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Oxidation with Fehlings of Benedicts solution
Reagents : contain complexed ions in an
Solution
Why Cu2+
ions are complexed?
- to prevent precipitation of Cu(OH)2
Steps: A few drops of the aldehyde or ketone are added
to the reagent. The mixture is warmed gently.
Results :
Ketone : No change in the blue solution
Aldehyde : A red brown precipitate of copper (I) oxide
Half-equations:
Overall equation:
Oxidation with Tollens Reagent (silver mirror test)
Reagents : contain diamminesilver(I) ions,
How to make? Add silver(I) nitrate solution and diluteammonia
Steps : A few drops of the aldehyde or ketone are
added to the reagent. The mixture is warmed gently.
Results:
Ketone : No change in the colourless solution
Aldehyde : produce silver mirror on the test tube
Half-equations:
Overall equation:
Oxidation with acidified potassium dichromate (VI) solution
Reagents : dilute sulfuric acid and potassium dichromate (VI) solution
Steps: Half-equations:
Results: Overall equation:
Ketone : No change in the orange solution Aldehyde : orange solution turns green
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Reduction
Reducing agents : in dry ether (ethoxyethane) or sodium tetrahydridoborate
(NaBH4) in ethanol Conditions: room temperature
LiAlH4: more reactivecan reduce esters, amides and carboxylic acids
: reacts violently with water and alcohol. (reaction must be in dry condition)
Aldehyde : Reduced into 10alcohol Ketone: Reduced into 2
0
Equation : + 2[H] Equation: + 2[H]
*CANNOT REDUCED C=C BOND. Reducin a ent for C=C BOND : H with nickel or latinum catal st
Nucleophilic addition
Reagents : HCN (Hydrogen cyanide) in the presence of KCN in cold alkaline condition
Nucleophile attacks the +Carbon atom
Why must have KCN? To produce sufficient CN-ion
Equation :
Mechanism : 1) with ethanal: produce 2-hydroxypropanenitrile
2) with propanone : produce 2-hydroxy-2-methylpropanenitrile
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Stereochemistry in nucleophilic addition
Eg : Ethanal
-ethanal is a planar molecule
- cyanide ion has equal chance of attacking plane of themolecule either from above or below
Mechanism
SN1 nucleophilic substitution in halogenoalkane
-Form a planar intermediate
- nucleophile has equal chance of attacking the planar
intermediate either from above or below
Mechanism
- Form racemic mixture (equal amount of enantiomer)no effect on plane of polarization of the plane-polarised
monochromatic light
- optical isomerism : form molecule with asymmetric carbon atom that has chiral centre (carbon atom that has 4
different groups bonding with it)
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Condensation reaction with Bradys reagent (2,4-dinitrophenylhydrazine)
-to test compound containing carbonyl group such as aldehyde and ketone
Reaction: condensation (a reaction in which two molecules join together to form one big molecule with the loss
of small molecule such as water)
Mechanism: nucleophilic addition-elimination reaction
Equation:
Results : A yellow precipitate
The derivative can be removed by and purified by
Each 2,4-dinitrophenylhydrazine derivatives have characteristic melting temperatures which can be compared
with values given in data books.
Reaction with Iodine in the presence of alkali (NaOH)
- Name : iodoform reaction
- To identify the presence of CH3CO group in aldehydes and ketones or CH3CH(OH) group in alcohols
- Compound which gives positive results : ethanol. Ethanol. Propan-2-ol, butanone
*Equation :
Results : precipitate of triiodomethane (CHI3) which has smell
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Filtration and Recrystallisation Determine Melting Point
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Carboxylic Acid
Preparation
1. of primary alcohols or aldehydes
Reagents :
Conditions : Reflux
Results : Orange solution turns green (chromium (VI)
Compound is reduced to chromium (III) )
Equation:
2. of a nitrile by boiling with a dilute acid
Equation:
Diagram of Reflux
Reductionwith
(lithium aluminium hydride) in
Dry ether
Neutralization to produce salts
-with reactive metal, eg zinc - with ammonia
-with metal hydroxides
- with carbonates and h dro encarbonates
Making acid chloride
- Reagent : Phosphorus (V) chloride or
phosphorus pentachloride
- testOH group
Making ester (reflux)
- Reactions with
in the presence of an
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Making Acid Chloride
Reagent : Solid phosphorus (V) chloride
Results : Steamy acidic fumes of ,
