Organic Flashcards
Define chiral carbon
A carbon atom that is bonded to 4 different groups, tetrahedrally arranged
How many hydrogen atoms are bonded to 1 carbon atom in a benzene ring
1
Define optical isomer
Molecules that contain chiral carbons so that the two enantiomers are non-superimposable mirror images
What is used to measure the rotation of polarised light?
What is it called if the light:
Rotates right?
Rotates left?
Polarimeter
Dextrorotatory
Levorotatory
Define racemic mixture
A mixture containing equal amounts of two enantiomers which produce equal but opposite rotation of polarised light so no overall rotation is observed
Why is the product formed from the nucleophilic addition of cyanide a racemic mixture?
Because the cyanide ion is equally likely to attack the carbon atom from the left or the right
And the carbonyl group is planar
Tests for aldehydes or ketones
Tollens reagent
Silver mirror when warmed with aldehyde
Ketone remains colourless
Fehlings solution
Brick red precipitate formed with aldehyde
Remains blue with ketone
What is the reducing agent in the nucleophilic addition reaction with a COOH or Aldehyde or ketone?
What is a stronger reducing agent than this one?
NaBH4 in aqueous solution
liAlH4
Outline the 2 stage nucleophilic addition reaction of a COOH
What type of alcohol does NaBH4 reduce
An aldehyde into?
A ketone into?
CH3COOH + 2[H] > CH3CHO + H2O
CH3CHO + 2[H] > CH3CH2OH
1 degree OH
2 degree OH
How is an ester named?
Ethyl methanoate
Ethyl is from OH
Methanoate is from COOH
What is the reaction for esterification?
What type of reaction is an esterification reaction?
OH + COOH > ester + H2O
H+
Reflux
Reversible reaction
Conc H2SO4 homogenous acid catalyst
Condensation reaction
Define homogenous catalyst
A catalyst which is in the same physical state as the reactants
What is the disadvantage of esterification?
It is a reversible reaction is a low yield is produced
What are the properties of an ester?
Volatile (evaporates easily) - produces sweet smell
No hydrogen bonds - lower b.p than reactants and is insoluble in water
Test for OH/COOH using esters
Esterification reaction - if fruity smell, OH/COOH is present
The reaction for the acid hydrolysis of an ester
Why must NaOH be in excess
Ester + water > OH + COOH
H+ reflux
conc H2SO4
Or NaOH as catalyst
Reversible reaction
To prevent formation of salt with COOH
The reaction for base hydrolysis of an ester
What happens to the reactant as a result of the base?
ester + OH- > carboxylate ion- + OH
Carboxylate ion- bonds with Na+ to form salt
I.e sodium ethanoate
What’s another name for glycerol?
Propan-1,2,3-triol
How are veg oils and animal fats produced?
Define saturated. What is the effect of this on the melting point?
Define unsaturated. What is the effect of this on the melting point?
Which product is saturated and which product is unsaturated?
Esterification of glycerol to produce a triester (which are the animal fats and veg oils)
Single bonds between carbon atoms
Lower SA, more VDW forces = higher m.p
Double bonds between carbon atoms
Lower SA, less VDW forces = lower m.p
Fats are saturated, oils are unsaturated
What is the reaction for the hydrolysis of fats and oils?
Triester + 3NaOH > glycerol + 3RCOO-Na+ Sodium salt (soap) produced
Reaction for the conversion of soap back into free fatty acids
RCOO-Na+ + H+ > RCOOH + Na+
Strong acid(I.e HCl)What are the uses of esters?
Sweet smell and taste = perfumes and food flavouring
They are Polar molecules = polar organic solvents dissolve in them
Low b.p = volatile so good glue solvents
Flexible = used as plasticisers for polymers, which is added during polymerisation
What is a disadvantage of a plasticiser?
Plasticiser molecules escape over time so the polymer becomes brittle and stiff
What is a different way of drawing a benzene ring?
With alternating carbon carbon double bonds
Why are benzene rings very stable
Long explanation
Each carbon atom is bonded to only 1 hydrogen atom
So there is a lone electron on each carbon atom
These lone delocalised electrons are in the p orbital
All the p-orbitals combine to make a ring of electrons above and below the structure
Electron density is shared across the entire structure
What is the order of bond lengths between carbon atoms?
C=C 135pm
Benzene 140pm
C-C 147pm
Define electrophile
A species that accepts a pair of electrons
What property of an electrophile makes it suitable for reactions with benzene? Why is it suitable?
It is very reactive
Which is required because benzene is so stable
Outline the 2 step reaction for the production of a nitronium ion
Why can this reaction occur?
H2SO4 + HNO3 > HSO4- + H2NO3+
H2NO3+ > NO2+ + H20
Because HNO3 acts as a base because it is less reactive than H2SO4
What is produced as a result of the electrophilic substitution of a nitronium ion
Nitrobenzene and a hydrogen ion
What is the final reaction step in the nitration of benzene?
Reformation of catalyst
H+ + HSO4- > H2SO4
What are the uses of nitrobenzene?
Nitro compounds decompose violently when heated - explosives
Nitrobenzene can be converted to phenylamine which can be used for dyes
Outline the reaction of the formation of an acyl carbocation?
What is the catalyst of this reaction known as?
This is the first step of what reaction?
AlCl3 + RCOCl > AlCl4- + RCO+
Halogen carrier catalyst
Friedel-crafts Acylation
What is produced in the electrophilic substitution of an acyl carbocation?
What are the conditions of this reaction?
Phenylketone + HCl +AlCl3
Reflux
AlCl3 catalyst
