organic mechnisms. meet the attackers press the space bar
TRANSCRIPT
ORGANIC MECHNISMSORGANIC MECHNISMS
MEET THE ATTACKERSMEET THE ATTACKERS
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MEET THE ATTACKERSMEET THE ATTACKERS
I AM A NUCLEOPHILE
I HAVE A LONE PAIR WHICH I CAN USE TO FORM A NEW BOND.
I ATTACK ELECTRON DEFICIENT AREAS (those with a + or )
MEET THE ATTACKERSMEET THE ATTACKERS
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MEET THE ATTACKERSMEET THE ATTACKERS
I AM AN ELECTROPHILE
I HAVE A + CHARGE or a CHARGE. I ATTACK ELECTRON
RICH AREAS SUCH AS C=C DOUBLE BONDS.
MEET THE ATTACKERSMEET THE ATTACKERS
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MEET THE ATTACKERSMEET THE ATTACKERS
AND I AM A FREE RADICAL
I HAVE AN UNPAIRED ELECTRON WHICH I WANT TO PAIR UP. I AM
VERY REACTIVE AND DON’T MIND WHERE I ATTACK… WATCH OUT!
THE BONDING IN A MOLECULEINFLUENCES WHAT WILL ATTACK IT
WHO IS ATTACKED?WHO IS ATTACKED?
THE BONDING IN A MOLECULEINFLUENCES WHAT WILL ATTACK IT
SINGLEA typical covalent bond with one shared pair – nothing to tempt an attacking species
WHO IS ATTACKED?WHO IS ATTACKED?
THE BONDING IN A MOLECULEINFLUENCES WHAT WILL ATTACK IT
SINGLE
MULTIPLE
A typical covalent bond with one shared pair – nothing to tempt an attacking species
Bond has twice as many electrons – species which like electrons will be attracted
WHO IS ATTACKED?WHO IS ATTACKED?
THE BONDING IN A MOLECULEINFLUENCES WHAT WILL ATTACK IT
SINGLE
MULTIPLE
NON-POLAR
A typical covalent bond with one shared pair – nothing to tempt an attacking species
Bond has twice as many electrons – species which like electrons will be attracted
Similar atoms have an equal attraction for the shared pair of the covalent bond
WHO IS ATTACKED?WHO IS ATTACKED?
THE BONDING IN A MOLECULEINFLUENCES WHAT WILL ATTACK IT
SINGLE
MULTIPLE
NON-POLAR
POLAR
A typical covalent bond with one shared pair – nothing to tempt an attacking species
Bond has twice as many electrons – species which like electrons will be attracted
Similar atoms have an equal attraction for the shared pair of the covalent bond
Atoms have different electronegativities and the shared pair will be attracted more to one end – species known as nucleophiles will be attracted to the slightly positive end
WHO IS ATTACKED?WHO IS ATTACKED?
THE BONDING IN A MOLECULEINFLUENCES WHAT WILL ATTACK IT
SINGLE
MULTIPLE
NON-POLAR
POLAR
A typical covalent bond with one shared pair – nothing to tempt an attacking species
Bond has twice as many electrons – species which like electrons will be attracted
Similar atoms have an equal attraction for the shared pair of the covalent bond
Atoms have different electronegativities and the shared pair will be attracted more to one end – species known as nucleophiles will be attracted to the slightly positive end
WHO IS ATTACKED?WHO IS ATTACKED?
ALKANES ARE RELATIVELY UNREACTIVE ORGANIC COMPOUNDS
ALKANES CONTAIN TWO BOND TYPES
C-H and C-C
WHAT ATTACKS ALKANES?WHAT ATTACKS ALKANES?
Both bonds are single – no electron rich areas
Bonds are non-polar - no electron deficient areas
Free radicals are very reactive and do attack
FREE RADICAL SUBSTITUTIONFREE RADICAL SUBSTITUTION
ALKENES ARE MUCH MORE REACTIVE THAN ALKANES
ALKENES CONTAIN A C=C BONDThere will be twice as many electrons between the carbon atoms as there are in a single bond
WHAT ATTACKS ALKENES?WHAT ATTACKS ALKENES?
C=C bond is double – an electron rich area
Bonds are non-polar - no electron deficient areas
ELECTROPHILIC ADDITIONELECTROPHILIC ADDITION
HALOGENOALKANES ARE MUCH MORE REACTIVE THAN ALKANES
HALOGENOALKANES CONTAIN A POLAR BONDThe halogen is more electronegative than the carbon attracts the shared electron pair.
WHAT ATTACKS HALOGENOALKENES?WHAT ATTACKS HALOGENOALKENES?
Bond is single – not an electron rich area
Bond is polar – the greater electronegativity of the halogen creates a dipole making the carbon atom electron deficient.
