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CHEMISTRY > Organic - 3.11 Amines > Flashcards

Organic - 3.11 Amines Flashcards

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1
Q

What is the structure of amines based on?

A

Ammonia, where hydrogen atoms have been replaced by alkyl or aryl groups.

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2
Q

What are the hydrogen atoms replaced with in amines?

A

Alkyl or aryl groups

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3
Q

What are quaternary ammonium compounds produced from?

A

Produced from tertiary amines where the nitrogen’s lone pair of electrons forms a dative covalent bond to the 4th alkyl group.

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4
Q

How many alkyl groups does a quaternary ammonium salt have?

A

Four

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5
Q

What is the shape of NH4+ and why?

A

Tetrahedral, four bonding pairs spread equally

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6
Q

What is the shape of NH3 and why?

A

Pyramidal, lone pair exerts a stronger repulsive force

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7
Q

What is the bond angle in amines?

A

107

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8
Q

What prefix is used if there are two identical R groups attached to a nitrogen?

A

di-

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9
Q

What prefix is used if there are three identical R groups attached to a nitrogen?

A

tri-

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10
Q

How are the groups ordered if there are two different alkyl or aryl groups present?

A

They are ordered alphabetically

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11
Q

When is the amine group denoted using amino-?

A

If other functional groups are present in the molecule

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12
Q

What is the hierarchy used in organic chemistry?

A
  1. Carboxyl (-COOH)
  2. Aldehyde (-CHO)
  3. Ketone (-CO-)
  4. Hydroxyl (-OH)
  5. Amines (-NH2, -RNH, -R2N)
  6. Alkene (-C=C-)
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13
Q

What do halogenoalkanes and ammonia form?

A

Amines

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14
Q

What are the conditions for the preparation of primary amines from halogenoalkanes?

A

Heat in a sealed flask with excess ammonia in ethanol.

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15
Q

What is the type of reaction for the preparation of primary amines from halogenoalkanes?

A

Nucleophilic Substitution

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16
Q

What is the overall reaction for the preparation of primary amines from halogenoalkanes?

A

R-X + 2NH3 -> R-NH2 + NH4X

17
Q

What are the conditions for the preparation of primary amines from nitriles by reduction?

A

Using hydrogen in the presence of a nickel catalyst or by using a reducing agent such as LiAl4 in ether.

18
Q

What are the two steps involved in the preparation of primary amines from nitriles?

A

1) Formation of a nitrile from a halogenoalkane
2) Reduction of the nitrile to form an amine

19
Q

How are aromatic amines prepared?

A

Prepared by the reduction of nitro compounds

20
Q

How is phenylamine prepared?

A

By reduction of nitrobenzene using tin and conc sulfuric acid as a reducing agent

21
Q

What are the conditions for the preparation of phenylamine?

A

Heat under reflux with tin and excess sulfuric acid, followed by adding conc NaOH.

22
Q

Why is concentrated NaOH added in the preparation of phenylamine?

A

To remove the hydrogen ion from the NH3+ group. The addition of concentrated alkali liberates the free amine.

23
Q

What are aromatic amines used for?

A

Used in the manufacture of dyes (azo dyes)

24
Q

What are the two basic properties of amines?

A

Weak bases
Lone pair of electrons on nitrogen atom of ammonia and amines accept a proton.

25
Q

What are two formulas for the reaction of amines with dilute mineral acids?

A

ammonia + acid -> ammonium salt
amine + acid -> alkyl ammonium salt

26
Q

What is the equation for the reaction of an amine with dilute HCl?

A

CH3NH2 + HCl -><- CH3NH3+Cl-
Methylamine + hydrochloric acid -><- phenylammonium chloride
(Reversible reaction)

27
Q

What is the equation for the reaction of an amine with dilute H2SO4?

A

2CH3CH2NH2 + H2SO4 -><- (CH3CH2NH3)2SO4
ethylamine + sulfuric acid -><- ethyl ammonium sulfate
(Reversible reaction)

28
Q

What happens when an amine reacts with water?

A

They accept a hydrogen ion from water to produce an alkylammonium ion and hydroxide ion.

29
Q

How does base strength decrease in amines?

A

Strongest: Primary Aliphatic Amine
Ammonia
Weakest: Primary Aromatic Amine

30
Q

Why are primary aliphatic amines stronger bases than ammonia?

A

Because of the alkyl group attached to the nitrogen. Alkyl group is electron donating causing a lone pair to be more available

31
Q

Why are primary aromatic amines weaker bases than ammonia?

A

Weaker bases because nitrogen’s lone pair of electrons can overlap with the delocalised pi electrons in the benzene ring. Lone pair is less available for accepting a proton.

32
Q

What makes amines nucleophiles?

A

They all contain a lone pair of electrons so they act as nucleophiles.

33
Q

What are the two steps in making a primary amine?

A

An amine and halogenoalkane react and initially a salt is formed.
Then the salt reacts with excess ammonia to form a primary amine.

34
Q

How is a secondary amine formed from a primary amine?

A

Further substitution reactions may occur. This is because the primary amine produced has a lone pair so it can act as a nucleophile and continue to react with any unused halogenoalkane.

35
Q

How is a tertiary amine formed from a secondary amine

A

The secondary amine produced also has a lone pair so it can act as a nucleophile.

36
Q

How is a quarternary ammonium salt formed from a tertiary amine?

A

The tertiary amine reacts with the halogenoalkare to form a quarternary ammonium salt.

37
Q

What are the conditions required for a primary amine to be produced?

A

Excess ammonia

38
Q

What are the conditions needed to produce a quaternary ammonium salt?

A

Excess halogenoalkane

39
Q

What are quarternary ammonium salts used for?

A

Cationic surfactants: found in detergents, fabric softeners and hair conditioners.

CHEMISTRY (34 decks)

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