��NAVODAYA VIDYALAYA SAMITI, NOIDA��E-CONTENT FOR CLASS XI CHEMISTRY�UNIT - 13 �HYDROCARBONS

PREPARED BY

SARITA MOL PGT CHEMISTRY

JNV HAVERI KARNATAKA

THIS IS AN AERIAL VIEW OF INDIAN OIL REFINERY LOCATED AT PANIPAT, INDIA

WHAT IS A HYDROCARBON?�

• COMPOUNDS CONTAINING CARBON AND HYDROGEN ONLY
• THEY ARE GOOD SOURCES OF ENERGY
• THEY ARE USED FOR MANUFACTURE OF POLYMERS
• THEY ARE USED FOR MAKING DYES AND DRUGS
• EXAMPLE: PETROL, DIESEL, KEROSENE ETC. CONTAIN MIXTURE OF HYDROCARBONS

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Drugs/ Medicine

PAPER

FOOD

CLASSIFICATION OF HYDROCARBONS

• SATURATED HYDROCARBONS
• (C-C)
• ALKANES
• CYCLOALAKNES
• UNSATURATED HYDROCARBONS
• (C=C, C≡C)
• ALKENES(OPEN AND CLOSED)
• ALKYNES(OPEN AND CLOSED)
• AROMATIC HYDROCARBONS
• (CLOSED CHAIN)
• BENZENOIDS
• NON BENZENOIDS

ALKANES (PARAFFINS )

• SATURATED OPEN CHAIN HYDROCARBONS WITH CARBON-CARBON SINGLE BONDS
• EXAMPLES: METHANE, ETHANE, PROPANE ETC.
• GENERAL FORMULA: C_nH_2n+2
• NOMENCLATURE: BY SUFFIXING ‘ANE’ TO THE PARENT NAME
• SHOWS CHAIN ISOMERISM IN COMPOUNDS
• NON POLAR MOLECULES WITH WEAK FORCES OF ATTRACTION ESPECIALLY IN CASE OF LOWER MEMBERS.

METHANE

• FIRST MEMBER OF THE ALKANE FAMILY
• CHEMICAL FORMULA: CH₄
• TETRAHEDRAL STRUCTURE
• CARBON ATOM LIES AT THE CENTRE
• FOUR HYDROGEN ATOMS LIE AT THE CORNERS
• BOND ANGLE H-C-H IS 109.5⁰
• OVERLAPPING TAKES PLACE BETWEEN SP³ HYBRID

ORBITALS OF CARBON AND 1S ORBITALS OF

HYDROGEN ATOM

PREPARTION OF ALKANES

PETROLEUM AND NATURAL GAS ARE MAIN SOURCE OF ALKANES. HOWEVER ALKANES ARE PREPARED BY FOLLOWING METHOD

1.FROM UNSATURATED HYDROCARBONS

WHEN ALKENES AND ALKYNES UNDERGO REDUCTION IN THE PRESENCE OF PLATINUM OR NICKEL CATALYST, THEY GIVE ALKANES.

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2.FROM ALKYL HALIDES

ALKYL HALIDES UNDERGO REDUCTION IN THE PRESENCE OF ZINC AND DILUTE HYDROCHLORIC ACID TO GIVE ALKANES.

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CH₃-Cl +H₂ -----^ZN/H+----> CH₄

C₂H₅-Br --^ZN/H+---------> C₂H₆

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WURTZ REACTION

WHEN ALKYL HALIDES REACTS WITH METALLIC SODIUM IN THE PRESENCE OF DRY ETHER WE GET ALKANES HAVING DOUBLE NUMBER OF CARBON ATOM PRESENT IN THE PARENT ALKYL HALIDE.

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3.FROM DECARBOXYLATION OF CARBOXYLIC ACIDS

SODIUM SALT OFCARBOXYLIC ACID IS REACTED WITH SODA LIME TO GET CORRESPONDING ALKANES.

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RCOO^-Na⁺ + NaOH/CaO 🡪 R-H + Na₂CO₃

KOLBE'S ELECTROLYTIC METHOD

AN AQUEOUS SOLUTION OF SODIUM OR POTASSIUM SALT OF CARBOXYLIC ACID ON ELECTROLYSIS GIVES ALKANES

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CHEMICAL PROPERTIES OF ALKANES

SUBSTITUTION REACTION

ONE OR MORE HYDROGEN ATOM OF ALKANES ARE REPLACED BY HALOGEN, THE REACTION TAKE PLACE AT HIGHER TEMPERATURE AND OR IN THE PRESENCE OF DIFFUSED SUNLIGHT .WHEN METHANE IS TREATED WITH CHLORINE IN THE PRESENCE OF SUNLIGHT, HYDROGEN ATOM OF METHANE CAN BE SUCCESSIVELY REPLACED BY CHORINE ATOM.

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COMBUSTION REACTION

ALKANES ON HEATING WITH OXYGEN GIVES CARBON DIOXIDE AND WATER

CONTROLLED OXIDATION OF ALKANES

ALKANES ON HEATING WITH REGULATED SUPPLY OF OXYGEN AT HIGHER PRESSURE IN THE PRESENCE OF SUITABLE CATALYST GIVE VARIETY OF PRODUCT

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AROMATIZATION

WHEN NORMAL ALKANES HAVING SIX OR MORE CARBON ATOMS ON HEATING TO 773K AT 10-20 ATM PRESSURE IN THE PRESENCE OF OXIDES OF VANADIUM, MOLYBDENUM, OR CHROMIUM SUPPORTED OVER ALUMINA GET DEHYDROGENATED AND CYCLISED TO BENZENE.

