Hydrocarbons
Alkenes
Unsaturated hydrocarbons
General formula is CnH2n
Alkenes are also called as olefins.(Oil nature compounds are formed)
Preparations :
- Controlled hydrogenation of alkynes
- Kolbe's electrolysis
- Elimination reaction
Controlled hydrogenation of alkynes :
Kolbe's electrolysis :
E2 elimination :
Elimination bimolecular reaction
Rate ∝ [substrate] [base]
Order = 2
One step mechanism
Intermediate = Transition state
E1 elimination :
Elimination unimolecular reaction
Rate ∝ [substrate]
Order = 1
Two steps mechanism
Intermediate ⇒ Carbocation
E1cb(Elimination unimolecular conjugate base) :
Markovnikov's rule :
In the case of unsymmetrical alkenes, the +ve part is added to double bonded carbon which has more no. of hydrogens to give stable carbocation.
Note : Negative part is added to double bonded carbon, which has less no. of hydrogens.
Anti Markovnikov's rule : Peroxide effect (or) Kharash effect.
Peroxides : H2O2
Mechanism : It involves 3 steps
H_{2}O \xrightarrow[]{h\nu} 2OH^{\cdot}
Chain propagation :
Addition of H2O :
In presence of H^\oplus | Oxymercuration - Demercuration | Hydroboration - Oxidation |
Carbocation | no Carbocation | no Carbocation |
Rearrangement of ring expansion is possible | no rearrangement and ring expansion | no rearrangement and ring expansion |
Markovnikov's product | Markovnikov's product | Anti Markovnikov's rule product |
H2O → Alcohol R − OH → Ethers |
H_{2}O_{2}/{OH}^\ominus → Alcohols Acids → Alkane |
Oxymercuration - Demercuration :
Reagent :
Hydroboration - Oxidation :
Ozonolysis :
Hydrogenation :
Syn addition | Anti Addition |
1) H2/Ni | X2/CCl4 |
2) KMnO4/OH^\ominus → Baeyer's reagent | X2/H2O |
OsO4 | RCO3H/H+/H2O |
Hydroboration and oxidation BH3/THF/H2O2/OH− |
— |
Reductive Ozonolysis :
- Zn/H2O
- (CH3)2S/CH2Cl2
- p(ph)3/CH2Cl2
Oxidative Ozonolysis :
- H2O
- H2O2
- RCO3H
Part1: View the Topic in this Video from 0:35 to 50:55
Part2: View the Topic in this Video from 0:06 to 21:16
Part3: View the Topic in this Video from 0:06 to 10:58
Part4: View the Topic in this Video from 0:07 to 13:41
Disclaimer: Compete.etutor.co may from time to time provide links to third party Internet sites under their respective fair use policy and it may from time to time provide materials from such third parties on this website. These third party sites and any third party materials are provided for viewers convenience and for non-commercial educational purpose only. Compete does not operate or control in any respect any information, products or services available on these third party sites. Compete.etutor.co makes no representations whatsoever concerning the content of these sites and the fact that compete.etutor.co has provided a link to such sites is NOT an endorsement, authorization, sponsorship, or affiliation by compete.etutor.co with respect to such sites, its services, the products displayed, its owners, or its providers.
1. General formula of Alkenes = [CnH2n]