Amines Flashcards

1
Q

What are the different mechanisms that amines can undergo

A
  • nucleophilic substitution with halogen alkanes
  • reduction of nitriles
  • nucleophilic addition-elimination with acyl chlorides
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2
Q

What are the conditions for making nitriles?

A

KCN warm ethanolic aqueous, reflux

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3
Q

What does the base strength of an Amine depend on

A
  • depend on how readily it will accept a proton H+
  • how many akyls groups it has : these release electrons away from itself towards the nitrogen atom (inductive effect), increasing the electron density of the nitrogen atom = better electron pair donor so more attractive to protons
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4
Q

Why are aromatic amines weak bases?

A

because the benzene ring draws electrons towards itself and the nitrogen lone pair gets partially delocalised onto the ring, so the electron density on the nitrogen decreases,making the lone pair much availavle

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5
Q

Why are tertiary amines less strong bases than secondary amines

A

because they are less soluble in water due to nitrogen crowding

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6
Q

What are cationic surfactants?

A

Quaternary salts

have an ionic hydrophilic “head” and a long alkyl hydrophobic “tail” that dissolves greases

surfactants reduce the surface tension of liquids

positive nitrogen is attracted toward negatively charged surfaces such as glass and plastics

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7
Q

What are the uses of quaternary salts

A

fabric softener and surfactants

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8
Q

How do soaps destroy dirt?

A

they form micelles which surround the dirt/grease molecules, with the hydrophobic tails in the centre dissolving the grease and the hydphillic heads roundthe outside dissolving in the water

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9
Q

Why are nitriles reduced and what are the conditions of this?

A

to form amines

hydrogen gas and nickel catalyst (palladium and platinum also works) or LiAH4 in ethoxyethane

raised temperature and pressure

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10
Q

What are the conditions for mononitration (only one NO2 group added during electrophilic substitution)

A

keep temperature below 55 degrees

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11
Q

Why are nitro compounds useful?

A

can be used as explosives (e.g. TNT)

and used in the manufacture of dyes

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12
Q

How are primary aromatic amines prepared? Draw the equations

A

1) Electrophilic substitution : warm benzene with concentrated nitric and sulfuric acids to get nitro benzene
HNO3 + H2SO4 → H2NO3+ + HSO4-

H2NO3+ → NO2+ H2O

2) reduction of nitro compounds using tin and concentrated hydrochloric acid to form an ammonium salt. NaOH added to give the amine.

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13
Q

What are the two different methods for making aliphatic amines, which is the preferred method and why? Also mention the pros and cons

A

reducing nitriles - preferred but it is a two step reaction so there’s a low yield and KCN is toxic

reaction of ammonia with halogenalkanes

the halogenalkane reaction is not preferred because some of the primary amines can undergo further reactions to form secondary, tertiary amines and quaternary ammonium salts. can be minimised by excess ammonia

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14
Q

Write and draw the equation for making ethylamine by reacting ammonia and bromoethane

(making aliphatic amines with halogen alkanes)

A

:)

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15
Q

Write and draw the equations for making aliphatic amines by reducing nitriles? (mention why the different reactants are used)

A
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16
Q

Draw the mechanism for nucleophilic substitution when ethylamine reacts with a large excess of chloromethane (example of excess halogenalakanes)

A
17
Q

Draw the mechanism when a large excess of propylamine reacts with chloromethane (example of excess amine). Name the product.

A
18
Q

Draw the mechanism for the basic action of amine with water

A
19
Q

What happens when amines react with acids. How are they regenerated back to amines. What happens when you react methylamine with HCL

A

all amines will react with acids to become ammonium salts. Addition of NaOH to an ammonium salt will convert it back

20
Q

Explain why methylamine is a stronger base than ammonia

A

lone pair on N accepts H+, Ch3 increases electron density on N by donating electros

has a positive inductive effect which makes the lone pair more available to accept proton

21
Q

What are amides?

A

carboxylic acid derivatives

contain the functional group -CONH2

22
Q

How do you make basic buffers from amines

A

amine + its salt or HCL

salt = amine chloride