Alcohols

                    Alcohols

Hydrocarbons are the parents of other organic compounds. When One or more hydrogen atoms are replaced by the different types of atoms or group of atoms from hydrocarbons then different types of organic compounds are formed .
           When hydrogen atoms are replaced from saturated aliphatic hydrocarbons by the hydroxyl group (-OH) ,then Alcohols are formed.
  For example-

                -H
  R-H ------------->    R-OH                                +OH

Where R is the alkAl group.

                   -H
 CH3-H ------------->     CH3-OH                         +OH              (Methanol)


So, Hydroxy derivatives of the aliphatic hydrocarbons are known as Alcohols.



Classification of Alcohols-

Hydroxy derivatives of the aliphatic hydrocarbons are known as Alcohols.
The general formula of the alcohols are R-OH. Where R is the Alkyl group.

Alcohols are classified on the basis of the number of the Hydroxyl groups (-OH) attached to the alkAl group.


(1) Monohydric Alcohols -

In the monohydric alcohols only one Hydroxyl group (-OH) attached to the alkAl group. The general formula of the monohydric alcohols are CnH2n+1OH or ROH.
   These are further classified as follows-

(A) Primary alcohols-

Those alcohols in which -OH group is attached to the 1° carbon atom is called primary alcohols.

For example-

           H

           |1°

      H-C-OH    (Methyl alcohol)

          |
          H

               H 

               |1°

      CH3-C-OH    (Ethyl alcohol)

               |
               H

(B) Secondary alcohols-

Those alcohols in which -OH group is attached to the 2° carbon atom is called secondary alcohols.

For example-

           CH3

           |2°

  CH3-C-OH    (Isopropyl alcohol)

           |
           H

  (C) Tertiary alcohols-

Those alcohols in which -OH group is attached to the 3° carbon atom is called tertiary alcohols.

For example-

           CH3

           |3°

  CH3-C-OH    (tert.butyl alcohol)

           |
           CH3

     

(2) Dihydric alcohols-

These are generally called as Glycol . The general formula of the Dihydric alcohols are (CH2)n(OH)2 , where n= 2,3,4 etc.
In this type of the alcohols 2--OH groups are attached to the two different carbon atoms.
For example-


  HO-CH2CH2-OH
 (Ethane-1,2-diol)


   CH3-CHOH-CH2-OH
  (Propane-1,2-diol)

(3) Trihydric alcohols-

In this type of the alcohols 3--OH groups are attached to the three different carbon atoms. In I.U.P.A.C. system these are known as alkanetriol.
For example-

     CH2-OH
     |
     CH-OH
     |
     CH2-OH
   
( Propane-1,2,3-triol)
Or Glycerol

Nomenclature of Haloalkanes

Nomenclature of Haloalkanes

The name of the haloalkanes are given by two different ways-

(1)Trivial or common system-

In this system haloalkanes are known as Alkyl halide.

       There nomenclature are performed by the adding halide word in the given alkyl group. In this system the name of the compound is written in the two different words.
   For example-
    CH3-Cl          (Methyl chloride)
CH3-CH2-Br     (ethyl bromide)                    

Prifixes of the different types of alkyl group-

(a) prefix- n

The means of prefix-n is normal. This is used in the straight chain of the Alkyl group.
 For example-

 CH3-CH2-CH2-Br                          (n-propyl bromide)


(b) prefix- iso

Prefix-iso is used for those Alkyl group in which methyl (--CH3) branch is present in the last of the chain.
For example-

CH3-CH-Br

         |

         CH3
  (Isopropyl bromide)


(c) prefix- neo


Prefix-neo is used for those Alkyl group in which two methyl (--CH3) group is attached in the last of the chain by a single carbon atom.
For example-

         CH3
         |
CH3-C-Br

         |

         CH3
  (neo butyl bromide)

(2) I.U.P.A.C. system-

In this system the monohalogen derivatives of the alkane is written as haloalkane.
For the naming of haloalkanes, fluoro, chloro, bromo or iodo prefix is writes before the longest carbon chain.
   The numbering is starts from the nearest halogen atom of the chain.
   The I.U.P.A.C. name of the haloalkanes is always writes in a single word.
  For example-

  CH3-CH-CH2-Br
           |
           CH3
   (1-bromo-2-methylpropane)



         CH3
         |
CH3-C-CH2-CH2-I
         |
         CH3
   (1-iodo-3,3-dimethylbutane)

Haloalkanes and Haloarenes

 Haloalkanes and Haloarenes

Haloalkanes- 
The word Haloalkane is made up by the two words, -
         Halo = halogen
         Alkane= Aliphatic hydrocarbon (containing single bond only)

So, Haloalkanes are those compounds which is formed when a hydrogen atom replaced by any halogen atom from the alkanes.

