11 Alkenes Flashcards
Classification of Carbocations
Carbocation = Ion with a +ve-charged C
1° Carbocation - 0 Alkyl Group(s)
2° Carbocation - 1 Alkyl Group(s)
3° Carbocation - 2 Alkyl Group(s)
4° Carbocation - 3 Alkyl Group(s)
Preparation of Alkenes
Dehydrohalogenation of Halogenalkanes
Mechanism: Elimination
Reagent(s): Ethanolic KOH
Condition(s): Heat under reflux
Preparation of Alkenes
Dehydration of Alcohols
Mechanism: Elimination
Reagent(s): Excess concentrated H2SO4/ Al2O3/ H3PO4
Condition(s): Heat
Saytzeff’s Rule
For elimination reactions of alcohols or halogenalkanes to alkenes, the preferred product is the alkene with the greater number of alkyl groups attached to the doubly bonded carbon.
AKA
For elimination reactions of alcohols or halogenalkanes to alkenes, the preferred product is the more substituted alkene.
Reaction of Alkenes
Addition of Hydrogen Halides, HX
Reagent(s) & Condition(s): dry HX(g)
Product(s): Monosubstituted Alkane
Markovnikov’s Rule
In the addition of a Hydrogen Halide, HX to the C=C bond of an unsymmetrical Alkene, the major product is the one in which the H atom of HX attaches itself to the doubly bonded carbon atom already bonded with the greater number of H atoms.
Mechanism-based Markovnikov’s Rule
In an Electrophile Addition reaction, the Electrophile adds to the unsymmetrical Alkene to produce the more stable Carbocation intermediate. Being formed faster in the slow step, the more stable Carbocation is more available to participate in the fast step to give the major product.
Reaction of Alkenes
Addition of Water, H2O (Laboratory Method)
Step 1
Reagent(s) & Condition(s): cold, concentrated H2SO4
Step 2
Reagent(s) & Condition(s): H2O, Heat
Product(s): Alcohol
Reaction of Alkenes
Addition of Steam, H2O(g) (Industrial Method)
Reagent(s) & Condition(s): H3PO4 on silica, high temperature and pressure
Product(s): Alcohol
Reactions of Alkenes
Addition of Halogens, X2 in CCl2
Reagent(s) & Condition(s): X2 in CCl4
Product(s): Disubstituted Alkane
Reactions of Alkenes
Addition of Halogens, X2 in H2O
Reagent(s) & Condition(s): X2 in H2O
Product(s): Monochlorinated Alcohol and Hydrogen Halide
Reactions of Alkenes
Mild Oxidation in Cold, Alkaline Medium
Reagent(s) & Condition(s): KMnO4 (aq), NaOH (aq), Cold
Product(s): Diol
Reactions of Alkenes
Strong Oxidation in Hot, Acidic Medium
Reagent(s) & Condition(s): KMnO4, H2SO4, Heat
Product(s): Carboxylic Acids, Ketones or Carbonic Acid/ Ethandioic Acid–> CO2 & H2O
Reactions of Alkenes
Addition of Hydrogen, H2
Reagent(s) & Condition(s) 1: H2, Ni & Heat
Reagent(s) & Condition(s) 2: H2, Palladium, Pd
Reagent(s) & Condition(s) 3: H2, Platinum, Pt
Product(s): Alkanes
