Chapter 4: Carbon and its Compounds

CHAPTER - 4

COMPOUND AND ITS CARBON

Carbon:-  (i)Most carbon compounds are poor conductors of electricity. Therefore, the bonding in these componds does not give rise to any ions

1. They have low melting and boiling points as compared to ionic compounds
2. Forces of attraction between the molecules are not very strong.
3. The atomic number of carbonis
4. It has four elements I its outermost shell and needs to gain or lose four electrons to attain noble gas configuration.

If carbon were to gain lose electrons:-

• It  could gain four electrons forming C^4-  anion. But it would be difficult for the nucleus with six protons to hold on to ten electrons.
• It could lose four electrons forming C⁴⁺ cation. But it would require a large amount of energy to remove electrons. Carbon overcomes this problem by sharing its valences electrons with other of carbon or with atoms of other elements.

 Bonding in carbon

 Carbon form covalent bounds.  

• Covalent bound formation involves sharing of electrons between bonding atoms which may be either same or different.
• The number of lectrons contributed by an atom for sharing is known as its covalency.

       For example 

1. Molecule of hydrogen  

   

2. Molecule of oxygen

3. Molecule of Nitrogen

4. Structure of methane

Methane CH₄  is widely used as a fixed and is a major component of bio-gas and compressed natural gas ( CNG) .

• CHARACTERISTICS OF COVALENT COMPOUND :-

1. These compounds are molecula in nature  i.e. , they exist as single molecules)
2. These are insoluble in water and soluble in benzene , kerosence and petrol etc.
3. These compounds are poor conductor of electricity.

Allotropes of carbon

  The property due to which an element exists intwo or more forms, which differ in their physical and chemical properties is known as ‘Allotropes’ and the various forms are called “Allotropes”.

• carbon exists in two allotropic  form
• (i) crystalline                 (ii)  amorphous.

The crystalline forms are diamond and graphite the amorphous forms are coat , characol etc.

• In diamound , each carbon is bonded to for other carbon atoms forming rigid 3-D dtructure. Diamond is the nardest substance. * in graphite each carbon is bonded to three other carbon atom. Graphite structure is formed by the hexagonal arrays. Graphite is smooth and slippery . it is very good conductor of electricity.
• Fullerenes form another class of carbon allotropes. The first one to be identified was C-60, which has carbon atoms arranged in the shape of a football.

Nature of carbon compounds.

Catenation:-     The property of elements to form long chains or rings by self linking of their own atoms through covalentbonds is called catenation. These compounds may have long, branched chains of carbon atoms may be linked by single, double or triple bound. The extent of catenation depends upon the strength of the bounds between the atoms involved in catenation.

Saturated and unsaturated compounds

• Compounds of carbon which are linked by only single bonds between carbon atoms are called saturated compounds.

For example,    C   -    C  

Carbon atom linked together with single bound.

But the valencies of each carbon atom remain unsatisfied , so each carbon atom is bonded to 3 hydrogen atoms:-

atom is bonded to 3 hydrogen atoms:-

 C₂H₆ is called methane.

Electron dot structure of ethane

Compounds of carbon having double or triple bounds between their carbon atoms are called unsaturated compounds.

For example,      

C ₂ H ₂  is called ethyne

.To satisfy the valency , carbon form double bond.

Strength of compound

The bonds that carbon forms with other elements are very strong, so these    compounds because very stable. Carbon form strong bonds is due to its small size. Nucleus hold shaired pair of electrons strougly.

Chains , branches and rings,

Straight chain compounds: the compounds which conatin straight chain of carbon atom e.g butane (c₄H₁₀ ) petane ( C₅H₁₂) etc.

Branched chain compounds:   Those compounds which are branched.

E.g.    ISO- butane  ( C₄H₁₀), isopentane ( C₅H₁₂)

Ring compounds:-  they  are also known as closd chain compounds.

Cyclic compounds are called ring coumpounds.

  E.g.  cyclohexane (C₆H₁₂)

           Cyclopropane ( C₃H₆)    etc. 

Hydrocarbons :-  All those compounds which contain only carbon and hydrogen are called hydrocarbon. The saturated hydrocarbon which contain single bond are called alkanes. The unsaturated hydro carbons which contain one or more double bonds are called alkanes those containing one or more triple bounds are called alkynes.

Functional group:-  The atoms or group of atoms which determine the properties of a copmpond is known as functional group.   

E.g.  –Cl  ,  -Br  ( choro/ bromo alkane

             -OH (alcohol) 

Homologous series :-  A series of compounds in which the same functional group substitutes hydrogen ina carbon chain is called a homologous series.   E.g   ,     CH₃C₁    and   C₂H₅C₁   →  these differ by a  →   CH₂ unit. 

 Nomenclature :-   For naming organic compounds based on their structures, are followed by UPSC rules.

IUPAC name of an organic compounds consists of 3 parts –

1. Prefix :- in case functional group is present , it is indicated in the name of the compound with either as a prefix or as a suffix.
2. Word root :- A word root indicates the nature of basic carbon skeleton.
3. Suffix :- while adding the suffix to the word rrot, the terminal ‘e’ of carbon chain is removed . if the carbon chain is unsaturated , then final ‘are’ is substituted by ‘en and yne’ respectively for double and triple bonds.

