What are amines?
Amines are compounds based on ammonia where hydrogen atoms have been replaced by alkyl/aryl groups. Amines are weak bases. Amines can act as nucleophiles and bases
Explain why 3-aminopentane is a stronger base than ammonia?
In 3-aminopentane the lone pair on N is more available to accept H+; because of the alkyl inductive effect
2 methods for the preparation of amines?
- reaction of haloalkanes with NH3
- reduction of nitriles
The amine CH3CH2CH2NH2 can be prepared by two different routes. Route A is a one-stage process and starts from CH3CH2CH2Br. Give the reagents and conditions for this route.
-NH3 in excess
- nucleophilic substitution
The amine CH3CH2CH2NH2 can also be prepared by a 2 stage process and starts from CH3CH2Br. Identify the intermediate compound and give the reagents and conditions for this route.
- intermediate compound CH3CH2CN (propanenitrile)
- reagent is KCN
- conditions are aqueous and ethanolic
- reagent for stage 2 is H2
- and condition is Ni catalyst
Give one disadvantage of the one stage process of making amines?
impure product due to further substitution
Give 2 disadvantagesof the 2 stage process of making amines?
- poisonous KCN
- lower yield because of 2 steps
This question is about amines. Give an equation for teh preparation of 1,6-diaminohexane by the reaction of 1,6-dibromohexane with an excess of ammonia
Br-(CH2)6-Br + 4NH3 –> H2N-(CH2)6-NH2 + 2NH4Br
Explain the formation of amines with the nucleophilic substitution reaction of haloalkanes with NH3 method(5)
- one stage process
- reagents: haloalkane and NH3
- conditions: NH3 in excess
- impure product due to further substitution
- secondary amine, tertiary amine and quaternary ammonium salt can also be made
Explain the formation of amines with the reduction of nitriles method (5)
- 2 stage process
- stage 1: reaction of haloalkane with KCN to make a nitrile in aqueous and ethanolic ocnditions
- stage 2: reaction of nitrile with hydrogen gas/ nickel catalyst
- will give a purer product
- lower yield as its a 2 stage process
- KCN is toxic
This question is about 2-bromopropane. Define teh term electronegativity. Explain the polarity of the C-Br bond in 2-bromopropane
- the relative tendedncy of an atom to attract a pair of electrons/ lectron density in a covalent bond
- Br is more electronegative than C
- so Br has a δ− whilst C has a δ+
Give a use for the organic product of the main organic species formed in the recation between a large excess of 2-bromopropane and ammonia
hair conditioner/cationic surfactant/ disinfectant
Benzene can be converted into phenylamine via a 2 stage synthesis. What reagents are used to produce the electrophile needed in the first stage? Write an equation to show the formation of this electrophile.
- reagents: concentrated HNO3, concentrated H2SO4
- equation: H2SO4 + HNO3 –> HSO4- + NO2+ + H2O
Phenylamine can be prepared by a process involving the reduction of nitrobenzene using tin and an excess of HCl. Give an equation for the reduction of nitrobenzene to form phenylamine. Use [H] to represent the reducing agent. Explain why an aqueous solution is obtained in this reduction even though phenylamine is insoluble in water.
- C6H5NO2 + 6[H] –> C6H5NH2 + 2H2O
- C6H5NH2 is present as an ionic salt or C6H5NH3+ or phenylammonium (chloride)
What is used to reduce nitrobenzene to phenylamine. Give one use for phenylamine
- Tin and excess of HCl
- used in making dyes
A student dissolves a few drops of propylamine in 1cm^3 of water in a test tube. Give an equation for the reaction that occurs. Describe what is observed when universal indicator is added to this solution.
CH3CH2CH2NH2 + H2O ⇌ CH3CH2CH2NH3+ + OH-
green to blue
Primary amines can be prepared by the reaction of halogenoalkanes with ammonia or by the reduction of nitriles. Justify the statement that it is better to prepare amines from nitriles rather than from halogenoalkanes
- with halogenoalkane: further reaction of primary amines therefore impure product/ micture of products/ lower atom economy
- with nitriles: no further reaction ORR single product tehrefore higher atom economy
Why are amines so reactive?
the lone pairs of electrons on the nitrogen due to the polar N-H bond
What shape are amines around the N? Bomd angle?
- trigonal pyrimadal
- 107 due to the lone pair on the N
What kind of intermolecular force is present in amines? Why?
- hydrogen bonding due to the polar N-H bond and lone pair of electrons on the N atom
Do amines ahve intermolecular forces which are stronger or weaker than the ones in alcohols?
weaker as N has a lower electronegativity than O so there is weaker hydrogen bonding
What state are amines at 298k?
short chains are gasses and long chains are volatile liquids
name and explain the smell of amines?
- fishy
- release of di/tri amines
Which primary amines are soluble in water/alcohols? why?
- up to 4 carbon atoms, as they can hyrogen bond to water molecules
- after this, non-polarity of hydrocarbon chain makes them insoluble
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3.1 Atomic structure26
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3.1.2 Amount of substance7
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3.1.3 Bonding38
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3.1.4 Energetics18
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3.1.6 Chemical equilibria10
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3.1.7 Oxidation, reduction and redox equations0
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3.1.8 Thermodynamics (evrythng frm hr=A-level only0
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3.1.9 Rate equations22
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Optical isomerism A219
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ALL of A1 Chemistry - tuition flashcards101
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Aldehydes and ketones28
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Periodicity104
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Transition metals A246
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Aromatic chemistry40
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enthalpy definitions13
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Amines51
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aromatics, amines and biochemistry44
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Organic synthesis21
