1. Factors affecting Nuecleophilic substitution reaction

2. Steric nature of the reactant
SN CH3-X, R-CH2X, allylic, benzylic
SN R3-CX, allylic, benzylic
Steric nature of the reactant

3. Nature of nucleophile small, strong Nu- favors SN2----
OH-, CH3O-, CH3CH2O-, CN-, RS-, RCN-, Br-, I-
weak, small Nu- favors SN1-----
H2O, CH3OH, CH3CH2OH, RSH, NH3, F
Nature of nucleophile

4. Solvent used SN2---- low moderate polarity solvent as: acetone, NMF
SN moderate to high polarity solvents as: water, methanol, ethanol
Solvent used

5. Leaving group all halogens, except F , are good leaving group
water is good leaving group ( not OH)
Leaving group

6. Question: Explain WHY?
then show the mechanism

7. Electrophilic Substitution Reactions

9. THE NITRATION OF BENZENE
Benzene is treated with a mixture of concentrated nitric acid and concentrated sulphuric acid at a temperature not exceeding 50°C. As temperature increases there is a greater chance of getting more than one nitro group, -NO2, substituted onto the ring.
Nitrobenzene is formed.
or:
H2SO4
heat

10. The formation of the electrophile
If you are going to substitute an -NO2 group into the ring, then the electrophile must be NO2+. This is called the "nitronium ion" or the "nitryl cation", and is formed by reaction between the nitric acid and sulphuric acid
The equation

11. THE HALOGENATION OF BENZENE
Benzene reacts with chlorine or bromine in an electrophilic substitution reaction, but only in the presence of a catalyst. The catalyst is either aluminium or ferric chloride (or aluminium (ferric) bromide if you are reacting benzene with bromine) or iron.
FeCl3
FeBr3

12. The formation of the electrophile
As a chlorine molecule approaches the benzene ring, the delocalised electrons in the ring repel electrons in the chlorine-chlorine bond
it is the slightly positive end of the chlorine molecule which acts as the electrophile. The presence of the aluminium chloride helps this polarisation.

13. Friedel-Crafts Acylation of Benzene
Named after Friedel and Crafts who discovered the reaction.
Reagent : normally the acyl halide (e.g. usually RCOCl) with aluminum trichloride, AlCl3, a Lewis acid catalyst.
The AlCl3 enhances the electrophilicity of the acyl halide by complexing with the halide.

14. Friedel-Crafts Acylation of Benzene
Electrophilic species : the acyl cation or acylium ion (i.e. RCO + ) formed by the "removal" of the halide by the Lewis acid catalyst, which is stabilised by resonance as shown below.
Other sources of acylium can also be used such as acid anhydrides with AlCl3

15. Addition Reactions

16. In an addition reaction, new groups X and Y are added to the starting material. A  bond is broken and two  bonds are formed.

17. Addition and elimination reactions are exactly opposite
Addition and elimination reactions are exactly opposite. A  bond is formed in elimination reactions, whereas a  bond is broken in addition reactions.

18. The double bond dissolves back to single bond and new bonds reach out to A and B whose bond is also dissolving
A-B can be :
H-H H-OH H-X OH-OH OH-X

19. Draw the product of each of these examples of A-B when they add to 1-propene.
H-H H-OH H-X OH-OH OH-X

20. Addition reactions
A reaction in which an atom or group of atoms is added
to a molecule. divided into:
1- Electrophlic Addition
mechanism

21. Electrophilic addition reactions - the general picture

22. addition to unsymmetrical alkenes
Why?
According to Markovnikov's Rule
Which is an empirical rule based on Markovnikov's experimental observations on the addition of hydrogen halides to alkenes.
The rule states that :
"when an unsymmetrical alkene reacts with a hydrogen halide to give an alkyl halide, the hydrogen adds to the carbon of the alkene that has the greater number of hydrogen substituents, and the halogen to the carbon of the alkene with the fewer number of hydrogen substituents"

23. Addition of H-X Markovnikov`s rule:
Reactivity rank: HI > HBr > HCl > HF.
It is an electrophilic addition reaction.
It Follows Markovnikov`s rule.
Markovnikov`s rule:
“In addition of HX to asymmetrical alkenes, the H+ of HX goes to the double-bonded carbon that already has the greatest number of hydrogens”

24. EXAMPLE: EXAMPLE Addition of HCl to 1-Propene.
Cont. Addition of H-X
EXAMPLE:
Addition of HCl to 1-Propene.
It is a regioselective reaction, follow Markovnikov`s rule.
Anti-Markovnikov addition
EXAMPLE
Addition of HBr to 1-Propene in presence of peroxide.
In the presence of peroxides (chemicals containing the general structure ROOR'), HBr adds to a given alkene in an anti-Markovnikovfashion

25. Markovnikov
Markovnikov
Not Markovnikov
WWU -- Chemistry

26. WWU -- Chemistry

27. MARKOVNIKOV RULE C H C H C l + HCl When adding HX to a double bond the
hydrogen of HX goes to the carbon
which already has the most hydrogens C H C H 3 2 C l
+ HCl
..... conversely, the anion X adds to the most
highly substituted carbon ( the carbon with
most alkyl groups attached).
WWU -- Chemistry

28. REGIOSELECTIVE REACTIONH C H C H 3 3 3
HCl C H C C H C H C C H + C H C H C H2 3 2 3 3 3 C l C l
major
minor
one of the possible products is formed
in larger amounts than the other one
Compare
REGIOSPECIFIC
only one of the possible products is
formed (100%).
WWU -- Chemistry

29. Mechanism (Markovnikov)
Secondary C+
Major product
WWU -- Chemistry

30. Mechanism (anti-Markovnikov)
Primary carbocation
Minor!
WWU -- Chemistry

31. Markovnikov Addition to an Alkene
WWU -- Chemistry

32. ADDITION OF H2O
ADDITION OF H2O to alkene
ADDITION OF H2O to aldehyde

33. ADDITION OF H2O to alkene
HBr and HCl easily add to alkenes. Since water also is a molecule of the type HX which can donate a proton, H2O should be able to add to alkenes in the same way as HBr, for example, resulting in the hydration of an alkene. However, for the addition of H2O to alkenes to occur acid catalysts are required.

34. ADDITION OF H2O to aldehyde
Form 1,1-diol (hydrate)
what is the type of the reaction?????
EXAMPLE:
Formation of chloral hydrate.

35. Nucleophilic Addtion
It is the most common reaction of aldehydes (RCHO) and ketones (RCOR)
e.g. The reaction of aldehydes and ketones with hydrogen cyanide
hydroxynitriles.

36. Mechanism
3 o C+
WWU -- Chemistry

37. Classify each of the following as either substitution, elimination or addition reactions.

38. SOME ADDITIONAL EXAMPLES
only major product is shown C H C H 3 3 C l
+ HCl C H C H 3 2 C l
+ HCl C H C H C H C H 3 2
+ HCl C l
WWU -- Chemistry