introduction to organic chemistry by dr afzal basha … · dr afzal basha shaik associate professor...
TRANSCRIPT
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INTRODUCTION TOORGANIC CHEMISTRY
BYDR AFZAL BASHA SHAIKASSOCIATE PROFESSOR
VIGNAN PHARMACY COLLEGE
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ORGANIC CHEMISTRY
OH
Study of hydrocarbons and their functional derivatives
FRIEDRICH WOHLER AND THE UREA
H3C CH3 Cl
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ATOMAtom, a basic unit of matter Greek word: Atomos; Atomos = Undivided/indivisible.
e Nuclear portion
Extranuclear portion Electrons
Protons
Neutrons
+ve charge
Electrostatic forces of attraction
-ve charge
p+ p+nn No Charge
e
In an atom number of protons and electrons are equal.
STRUCTURE OF ATOM
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1. Electrons revolve around nucleus the and due to oppositecharges between electrons and protons, they are heldtogether by electrostatic forces of attraction/columbicforce.
2. Neutrons have no charge and nuclear force held neutronsand protons together.
3. The number of electrons in the atoms is not constant
4. Atom either looses or gain an electron and participate in achemical reaction to gain stability.
5. If an atom looses an electron it will gain positive charge andwhen an atom gain an electron it will have negative charge.
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6. The place where the electron is located is called as orbital.
7. An orbital can accommodate a maximum of 2 electrons.
8. Orbitals also called as subshells and a group of orbital's are called as orbits or shells.
9. Different types of orbital's are s, p, d, f and orbits/ shells include K, L, M, N.
10. According to octets rule configuration the outermost shell should contain 8 electrons.
11. If the atom does not contain 8 electrons it will either gain or loose electrons and see that the outermost shell contain 8 electrons in order to get stabilized.
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Hydrogen atom:
+
e In 1s orbital 1e
K subshell of H atom
Nucleus 1 neutron 0 protons
H
Gain 1e
loose 1e
H
H
Hydride ion
Proton
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Helium-A neutral atom
It contain 2 electrons in its only 1s orbital. It cannot gain orloose electron as the 1s orbital is completely filled with twoelectrons. So it is inert.
Helium is used as a mobile phase in gas chromatography,where the detector used when Helium as the mobile phase isthermal conductivity detector as Helium has high thermalconductivity.
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eee
Li
Gain 1e
Loose 1e
Li
Li
Electro positive atoms will lose electron and gain stabilitywhere as the electronegative atom will gain electron and getstabilized.
Lithium-An electropositive element
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VALENCY: The combining capacity of an atom is known as its valency.
In other words Valency is simply the ability of an atom toform number of bonds.
example:-1.H atom contain 1 electron, it needs 1 electron to get to form
bond. So valency of H is 1.2.Carbon is 4th group element.f outermost shell contain 4
electrons it can form 4 bonds. So valency is 4.3.Nitrogen valency is 3. So it can form 3 bonds.4.Oxygen valency is 2. So it can form 2 bonds5.Chlorine(halogens) valency is 1. So it can form 1 bond.
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C CH
H HHC C H
HHH H-C C-H
Four single bonds Two single bonds &
One double bond
One single bond &
One triple bond
H H Cl H H Hydrogen atom can form only one single bond
O OO OH H
N N N HN NH NHH
HOne Triple bond One double bond &
One single bondThree Triple bonds
Nitrogen atom
H XX C X
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ATOMIC NUMBER /PROTON NUMBER (Z)
Number of protons in an atom.
MASS NUMBER (A)
Total number of protons and neutrons.
A= Z+N
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ISOTOPES
1. Isotopes posses some atomic number but different mass number.
2. All isotopes have some chemical properties due to same number of electrons.
3. Isotopes posses different physical properties.
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TYPES OF CHEMICAL BONDS
1. Covalent bond 2. Ionic bond3. Co-ordinate covalent bond/dative bond
Covalent bond:Covalent bond formation involves sharing of electrons by
two atoms in order to satisfy their valencies.
H Cl H Cl H ClCovalent bond
Cl Cl Cl Cl Cl Cl
Chlorine atom
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Covalent bond two types1.Polar covalent bond
2.Non polar covalent bonds:
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Polar molecule have dipole moment.Dipole moment is given by
μ= e x dwhere μ=dipole moment
e=charged=distance
Units of μ is Debye
Dipole moment can be determined by Oscillometry.
Molecules which have polar covalent bond are soluble in polarsolvent and non polar molecule in non polar solvent. i.e. Likedissolves like.
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HOW THE COVALENT BOND IS FORMED?
THE CONCEPT OF HYBRIDIZATION
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HYBRIDIZATION: Intermixing of atomic orbitals of the same atom to from hybridized orbital.
Atomic orbitals hybridized orbitals
Hybridizing orbital will have same energies
Will have different chemical energies
Number of hybridizing orbital =Number of hybridised orbital
Carbon atom form 4 covalent bonds and can have 3 states of hybridization
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sp3 sp2 spTetrahedral Trigonal Linear Hybridization Hybridization Hybridization
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Carbon atom of alkanes will have sp3 hybridization
sp3 hybridization : one s-orbital and three p-orbitals
px
2s
Energy
four sp3 hybridized orbitals
py pz
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px
2s
Energy
three sp2 hybridized orbitals
py pz
Unhybridized p-orbital
sp2 hybridization : one s-orbital and two p-orbitals
Carbon atom of alkenes and aromatic compounds will have sp2 hybridization
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px
2s
Energy
two sp hybridized orbitals
py pz
Two unhybridized p-orbitals
sp hybridization : one s-orbital and one p-orbital
Carbon atom of alkynes will have sp hybridization
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Ionic bond:Ionic bond is a force of attraction between two opposite charged ions.Eg:
Na+-----Cl-
Ionic bond/electrostatic bond/columbic bond
Most of the molecules will show their action by interacting with receptor through ionic bond.Eg:
NCH3
H
H
COO
Adrenaline
Adrenergic receptors
Ionic bond
Cationic or anionic bonding site
HO
HO
HO H3C CO
OH2C
H2C N
CH3CH3CH3
COO
Acetyl cholineIonic bond
Cholinergic receptor
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Surfactants:
Surfactants
non-ionic Cationic Anionic
•The concentration of ions in an ionic solution can be determined by conductometry because ions has capacity of conducting electricity.• In ion exchange chromatography usually conductivity detector is used.• Ionic compounds are soluble in polar solvents like water.