CHEMICAL PROPERTIES OF CARBON COMPOUND .

(i)  Combustion :- carbon burns in oxygen to give carbon dioxide along with the release of heat and heat .

 C  +   O₂     →    CO₂ +  heat and light.

CH₄  +  O₂    →    CO₂  +  H₂O + heat and light

CH₃CH₂OH + O₂ →  CO₂ + H₂O + heat and light

Saturated hydrocarbon will give a clean flame unsaturated carbon compounds will give a yellow flame with lots of balck soke. The gas slove used at home has inlets for air so that a sufficiently oxygen-rich mixture is burnt to give a clean blue flame. Fuel such as  coal  and  petroleum  have some amount of nitrogen and sulphur in them. The combustion results in the formation of oxides of sulphur and nitrogen which are major pollutants in the environment.

•  Coal Coal and petroleum has been formed from biomass. Coal is the remains of trees, forms that lived millions of year ago . oil and gas are the remains of millions of tiny plants and animals that lived in the sea.

(ii) Oxidation :-   The substance which are used for oxidation are known as oxidizing agent.

E.g  alkaline kMnO₄  , acidifed  k₂ Cr₂O₇ .

CH₃CH₂OH   →    CH₃COOH

(iii) Addition Reaction  unsatured hydrocarbons ( alkenes and alkynes) add hydrogen in the presence of catalysts to give saturated hydrocarbons. 

Catalyst are substance that cause a reaction to occur or proced ata different rate without the reaction itself being affected

  (IV) Substitution Reaction 

Saturated hydrocarbons give substitution reaction e.g methane in presence of sunlight undergo chlorination.

CH₄  +  Cl₂    →    CH₃Cl +  Hcl (in the presence of sunlight )

Carbon compounds ethanol and ethanoio acid

 Alcohol :-  compounds containing –OH group attached to a carbon atom are known as alcohol.

E.g, Ethanol ( C₂H₅OH ) : Commonly known as alcohol.

 Properties of ethanol

Ethanol is a liquid at room temperature and is soluble n a water . in take of ever a small quantity of pure ethanol ( called absolute alcohol ) can be lethal.

Reactions of ethanol

2Na  +  2CH₃CH₂OH    →   2CH₃CH₂ONa⁺  +  H₂ 

                                                 Sodium ethoxide

Ethanol reacts with sodium to liberate H₂ gas.

Reaction with cone. H₂SO₄

Heating ethanol at 443 K with excess concentrated sulphuric acid results in the dehydration of ethane to give ethane.

                              HO⁺ conc

Alcohol as a fuel :- alcohol (ethanol) is added to petrol up to  20% and the mixture is called gasol.

Harmful effects of drinking  Alcohol :

• If the alcohol is used for drinking purpose conatins some methyl alcohol ( CH₃OH) as impurity then it may cause series poisoning and loss of eye sight.
• It damage liven if taken regularly in large quantities.
• Dyes are also added to colour the alcohol blue so that it can be identified easily.
• This is called denatured alcohol.

Ethanoic Acid :-  Ethanoic acid, commercially known as acetic acid belongs to a group of a acids called carboxylic acid. 

Reactions of ethanoic  acid :

1. Esterification Reaction :- ethanoic acid reacts with absolute ethanol in the presence of an acid catalyst to give an ester.

Ester are sweet – smelling substances.

These are used in making perfums.

•  Saponification :-   ester is converted back to alcohol and sodium salt of carboxylic acid . this reactionis known as saponification because it is used in the preparation of soap.

2. Reaction with a base

  NaOH  +  CH₃COONa  +  H₂O

3. Reaction with carbonates and bicarbonates

Ethanoic acid reacts with carbonates and hydrogencarbonates to give rise toa salt, carbon dioxide and water . the salt produced is commonly called sodium acetate.

   2CH₃COOH  +  Na₂CO₃    →     2CH₃COONa +  H₂O + CO₂

  CH₃COOH +  NaHCO₃     →     CH₃COONa + H₂O +  CO₂

SOAP AND DETERGENTS

Soap :-   soaps are sodium or potassium molecules is towards the oil droplet while the ionic- end faces outsides. The soap micelle thus helps in pulling out the dirt in water and clothes can be cleaned. salts of long chain acid carboxylic acid. Structures of soap molecules called micelle , where one end of the

Micelles :-  soaps re the molecules in which the two ends have differing properties, one I hydrophilic, it interacts with water , while the other end is hydrophobic i.e it interacts with hydrocarbons. These molecules have a unique orientation that keeps the hydrocarbon portion out of water . this is called

Detergent :- they are ammonium or sulphate salts of long chain carboxylic acids. The charged ends of these compounds do not form insoluble precipitates with the calcium and magnesium oins  in hard water. Thus, they remain effective in hard water. Detergents are used to make shampoos and products for cleaning soaps.