Amines and Amides Flashcards
What is an amine?
Where one or more hydrogens have been replaced on an ammonia molecule by an alkyl or aromatic group
What is a primary/secondary/tertiary amine?
Where one H has been replaced on the ammonia/where 2 Hs have been replaced/ where 3 Hs have been replaced
What is a quarternary ammonium ion?
If a fourth organic group is added.
How does a quarternary ammonium salt form?
Because the quarternary ammonium ions are positive they hang around negative ions that are near. The two ions form complexes called quarternary ammonium salts.
Give an example of a quarternary ammonium salt?
Tetramethylammonium chloride
((CH3)4N+Cl-)
How do small amines smell?
Smell similar to ammonia with a slightly fishy twist
How do larger amines smell?
Smell very fishy
What are the two possible suffixes when naming amines?
- amine / - amine ion
If all the organic products are the same and there are multiple what do you have to add to the beginning of the name?
Di, tri, tetra
If there are more than one type of organic product how do you list them? Give an example?
In alphabetical order. e.g. methylpropylamine
What are cationic surfactants?
Surfactants that are positively charged.
What are surfactants?
Compounds that are partly soluble and partly insoluble in water
What can be used as a cationic surfactant?
Quarternary ammonium salts with at least one long hydrocarbon chain
What part of the cationic surfactant compound is insoluble in water?
The long hydrocarbon chain
What does the long hydrocarbon chain bind to?
It will bind to substances such as grease/oil
What part of the cationic surfactant compound is soluble in water?
The positively charged head group
What are cationic surfactants useful for and why?
Useful in detergents because of the soluble positive head group and the insoluble long hydrocarbon chain
How does a cationic surfactant act as a detergent?
The non-polar end will bind to grease and the polar head group will be attracted to and dissolve in water - allowing spots of grease to mix with water and be washed away.
What are the uses of cationic surfactants?
fabric conditioners
hair products
detergents
How can cationic surfactants be used in hair/fabric products?
When hair or fabric gets wet they pick up negative charges on their surface. The (+ve)ly charged ammonium ion which is part of the surfactant is attracted to these (-ve) charged surfaces and forms a coating over the surface.
This coating prevents build-up of static electricity so keeps fabric and hair flat+smooth.
Describe the first way to make aliphatic amines?
Halogenoalkanes heated with excess ethanolic NH3 = a mixture of primary secondary tertiary amines + quarternary ammonium salts
Outline the mechanism that results in the formation of aliphatic amines?
Nucleophilic substitution
How are further substitutions possible?
Excess ethanolic ammonia
Give an example of a primary amine:
methylamine
Give an example of a secondary amine:
dimethylamine
Give an example of a tertiary amine:
trimethylamine
Give an example of a quartnerary amine:
tetramethylamine ion
What are non-aromatic amines known as?
Aliphatic amines
Give the name of the molecule where one of the H’s in ammonia is replaced by a benzene molecule:
Phenylamine - it is a primary amine
Are amines electrophiles or nucleophiles?
Nucleophiles
Give two ways that primary aliphatic amines can be prepared?
Reaction of EXCESS ammonia with halogenoalkanes
Reduction of nitriles
How can aromatic amines be prepared?
By the reduction of nitro compounds
What are aromatic amines used in?
The manufacture of dyes
How strong are amines in terms of basic strength?
Amines are weak bases
What is the long hydrocarbon tail in cationic surfactants, in terms of polarity?
It is non-polar
How does a proton bond to an amine? And where do the electrons originate from? And what does it produce?
Via a dative covalent bond, both electrons originate from the lone pair on the nitrogen, it produces an ammonium ion.
What is the strength of the base dependant on? And what makes the base stronger?
The availability of the lone pair of electrons on the nitrogen. The higher the electron density, the more readily available the electrons are.
What is electron density of the nitrogen determined by?
The type of group attached to the nitrogen
How can amines act as a base?
They have a lone pair of electrons which allows them to accept a proton
Draw the mechanism for the reaction between excess ammonia and a halogenoalkane:
Ammonia acts as a nucleophile and attacks the delta positive on the carbon atom (due to the negative charge of the chlorine)
An intermediate is formed - an alkylammonium salt - with a positive nitrogen and negative Cl-
A SECOND(xs) ammonia gives up a lone pair of e- to a hydrogen bonded to the nitrogen, which breaks away from the salt.
