Topic 17 Flashcards by Lucia Noursadeghi

SN1 reactions

Nucleophilic substitution reactions
Tertiary halogenoalkanes and a nucleophile
2 step reaction (intermediate formed)
Both enantiomers formed, racemic mixture, no optical activity

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SN2 reactions

Nucleophilic substitution reactions
Primary halogenoalkanes and a nucleophile
1 step reaction
1 enantiomer formed, optical activity

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Tests for oxidation (3)

Acidified potassium dichromate solution (orange to green)
Fehling’s or Benedict’s solution (blue solution to red precipitate)
Tollens’ reagent (colourless solution to silver mirror)
For all: Heat in water bath

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Test for a carbonyl compound (aldehyde or ketone only)

Brady’s reagent

Forms a bright orange precipitate

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Test for CH3-CO group

Alkaline solution of iodine
Warmed and cooled
Yellow precipitate formed (CHI3)
Triiodomethane reaction

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Formation of a hydroxynitrile

Reagents: carbonyl compound, hydrogen cyanide
Conditions: aqueous alkaline solution containing KCN
Products: hydroxynitrile
Observations: product is a racemic mixture
Reaction: nucleophilic addition

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Ethanoic acid and sodium reaction (simple)

Sodium ethanoate (ionic) and hydrogen

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Ethanoic acid and sodium hydroxide reaction (simple)

Sodium ethanoate (ionic) and water

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Ethanoic acid and sodium carbonate reaction (simple)

Sodium ethanoate (ionic) and water and carbon dioxide

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Carboxylic acid and ammonia reaction (simple)

eg. ammonium ethanoate (ionic)

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Carboxylic acid and amine reaction (simple)

eg. methylammonium ethanoate (ionic)

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Reduction of a carboxylic acid

Reactants: carboxylic acid, reducing agent LiAlH4
Conditions: solvent = dry ether
Products: primary alcohol and water
Observations:
Reaction:

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Halogenation of a carboxylic acid

Reactants: carboxylic acid, PCl5
Conditions: anhydrous, no heat
Products: acyl chloride, POCl3, HCl (g)
Observations: HCl = misty fumes, separate products by fractional distilation
Reaction:

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Esterification of a carboxylic acid

Reactants: carboxylic acid, alcohol
Conditions: acid catalyst (conc. H2SO4)
Products: ester (alcohol-acid), water
Observations:
Reaction: condensation

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Forming carboxylic acids by oxidation

Reactants: primary alcohol, excess acidified potassium dichromate solution
Conditions: heat under reflux
Products: carboxylic acid, water
Observations: orange to green
Reaction: oxidation

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Hydrolysis of nitriles

Acid:
Reactants: nitrile, water, HCl
Products: carboxylic acid, ammonium chloride
Note: in equilibrium, lower yield

Alkaline:
Reactants: nitrile, water, sodium hydroxide
Products: salt eg. sodium ethanoate, NH2
Note: react salt with acid to form carboxylic acid

Conditions for both: Heat under reflux!!

Formation of an acyl chloride

Reactants: carboxylic acid, PCl5
Conditions: anhydrous, no heat
Products: acyl chloride, POCl3, HCl (g)
Observations: HCl = misty fumes, separate products by fractional distilation
Reaction: halogenation

Acyl chloride and water reaction

Reactants: acyl chloride, water
Conditions:
Products: carboxylic acid and HCl
Observations: HCl = misty fumes
Reaction: condensation

Acyl chloride and alcohol reaction

Reactants: acyl chloride, alcohol
Conditions: room temp
Products: ester, HCl
Observations: HCl = misty fumes
Reaction: condensation

Acyl chloride and concentrated ammonia

Reactants: acyl chloride, concentrated ammonia
Conditions:
Products: amide, HCl
Observations: HCl reacts with ammonia forming ammonium chloride (white smoke)
Reaction:

Acyl chloride and primary amine

Reactants: acyl chloride, primary amine
Conditions:
Products: N-substituted amide, HCl
Observations: HCl reacts with amine forming RNH3+Cl- salt (white smoke)
Reaction:

Hydrolysis of esters

Acidic:
Reactants: ester, water, moderately concentrated acid catalyst
Products: carboxylic acid, alcohol
Note: reversible, low yield

Alkaline:
Reactants: ester, sodium hydroxide
Products: salt, alcohol
Note: react salt with acid to form carboxylic acid

Explain chiral

Asymmetric C atom joined to 4 different groups

2 non-superimposable mirror images (optical isomers)

Why a hydroxynitrile formed in nucleophilic addition has no optical activity

Trigonal planar carbonyl compound
Equal chance of CN attacking from either side of the molecule
Racemic mixture formed

Racemic mixture

Equimolar mixture of two enantiomers tat has no optical activity overall

What does the initial attack in the test with bradys reagent involve?

A nucleophile

What does the product of the test with bradys reagent contain

C=N

What do the reagents provide in the formation of a hydroxynitrile?

HCN and KCN HCN provides CN- ions and H+ ions KCN increases the concentration of CN- ions, insufficient with HCN alone