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Some Basic Principles Of Organic Chemistry

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Some Basic Principles of Organic Chemistry PDF Notes, Important Questions and Formulas

Some Basic Principles of Organic Chemistry

Isomerism

DEFINITION:

Compounds having same molecular formula (M.F.) but differ in their properties are known as isomers and this phenomenon is known as isomerism.

Classification

 

STRUCTURAL ISOMERISM

Compounds having same M.F. and different in connectivity of atom (Structure is different)

 

CHAIN ISOMERISM

Compounds having same molecular formula but differing in the length of the principal chain.

 

Example 1

CH3-CH2-CH2-CH3 butane (n-butane)

And

 

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Example 2

CH3 – CH2 – CH2 – COOH butanoic acid

And

 

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E.g. Isoheptane

CH3 – CH – CH2 - CH2 – CH2- CH3

             I

         CH3

*Isooctane (exception of ISO group)

 begin mathsize 12px style table attributes columnalign left end attributes row cell        CH subscript straight 3       CH subscript straight 3 end cell row cell          straight l            straight l end cell row cell straight H subscript straight 3 straight C minus straight C minus CH subscript straight 2 minus CH minus CH subscript straight 3 end cell row cell          straight l end cell row cell        CH subscript straight 3 end cell end table end style

*Neo Group   

 begin mathsize 12px style table attributes columnalign left end attributes row cell       CH subscript straight 3 end cell row cell         straight l end cell row cell straight H subscript straight 3 straight C minus straight C minus end cell row cell          straight l end cell row cell        CH subscript straight 3 end cell end table end style

* To Prepare the neo compound firstly the above group

              begin mathsize 12px style table attributes columnalign left end attributes row cell         CH subscript straight 3 end cell row cell           straight l end cell row cell left parenthesis straight H subscript straight 3 straight C minus straight C -) end cell row cell           straight l end cell row cell         CH subscript straight 3 end cell end table end style                                   

Is written. After that required no. of carbon is added in the straight chain.

E.g. neopentane

 begin mathsize 12px style table attributes columnalign left end attributes row cell      CH subscript straight 3 end cell row cell        straight l end cell row cell straight H subscript straight 3 straight C minus straight C minus CH subscript straight 3 end cell row cell         straight l end cell row cell        CH subscript straight 3 end cell end table end style

Neoheptane

 begin mathsize 12px style table attributes columnalign left end attributes row cell        CH subscript straight 3 end cell row cell         straight l end cell row cell CH subscript straight 3 minus straight C minus CH subscript straight 2 minus CH subscript straight 2 minus CH subscript straight 3 end cell row cell         straight l        end cell row cell      CH subscript straight 3 end cell end table end style

POSITION ISOMERISM

Compounds having same molecular formula and same principal chain but differ in the position of functional group; multiple bond and substitutent group are known as position isomers.

 

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The above example can be best understood taking the following example

 begin mathsize 12px style table attributes columnalign left end attributes row cell straight C minus straight C minus straight C minus straight C space and space straight C to the power of straight 3 minus straight C to the power of straight 2 minus straight C to the power of straight 1 end cell row cell                           straight l end cell row cell                          straight C end cell end table end style

In this, the last carbon has been placed to IInd position to form chain isomer the same has happier with above example and hence they are chain isomer to each other

 

 

Nomenclature of Organic Compounds

Chapter Cover: Classification of carbon and hydrogen atoms, Types of alcohols and Amines, Definition of chiral carbon, Olephenic and acetylenic bonds, Vinylic carbon allylic carbon and benzylic carbon.

1.        KEKULE'S PRINCIPLE

  1. Carbon has four valencies.
  2. Carbon has a property of catenation. It can make a large chain with addition of other carbons.
  3. A carbon atom can share 2, 4 or 6 electrons with other carbons & can form single, double or triple bond.
  4. For a carbon atom, it is not possible to make more than 3 bonds with adjacent carbon atom because carbon atoms complete its octet from overlapping which consists directional property.

 

2.     DEGREE OF CARBON

No. of carbon attached to carbon atom is called degree of carbon there are for types: –

  1. Primary carbon (1° carbon)
  2. Secondary carbon (2° carbon)
  3. Tertiary carbon (3° carbon)
  4. Quaternary carbon (4° carbon)

 begin mathsize 12px style table attributes columnalign left end attributes row cell                             1 to the power of straight o CH subscript 3 end cell row cell                                  straight l end cell row cell Ex.     straight C with 1 to the power of straight o on top straight H subscript 3 minus straight C with 2 to the power of straight o on top straight H subscript 2 minus straight C with 3 to the power of straight o on top straight H minus straight C to the power of 4 to the power of straight o end exponent minus straight C with 1 to the power of straight o on top straight H subscript 3 end cell row cell                             straight l        space straight l end cell row cell                          subscript straight 1 to the power of straight o end subscript CH subscript 3    subscript straight 1 to the power of straight o end subscript CH subscript 3 end cell end table end style

3.     DEGREE OF HYDROGEN

Degree of carbon on which that hydrogen attached. there are three types

  1. Primary hydrogen (1° hydrogen)
  2. Secondary hydrogen (2° hydrogen)
  3. tertiary hydrogen (3° hydrogen)

Ex. How many 1°, 2° & 3°H atoms are present in

 

(A) 3,0,5                                   (B) 3,5,0

(C) 4,3,0                                   (D) 0,5,3

 

4.     DEGREE OF ALCOHOL

Degree of carbon on which alcohol atom attached.

There are three types.

  1. Primary alcohol (1° alcohol)
  2. Secondary alcohol (2° alcohol)
  3. tertiary alcohol (3° alcohol)

 

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 5.     DEGREE OF AMINE

They are named according to the number of carbons attached to nitrogen.

there are three types.

