Practicals Flashcards
Define a primary/secondary/tertiary alcohol
C-OH where C atom is bonded to 1/2/3 akyl groups
Outline the oxidation of primary alcohols through distillation
R-OH +[O] -(distill)-> R-CHO + [O] -(reflux)-> R-COOH
Outline the oxidation of primary alcohols through reflux
R-OH + 2[O] -(reflux)-> R-COOH
Outline the oxidising agent used for the distillation of primary alcohols
Tollens = silver mirror
or
Fehling’s = brick red
Outline a reducing agent for alcohols and/or aldehydes
Kr2Cr2O7
H2SO4
Outline the colour change when a primary alcohol is oxidised with K2Cr2O7
Orange -> green
List what’s used for the distillation apparatus
- Pear shaped flask
- Anti-bumping granules
- Bung
- Thermometer
- Condenser
- e- heater
- Ice bath
- Flask
Why are anti-bumping granules used for distillation/reflux?
Only make small bubbles form = smooth boiling
Why is an e- heater used for distillation?
Alcohol used is flammable (risk)
Why does H2O in the condenser enter from the bottom and leave the top?
Ensure condenser completely fills
Why is an ice bath used at the end of distillation?
Ensure that volatile reactants/products don’t escape as a gas
Define reflux
Continual evaporation + condensation
List what’s used in the reflux apparatus
- Pear shaped flask
- Anti-bumping granules
- Bung
- Condenser
- e- heater
What organic liquid is normally purified?
Cyclohexanol -> cyclohexene
Which has a higher bp and why? Cyclohexanol or cyclohexene?
Cyclohexanol
Cyclohexanol = H bonds from R-OH
Cyclohexene = VDWs
H bonds > VDWs
Outline the steps that occur for the elimination of cyclohexanol (not like usual mechanism)
- H+ from catalyst (H3PO4) attacked by e- pair on R-OH
- H of adjacent C to C-OH2 donates e- pair to form C=C
- e- pair donates to O+ to form cyclohexene, H2O & reformed H+
What apparatus is used for the 1st stage of purification of an organic liquid?
Distillation
Outline the 2nd step of the purification of an organic liquid
Add a base (Na2CO3) -> open tap to release CO2
Outline the 3rd step of the purification of an organic liquid and it’s purpose
Put mixture in separating funnel
Cyclohexanol = top layer
H3PO4(aq) = bottom layer (more dense)
Cyclohexanol separates
Use tap to drain (aq) layer
Outline the 4th step of the purification of an organic liquid
+ drying agent (CaSO4) to absorb H2O & other aqueous substances
Outline the 5th step of the purification of an organic liquid
Distill again
Outline the organic solid that’s normally purified
Aspirin
Outline the reagents and mechanism that occurs for the formation of Aspirin
2-hydroxybenzoic acid + ethanoic anhydride
Nucleophilic addition elimination
Outline the steps for the nucleophilic addition elimination to form aspirin
- :OH on 2-hydroxybenzoic acid attacks C+ on ethanoic anhydride - C=O breaks
- O-H on acid breaks to remove O+. :O- on anhydride forms C=O again, breaking C-O bond
Aspirin forms - H+ from O-H forms with broken of CH3COO- from anhydride to form CH3COOH
What practical is used for the purification of an organic solid?
Recrystallisation
Outline the 1st step of the purification of an organic solid
Dissolve aspirin in min amount of hot solvent (ethanol)
Outline the 2nd stage of the purification of an organic solid
Gravity filtration - remove insoluble impurities
Use funnel and filter paper
Outline the 3rd stage of the purification of an organic solid
Put solvent, aspirin & soluble impurities in ice bath
Aspirin crystallises out
Outline the 4th stage of the purification of an organic solid
Wash aspirin in ice cold solvent under reduced Pa
Use Buchner flask and vacuum
How do you compare a pure organic solid to an impure organic solid?
MP determination - compare to databook
Pure - high MP and low range
Impure - low MP & high range
