Amines
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Transcript of Amines
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Substance Reagent ObservationPrimary alcohol
Cr2O72-
Secondary alcohol
Cr2O72-
Tertiary alcohol
Cr2O72-
Ketone Cr2O72-
Aldehydes Cr2O72-
Acids Cr2O72-
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AminesAmines
L.O: Explain basicity of amines.Preparation of aliphatic amines by substitution of halogenoalkanes.Preparation of aromatic amines by reduction of nitroarenes Synthesis of azo dyes by diazotisation and coupling.
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Amphetamine, phenylephrine and adrenaline are all amines
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Ammonia and some common amines
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N-methyl propylamine
The shortest alkyl contain one carbon atom connected to the N atom, so N-methyl is added as the prefix.
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N,N-diethylpropylamine
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The four kinds of amines
Primary amine: only one carbon chain attached to the nitrogen.
Secondary amine: nitrogen attached to 2 carbon chains
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Why are amines basic?
Amines are weak bases. They are proton acceptors.
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Reaction of methylamine as a base
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Reaction of phenylamine and nitric acid
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Making primary aliphatic amines
• Halogenoalkanes are gently warmed in a an alcohol solvent with excess ammonia.
• The reaction proceeds by a nucleophilic substituion mechanism.
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Steps involved in making aliphatic amines
• Step 1: Reacting ammonia with the halogenoalkane
• Step 2: Removing halogen ions with excess ammonia
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Making a secondary amine• The lone pair of electrons on the N atom can still
attack the δ+ carbon attached to the halogen on another halogenoalkane
• Tertiary and quaternary amines are likewise also possible
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Qs
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Reduction of nitrobenzene to make phenylamine (aniline)
Nitroarenes can be reduced using a mixture of Sn and concentrated HCl, heated under reflux, followed by neutralisation.
[H] represents the reducing agent.
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azo dyes
Made in two steps:1)Formation of diazonium ion2)coupling
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1) Diazotisation reaction
Nitrous acid (HNO2) is made by reacting sodium nitrite (NaNO2) with excess HCl
The phenylamine and nitrous acid are then mixed at temps below 10 °C
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Coupling
Notice that the reaction conditions are alkaline!
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E110 is a yellow colouring agent that is commonly added to a variety of foods.E110 contains an azo dye made from an amine and a phenol.Describe how you would prepare a sample of an azo dye in the laboratory from an amine, a phenol and any other necessary reagents.Include in your answer•essential reagents and conditions for each stage•names of any functional groups formed during the process [7]
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1st stagearomatic amine / named aromatic amine / structure (1)sodium nitrite / nitrous acid (1)HCl/H2SO4 (but not conc) /H+ (1)at <10°C (1)which forms a diazonium salt / ion (1)if more than four are given, mark any wrong reagents, conditions first
2nd stagethe product from the first stage mixed with the phenol (1)(in excess) hydroxide / alkali (1)
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