1-Carbon and Its Compounds

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1. Bonding in CarbonCarbon form covalent bonds.Formation of covalent bond : Covalent bondformation involves sharing of electrons betweenbonding atoms which may be either same ordifferent.Covalency : The number of electrons contributedby an atom for sharing is known as its covalency.Characteristics of covalent compounds :(i) These compounds are molecular in nature

(i.e. they exist as single molecules)(ii) These are insoluble in water and soluble in

benzene, kerosene and petrol etc.(iii) These compounds are poor conductor of

electricity.2. Allotropy in Carbon

The property due to which an element exists intwo or more forms, which differ in their physicaland some of the chemical properties is known as“Allotropy” and the various forms are called“Allotropes”.• Carbon exists in two allotropic form (i)

crystalline (ii) amorphous. The crystallineforms are diamond and graphite whereasthe amorphous forms are coal, charcoal,lamp black etc.

• Fullerenes form another class of carbonallotropes. The first one to be identified wasC-60, which has carbon atoms arranged inthe shape of a football.

3. Unique Nature of CarbonCatenation : The property of elements to formlong chains or rings by self linking of their ownatoms through covalent bonds is calledcatenation. The extent of catenation dependsupon the strength of the bonds between theatoms involved in catenation.

4. Saturated and Unsaturated Carbon CompoundsIn saturated compounds the valencies of all thecarbon atoms are satisfied by single bondsbetween them.While in the unsaturated compounds, thevalencies of all the carbon atoms are not satisfiedby single bonds, thus in order to satisfy theirvalencies, they form double or triple bondbetween the carbon atoms.

5. Straight chain compounds : The compoundswhich contain straight chain of carbon atomse.g. normal butane (C4H10), normal pentane(C5H12) etc.

6. Branched chain compounds : Thosecompounds which are branched e.g. iso-butane(C4H10), isopentane (C5H12), neopentane(C5H12) etc.

7 Closed chain compounds or Ring compounds :Cyclic compounds are called closed chain or ringcompounds e.g. cyclohexane (C6H12),cyclopentane (C5H10), cyclobutane (C4H8),cyclopropane (C3H6) etc.

8. HydrocarbonsAll those compounds which contain just carbonand hydrogen are called hydrocarbons.

9. Functional GroupThe atom or group of atoms which determinethe properties of a compound is known asfunctional group. e.g. –OH (alcohol), –CHO(aldehyde), > C = C < (alkene), – C º C – (alkyne)etc.

10. Homologous SeriesA series of compounds in which the samefunctional group substitutes hydrogen in acarbon chain is called a homologous series. e.g.CH3Cl and C2H5Cl differ by a –CH2 unit.

Key Concepts

Carbon and its Compounds

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11. NomenclatureChemists developed a set of rules, for namingorganic compounds based on their structureswhich is known as IUPAC rules.The IUPAC name of an organic compoundsconsists of three parts.Prefix – word root – SuffixWord Root : A word root indicates the nature ofbasic carbon skeleton.

• In case a functional group is present, it isindicated in the name of the compound witheither as a prefix or as a suffix.

• While adding the suffix to the word rootthe terminal ‘e’ of carbon chain is removed

• If the carbon chain is unsaturated then thefinal ‘ane’ in the name of the carbon chainis substituted by ‘ene’ or ‘yne’ respectivelyfor double and triple bonds.

3 2 2

H H H| | |

1. Halogen Chloro, bromo, Iodo Cl, Br, I H C C C Br Bromopropane| | |

H H HH H| |

2.Alcohol ol OH H C C OH ethanol| |

H H3. Aldehyde al CHO CH CH CH CHO B

- - - - - - - -

- - - - - -

- - -

Functional group Prefix/Suffix Functional group Example IUPAC Name

3 3

3 2

2 3 2 2

3 3

3 2

utanal4. Ketone one CO CH COCH Propanone5. Carboxylic acid oic acid COOH CH CH COOH Propanoic acid6. Amine Amino NH CH CH NH Amino ethane7. Ester oate COOR CH COOCH Methyl ethanoate8. Double bond ene CH CH CH P

- - -- - -

- -- - -

- = -

3 2

ropene9. Triple bond yne CH CH C CH Butyne- - º -

12. Chemical Properties of Carbon Compounds :(i) Combustion : Carbon compound undergo

combustion reaction to produce CO2 andH2O with the evolution of heat and light.

4 2 2 2CH O CO H O heat and light+ ¾¾® + +(ii) Oxidation :

4alk. KMnO /3 2 3ethanol ethanoic acid

CH CH OH CH COOHD¾¾¾¾¾¾®

The substance which are used for oxidationare known as oxidising agent. e.g alkalineKMnO4, acidified K2Cr2O7.

(iii) Addition reaction :Unsaturated hydrocarbons (alkenes andalkynes undergo addition reaction inpresence of catalysts e.g.

C = CR

R

R

R 2

NiH

H H| |

R C C R| |

H H

¾¾¾® - - -

(iv) Substitution reaction : Saturatedhydrocarbons give substitution reactione.g. methane in presence of sunlightundergo chlorination.

13. Some Important Carbon CompoundsAlcohols : Compounds containing –OH groupattached to a carbon atom are known as alcohols.Example : Ethanol (C2H5OH) : commonly knownas alcohol.Properties of ethanol :1. Reaction with sodium : Due to its weakly

acidic nature, ethanol reacts with sodiumto librate H2 gas.

2 5 2 5 2Sodium ethoxide

2C H OH 2Na 2C H ONa H+ ¾¾® +

2. Reaction with conc. H2SO4 :

2 4conc. H SO3 2 2 4 2443K

CH CH OH C H H O¾¾¾¾¾¾® +

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Alcohol as a fuel : Alcohol (ethanol) is added topetrol upto 20% and the mixture is called“gasol”.Harmful Effects of Drinking Alcohol :(i) If the alcohol used for drinking purposes

contains some methyl alcohol (CH3OH) asimpurity then it may cause seriouspoisoning and loss of eye sight.

(ii) It is habit forming and damages liver if takenregularly in large quantities.

Ethanoic Acid (Acetic Acid) CH3COOH:Ethanoic acid, commercially known as acetic acidbelongs to a group of acids called carboxylicacid.

Chemical properties :(i) Reaction with a base :

3 3 22CH COOH 2NaOH 2CH COONa H O+ ¾¾® +

(ii) Reaction with carbonates and bicarbonates :

3 2 3 32CH COOH Na CO 2CH COONa+ ¾¾®

2 2CO H O+ +

3 3 3 2CH COOH NaHCO CH COONa H O+ ¾¾® + 2CO+

(iii) Reaction with alcohol : (Esterification)

3 2 5 3 2 5 2Ethyl ethanoate (ester)

CH COOH C H OH CH COOC H H O+ ¾¾® +

Esters react is the presence of an acid or a baseto give back the alcohol and carboxylic acid-thisreaction is known as saponification.

14. Soaps and Detergents :Soaps : Soaps are sodium or potassium salts oflong chain acid carboxylic acids.Detergent : They are ammonium or sulphuratesalts of long chain carboxylic acids.

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1-Carbon and Its Compounds