CBSE Class 11 Chemistry Organic Chemistry Some Basic Principles And Techniques Notes

 Organic chemistry : Some Basic Principles and Techniques Organic compounds are the hydrocarbons and their derivatives and organic chemistry is that branch of chemistry that deals with the study of these compounds

Tetravalency of carbon

The atomic number of Carbon is 6 and its electronic configuration is 2,4 i.e. it has 4 valence electrons. Thus carbon is always tetracovalent, i.e. it forms 4 covalent bonds with other atoms

 Due to tetravalency of carbon it has a tetrahedron shape.

Catenation- The self linking property of carbon is known as catenation. This is the main reason of existence of such large number of compounds 

 Functional groups:A functional group may be defined as an atom or a group of atoms present in a molecule which largely determines the chemical properties.

CLASS OF ORGANIC                  NAME OF FUNCTIONAL                 STRUCTURE              COMPOUNDS            GROUP  

Alkenes                                                 double bond                                  =C=C=

Alkynes                                                triple bond                                    - C Ξ C -

Halogens                                              halogen -                                      X ( F,Cl,Br,I )

Alcohols                                                hydroxyl                                        -OH

Aldehydes                                           aldehydic(formyl)                             -CHO

Carboxylic acids                                           carboxyl                                -COOH

Acid amides                                           amides                                      -CONH2

Primary amines                                      amino                                         - NH2 

HOMOLOGOUS SERIES

Homologous series is defined as a family or group of structurally similar organic compounds all members of which contain the same functional group, show a gradation in physical and similarity in chemical properties and any two adjacent members of which differ by -CH2 group. The individual members of this group are called homologues and the phenomenon is called homology.

NOMENCLATURE OF ORGANIC COMPOUNDS

Organic chemistry deals with millions of compounds. In order to clearly identify them, a systematic method of naming known as IUPAC system of nomenclature is adopted. The names are such that the listener can deduce the structure from it. The IUPAC name consists of three parts:

Prefix            Word root             Suffix               EX: 3 methlyoctane

NOMENCLATURE OF ALKANES Straight chain alkanes:

The names of such compounds is based on their chain structure,and end with suffix ‘-ane’ and carry a prefix indicating the number of carbon atoms present in the chain.

Branched chain hydrocarbons:

1.) The longest carbon chain in the molecule is identified.

2.) The numbering is done in such a way that the branched carbon atoms get the lowest possible value.

3.) The names of the alkyl groups attached as a branch are then prefixed to the name of the parent alkane and its position is indicated by numbers.

4.) The lower number is given to the first in alphabetical order.

5.) The carbon atom of the branch that attaches to the root alkane is numbered 1.

Organic compounds having Functional Groups:

The longest chain of carbon atoms containing the functional groups is numbered in such a way that the functional group attached to the carbon atom gets the lowest possible number in the chain. When there are more functional groups then a priority order is followed as: -COOH, -SO₃H, -COOR, COCl, -CONH₂, -CN, -HC=O, =C=O, -OH, -NH₂, =C=C=, -CΞ C-.

ISOMERISM

Two or more compounds having the same molecular formula but different physical and chemical properties are called isomers and this phenomenon is called isomerism. 

Chain isomerism: When two or more compounds having same molecular formula but different carbon skeletons are referred to as chain isomers.

Position Isomerism : Compounds which have the same structure of carbon chain but differ in position of double or triple bonds or functional group are called position isomers and this phenomenon is called Position Isomerism. e g
CH₃-CH₂-CH=CH₂ CH₃-CH = CH – CH₃ 

Functional Isomerism :Compounds which have the same molecular formula but different functional group are called functional isomers and this phenomenon is called functional Isomerism. e g
CH₃ – CH₂ – OH CH₃ – O – CH₃ 

Metamerism:It is due to the presence of different alkyl groups on either side of functional group in the molecule. Ex. C₄H₁₀O represents C₂H₅OC₂H₅ and
CH₃OC₃H₇

CBSE Class XI Chemistry Organic chemistry - Some Basic Principles and Techniques Concepts.