CBSE Chemistry Subject Notes

CBSE Guess > eBooks > Class X > Carbon and Its Compounds By Mrs. Kritika Bhola

Chemistry

Previous Index Next

Carbon and Its Compounds

HOMOLOGOUS SERIES

A group of organic compounds having similar structures and similar chemical properties in which the successive compounds differ by CH2 group.

Two adjacent homologous groups differ by 1 carbon atom and 2 hydrogen atoms .

General formula of Alkanes ---  CnH2n+2

Characteristics of a Homologus Series

  1.  All members represented by same general formula.
  2. Two adjacent homologues differ by a CH2
  3. Difference between molecular masses of any 2 homologues is 14μ.
  4. All compounds show similar chemical properties.
  5. There is gradual change in their physical properties with increase in molecular masses. ( melting , boiling points and densities increase)

Alkenes ---- CnH2n

Alkynes ---- CnH2n-2

Functional Groups

An ‘atom’ or a ‘group of atoms’ which makes a carbon compound reactive and decides its properties.

  1. Halo Group :   −X  (  X can be  Cl, Br or I)

    Chloro , Bromo and Iodo group ----
    When 1 H atom of an alkane is replaced by a halogen atom, we get Haloalkane.
    Eg. CH4 → Replace one H by Cl → CH3Cl

    General  formula  is  CnC2n+1–X   (  X  may be Cl ; Br  ;I  )

    Chloromethane – CH3 Cl   ---- methyl chloride
    Bromomethane -  CH3Br   ---- methyl  bromide
    Chloroethane    -  C2H5Cl  ----  ethyl  chloride
    Chloropropane  -  C3H7Cl  ----  propyl chloride

  2. Alcohol Group :  −OH  ( alcoholic  /  hydroxyl group)

    Alcohol group is made up of  1 oxygen and 1 hydrogen atom joined together.
    1 H atom is replaced by an alkane  by a hydroxyl group ( OH  group)
    CH4  → Replace  1 H by  OH → CH3OH

    General formula  is  CnH2n+1OH
    Methanol  - CH3OH  ---- methyl  alcohol
    Ethanol - C2H5OH ---- ethyl alcohol
    Propanol  - C3H5OH ----  propyl  alcohol

  3. Aldehyde  Group :

    It consists of 1 carbon, 1 hydrogen and 1 oxygen atom joined together.

    General formula  ---  CnH2nO
    Methanal  -  HCHO ---  formaldehyde
    Ethanal -  CH3CHO ---- acetaldehyde
    Propanal – CH3CH2CHO  ---  propionaldehyde
    Butanal  -  CH3CH2CH2CHO

  4. Ketone  Group :

    It consists of 1 carbon and 1 oxygen atom. A ketone group must contain at least 3 carbon atoms.
    General formula --  CnH2nO
    Propanone  -  CH3COCH3 ----  acetone  ( simplest ketone)
    Butanone - CH3COCH2CH3
    Pentanone - CH3COCH2CH2CH3

  5. Alkene  Group  :

    It is a Carbon – carbon double bond.
    Ethene   -  CH2 = CH2  
    Propene -  CH3− CH = CH2

  6. Alkyne Group  : CC
    Ethyne  -  CH≡CH
    Propyne  - CH3−C≡CH

 

Previous Index Next

Submitted By Mrs. Kritika Bhola
Email Id : [email protected]