NUCLEOPHILIC SUBSTITUTIONNUCLEOPHILIC SUBSTITUTION
THESE ARE USED TO REPRESENT THE MOVEMENT OF ELECTRONS
CURLY ARROWSCURLY ARROWS
THESE ARE USED TO REPRESENT THE MOVEMENT OF ELECTRONS
CURLY ARROWSCURLY ARROWS
ELECTRONS MOVE FROM AREAS OF HIGH ELECTRON DENSITY TO ONES WITH A LOWER ELECTRON DENSITY
THESE ARE USED TO REPRESENT THE MOVEMENT OF ELECTRONS
CURLY ARROWSCURLY ARROWS
ELECTRONS MOVE FROM AREAS OF HIGH ELECTRON DENSITY TO ONES WITH A LOWER ELECTRON DENSITY
For example…from LONE PAIRS
DOUBLE BONDS
THESE ARE USED TO REPRESENT THE MOVEMENT OF ELECTRONS
CURLY ARROWSCURLY ARROWS
ELECTRONS MOVE FROM AREAS OF HIGH ELECTRON DENSITY TO ONES WITH A LOWER ELECTRON DENSITY
For example…from LONE PAIRS
DOUBLE BONDS
to POSITIVE SPECIESTHE END OF POLAR BONDS
THESE ARE USED TO REPRESENT THE MOVEMENT OF ELECTRONS
CURLY ARROWSCURLY ARROWS
THESE ARE USED TO REPRESENT THE MOVEMENT OF ELECTRONS
ARROWS WITH TWO ‘HEADS’ INDICATE THE MOVEMENT OF TWO (A PAIR OF) ELECTRONS
CURLY ARROWSCURLY ARROWS
THESE ARE USED TO REPRESENT THE MOVEMENT OF ELECTRONS
ARROWS WITH TWO ‘HEADS’ INDICATE THE MOVEMENT OF TWO (A PAIR OF) ELECTRONS
CURLY ARROWSCURLY ARROWS
A PAIR of electrons moves from here… to here
THESE ARE USED TO REPRESENT THE MOVEMENT OF ELECTRONS
ARROWS WITH TWO ‘HEADS’ INDICATE THE MOVEMENT OF TWO (A PAIR OF) ELECTRONS
CURLY ARROWSCURLY ARROWS
A PAIR of electrons moves from here… to here
ARROWS WITH ONE ‘HEAD’ INDICATE THE MOVEMENT OF JUST ONE ELECTRON
THESE ARE USED TO REPRESENT THE MOVEMENT OF ELECTRONS
ARROWS WITH TWO ‘HEADS’ INDICATE THE MOVEMENT OF TWO (A PAIR OF) ELECTRONS
CURLY ARROWSCURLY ARROWS
A PAIR of electrons moves from here… to here
ARROWS WITH ONE ‘HEAD’ INDICATE THE MOVEMENT OF JUST ONE ELECTRON
ONE electron moves from here… to here
THESE ARE USED TO REPRESENT THE MOVEMENT OF ELECTRONS
ARROWS WITH TWO ‘HEADS’ INDICATE THE MOVEMENT OF TWO (A PAIR OF) ELECTRONS
CURLY ARROWSCURLY ARROWS
A PAIR of electrons moves from here… to here
ALWAYS BE PRECISE WITH THE POSITIONING OF ANY ARROWSALWAYS BE PRECISE WITH THE POSITIONING OF ANY ARROWS
ARROWS WITH ONE ‘HEAD’ INDICATE THE MOVEMENT OF JUST ONE ELECTRON
ONE electron moves from here… to here
NUCLEOPHILES:- possess a lone pair of electrons
DRAWING CURLY ARROWSDRAWING CURLY ARROWS
NUCLEOPHILES:- possess a lone pair of electrons
DRAWING CURLY ARROWSDRAWING CURLY ARROWS
HYDROXIDE ION
negative charge
H Olone pair
more lone pairs
NUCLEOPHILES:- possess a lone pair of electrons
DRAWING CURLY ARROWSDRAWING CURLY ARROWS
HYDROXIDE ION
negative charge
H Olone pair
more lone pairs
AMMONIA MOLECULE
Nucleophiles don’t need to have negative charge… BUT they must have a lone pair
lone pair
H
H N
H
NUCLEOPHILES:- possess a lone pair of electrons
DRAWING CURLY ARROWSDRAWING CURLY ARROWS
HYDROXIDE ION
negative charge
H Olone pair
more lone pairs
AMMONIA MOLECULE
Nucleophiles don’t need to have negative charge… BUT they must have a lone pair
lone pair
H
H N
H
ELECTROPHILES:- attract a lone pair of electrons
DRAWING CURLY ARROWSDRAWING CURLY ARROWS
ELECTROPHILES:- attract a lone pair of electrons
DRAWING CURLY ARROWSDRAWING CURLY ARROWS
HYDROGEN ION HThere are no electrons in the outer shell of hydrogen so it has space to accept two electrons
ELECTROPHILES:- attract a lone pair of electrons
DRAWING CURLY ARROWSDRAWING CURLY ARROWS
HYDROGEN ION HThere are no electrons in the outer shell of hydrogen so it has space to accept two electrons
HYDROGEN CHLORIDE
contains a POLAR BOND; the end will attract the electron pair H Cl
ELECTROPHILES:- attract a lone pair of electrons
DRAWING CURLY ARROWSDRAWING CURLY ARROWS
HYDROGEN ION HThere are no electrons in the outer shell of hydrogen so it has space to accept two electrons
HYDROGEN CHLORIDE
contains a POLAR BOND; the end will attract the electron pair H Cl
DRAWING CURLY ARROWSDRAWING CURLY ARROWS
When moving electrons about, it is essential to check that the charges on the reactants and products balance.