               - H
   R-H  -------------->      R-X
                +X

Where ,   R  =  Alkyl group
              X  = Halogen ( F,Cl, Br, I)
For example-
   
                           - H
         CH3-H  --------------> CH3-Cl
                           +Cl


Haloarenes- 
The word Haloarene is made up by the two words, -
         Halo = halogen
   Arene= Aromatic hydrocarbon

So, Haloarenes are those compounds which is formed when a hydrogen atom replaced by any halogen atom from the arenes.

               - H
   Ar-H  -------------->      Ar-X
                +X

Where ,  Ar  =  Aromatic hydrocarbon
              X  = Halogen ( F,Cl, Br, I)
For example-
   
                           - H
         C6H5-H  --------------> C6H5-Cl
                           +Cl


Classification of Halogen derivatives of Hydrocarbon -

(A) On the basis of Nature of carbon chain - 
On this basis the Halogen derivatives of Hydrocarbons are of two types :-
(1) Aliphatic Halogen Compounds  -

Aliphatic Halogen Compounds are divided into three groups-

(a) Haloalkanes - The Halogen derivatives of the alkanes are called Haloalkanes.
These are called mono, di ,tri, tetra or polyhaloalkane on the number of hydrogen atom replaced by a halogen atom.
 For example-

         H
         |
    H-C-Cl     ( ChloroMethane)
         |
         H


         H
         |
    H-C-Cl     ( diChloroMethane)
         |
         Cl


         Cl
         |
    H-C-Cl     (tri ChloroMethane)
         |
         Cl

         Cl

         |
    Cl-C-Cl  ( tetra ChloroMethane)
         |
         Cl

Mono Halogen derivatives are also called alkyl halides or Haloalkanes.

Classification of alkyl halides-

(|) Primary (1°) alkyl halide - 

When Halogen atom is attached by 1° carbon atom is known as primary alkyl halide.
   For example-


         H
         |
    H-C-Cl     ( ChloroMethane)
         |
         H

(||) Secondary (2°) alkyl halide - 

When Halogen atom is attached by 2° carbon atom is known as secondary alkyl halide.
   For example-


             H
             |
    CH3-C-Cl  ( 2-ChloroPropane)
             |
             CH3

(|||) Tertiary (3°) alkyl halide - 

When Halogen atom is attached by 3° carbon atom is known as tertiary alkyl halide.
   For example-


             C H3
             |
    CH3-C-Cl  ( 2-Chloro 2- methyl
             |            Propane)
             CH3

(b) Haloalkenes - The Halogen derivatives of the alkenes are called Haloalkenes. 

For example-

CH2=CH-Cl    ( Chloroethene)

(c) Haloalkynes - The Halogen derivatives of the alkynes are called Haloalkynes. 

For example-

      _ 

CH=C-Cl    ( Chloroethyne)

(2) AromaticHalogen Compounds  -

Aromatic Halogen Compounds are divided into two groups-

(a) Nuclear Halogen derivatives-

When one or more hydrogen atom are replaced by one or more Halogen atom from an aromatic ring then formed compound is called nuclear halogen derivative or Haloarene or aryl halide.
For example-
  C6H5-Cl     ( chlorobenzene)


(b) Side chain  Halogen derivatives-

When one or more hydrogen atom are replaced by one or more Halogen atom from a side chain of aromatic ring then formed compound is called side chain halogen derivative or  aryl alkyl halide.
For example-
       C6H5CH2-Cl           
  ( Phenyl chloro methane )



(B) On the basis of hybridisation of the C -X bond-   




(a) Csp3--- bond containing compounds-


In this type of monohalogen Compounds , the halogen atom is attached to the directly to the sp3 hybridised carbon atom.

(1) Haloalkane or alkyl halide -
In Haloalkane , Halogen atom is attached to the alkyl group (R) . These are further divided into primary (1°), secondary (2°) , or tertiary (3°) .

For example-


         H
         |
    H-C-Cl     ( ChloroMethane)                   (1°)
         |
         H

             H
             |
    CH3-C-Cl  ( 2-ChloroPropane)               (2°)
             |

             CH3

             C H3

             |

    CH3-C-Cl  ( 2-Chloro 2- methyl             

             |            Propane)                             (3°)

             CH3

(2) Alylic halide-
In this type of halides, the halogen atom is attached to the next carbon ( sp3) of carbon - carbon double bond ( C= C).
For example -
   CH2 = CH- CH2-X

(3) Benzylic halide-

In this type of halides, the halogen atom is attached to the next carbon ( sp3) of  aromatic ring.
For example
 C6H5-CH2-Cl

(b) Csp2--- bond containing compounds-

In this type of monohalogen Compounds , the halogen atom is attached to the directly to the sp2  hybridised carbon atom(C=C).