N Cl
ionic bond
R S
O
O
O Na
ionic bond
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•NaCl is soluble in water due ion-dipole force. This process is called ion solvation.
•Diclofenac-NSAID is having less water solubility , hence it isconverted into its sodium salt diclofenac sodium which has betterwater solubility.
HO
H HO
Hδ
δδ
δ
δ
δ
H
O
H
H
O
H
H
O HNa+δδ
H
O
H
δδ
δ
Cl-
OH
H
O
Hδ
H
Hδ
δ
(ion solvation)ion-dipole force
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Co-ordinate covalent bond/ dative bond:
Two chemical species
Electro rich species Electro deficient species
Metal cations
+ NaOH
Strong base
Diclofenac
(Less water solubility)
OH
O
HN
Cl
Cl
Diclofenac sodium(More water soluble)
Na+O-
O
HN
Cl
Cl
NH2 OH SH
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Sequestering agent: Disodium EDTA Chelating agent: Salicylaldoxime
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Electron rich species + M+
ESR-M+ complex•Water soluble ESR
sequestering agentEg: disodium EDTA
•Water soluble ESR form water soluble complex
Electron deficient spices
• water insoluble ESR
chelating agentEg: salicyl aldoxime
• water insoluble complex
HOOCH2CN
HOOCH2C
H2C
H2C N
CH2COONaCH2COONa
HC
O H
NOH
M
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Dimercaprol (British antilewisite (BAL): Sequestering agent used as antidote for Arsenic and mercury poisoning
Lewisite is an arsenic poison
SH
SH
OH
+ As
DIMERCAPROL
SH
SH
OH
M
Polar complex Water soluble
Eliminated through urine
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AROMATICITY
Aromatic Antiaromatic Non-aromatic
Cyclic cyclic Cyclic/acyclic
Have SP3 hybridized atom
Have SP2 hybridized atom
SP3/SP2 hybridized atom
Delocalization of electron
Delocalization of electron planar
No delocalization ofelectron
planar Planar Non planar
Obey huckel’s rule (4n+2=π e- )
Obey 4n rule Doesn’t obey 4n+2(or) 4n rule
Highly stable Highly unstable Intermediate stability
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HH
H
HH
H
SP3
non aromatic
cycloprpane
loss of HSP2 hybridization
cyclopropyl anion
antiarommatic
SP3
H
SP2
loss of H
cyclopropene cyclopropenyl cation
aromatic
cyclic SP2 hybridized carbon atom
delocalization of electron planar
4n+2=π
4n+2=44n=4-2=2n=1/2
4n+2=24n=0n=0
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cyclobutadiene anti-aromatic
* cyclic* SP2 hybridization
* delocalization * planar
4n+2=πe-
4n+2=44n=2n=1/2
4n=4n=1 obeys 4n rule
HH SP3
non aromatic
cyclopentadiene
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HH SP3
non aromatic
cyclopentadiene
H Hloss of H loss of H
cyclopentadenylanion-aromaticcyclicSP2 hybridization
delocalizationplanar4n+2=6n=1
cyclopentadenyl-aromaticcyclicSP2 hybridization
delocalizationplanar4n+2=4n=1/24n=4n=1
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HH
cycloheptatriene
Non-aromatic
loss of H loss of HH
H
cyclopentatriene Anion--anti-armaticcyclic
delocalizationSP2 hybridization
planar
4n+2=84n=8n=2
cycloheptatrienecation - aromaticTropyllium ion4n+2=64n=4n=1
Benzene
Aromatic
cyclicSP2 hybridization
delocalozationplanar4n+2=πe-
4n+2=6n=1
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cyclo-octatetraene tub shape identif ied by x-ray spectroscopy-non aromatic
Annulenes
H
H
Annulenes are monocyclic ring with unsaturation and delocalization •Cyclic•SP2 hybridization •Delocalization -retarded
It seems to be aromatic but actually is non-aromatic
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(14) Annulenes – aromatic 4n+2=44n=12n=3 ----- Aromatic
(16) Annulenes - antiaromatic
Cyclic SP2 hybridization DelocalzationPlanar4n=16N=4----- Antiaromatic
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1. Aromaticity in fused rings:
Azulene
Cyclic SP 2 hybridization Delocalization Planarity4n+2=10N=8N=2
Aromatic
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Napthalene
Anthracenearomatic
phenanthrenearomatic
Non - aromatic
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Hetrocyclic rings :1) Pyrrol ---- Aromatic
N
HCyclic SP2 hybridization DelocalizationPlanar4n+2=6 (N lone pair is involved)4n=4N=1
N
2) Pyridine ---- Aromatic
CyclicSP2 hybridization Delocalization 4n+2=64n=4n=1
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3) Furan ---- Aromatic
O S
involved in delocalization
not involved in delocalization
4) Thiophene
4n+2=6N=1
5) Imidazolopyridine ---- Non aromatic
N
N
SP3
SP3