Amines

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Why are amines so reactive?
The lone pair of electrons on the Nitrogen- due to the polar N-H bond
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What shape are amines around the N? Bond angle?
Trigonal pyrimidal, 107 due to lone pair on N
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What kind of intermolecular forces do they have? Why?
Hydrogen bonding due to the polar N-H bond and lone pair of electrons on N atom
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Do amines have intermolecular forces which are stronger or weaker than alcohols? Why?
Weaker as N has a lower electronegativity than O so weaker hydrogen bonding
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What state are amines at 298K?
Short chains are gases longer chains are volatile liquids
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Which primary amines are soluble in water/alcohols? Why?
Up to 4 carbon atoms as they can hydrogen bond to water molecules. After this, non polarity of hydrocarbon chain makes them insoluble
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What kind of solvents are most other amines soluble in?
Less or non-polar solvents
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Solubility of phenylamine? Why?
Not very soluble due to the non-polarity of the benzene ring- C6H5 cannot form hydrogen bonds
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How can/when do amines act as bases?
When they bond with a H+ ion
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How can/when do amines act as nucleophiles?
When they bond with an electron-deficient C atom
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What is the product from the basic action of an amine with water?
RNH3+ ammonium ion which forms a salt with an anion
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Is the product (ammonium ion) soluble in water? Why?
Yes as it is ionic so is attracted to the polar bonds in H2O
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How can you regenerate the soluble amine from the ammonium salt?
Add a strong base (NaOH) it removes H+ ions from ammonium ion
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In order to be the strongest base what must a particular amine have?
Greatest electro density around the N atom making it a better electron pair donor
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What does positive/negative inductive effect mean?
Positive means it donates electrons and increases the density around N and Negative means it removes electrons decreases density around the N
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What effect do alkyl groups have on electron density and base strength?
Positive inductive effect increases electron density around N so it's a stronger base
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What effect do aryl groups have on electron density and bast strength?
Negative inductive effect decreases electron density around N so weaker base
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Why are tertiary amines never good bases?
They are insoluble in water
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How can primary amines then form secondary, tertiary and ammonium ions?
Multiple substitutions; the primary amine is a nucleophile that attacks the original haloalkane
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What are the problems with this method?
Not as efficient as low yield of primary amine due to the multiple substitutions
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How would you maximise yield?
Use excess ammonia
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What type of mechanism is the reaction of a haloalkane with a cyanide ion?
Nucleophilic substitution
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What conditions does this reaction require? What is the product formed?
Ethanol as a solvent and a Nitrile is formed
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How do you get from a nitrile to a primary amine?
Reduction using Nickel/Hydrogen catalyst
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Why is this a purer method of synthesising amines?
Only the primary amine is formed
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What conditions are needed to form nitrobenzene from benzene?
Conc H2SO4 and HNO3 to form the NO2+ ion for the electrophilic attack
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How do you form an ammonium chloride salt from nitrobenzene? What conditions are needed?
Reduce the nitrile using Tin/HCl forms an ammonium salt with Cl- ions at room temp
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Equation for the reaction of nitrobenzene to phenylamine?
C6H5NO2 + 6[H] ---> CH5NH2 + 2H2O
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What mechanism is used for forming amides from acyl chlorides and amines?
Nucleophilic addititon/elimination
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What are cationic surfactants?
Quaternary ammonium salts with a cation that is charged at one end (N+) and non polar at the other
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How do cationic surfactants work in fabric/hair conditioners?
Negative charges on the surface of the fabric/hair are attracted to the cation removing them from the surface prevents build up of static electricity and keeps hair flat and fabric smooth
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How do cationic surfactants sit when placed in water?
Charged end in the water non polar end sticking out of water/at the surface
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Other cards in this set

Card 2

Front

What shape are amines around the N? Bond angle?

Back

Trigonal pyrimidal, 107 due to lone pair on N

Card 3

Front

What kind of intermolecular forces do they have? Why?

Back

Preview of the front of card 3

Card 4

Front

Do amines have intermolecular forces which are stronger or weaker than alcohols? Why?

Back

Preview of the front of card 4

Card 5

Front

What state are amines at 298K?

Back

Preview of the front of card 5
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