‘BALANCING THE BOOKS’
H O H C C Br
H
3
H
H C C O H
H
3
H
Br
This is the basic mechanism for the nucleophilic substitution of bromoethane.
DRAWING CURLY ARROWSDRAWING CURLY ARROWS
When moving electrons about, it is essential to check that the charges on the reactants and products balance.
‘BALANCING THE BOOKS’
H O H C C Br
H
3
H
H C C O H
H
3
H
Br
This is the basic mechanism for the nucleophilic substitution of bromoethane. To see how it works, it helps to show the electrons involved.
DRAWING CURLY ARROWSDRAWING CURLY ARROWS
When moving electrons about, it is essential to check that the charges on the reactants and products balance.
‘BALANCING THE BOOKS’
H O H C C Br
H
3
H
H C C O H
H
3
H
Br
DRAWING CURLY ARROWSDRAWING CURLY ARROWS
When moving electrons about, it is essential to check that the charges on the reactants and products balance.
‘BALANCING THE BOOKS’
H O
The hydroxide ion has a – ive charge, The oxygen has eight electrons in its outer shell. Because it has a lone pair, the ion will act as a nucleophile
DRAWING CURLY ARROWSDRAWING CURLY ARROWS
When moving electrons about, it is essential to check that the charges on the reactants and products balance.
‘BALANCING THE BOOKS’
H O H C C Br
H
3
HIn bromoethane, C2H5Br, the C-Br bond is polar because the electronegativity of Br is greater than C. It will susceptible to attack by nucleophiles.
In addition reactions, 2 or more substances react to form a single product only
ADDITION REACTIONSADDITION REACTIONS
C2H4(g) + Br2(l) ——> CH2BrCH2Br(l) ethene 1,2 - dibromoethane
Reactant 1 + Reactant 2 Product
Example : Bromine undergoes addition reaction with ethene
Reactant Product 1 + Product 2
ELIMINATION REACTIONSELIMINATION REACTIONS It is opposite of addition reaction. One substance react to form 2 products
C3CH2OH ————> CH2=CH2 + H2O ethenol ethene
Example :Dehydration of ethenol
CONDENSATION REACTIONCONDENSATION REACTION Involves addition reaction followed by an elimination reaction Two reactants combine to form a larger molecule with the elimination of a small molecule like water
CH3CH2OH(l) + CH3COOH(l) CH3COOC2H5(l) + H2O(l)
ethanol ethanoic acid ethyl ethanoate + water
Example : formation of ester from carboxylic acid
SUBSTITUTION REACTIONSUBSTITUTION REACTION
One atom or group of atoms replaced by another atom or group of atoms
Reactant 1 + Reactant 2 Product 1 + Product 2
OXIDATION AND REDUCTIONOXIDATION AND REDUCTION reactions when oxidation or deduction takes place
Example : oxidation of primary alcohol to form aldehyde
HYDROLYSISHYDROLYSIS Splitting up a molecule by reacting with water
CH3CH2Br + H2O CH3CH2OH + HBr
Example :hydrolysing of bromoethane
Note[O] means oxidising agent
POLYMERISATIONPOLYMERISATION
Joining of small (monomers) together in to a long chain 2 types of polymerization are there . They are Adition polymerisation and condensation polymerization
Polymer could be represented by :-[M]n-
There are 3 ways to split the shared electron pair in an unsymmetrical covalent bond.
UNEQUAL SPLITTINGproduces : IONS (negative ions are calledCarbanion. Positive ions are called Carbocation)known as HETEROLYTIC FISSION
EQUAL SPLITTINGproduces RADICALSknown as HOMOLYTIC FISSION
• If several bonds are present the weakest bond is usually broken first • Energy to break bonds can come from a variety of energy sources - heat / light • In the reaction between methane and chlorine either can be used, however... • In the laboratory a source of UV light (or sunlight) is favoured.
HOMOLYTIC AND HETROLYTIC FISSIONHOMOLYTIC AND HETROLYTIC FISSION
The formation of a carbocation from a halogenoalkane is an example of ??
heterolytic fission.
Free radical – species with an unpaired electron Electrophile – species that accepts a pair of electrons which are attracted to region of higher electron density Nucleophile – species that donates a pair of electrons which attacks region of lower electron density