AS Organic Reactions and Conditions

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  • Created by: Char1801
  • Created on: 25-12-18 11:27

Incomplete Combustion

Reagent and Conditions Required:

Limited Supply of Oxygen

Explanation:

CO is formed rather than CO2 due to limited availability of O2

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Production of NO2 from O2 and N2 (car engines)

Reagent and Conditions Required:

High temperature

Explanation:

O2 and N2 are present in air, only high temperature provided by car engines is able to break apart the stable N-triple-bond-N

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Thermal Cracking

Reagent and Conditions Required:

High temperature and high pressure

Explanation:

Produces high % of alkenes

Energetic conditions are required as no catalyst = high activation energy

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Catalytic Cracking

Reagent and Conditions Required:

Zeolite catalyst and high temperature

Explanation:

Produces cycloalkanes and aromatic alkanes

High temperature still required (but not as high as thermal cracking)

Memory trick = ‘C’s… catalytic cracking= cyclo…

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Alkanes -> Haloalkanes

FREE RADICAL SUBSTITUTION

Reagent and Conditions Required:

Reagent = Halogen

Condition = UV light

Explanation:

Alkane is very unreactive due to strong C-C and C-H bonds (bonding pair is held close to nuclei) and non-polar bonds. Reactive free-radicals must be formed for reaction to initiate

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Haloalkane –> Alkene

ELIMINATION

Reagent and Conditions Required:

Reagent = KOH

Conditions = aqueous ethanol (alcoholic) for solvent AND high temperature

Explanation:

Aqueous (water) splits the KOH to K+ and OH-

Ethanol acts as a solvent: mixes polar OH- with relatively non-polar haloalkane.

Hotter temperature causes elimination

OH- acts as a base – accepts H+

Memory trick: ‘E’s Elimination – ethanolic

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Haloalkane -> Amine

NUCLEOPHILIC SUBSTITUTION

Reagent and Conditions Required:

NH2

Explanation:

Remember x2 NH2 required:

1st NH2 produces a positive charge on the N as neutral nucleophile donates a lone pair and form a new bond.

2nd NH2 acts as a base and accepts an H+

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Haloalkane -> Nitrile

NUCLEOPHILIC SUBSTITUTION

Reagent and Conditions Required:

Reagent = KCN

Conditions = Ethanol/water mixture

Explanation:

Aqueous (water) splits the KCN to K+ and CN-

Ethanol acts as a solvent: mixes polar CN- with relatively non-polar haloalkane

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Haloalkane –> Alcohol

NUCLEOPHILIC SUBSTITUTION

Reagent and Conditions Required:

Reagent = KOH

Conditions = Water and lower temperature than elimination

(NO ETHANOL)

Explanation:

OH- acts as a nucleophile ­– donates pair of electrons and forms bond with slightly positive carbon.

Memory trick = Substitutes get cold – but careful the mixture is still warmed (just not as hot as elimination)

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Alkene -> Alkane

ELECTROPHILIC ADDITION

Reagent and Conditions Required:

Reagent = H2

Conditions = Ni Catalyst and heat

Explanation:

Dipole induced in H2 by high electron density of C=C

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Alkene –> Haloalkane

ELECTROPHILIC ADDITION

Reagent and Conditions Required:

HX (e.g. HBr) OR X2 (e.g. Br2)

Explanation:

Slightly positive H attracted to high electron density of C=C

Dipole induced in non polar Br2 by high electron density of C=C

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Alkene -> Alcohol

ELECTROPHILIC ADDITION OF H2SO4 FOLLOWED BY HYDROLYSIS BY H2O

Reagent and Conditions Required:

Reagent = H2O (steam)

Conditions = Conc. sulfuric acid catalyst and high temperature

Explanation:

Sulfuric acid reacts with alkene in first step and forms a ….. hydrogen sulfate.

This then is replaced by OH of water

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Alcohol -> Alkene

Reagent and Conditions Required:

Conditions = Conc. sulfuric acid catalyst and heat

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Primary or Secondary Alcohol -> Aldehyde or Ketone

Reagent and Conditions Required:

Heat

Distillation

Acidified K2Cr2O7 (potassium dichromate)

Explanation:

Product can be removed by distillation upon formation due to lower boiling point than reactants. –OH -> C=O and therefore product loses ability to hydrogen bond

 

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Primary Alcohol -> Carboxylic Acid

Reagent and Conditions Required:

Heat

Reflux

Acidified K2Cr2O7 (potassium dichromate)

Conditions:

Initial products (intermediates) aldehyde must remain in the reaction mixture to be oxidised again to carboxylic acid

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Glucose -> Ethanol

FERMENTATION

Reagents and Conditions Required:

Yeast

*Between 25 and 42oC

Anaerobic

Neutral pH

Explanation:

Higher temperatures would kill the yeast fungi. Lower temperatures and the reaction would be too slow

= most important conditions

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