phosphorus trichloride oxide (phosphorus oxychloride)
POCl3, acyl chloride (separated by fractional filtration_
Equation:
- must be dry condition :acyl chlorides react readily
with water vapour
Equation :
Making Ester
Reagent : carboxylic acid, alcohol and strong acid
catalyst : H2SO4 (equilibrium reaction)
Name : (condensation)
Equation :
Alternative : use more reactive acyl chloride or acid
anhydride
Equation :
Neutralisation
Eg Q : to determine the amount of citric acid in fruit
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Acyl chloride
Amines
Results : Produce a substituted amide
Equation :
Concentrated Ammonia
- Take place without heating
- Produce amide
Equation :
Alcohol
Reaction : Esterification
- non-reversible reaction, higher yield of ester
- take place without heating
Equation :
Water
Equation :
- Vigorous reaction
Results : steamy fumes of HCl
*Acid chloride need to be kept dry (water
vapour in air will react with it)
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Additional Reaction : (Unit 5)
1. Phenol
Equation :
CH3COCl + C6H5OH CH3COOC6H5 + HCl
Product : Phenyl ethanoate
- less vigorous as that between alcohols and ethanol chloride
- reactivity of theOH group is modified by the benzene ring
- to manufacture aspirin (2-hydroxybenzoic acid)
2. Friedel-Crafts acylation
Product : Ketone
Reagent : benzene, acid chloride and aluminium chloride (AlCl3) (catalyst)
Equation : C6H6 + CH3COCl + HCL
Benzene ethanoyl chloride phenylethanoate
Mechanism :
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Ester
Hydrolysis with Acid
Equation :
- reversible, small yield
Hydrolysis with Base
Equation :
- saponification (using KOH)
- non-reversible, higher yield
Condensation polymerization (form polyester)
Eg :1. Benzene-1,4-dicarboxylic acid and ethane-1,2-diol =
- making plastic bottles
alternative : diacyl chlorides, diacid anhydrides
2. Nylon: make at room temperature, non-biodegradable
Equation :
Transesterification
1. reaction of vegetable oils (triglyceride or ester) with methanol
or ethanol
Reagent : sodium hydroxide (catalyst)
Product: methyl ester (biodiesel-greener fuel)
- very efficient (yield of 98%)
- low temperatures (50C) and atmospheric pressure
-cheap and readily available catalyst
Equation:
2. reaction of an ester with an acid (manufacture margarine)
Adv : produce fewer trans fats compared with hydrogenation
(nickel catalyst)
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rt
Benzene or
methylbenzene
Combustion
Observation : yellow flame (incomplete combustion)
Equation :
(Benzene) 2C6H6 + 15O2 CO2 + H2O
(Methylbenzene) C6H5CH3 + 9O2 CO2 + H2O
(Addition reaction) hydrogenation
Reagent: Raney nickel catalyst (finely divided with a
very large surface area and very high catalytic
activity)
Temperature : 150C
Equation :
(Benzene) + 3H2
(Methylbenzene)
Halogenation
1. Addition reaction (only for benzene) = free radical reaction
Condition : UV light Product : 1,2,3,4,5,6-hexachlorocyclohexane
Equation :
(benzene) + 3Cl2 uv, heat
2. electrophilic substitution
Condition : catalyst of iron (III) bromide or iron filings (halogen carrier)
Temperature : room temperature Equation for catalyst : 2Fe + 3Cl2 2FeCl3
Equation :
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Benzene or
methylbenzene(toluene)
Nitration
(Benzene)
Reagent : concn nitric acid and concn sulfuric acid (catalyst) [nitrating mixture]
Temperature : 55C
- Both H2SO4 and HNO3are corrosive -HNO3is powerful oxidant
- Electrophile is nitronium ion, NO2+
-Equation for electrophile : HNO3 + 2H2SO4
- nitric acid acts as a base and accepts protons from the sulfuric acid
Product:nitrobenzene* use to produce phenylamine (C6H5NH2) for diazonium dye
(Methylbenzene or toluene) : use same reagent but at lower temperature
WHY?
Temperature :
- above 55C further substitution
HOW?
- Use cold water and slow dropwise
addition of benzene to the mixture
to maintain temperature
-exothermic reaction : acid react
and give out heat
Sulphonation (replace withSO3H)
-Reagent : fuming sulfuric acid ( concn H2SO4contains sulfur trioxide)
- Electrophile:sulfur trioxide Product : acid
- Temperature : room temperature
Equation :
+ H2SO4
C6H6 + H2SO4 ____ + H2O
FriedelCrafts reaction (electrophilic
substitution)
1. Alkylation 2. Acylation
- Reflux benzene with a halogenoalkane/ acyl
chloride
- halogen carrier catalyst :AlCl3
Product : alk lbenzene/ ketoneMethylbenzene is more reactive as methyl group donate electron density to the ring making
it more susceptible for electrophilic attack.
