Revision Notes: Hydrocarbons Notes | Study Mock Test Series for JEE Main & Advanced 2022 - JEE

JEE: Revision Notes: Hydrocarbons Notes | Study Mock Test Series for JEE Main & Advanced 2022 - JEE

The document Revision Notes: Hydrocarbons Notes | Study Mock Test Series for JEE Main & Advanced 2022 - JEE is a part of the JEE Course Mock Test Series for JEE Main & Advanced 2022.
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  • Compounds of carbon and hydrogen.
  • Classification of Hydrocarbons:
    Revision Notes: Hydrocarbons Notes | Study Mock Test Series for JEE Main & Advanced 2022 - JEE

Alkane

  • Open chain saturated hydrocarbon with general formula (CnH2n+2). 
  • All the C atoms are single bonded i.e. sp3 hybridised.

Conformations of Alkane

  • Conformations are the different arrangement of atoms that can be converted into one another by rotation about single bonds. 
  • Eclipsed Conformation: H atoms on two adjacent carbon atoms are closest to each other i.e. dihedral angle is 0.
    Revision Notes: Hydrocarbons Notes | Study Mock Test Series for JEE Main & Advanced 2022 - JEE
  • Staggered Conformation: H atoms on two adjacent carbon atoms are farthest to each other i.e. dihedral angle is 60.
    Revision Notes: Hydrocarbons Notes | Study Mock Test Series for JEE Main & Advanced 2022 - JEE

Preparation of Alkanes:

  • Reduction of Alkyl Halides:
    RX + Zn: + H+  → RH + Zn2+ + X-
    4RX + LiAlH4    → 4RH + LiX + AlX3 (X≠ F)                    
    RX + (n - C4H9)3 SnH  → R-H + (n - C4H9)3 SnX
  • Grignard Reagent:
    Revision Notes: Hydrocarbons Notes | Study Mock Test Series for JEE Main & Advanced 2022 - JEE         
  • Hydrogenation of Alkenes:
    Revision Notes: Hydrocarbons Notes | Study Mock Test Series for JEE Main & Advanced 2022 - JEE
  • Wurtz Reaction:
    2RX  + 2Na  → R-R + 2NaX
    2Na + 2CH3CH2CH2Cl  →  CH3CH2CH2CH2-CH2CH3 + 2NaCl
  • Corey House Reaction:
    Revision Notes: Hydrocarbons Notes | Study Mock Test Series for JEE Main & Advanced 2022 - JEE
  • Decarboxylation of a mixture of the sodium salt of a carboxylic acid:
    RCOONa +NaOH(CaO) → RH +  Na2CO3
  •  Kolbe's electrolytic method:
    2 RCOOK + 2H2O → R-R + 2CO2 + H2+ 2KOH

 Chemical Properties of Alkane

  • Direct Halogenation
    RH + X2→ RX + HX
    Order of Reactivity of X2:    F2 > Cl> Br2; I2 does not react
    a. Initiation Step
    Cl-ClRevision Notes: Hydrocarbons Notes | Study Mock Test Series for JEE Main & Advanced 2022 - JEE2Cl.
    b. Propagation Step
    H3C-H +Cl → H3C + H-Cl
    H3C + Cl-Cl → H3C-Cl +Cl
    c. Termination Step 
    Cl + Cl →Cl-Cl
    H3C + H3C → H3C-CH3
    Cl + H3C → Cl-CH3
  • Nitration 
    Nitration of alkane is made by heating vapours of alkanes and HNOat about 400oC to give nitroalkanes.
    This is also known as vapour phase nitration.
    Revision Notes: Hydrocarbons Notes | Study Mock Test Series for JEE Main & Advanced 2022 - JEE
  • Combustion:
    Alkanes burn readily with non luminous flame in presence of air or oxygen to give CO2 & water along with evolution of heat.
    C2H6 + 7O→ CO2 +6H2O + heat
  • Aromatization
    Alkanes having six to 10 carbon atoms are converted into benzene and its homologues at high pressure and temperature in presence of catalyst.
    Revision Notes: Hydrocarbons Notes | Study Mock Test Series for JEE Main & Advanced 2022 - JEE
  • Oxidization of 30 alkane:
    Tertiary alkanes are oxidized to tertiary alcohols by KMnO4
     R3CH + KMnO4 → R3COH