  1. Primary Amine (1° Amine)
  2. Secondary Amine (2° Amine)
  3. tertiary Amine (3° Amine)

 

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6.     CHIRAL CARBON OR ASYMMETRIC CARBON ATOM

Chiral carbon or asymmetric carbon atom is a carbon atom that is attached to four different types of atoms for groups of atoms

 begin mathsize 12px style table attributes columnalign left end attributes row cell                straight F end cell row cell                 straight l end cell row cell Ex.        Br minus to the power of asterisk times straight C minus straight I end cell row cell                 straight l end cell row cell                Cl end cell end table end style

7.     OLEPHENIC AND ACETYLENIC BONDS

  1. Olephenic bond :

Alkenes are also called olefins because they form oily liquids on reaction with chlorine gas. An alkene consists of at least one double bond. This double bond is known as the olefinic bond.

Ex. CH3CH=CH2 Propane

  1. Acetylenic bonds :
    Acetylene, also called ethane, the simplest and best known member of the hydrocarbon series containing one or more pairs of carbon atoms linked by triple bonds, called acetylenic bond.

EX       CH ≡ CH            Ethyne

 

8.     VINYLIC CARBON ALLYLIC CARBON AND BENZYLIC CARBON

  1. Vinylic Carbon : 
    Vinylic carbon is a carbon that is involved in a double bond with another carbon. It is sp2 hybridized. Vinylic carbon makes a double bond with another carbon which is also sp2 hybridized. Both carbons involved in this bond are vinylic carbons.

 

 

  1. ALLYLIC CARBON :
    Allylic carbon can be described as the carbon atom that is adjacent to the double bond. This carbon atom is the nearest to the double bond, but it is not a part of the double bond.
    The carbon atoms in the double bond are sp2 hybridized. But the allylic carbon is sp3 hybridized. It is bonded to the sp2 hybridized carbon atom through a single bond.

 

  1. BENZYLIC CARBON
    A benzylic carbon is a saturated carbon that is directly attached to a benzene ring

 


GOC

HOMOLYTIC BOND FISSION

HOMOLYSIS

The bond cleavage in which each bonded atom gets their own contribution

Cleavage takes place due to

 

HELP (H = Heat, E = Electricity,

L = light, P = Peroxide)

  • Favoured when E.N. difference is less or zero.
  • Cleavage favoured in non-polar solvent.

 

HETROLYTIC BOND FISSION

 

  • It is formed when the electronegativity difference between the bonded atoms is more
  • Formation is favoured by polar solvent

 

+ve charge of the solvent attracts the –ve pole of compound and the –ve pole of the solvent attracts +ve pole of compound and the bond breaks.

 

INTERMEDIATES OF ORGANIC COMPOUNDS

 

 

Free Radical

Carbocation

Carbanion

1

Lone Pair

0

0

1

2

Bond pair

3

3

3

3

Unpaired e-

1

x

x

4

Bond Angle

1200

1200

1070

5

Hybridisation

Sp2

Sp2

Sp3

6

Shape

Trigonal planer

Trigonal planer

Pyramidal

7

Magnetic Property

Paramagnetic

Diamagnetic

Diamagnetic

8

Stability order (As per inductive effect)

30>20>10

30>20>10

10>20>30

9

e- rich /deficient /poor

ED(Deficient)

ED

ER(Rich)

10

Reactivity order

10>20>30

10>20>30

30>20>10

11

+I/-I (stabilized)

+I

+I

-I

 

ELECTRONIC DISPLACEMENT EFFECT

The displacement of electrons within the same molecule is known as electronic displacement. These effects affect the stability of a species or compound and it also affect the acidic & basic strength.

 

Electronic Displacement Effect is divided into two parts:

(1)Permanent effect        (2) Temporary effect

(1)  Permanent effect:

  1.  Inductive effect
  2.  Mesomeric (resonance) effect
  3.  Hyperconjugation

 

(2)  Temporary effect:

  1. Electromeric effect
  2. Inductomeric effect

 

 I. Induction effect:

It is an effect in which permanent polarization arises due to partial displacement of σ-electron along carbon chain or partial displacement of sigma-bonded electron toward more electronegative atom in carbon chain.

 

 

Magnitude of partial positive charge

1 > + δ2 > δ3 = δ- (net charge remain constant in a molecule having inductive effect)

Inductive effect

It is a permanent effect

 

 

* O- < O < O+ (-I effect order)

  • It is a permanent effect.
  • It is caused due to electronegative difference.
  • It operates via bonded electron
  • It is distance dependent effect.
  • As distance increases, its effect decreases.
  • It can be neglected after third carbon.
  • It is establishing effect.
  • It is divided into 2 parts. (On the basis of electronegativity w.r.t hydrogen atom)

1)  +I effect

2)  – I effect

If any atom or group having electronegativity greater than that of hydrogen. Than it is considered as – I effect and vice-versa.


+I effect

  1.  e– releasing group
  2. EN less than H
  3. Those group which are showing + I effect, disperses Partial – ve charge on the C-chain

 

– I effect

            i.      e– accepting group

          ii.      EN greater than H

        iii.      Those group showing –I effect disperses + ve charge on the C-chain

 

Order of –I effect showing group:

 


            (-I order) -C≡CH>- CH=CH2


Order of +I effect showing group

 

>-CH2Me  > CT3  > CD3 > CH3 > T > D >H

Bond Strength: CT3 > CD3 >CH3

(+I of T > D > H)

Q. Why carbon - hydrogen bond is longer than C - T bond
Ans As the mass increases, vibration decreases as a result of which the heavier isotope will be more closer to the C-atom for a longer time. Therefore C – T bond is stronger C – T > C – D > C – H Which implies that C – H bond has longest bond.

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