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Mechanism of Electrophilic substitution reactions
Halogenation Nitration
Alkylation (Friedel-Crafts reaction) Acylation (Friedel-Crafts reaction)
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Phenol
- oxygen atom on hydroxyl group of a phenol has two lone pairs electrons
- one of the lone pairs on oxygen atom donate electron density into its benzene ring, making it more susceptibleto electrophilic attack.
- make phenol more acidicthan alcohol
-its a weak acid it is fairly insoluble in water reacts with NaOH produces sodium phenoxide (colourless
solution) doesnt react with Na2CO3or hydrogencarbonate solutions (very weakly acidic) reacts with Na
to produce sodium phenoxide and hydrogen gas
Reaction with bromine water
- without heating and catalyst
Results : 1. bromine water is decolourised
2. white precipitate of 2,4,6-tribromophenol
3.smell of antiseptic
Equation :
Reaction with dilute nitric acid
- reagent: dilute nitric acid
Results : white precipitate of 2,4,6-trinitrophenol
Equation :
Coupling reactions of diazonium ions : making azo dye
Condition : ice cold alkaline solution (NaOH) of phenol and benzenediazonium chloride solution
* Benzenediazonium ion carries a positive charge and is a strong electrophile
* coupling : joing two aromatic rings together
- no N2gas is produced
Equation :
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Smell :fishy or smell of decay
Solubility : 1,2 & 3 can form
hydrogen bonds with H2O
Boiling point: 1>2 > 3
- no H bonding in 3 amine
Alkaline nature :
-methyl amine > ammonia >phenyl amine
- It has a lone pair on nitrogen
atom
Equations:
1. bases (amine)
(phenylamine)
2. form salts (amine)
(phenylamine)
Complex ion formation with copper (II)
ions (ligand exchange)
Results: blue precipitate dissolves to
form a deep blue solution
Equation:
Treatment with ethanoyl chloride (Ethanoylation) and
halogenoalkanes (condensation)
- amine acts as _____, product : amide(ethanoylation)
2& 3Amine (condensation)
Eg: making paracetamol using 4-nitrophenol with tin and
HCl (reduction)
Equation :
Reaction of phenylamine with nitrous acid to form _________
1. Prepare nitrous acid, HNO3in situ, HNO3unstable ( at room temperature) : Reagent: _____NaNO3,
Equation : NaNO3 + ______ Condition : ice-water mixture, temp: below___
If tempt above ___, it will produce _______. If tempt below ___, it will produce ____
Equation for tempt> 5C : Equation for tempt< 5C :
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Amide
Preparation : (Name : ethanoylation : replacement of a Hydrogen atom attached to a nitrogen or oxygen atom by CH3CO- using ethanoyl
chloride or ethanoic anhydride)
1. Reaction of an amine with ethanoyl chloride 2. Reaction of an ammonia with an acid chloride
Equation : Equation :
Benzenediazonium ions
- very unstable
Displacement structure
- a strong electrophile due to the positive
char e on one nitro en atom
Laboratory Preparation of benzenediazonium compound
Reagent : Steps:
Temperature :
Condition :Ice bath
Coupling reaction with phenol in cold NaOH to form a dye
Equation :
Diazonium compound
stable, unreactive
- dye ~ can form hydrogen
bonds with groups in cotton
and wool
- coloured dye ~ extensive
delocalized electron system
that spread across the entire
molecule through N N coupling
Manufacture of Paracetamol
Steps : Advantage : no chiral centre in paracetamol molecule
- 100% atom economy - manufacturing process easier (no filtration)
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POLYMERIZATION
1. Condensation polymerization
i) Polyesters : Terylene (PET)
Equation :
ii) Polyamides :
a) Nylon : - used in stockingsadd durability (tough) b) Kevlar: make bulletproof vest
Equation : Equation :
2. Addition polymerization : DISADVANTAGE : very resistant to a range of chemicals (non-biodegradable)
i) Poly(propenamide) ii) Poly(ethenol) : -hydrogen bondingsoluble laundry bags or liquid
Equation : detergent capsules (liquitabs)
Equation:
Manufacturing of Poly(ethenol)
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Acidity and Basicity and the formation of zwitterions
Zwitterion Acidity :
Basicity
- solid in room temperature
Reason :
Separation and identification by chromatography
Effect of aqueous solutions on plane
polarized monochromatic light
Reaction with Ninhydrin
Stuctural formula
Formation of peptide groups in
proteins by condensation
polymerization
AMINO ACIDS
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Diagram for preparation of phenylamine