Alkene (olefins)

  • Open chain, Unsaturated hydrocarbons with general formula (CnH2n).
  • At least one  >c=c<  (double bond) group i.e. sp2 hybridisation, is present throughout the chain.
  • Allene: alkene molecule in which at least one C has double bonds with each of the adjacent carbon i.e. -c=c=c- group. 
  • Isomeric with saturated cycloalkanes.
    Revision Notes: Hydrocarbons Notes | Study Mock Test Series for JEE Main & Advanced 2022 - JEE

Geometric Isomers:
Revision Notes: Hydrocarbons Notes | Study Mock Test Series for JEE Main & Advanced 2022 - JEE
Z is used if the higher - priority substituents on each C are on the same side of the double bond. letter E is used if they are on opposite sides
Revision Notes: Hydrocarbons Notes | Study Mock Test Series for JEE Main & Advanced 2022 - JEE         

Heats of Hydrogenation: Heat of hydrogenation increases with increase in stability of alkene.
Revision Notes: Hydrocarbons Notes | Study Mock Test Series for JEE Main & Advanced 2022 - JEE       
Order of heat of hydrogenation: 1-Butene> cis-2-Butene > trans-2-Butene
Order of stability: 1-Butene> cis-2-Butene > trans-2-Butene

Preparation of Alkenes:
1. Cracking of petroleum:
Revision Notes: Hydrocarbons Notes | Study Mock Test Series for JEE Main & Advanced 2022 - JEE
2. Dehydrohalogenation of alkyl halides:   RCH2CH2X + alc.KOH → RCH = CH2
3. Dehydration of Alcohols:
Saytzeff Rule: In dehydration and dehydrohalogenation the preferential order for removal of an H is 3° > 2° > 1°
Revision Notes: Hydrocarbons Notes | Study Mock Test Series for JEE Main & Advanced 2022 - JEE
 4. Reduction of alkynes:
Revision Notes: Hydrocarbons Notes | Study Mock Test Series for JEE Main & Advanced 2022 - JEE

Chemical Properties:
1. Electrophilic Polar Addition Reactions

Reagent
Product
Name
Structure
Name
Structure
Halogens
(Cl2, Br2 only)
X:X
Ethylene dihalide
CH2XCH2X
Hydrohalic acids
H:X
Ethyl halide
CH3CH2X
 
Hypohalous acids
 
X:OH
 
Ethylene halohydrin
 
CH2XCH2OH
 
Sulfuric acid (cold)
 
H:OSO2OH
 
Ethyl bisulfate
 
CH3CH2OSO3H
 
Water (dil. H3O+)
 
H:OH
 
Ethyl alcohol
 
CH3CH2OH
Borane
 
H2B:H
Ethyl borane
(CH3CH2BH2) → (CH3CH2)3B
Peroxyformic acid
 
     H:O-OCH=O    
(HCO3H)
Ethylene glycol
CH2OHCH2OH


2. Addition of Hydrogen Halides to Alkenes: Markovnikov’s Addition:
R - CH = CH2 + HBr → R – CHBr – CH3
Mechanism:
R - CH = CH2 + HBr → R – CH+ - CH +Br-
R – CH+ - CH3 + Br- → R – CHBr - CH3
Anit- Markovnikov’s Addition (Peroxide Effect):
R - CH = CH2 + HBr + (C6H5CO)2O2 → R – CHBr – CH3
Mechanism
Initiation:
R - O - O - R  →  2RO
RO. +  HBr  →  Br.   +   ROH
Propagation
CH3CH = CH2   + Br →   CH3•CH - CH2Br
CH3CHCH2Br + HBr→ CH3CH2CH2Br + Br
Termination:
2RO  →  R - O - O - R  
Br + Br→Br2


3. Addition of Water to Alkenes: Acid Catalyzed Hydration:
Revision Notes: Hydrocarbons Notes | Study Mock Test Series for JEE Main & Advanced 2022 - JEE