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PYROLYSIS

HIGHER ALKANES ON HEATING AT HIGHER TEMPERATURE DECOMPOSE TO FROM LOWER ALKANES

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CONFORMATIONS OF ETHANE��

ALKENES

• UNSATURATED HYDROCARBONS CONTAINING ATLEAST ONE DOUBLE BOND
• EXAMPLE: ETHENE, PROPENE, BUTENE
• GENERAL FORMULA: C_nH_2n
• NOMENCLATURE: BY SUFFIXING ‘ENE’ TO THE PARENT NAME
• SHOWS CHAIN, POSITION, AND GEOMETRICAL ISOMERISM
• EASILY ATTACKED BY ELECTROPHILIC REAGENTS

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ETHENE

• FIRST MEMBER OF THE ALKENE FAMILY
• CHEMICAL FORMULA: C₂H₄
• PLANAR STRUCTURE
• TWO CARBON ATOM LIE IN SAME PLANE
• TWO HYDROGEN EACH ARE ATTACHED TO CARBON ATOMS
• BOND ANGLE C-H IS 120⁰
• OVERLAPPING TAKES PLACE BETWEEN SP² HYBRID

ORBITALS OF CARBON AND 1S ORBITALS OF

HYDROGEN ATOM

PREPARATION OF ALKENES�

FROM ALKANES

ALKANES ON PARTIAL REDUCTION WE GET ALKENES.

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FROM ALKYL HALIDE

ALKYL HALIDES ON HEATING WITH ALCOHOLIC POTASH (KOH DISSOLVED IN ALCOHOL),WE GET CORRESPONDING ALKENE.

FROM ALCOHOLS

ALCOHOLS ON REACTING WITH CON H₂SO₄ GIVE ALKENES

CHEMICAL REACTIONS OF ALKENES�

REACTION WITH HYDROGEN HALIDES

HYDROGEN HALIDES ADDED TO UNSYMMETRICAL ALKENES FORM ALKYL HALIDES. HERE THEY OBEY MARKOVNIKOVS RULE.

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OZONOLYSIS OF ALKENE

IT INVOLVES ADDITION OF OZONE TO FROM OZONIDE AND CLEAVAGE OF OZONIDE TO FORM SMALLER MOLECULES.

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ALKYNES

• USATURATED HYDROCARBONS WITH ATLEAST ONE TRIPLE BOND
• EXAMPLES: ETHYNE, PROPYNE, BUTYNE ETC.
• GENERAL FORMULA: C_nH_2n-2
• NOMENCLATURE: BY SUFFIXING ‘YNE’ TO THE PARENT NAME
• SHOWS CHAIN AND POSITION ISOMERS
• WEAKLY POLAR AND SHOWS ACIDIC BEHAVIOUR

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ETHYNE

• FIRST MEMBER OF THE ALKYNE FAMILY
• CHEMICAL FORMULA: C₂H₂
• LINEAR STRUCTURE
• TWO CARBON ATOM LIE IN SAME PLANE
• ONE HYDROGEN EACH IS ATTACHED TO CARBON ATOMS
• BOND ANGLE C-H IS 180⁰
• OVERLAPPING TAKES PLACE BETWEEN SP HYBRID

ORBITALS OF CARBON AND 1S ORBITALS OF

HYDROGEN ATOM

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PREPARATION OF ALKYNES

FROM CALCIUM CARBIDE

WHEN CALCIUM CARBIDE IS TREATED WITH WATER, ETHYNE IS RELEASED.

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CHEMICAL REACTIONS OF ALKYNES

REDUCTION

ADDITION OF HYDROGEN TO ALKYNES PRODUCES ALKANES.

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ALKANES?

C₂H₆

C₄H₁₀

C₂₀H₄₂

C₁₅H₃₀

C₈H₁₈

C₇H₁₄

C₆₀H₁₂₂

C₁₀H₂₀

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C₄H₈

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AROMATIC HYDROCARBONS

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• ALSO KNOWN AS ‘ARENES’
• MOST OF THEM POSSESS ‘AROMA’-MEANING PLEASANT SMELL
• CAN BE CLASSIFIED INTO BENZENOIDS AND NON BENZENOIDS
• MOST OF THEM ARE RING COMPOUNDS
• EXAMPLES: BENZENE, NAPHTHALENE, TOLUENE ETC.
• OBEY HUCKEL’S RULE OF AROMATICITY

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HUCKEL’S RULE OF AROMATICITY

• Molecule should be Planar.
• It should possess alternate single and double bonds.
• It should contain (4n+2) pie electrons, where n=0,1,2,3,..

BENZENE

BENZENE

• BENZENE CONSIDERED AS PARENT AROMATIC COMPOUND
• CHEMICAL FORMULA: C₆H₆
• KEKULE STRUCTURE
• ALTERNATE SINGLE AND DOUBLE BONDS
• HIGHLY STABLE DUE TO RESONANCE
• SIX CARBON ATOMS FORM CLOSED CHAIN
• ONE HYDROGEN IS ATTACHED TO EACH CARBON

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ELECTROPHILIC SUBSTITUTION REACTIONS OF BENZENE

CHEMICAL REACTIONS OF HYDROCARBONS IN GENERAL

• COMBUSTION REACTIONS
• ADDITION REACTIONS
• SUBSTITUTION REACTIONS
• POLYMERISATION REACTIONS
• OXIDATION REACTIONS

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COMBUSTION REACTIONS

ADDITION REACTIONS

SUBSTITUTION REACTIONS

POLYMERISATION REACTIONS

OXIDATION REACTIONS

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