons go to one of the bonded atoms
Reagent to convert halogenoalkanes to alkenes
NaOH in ethanol
Explain the acidity of phenol
- lone pair on the oxygen overlaps with the pi system on the ring
- hydrogen lost more easily which forms a phenoxide ion
What is the test to distinguish between phenols and carboxylic acids?
Na2CO3
—> phenol doesn’t react, carbox does
How are chloroalkanes formed from alcohols?
- HCl and anhydrous ZnCl2 OR PCl3
—> nucleophilic substitution
How are bromoalkanes formed from alcohols?
- KBr and conc H2SO4
Reaction of alcohols with ethanoyl chloride
- addition elimination reaction that produces esters and HCl
