Organic Chemistry Presentation
Submitted By :
• Rubab Saeed (23251071077)
• Syeda Hafsa Shah (23251071082 )
• Shumaim Razzaq(23251071082)
Submitted To : Dr.Shaista Gillani
CLASS: BS-II (Semester 4-Section B)
Department : Chemistry
Topic :
• Hydroboration including
regioselectivity and regiospecificity
• Oxymercuration and demercuration
BS-II semster 4 section B
Rubab Saeed (23251071077)
syeda Hafsa shah(2325107082)
Shumaim Razzaq(2325107080)
2
BS-II semster 4 section B
• It is an organic chemical reaction in which borane(BH3) or a
boron containing compound adds across a carbon-carbon
double bond (alkene) or triple bond (alkyne).
• For Example:
Rubab Saeed (23251071077)
syeda Hafsa
shah(2325107082) Shumaim
Razzaq(2325107080)
1
BS-II semster 4 section B
Hydroboration in alkenes takes place in two steps reaction:
1. Hydroboration: (BH3) adds to the alkene so that boron attaches to
the less substituted carbon and hydrogen to the more substituted
one (anti-Markovnikov rule).
2. Oxidation: The organoborane intermediate is then treated with
hydrogen peroxide (H2O2) and a base usually (NaOH) to give an
alcohol.
Mechanism:
•
•
Step 1:Electrophilic attack of BH3 on the double bond.
Step 2:concentrated addition of B and H and oxidation of C-B to C-OH.
Rubab Saeed (23251071077)
syeda Hafsa shah(2325107082)
Shumaim Razzaq(2325107080)
BS-II semster 4 section B
1. Anti-Markovnikov Addition: The hydrogen attaches to the
more substituted carbon, and the boron to the less substituted
one. It is the opposite of Markovnikov rule .
2. Syn Addition: Both hydrogen and boron ad to the same side of
alkene, leading to syn stereochemistry.
3. Reagent: Commonly used BH3 (borane) or B2H6 (diborane)
often in a solvent THF.
4. Formation of Alcohol: the end product is alcohol and the –OH
group ends up with less substituted carbon atom .
5. Two-Step Reaction:
• Step 1: Hydroboration – Addition of BH₃ (or a borane source) to
the alkene.
• Step 2: Oxidation – Treatment with H₂O₂/NaOH to replace
boron with an –OH group.
Rubab Saeed (23251071077)
syeda Hafsa shah(2325107082)
Shumaim Razzaq(2325107080)
3
BS-II semster 4 section B
Hydroboration is regioselective , meaning it favours the formation of
one constitutional isomer over others,it follows anti markovonikov rule
Why anti Markovnikov Rule:
• Electronic and steric factors guide this addition .
• The transition state is a four membered cyclic structure where :
o Boron prefers the less substituted carbon.
o Hydrogen goes to the more substitued carbon.
Rubab Saeed (23251071077)
syeda Hafsa shah(2325107082)
Shumaim Razzaq(2325107080)
4
BS-II semster 4 section B
Rubab Saeed (23251071077)
syeda Hafsa shah(2325107082)
Shumaim Razzaq(2325107080)
5
BS-II semster 4 section B
Rubab Saeed (23251071077)
syeda Hafsa shah(2325107082)
Shumaim Razzaq(2325107080)
6
BS-II semster 4 section B
Rubab Saeed (23251071077)
syeda Hafsa shah(2325107082)
Shumaim Razzaq(2325107080)
9
BS-II semster 4 section B
It involves electrophilic addition of of Hg2+ to the alkene on
reaction with mercury(II)acetate [(CH3CO2)]2Hg, often
abbreviated Hg(OAc)2 in aqueous tetrahydrofuran (THF)
solvent. When the intermediate organomercury compound is
then treated with sodium borohydride, NaBH4 demercuration
occurs to produce an alcohol.
For Example:
Rubab Saeed (23251071077)
syeda Hafsa shah(2325107082)
Shumaim Razzaq(2325107080)
7
BS-II semster 4 section B
• Step 1:Electrophilic addition if Hg+ gives a mercurium ion .
• Step 2:The mercurium ion reacts with water as in
halohydrinformation.Loss of a proton gives an organomercury
product.
• Step 3:Reaction with NABH4 removes the mercury.The product of the
reaction is more highly substituted alcohol, corresponding to
Markovnikov regiochemistry.
Rubab Saeed (23251071077) syeda Hafsa
shah(2325107082) Shumaim
Razzaq(2325107080)
8
BS-II semster 4 section B
• The overall reaction results in the addition of the OH group
to the more substituted carbon, while the hydrogen from
water adds to the less substituted carbon.
• This is consistent with Markovnikovs rule. Which states that
in the addition of HX to an alkene , the hydrogen atom adds
to the carbon atom with more hydrogen atom already
present , and the X group adds to the carbon with fewer
hydrogen atoms.
Rubab Saeed (23251071077)
syeda Hafsa shah(2325107082)
Shumaim Razzaq(2325107080)
BS-II semster 4 section B
Rubab Saeed (23251071077)
syeda Hafsa shah(2325107082)
Shumaim Razzaq(2325107080)
10
BS-II semster 4 section B
Rubab Saeed (23251071077)
syeda Hafsa shah(2325107082)
Shumaim Razzaq(2325107080)
11
BS-II semster 4 section B
15
Rubab Saeed (23251071077)
syeda Hafsa shah(2325107082)
Shumaim Razzaq(2325107080)
12
BS-II semster 4 section B
McMurry Organic Chemistry 8th edition
Marchs Advanced Organic Chemistry 7th
edition (Micheal B.Smith)
Rubab Saeed (23251071077)
syeda Hafsa shah(2325107082)
Shumaim Razzaq(2325107080)
16
BS-II semster 4 section B
We would like to express our sincere gradtitude
ro Mrs.Shaista Gillani for herguidance and
support throughput the presentaion.WE are also
thankful to Lahore College For Women
University for providing us with the oppurtunity
and resources.
Rubab Saeed (23251071077)
syeda Hafsa shah(2325107082)
Shumaim Razzaq(2325107080)
17
BS-II semster 4 section B
Rubab Saeed (23251071077)
syeda Hafsa shah(2325107082)
Shumaim Razzaq(2325107080)
18
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