AS Mechanisms Flashcards
Halogenoalkane + hydroxide ions (aq)
RX + OH^-
Mechanism: Nucleophilic substitution
Product: alcohol and halide
Halogenoalkane + cyanide ions
RX + CN^-
Reactant: KCN or HCN (ethanolic)
Chain lengthens by 1 C
Mechanism: Nucleophilic Substitution
Product: nitrile and halogen ion (halide)
Halogenoalkane + ammonia
RX + NH3
Mechanism: Nucleophilic Substitution
Products: amine and ammonium ion (NH4X)
Conditions: sealed copper tube, excess ammonia
Reactant: warm conc. ethanolic ammonia
Ammonia acts as a Nucleophile and then a base
Halogenoalkane + hydroxide ions (ethanolic)
RX + OH^-
Product: alkene + halide (e.g potassium bromide ) + water
Reactant: NaOH or KOH
Mechanism: Elimination
Conditions: ethanolic
Hydroxide ion acts as a base as it accepts a proton
Alkenes + bromine (halogen)
R1=R2 + X2
Product: dibromoalkane
Reactant: Br2
Mechanism: Electrophilic Addition
Conditions:
Alkenes + sulfuric acid
R1=R2 + H2SO4
Product: alkylhydrogensulfate
Reactant: conc. H2SO4
Mechanism: Electrophilic Addition
Conditions: conc. sulfuric acid
Name of the intermediate
Carbocation
Preference of intermediates
Tertiary>secondary>primary
More stability is created by a tertiary carbocation having more electron donating alkyl groups than a primary carbocation
Alkenes + hydrogen bromide
R1=R2 + HX
Product: bromoalkane (Halogenoalkane)
Reactant: HX
Mechanism: Electrophilic Addition
Conditions:
Free radical sub of ozone
(UV light) Cl2 —> 2Cl’
Alkanes + bromine
Mechanism: Free radical substitution
Conditions: UV light
Free radical step 1
Initiation
Zero radicals —> 2 radicals
Free radical step 2
Propagation
One radical —> one radical
Reaction 1: react with new radical formed from initiation
Reaction 2: Reaction 1 product with original reactant
Alcohols + sulfuric acid or phosphoric acid
R-OH + H2SO4 or H3PO4
Product: Alkenes
Reactant:
Mechanism: Acid catalysed elimination
Conditions:
Catalyst: H2SO2 or H3PO4
Alkene + water
R1=R2 + H20
Product: Alcohol
Reactant: H20
Mechanism: ——- acid catalysed addition, hydration
Conditions:
Catalyst: H3PO4
Halogenoalkane —> alcohol
Reactant: aqueous hydroxide ions
Mechanism: Nucleophilic substitution
Conditions: Heat under reflux
Halogenoalkane —> nitrile
Chain length +1
Reactant: cyanide ion (alcoholic)
Mechanism: Nucleophilic substitution
Conditions: heat under reflux
Halogenoalkane —> amine
Reactant: Ammonia (alcoholic)
Mechanism: Nucleophilic substitution
Conditions: heat under pressure (sealed copper tube)
Halogenoalkane —> alkene
Reactant: ethanolic hydroxide ions
Mechanism: elimination
Conditions: heat under reflux
Alkene —> dihaloalkane
Reactant: X2
Mechanism: Electrophilic addition
Condition: room temp
Alkene —> Haloalkane
Reactant: HX
Mechanism: Electrophilic Addition
Conditions: room temp
Alkene —> alkylhydrogensulfate
Reactant: conc. sulfuric acid
Mechanism: Electrophilic Addition
Catalyst: conc. sulfuric acid
Conditions: conc. sulfuric acid
Alcohols —> Alkenes
Reactants:
Catalysts: conc. H2SO4 or H3PO4
Mechanism: elimination
Conditions:
Alkenes —> alcohols
Reactants: H2O + H3PO4
Catalysts: H3PO4
Mechanism: Hydration or acid catalysed Electrophilic addition
Conditions: 70 atm 300 degrees catalyst
Alkene —> Halogenoalkane
Reactant: X2
Mechanism: Free Radical Substitution
Conditions: UV light
Alkene —> polymer / poly(alkene)
Reactant: Ziegler-Natta
Mechanism: Addition Polymerisation
Catalyst: Ziegler-Natta catalyst
Conditions: High pressure
Primary alcohol —> aldehyde
Reactant: conc sulfuric acid and potassium dichromate
Mechanism: Partial Oxidation
Conditions: heat and distill
Catalyst: conc H2SO4 + K2CR2O7
Secondary alcohol —> ketone
Reactant: conc sulfuric acid and potassium dichromate
Mechanism: Oxidation
Conditions: heat under reflux
Catalyst: conc H2SO4 + K2CR2O7
Aldehyde —> carboxylic acid
Reactant: conc sulfuric acid and potassium dichromate
Mechanism: Oxidation
Conditions: heat under reflux + excess oxidising agent
Catalyst: conc H2SO4 + K2CR2O7
alkylhydrogensulfate –> alcohol
Product: alcohol + sulfuric acid reformed Reactant: water
Mechanism: Hydrolysis (nucleophilic substitution)
Conditions: warm/heat
Heterolytic fission example
In Nucleophilic substitution the covalent bond between the carbon atom and the halogen atom breaks.
This is heterolytic fission as both electrons move onto the halogen