A PRIMARY AMINE and an ammonium chloride salt is produced. NH4+Cl-
What is the name of the mechanism of the reaction between excess ammonia and halogenoalkanes?
Nucleophilic substitution
Why does the method to produce an aliphatic amine using a halogenoalkane and xs ammonia have a downside?
The reaction produces primary, secondary, tertiary and quarternary salts, so the product formed is IMPURE.
Why do further reactions take place in the reaction between xs ammonia and halogenoalkanes take place after a primary amine has formed?
Because the primary amine still contains a nitrogen which still has a lone pair on it so it acts as a nucleophile. The amine can react with any remaining halogenoalkanes to produce secondary amines - then reacts further for tertiary and quartnerary.
Instead of using two ammonia molecules you use two amines.
What experimental conditions do you need for reducing nitriles to form aliphatic amines in INDUSTRY?
a nickel/platinum catalyst, high temperature, high pressure and hydrogen gas
What is the reaction called where you produce aliphatic amines by reducing nitriles in industry?
Catalytic hydrogenation
Why is reducing nitriles a good way to make aliphatic amines?
Because it only produces primary amines so the product is PURE
What is the difference between reducing nitriles in industry compared to in the lab - to produce aliphatic amines?
In the lab you can use LiAlH4 (lithium aluminium hydride) which is dissolved in dry ether whereas it is too expensive to use in industry
Give the equation for reducing a nitrile in the lab?
CH3C=N + 4[H] – (LiAlH4) – (dilute acid) –> CH3CH2NH2
Give the equation for reducing a nitrile in industry?
CH3C=N + 2H2 – (Ni/Pt) – (high temp/pressure) –> CH3CH2NH2
What is lithium aluminium hydride? in terms of an agent…
A strong reducing agent
What does the [H] represent in the reduction of amine reaction, when using LiAlH4? And what is this reaction called?
A reducing agent — Reduction
How are aromatic amines made?
By reducing nitro compounds e.g. nitrobenzene
What are aromatic amines used to make?
Dye stuffs and pharmaceuticals
What is step 1 to making an aromatic amine?
Heat (UNDER REFLUX) nitrobenzene with conc HCl and TIN to form a salt such as C6H5NH3+Cl-
What is step 2 to making an aromatic amine?
The salt produced in step 1 is reacted with an alkali such as NaOH to produce an aromatic amine such as phenylamine.
Name the nucleophilic addition-elimination reactions of ammonia and primary amines with acyl chlorides and acid anhydrides:
Acyl chlorides react with ammonia to form primary amiDes
Acyl chlorides react with primary amines to form N-substituted amides
Acid anhydrides react with ammnonia forms a primary amide and a carboxylic acid
Acid anhydrides react with primary amines to form an N-substituted amide and a carboxylic acid
Give the order of base strength when talking about: aliphatic primary amine, aromatic amines, ammonia from weakest to strongest:
WEAKEST aromatic amines, ammonia, aliphatic primary amines STRONGEST BASE
Describe why aromatic amines are really weak bases?
The benzene is an electron withdrawing group sp it pulls electrons away from nitrogen into the ring structure. electron density at nitrogen reduces so lone pair availability is reduced and aromatic amines are less basic.
Describe why aliphatic amines are stronger bases than aromatic bases?
Alkyl groups are electron pushing groups, so they push electrons towards nitrogen so the electron density at nitrogen increases so lone pair availability increases and primary aliphatic amines are more basic.
Give the reaction between propylamine and water and what the observation will be when universal indicator is added:
CH3CH2CH2NH2 + H20 <–> CH3CH2CH2NH3+ + OH-
It would turn blue - as it is a weak base
What effect does the benzene ring have on the basic strength of an amine?
The nitrogen lone pair is delocalised into the ring - reduces electron density so reduces availability of lone pair of nitrogen
Why can’t you form aromatic amines via nucleophilic substitution?
Benzene can only be attacked by nucleophiles not electrophiles
How is benzene converted to nitrobenzene in preparation for the formation of aromatic amines (phenylamine)?
conc sulphuric acid
conc nitric acid
under 55 degrees
electrophilic sub
