Organic Chemical Organic Chemical ReactionsReactions

You will learn the different types of You will learn the different types of organic reactions you need to know like organic reactions you need to know like

electrophilic addition, free radical electrophilic addition, free radical substitution, nucleophilic substitution substitution, nucleophilic substitution and elimination, hydrolysis, reduction, and elimination, hydrolysis, reduction,

oxidation and polymerisationoxidation and polymerisation

Electrophilic substitutionElectrophilic substitution

► Ethene reacts with Halogens or sulphuric Ethene reacts with Halogens or sulphuric acidacid

► An electrophile is a positive (relative), An electrophile is a positive (relative), species that is attracted towards a species that is attracted towards a negative centrenegative centre

► Which bond on ethene is a very negative Which bond on ethene is a very negative centre?centre?

► Recall: Addition of bromine to ethene …Recall: Addition of bromine to ethene …the test for an alkenethe test for an alkene

► Recall: Addition of steam to make alcoholsRecall: Addition of steam to make alcohols

Reactions of halogens with Reactions of halogens with etheneethene

► What is the order of reactivity with the halogens? What is the order of reactivity with the halogens? ► CHCH22=CH=CH22 + X + X22 CH CH22X=CHX=CH22XX► Write the equation for bromine and name the Write the equation for bromine and name the

productproduct► BrBrδδ++-Br-Brδδ- - This is an induced dipole, now the This is an induced dipole, now the BrBrδδ++ is is

attracted to the attracted to the ππ (pi) bond (pi) bond► This is the electrophileThis is the electrophile► A more stable sigma bond forms and a bromine ion A more stable sigma bond forms and a bromine ion

is producedis produced

► There is a positive charge on the carbon There is a positive charge on the carbon without the bromine which then attracts the without the bromine which then attracts the negative bromine ionnegative bromine ion

►HH22C=CHC=CH2 2 + + BrBrδδ++-Br-Brδδ- -

►HH22CC++-CH-CH22Br + BrBr + Br- - BrBrHH22C-CHC-CH22BrBr

► Result formation of dibromoethaneResult formation of dibromoethane

Hydrogen HalidesHydrogen Halides

► The bond strength increases with increasing The bond strength increases with increasing electronegativityelectronegativity

► Predict which will react the fastest HCl/HBr/HIPredict which will react the fastest HCl/HBr/HI► This time the Hydrogen ion acts as the This time the Hydrogen ion acts as the

electrophile as the bond is Helectrophile as the bond is Hδδ++-Br-Brδδ- -

►Hydrogen is the positive or electron deficient, it Hydrogen is the positive or electron deficient, it goes by the same mechanism except there is a goes by the same mechanism except there is a permanent dipole not induced which will have permanent dipole not induced which will have what effect on the rate?what effect on the rate?

Sulphuric acid catalysed Sulphuric acid catalysed reactions with ethenereactions with ethene

► HH22C=CHC=CH2 2 + + δδ++H-OH-Oδδ--SOSO33H HH H22CC++-CH-CH22HH + HSO + HSO44--

► HH33C-HC-H22CCδδ++-O -O δδ--SOSO33H + HH + H22O CHO CH33CHCH22OH + HOH + H22SOSO44

►Why does the oxygen of water attack the Why does the oxygen of water attack the positive centre?positive centre?

Nucleophilic SubstitutionNucleophilic Substitution

►A nucleophile: A species that donates a A nucleophile: A species that donates a pair of electrons to a electron deficient pair of electrons to a electron deficient atom in order to form a covalent bondatom in order to form a covalent bond

►Species in ammonia, hydroxide and Species in ammonia, hydroxide and cyanide ionscyanide ions

►Species that are attacked: Compounds Species that are attacked: Compounds that have electronegative elements that have electronegative elements bonded to carbons. E.g. haloalkanes like bonded to carbons. E.g. haloalkanes like 1-bromomethane1-bromomethane

►Products made = Products made = usually alcoholsusually alcohols or or aminesamines

►Name some substances that have lone Name some substances that have lone pairs of electronspairs of electrons

►HH33CHCH22CCδδ++ BrBrδδ-- + + ÖÖHH--

►HH33C-HC-H22CCOH + Br OH + Br --

►What conditions are best for this? Find out.What conditions are best for this? Find out.►Weak base, water solvent and low Weak base, water solvent and low

temperaturetemperature

Nucleophilic EliminationNucleophilic Elimination

►The formation of alkenes from The formation of alkenes from haloalkaneshaloalkanes