4. Oxymercuration-Demercuration:
Revision Notes: Hydrocarbons Notes | Study Mock Test Series for JEE Main & Advanced 2022 - JEE
Examples:
Revision Notes: Hydrocarbons Notes | Study Mock Test Series for JEE Main & Advanced 2022 - JEE


5. Hydroboration-Oxidation:
Revision Notes: Hydrocarbons Notes | Study Mock Test Series for JEE Main & Advanced 2022 - JEE
Examples:
Revision Notes: Hydrocarbons Notes | Study Mock Test Series for JEE Main & Advanced 2022 - JEE


6. Halogen Addition in Non-polar Solvent:
Revision Notes: Hydrocarbons Notes | Study Mock Test Series for JEE Main & Advanced 2022 - JEE


7. Halogen Addition in Aqueous Medium:
Revision Notes: Hydrocarbons Notes | Study Mock Test Series for JEE Main & Advanced 2022 - JEE


8. Syn – Hydroxylation: Formation of di-oles.
Revision Notes: Hydrocarbons Notes | Study Mock Test Series for JEE Main & Advanced 2022 - JEE


9. Ozonolysis of Alkenes:
Revision Notes: Hydrocarbons Notes | Study Mock Test Series for JEE Main & Advanced 2022 - JEE 

Alkyne

  • Saturated open chain hydrocarbon with general formula (CnH2n-2).
  • At least one -c≡c-  (triple bond) group i.e. sp hybridisation, is present throughout the chain.
  • Physical properties of alkynes are similar to those of the corresponding  alkenes

Preparation
1. Dehydrohalogenation of vic-Dihalides or gem-Dihalides
Revision Notes: Hydrocarbons Notes | Study Mock Test Series for JEE Main & Advanced 2022 - JEE

2. Dehalogenation of vic-Tetrahalogen Compounds
Revision Notes: Hydrocarbons Notes | Study Mock Test Series for JEE Main & Advanced 2022 - JEE

3. Alkyl Substitution in Acetylene; Acidity of º C-H
 Revision Notes: Hydrocarbons Notes | Study Mock Test Series for JEE Main & Advanced 2022 - JEE

4. From Calcium Carbide:
CaC2 +2H2O →   Ca(OH)2+ C2H2

5. Kolbe’s Electrolysis:
Revision Notes: Hydrocarbons Notes | Study Mock Test Series for JEE Main & Advanced 2022 - JEE

Chemical Properties
1. Hydrogenation: RC ≡ CCH2CH3 + 2H2 →  CH3CH2CH2CH2CH3
2. Hydro-halogenation:
Markovnikov addition: RC≡CH +HBr → RCBr=CH2 +HBr→ RCBr2-CH3
Anti-markovnikov addition: RC≡CH +HBr +peroxide → RCH=CHBr
Revision Notes: Hydrocarbons Notes | Study Mock Test Series for JEE Main & Advanced 2022 - JEE  

Aromatic Hydrocarbons: 
For being aromatic a hydrocarbon should

  • be a cyclic compounds.
  • have planarity in geometry.  
  • have complete delocalization of electrons over ring.
  • follow Huckel Rule i.e. number of ?? electrons in ring = (4n+2).
    Revision Notes: Hydrocarbons Notes | Study Mock Test Series for JEE Main & Advanced 2022 - JEE

Benzene (C6H6)
1. Structure:
Revision Notes: Hydrocarbons Notes | Study Mock Test Series for JEE Main & Advanced 2022 - JEE
2. Chemical Reactions of Benzene:
Revision Notes: Hydrocarbons Notes | Study Mock Test Series for JEE Main & Advanced 2022 - JEE

Anti-aromatic Hydrocarbons:
Highly unstable compounds.
Number of π electrons in ring = 4n.
Example:
Revision Notes: Hydrocarbons Notes | Study Mock Test Series for JEE Main & Advanced 2022 - JEE

The document Revision Notes: Hydrocarbons Notes | Study Mock Test Series for JEE Main & Advanced 2022 - JEE is a part of the JEE Course Mock Test Series for JEE Main & Advanced 2022.
All you need of JEE at this link: JEE

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