C18 Organic Chem 3 Flashcards
Formula for Benzene
C6H6
Kekule Model for Benzene
Suggested that it was a planar ring of carbon atoms with alternating single and carbon bonds which constantly flipped
How was Kekule Model for Benzene disproved
X-ray diffraction showed the carbon to carbon bonds were equal in length
Delocalised Model
Each carbon atom has one p orbital which sticks above and below the plane of the ring.
These p orbitals overlap sideways, forming a ring of pi bonds that are delocalised around the carbon ring
Evidence for Delocalised Model
Enthalpy changes of Hydrogenations show the differences in the predicted and actual as benzene is more stable than the Kekule Structure
Why are electrophiles more susceptible to attack for alkenes that benzene
Alkenes have C=C bonds which have a high electron density which attracts electrophiles.
Benzene has a ring of delocalised electrons so the electron density / negative charge is more spread out so the attractions is reduced
Combustion of benzene
Smoky flame due to lack of oxygen
What reactions do arenes go under
Electrophilic substitution
Benzene to halobenzene
Halogen
FeBr3
Electrophilic substitution
Draw mechanism for
Benzene
Br2
FeBr3
search it up like fr fr fr
Friedel Crafts Reactions
Alkylation
Acylation
Friedel Crafts Alkylation Reactions
Haloalkane
AlCl3
Reflux
Friedel Crafts Acylation Reactions
Acyl Chloride
AlCl3
Reflux
Benzene to Nitrobenzene
Conc. HNO3 & Conc. H2SO4
Below <55 degrees Celsius
Why is Phenol more reactive than Benzene
Lone pair of electrons on the oxygen atom is donated to the delocalised ring of electrons on benzene
which increases its electron density
so it’s more susceptible to attack by electrons.
Haloalkane to Amine
Excess of ethanolic ammonia and heat in sealed tube under high pressure
Nucleophilic Substitution
Nitrile to Amine 1
LiAlH4 in dry ether
Dilute Acid
Reduction
Nitrile to Amine 2
Hydrogen
Ni cat.
High temp high pressure
Hydrogenation
Nitrobenzene to Aromatic Amine
Sn
Conc. HCl
Reflux
NaOH
Reduction
Order of strongest bases of:
phenylamine
ammonia
methylamine
and why
phenylamine
ammonia
methylamine
In phenylamine, the lone pair on N atom is donated to the delocalised ring of electrons so makes the lone pair less readily available
In methylamine, the alkyl groups are electron releasing so electron density on N atom increases making the lone pair more readily available to accept a proton
Amine are good…
Bases
Small Amine + water
+ and OH-
Amine + acid
Ammonium salt
Amine to N substituted Amide
Acyl Chloride
HCl
But Amine also reacts with HCl to form a salt
Solid white mixture of products form
Acyl Chloride to Primary Amide
Conc. NH3
Acyl Chloride to N substituted Amine
Primary Amine
Polyamide
2 amino acids
dicarboxylic acid and diamine
diacyl chloride and di amine
Protein to amino acids
6 mol/dm3 HCl
heat under reflux
NaOH
Why are amino acids amphoteric
Contains basic amino group and acidic carboxyl group
Amino acids normally exist as
zwitterions
2-amino-acids
When their is 1 carbon attached to the c=o carboxyl and amino group
Chromatography steps
Spot (of hydrolysate) on
paper/tlc/thin layer chromatogram
Marker spots of known aminoacids/measure Rf
Run in (suitable)
solvent/discussion of comparative
solubilities in phases
(Spray with) ninhydrin (and
heat)
Compare Rf values of marker spots
with hydrolysate spots
Grignard Reagent formula
R - Mg - X
How to make a Grignard Reagent
Haloalkane
Reagent : Mg in dry ether
Conditions: reflux
Grignard Reagents reactions
CO2
Carbonyls
R-Mg-X to Carboxylic acid
CO2 in dry ether
Dilute HCl
R-Mg-X to Alcohol
Carbonyl in dry ether
Dilute HCl
When is Steam Distillation used
- organic liquids have very high BPs
- some organic liquids decompose when heated
What is the main concept of steam distillation
Presence of steam lowers the boiling point of the immiscible product so it can evaporate at a lower BP before it decomposes
When do you use a separating funnel
If a product is insoluble in water, then you can use separation to remove any impurities that do dissolve in water
Solvent extraction is used when
Compounds in a mixture are both soluble in water
Process of solvent extraction
Add impure compound into separating funnel
Add water
Shake well
Add an organic solvent so products will dissolve in it
Add a salt so the organic product moves into the organic layer
Separates into product and aqueous layer with the impurities
Discard layers
Drying agents
Add an anhydrous salt like CaCl2 or MgSO4 and filter it
Hot filtration
for when u want the solid
Place filter paper on Buchner funnel
Wet paper with solvent
Turn vacuum on and pour mixture into the funnel.
Flask is under reduced pressure so liquid is sucked into the flask
Rinse solid with solvent
Wash off any of the original liquid
Recrystillisation
Very hot solvent is added to the impure solid until it dissolves to give a saturated solution of the impure product
Filter
Let solution cool slowly
Crystallises
Remove crystals by filtration under reduced pressure
Choice of solvent
Very soluble when hot
Insoluble when cool
Measuring Melting Points of an Organic Solid
Pack a small sample of the solid into a glass capillary tube
Place into a heating element
Increase temp so it melts
Measure the melting range
Compare with data book values
Do impurities increase or decrease BP
INCREASE
Do impurities increase or decrease MP
DECREASE
Recrystillation
Insoluble impurities are removed by
the hot filtration
Soluble impurities are removed by
the cold filtration