►HH33CHCH22CCδδ++ BrBrδδ-- + + ÖÖHH--

►HH33C-HC-H22CCOH + Br OH + Br --

► H H

ÖÖHH-- ► C CC C► ► BrBr

►What alkene will be produced?What alkene will be produced?►Ethene and a bromide ionEthene and a bromide ion

Mechanism

ConditionsConditionsConditionsConditions EliminationElimination SubstitutionSubstitution

SolventSolvent EthanolEthanol WaterWater

BaseBase StrongStrong WeakWeak

TemperatureTemperature HighHigh LowLow

Free Radical SubstitutionFree Radical Substitution

►The reaction between chlorine and The reaction between chlorine and alkanes (with UV light)alkanes (with UV light)

►What are the products of this reaction?What are the products of this reaction?►What is the mechanism? Find outWhat is the mechanism? Find out

► Chlorine Chlorine UV light UV light 2 Chlorine radicals2 Chlorine radicals

► What is a radical? Define it.What is a radical? Define it.► Why are they so reactive?Why are they so reactive?► What do steal off other atoms?What do steal off other atoms?► What substances would be likely to form What substances would be likely to form

radicals?radicals?

2

► Find out the mechanism of how a free Find out the mechanism of how a free radical reaction is started, carries on radical reaction is started, carries on the chain reaction and endsthe chain reaction and ends

► 3 step reaction:3 step reaction:

► InitiationInitiation► Molecular bond is broken, represented Molecular bond is broken, represented

► ClCl22 2Cl 2Cl..

► Cl-ClCl-Cl

►This called homolytic fission, write a This called homolytic fission, write a definition for thisdefinition for this

►This means that both atoms in the This means that both atoms in the bond get 1 electron eachbond get 1 electron each

►Opposite is called heterolytic fission, Opposite is called heterolytic fission, you know this what is this process?you know this what is this process?

►Hetero and homoHetero and homo

►PropagationPropagationThe radical reacts with other reactant. The radical reacts with other reactant.

ClCl.. + CH+ CH4 4 HCl + HCl + ..CHCH33

HH3 3 CC. . + ???+ ???

Write down what the products are if it Write down what the products are if it collides with Clcollides with Cl22 or CH or CH44

►TerminationTermination►What must happen for the reaction to stop?What must happen for the reaction to stop?►How can you get rid of the radicals?How can you get rid of the radicals?

►HH3 3 CC. . + Cl+ Cl. . CHCH33ClCl

►What other termination products could be What other termination products could be formed?formed?

► Reactions that this happens in:Reactions that this happens in:1.1. Thermal CrackingThermal Cracking2.2. Alkane halogenationAlkane halogenation

HydrolysisHydrolysis

► Esterification is Esterification is reversiblereversible

► This reaction to make This reaction to make an ester is called an ester is called condensation as water condensation as water is producedis produced

► To break up an ester is To break up an ester is called hydrolysis as it called hydrolysis as it uses wateruses water

Reduction and oxidationReduction and oxidation

►Write down the different types of oxidationWrite down the different types of oxidation►Write down the different types of reductionWrite down the different types of reduction►MnMn7+ 7+ + 5 e+ 5 e-- Mn Mn2+2+

► Is this oxidation or reduction?Is this oxidation or reduction?►MgMg(s) (s) + Fe+ Fe2+2+

(aq) (aq) FeFe(s) (s) + Mg+ Mg2+2+(aq) (aq)

►What is this called?What is this called?►CHCH22CHCH2 2

KK22CrCr

22OO

7 7 CHCH22OHCHOHCH22OHOH►What is the species and process called? What is the species and process called? ►Alcohols into ketones and aldehydes (and Alcohols into ketones and aldehydes (and

carboxylic acids when done further)carboxylic acids when done further)

PolymerisationPolymerisation

►What does this mean?What does this mean?►Name some natural and synthetic Name some natural and synthetic

polymers.polymers.►What is the difference between addition What is the difference between addition

and condensation polymerisation, find and condensation polymerisation, find out. out.

►What types of molecules take part in this What types of molecules take part in this reaction? List them.reaction? List them.

►What do they have in common?What do they have in common?