(1) Vinylic halide-
In this type of halides, the halogen atom is attached to the sp2 hybridised carbon - carbon double bond ( C= C).
For example -
   CH2 = CH-X

(2) Aryl halide-
In this type of halides, the halogen atom is attached to the directly aromatic ring.
For example -

C6H5-Cl

(c) Csp--- bond containing compounds-

In this type of monohalogen Compounds , the halogen atom is attached to the directly to the sp  hybridised carbon atom(C-C triple bond).

For example-

       _

H-C=C-Cl

Allotropes of carbon

           Allotropes of carbon

 The various physical forms in which an element can exist are called allotropes of the element. The carbon elements exists in three solid forms called allotropes. The three allotropes of the carbon are -
(1) Diamond
(2) Graphite
(3) Buckminster fullerene

              (1) Diamond

Diamond is a colourless transparent substance having extraordinary shining. Diamond is quite heavy. Diamond is extremely hard. It is the hardest natural substance known. Diamond does not cunduct electricity. Diamond burns on strong heating to form carbon dioxide. If we burn diamond in Oxygen , then only CO2 gas is formed and nothing is left behind. This shows that diamond is made up of carbon only.

Structure of Diamond - 

A Diamond crystal is a very big molecule of carbon atoms. Each carbon atom in the diamond crystal is linked to four other carbon atoms by strong covalent bonds. The four surrounding carbon atoms are at the four vertices of a regular tetrahedron.

        The diamond crystal is, therefore, made up of carbon atoms which are powerfully bonded to one another by a network of covalent bonds. Due to this, diamond structure is very rigid. The rigid structure of Diamond makes it a very hard substance. The compact and rigid three dimensional arrangements of carbon atoms in diamond gives it a high density. The melting point of diamond is also very high. Diamond is a non conductor of electricity.

Uses of Diamond - 
(1) Diamonds are used in cutting instruments like glass cutters, saw for cutting marble and in rock drilling equipment.
(2) Diamonds are used for making jewellery.
(3) Sharp edged diamonds are used by eye surgeons as a tool to remove cataract from eyes with a great precision.

             (2) Graphite

Graphite is a greyish - black opaque substance. Graphite is lighter than diamond. Graphite is soft and slippery to touch. Graphite conductes electricity. Graphite burns on strong heating to form carbon dioxide. If we burn graphite in Oxygen,then only carbon dioxide gas is formed and nothing is left behind. This shows that graphite is made up of carbon only.

Structure of graphite - 


The structure of graphite is very different from that of diamond. A graphite crystal consists of layers of carbon atoms or sheets of carbon atoms.

          Each carbon atom in a graphite layer is joined to three other carbon atoms by strong covalent bonds to form flat hexagonal rings. The various layers of carbon atoms in graphite are quite far apart so that no covalent bonds can exist between them. The various layers of carbon atoms in graphite are held together by weak van der Waals forces. Due to the sheet like structure, graphite is a comparatively soft substance. Graphite is a good conductor of electricity , due to the presence of free electrons .

Uses of Graphite- 
(1) Due to its softness, powdered graphite is used as a lubricant for the fast moving parts of the machinery.
(2) Graphite is used for making carbon electrodes in dry cells and electric arcs.
(3) Graphite is used for making the cores of our pencils called pencil leads and black paints.


       (3) Buckminster fullerene

Buckminster fullerene is an allotrope of carbon Containing clusters of 60 carbon atoms joined together to form spherical molecules. Since there are 60 carbon atoms in a molecule of Buckminster fullerene ,so its formula is C60
( C- sixty ) .
Structure of Buckminster fullerene - 

Buckminster fullerene is a football shaped spherical molecule in which 60 carbon atoms are arranged in interlocking hexagonal and pentagonal rings of carbon atoms. There are 20 hexagons and 12 pentagons of carbon atoms in one molecule of Buckminster fullerene .

    This allotrope was named Buckminster fullerene after the American architect Buckminster Fuller because its structure resembled the framework of domeshaped halls designed by Fuller for large international exhibitions .

Buckminster fullerene is a dark solid at room temperature. Just like diamond and graphite, Buckminster fullerene also burns on heating to form carbon dioxide. If we burn Buckminster fullerene in Oxygen then only carbon dioxide is formed and nothing is left behind. This shows that buckmbuckmi is made up of carbon only. Buckminster fullerene is neither very hard nor soft.
 Other properties of Buckminster fullerene are still being investigated.