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CHEMISTRY A LEVEL > 3.3 Halogenoalkanes > Flashcards

3.3 Halogenoalkanes Flashcards

1
Q

Draw the displayed formula for 1-bromopropane

A

(see page 1 in the chemrevise revision guide)

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2
Q

Draw the displayed formula for 2-chloro-2-methylbutane

A

(see page 1 in the chemrevise revision guide)

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3
Q

Describe a primary halogenoalkane, draw an example.

A

One carbon is attached to the carbon adjoining the halogen.

see page 1 in the chemrevise revision guide

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4
Q

Describe a secondary halogenoalkane, draw an example.

A

Two carbons are attached to the carbon atom adjoining the halogen.

(see page 1 in the chemrevise revision guide)

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5
Q

Describe a tertiary halogenoalkane, draw an example.

A

Three carbons are attached to the carbon atom adjoining the halogen.

(see page 1 in the chemrevise revision guide)

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6
Q

What two reactions do halogenoalkanes undergo?

A

Halogenoalkanes undergo either
- substitution
- elimination
reactions.

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7
Q

Describe a substitution reaction in halogenoalkanes with words.

A

Swapping a halogen atom for another atom or group of atoms.

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8
Q

What is a nucleophile?

A 
Electron pair donator 
e.g.
\:OH- 
\:NH3
CN-

:Nu represents any nucleophile

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9
Q

Which is fastest to substitute, iodoalkanes or fluoroalkanes? Explain why.

A

The rate of substitution reactions depends on the strength of the C-X bond.
The weaker the bond, the easier it is to break and the faster the reaction.

The iodoalkanes are the fastest to substitute and the fluoroalkanes are the slowest. The strength of the C-F bond is such that fluoroalkanes are very unreactive.

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10
Q

What is the bond enthalpy in decreasing order of the halogenoalkanes in substitution reactions?

A

(see page 1 in the chemrevise revision guide)

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11
Q

Draw the general mechanism for a nucleophilic substitution reaction.

A

(see page 1 in the chemrevise revision guide)

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12
Q

Give the definition of hydrolysis.

A

Hydrolysis is defined as the splitting of a molecule by a reaction with water.

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13
Q

Water is a _____ nucleophile but it can react _____ with halogenoalkanes in a ________ reaction.

A

Water is a poor nucleophile but it can react slowly with halogenoalkanes in a substitution reaction.

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14
Q

How can the reactivity of the different halogenoalkanes in substitution reactions be recorded experimentally?

A

Aqueous silver nitrate is added to a halogenoalkane. The halide leaving group combines with a silver ion to form a silver halide precipitate.
The precipitate only forms when the halide ion has left the halogenoalkane and so the rate of formation of the precipitate can be used to compare the reactivity of the different halogenoalkanes.
The quicker the precipitate is formed, the faster the substitution reaction and the more reactive the halogenoalkane.

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15
Q

Which precipitate forms faster (and what colour is each) in the hydrolysis reactions of halogenoalkanes:
AgI
AgBr
AgCl

A

(see page 2 in the chemrevise revision guide)

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16
Q

When halogenoalkanes undergo a nucleophilic substitution with aqueous hydroxide ions what is the change in the functional group (like what product does it form)

A

halogenoalkane -> alcohol=

17
Q

When a halogeneoalkane reacts with aqueous hydroxide ions, what are the:

  • conditions
  • the reagent
  • the mechanism
  • the type of reagent
A

(see page 2 in the chemrevise revision guide)

18
Q

Draw the overall equation for when 1-bromopropane reacts with KOH.

Draw the mechanism for this reaction, giving the name of the mechanism.

A

(see page 2 in the chemrevise revision guide)

19
Q

Draw the overall equation for when 2-bromo-2-methylpropane reacts with KOH.

Draw the mechanism for this reaction, giving the name of the mechanism.

A

(see page 2 in the chemrevise revision guide)

20
Q

When halogenoalkanes undergo a nucleophilic substitution with cyanide ions what is the change in the functional group (like what product does it form)

A

halogenoalkanes -> nitrile

21
Q

When a halogeneoalkane reacts with cyanide ions, what are the:

  • conditions
  • the reagent
  • the mechanism
  • the type of reagent
A

(see page 3 in the chemrevise revision guide)

22
Q

Draw the overall equation for when 1-bromopropane reacts with KCN.

Draw the mechanism for this reaction, giving the name of the mechanism.

A

(see page 3 in the chemrevise revision guide)

23
Q

Write the structural formula for propanenitrile.

A

(see page 3 in the chemrevise revision guide)

24
Q

Draw the displayed formula for 3-methylbutanenitrile.

A

(see page 3 in the chemrevise revision guide)

25
Q

When halogenoalkanes undergo a nucleophilic substitution with ammonia what is the change in the functional group (like what product does it form)

A

halogenoalkane -> amine

26
Q

When a halogenoalkane reacts with ammonia, what are the:

  • conditions
  • the reagent
  • the mechanism
  • the type of reagent
A

(see page 3 in the chemrevise revision guide)

27
Q

Draw the overall equation for when 1-bromopropane reacts with NH3.

Draw the mechanism for this reaction, giving the name of the mechanism.

A

(see page 3 in the chemrevise revision guide)

28
Q

Why is there usually a lower yield when reacting a halogenoalkane with ammonia? What can we do to minimise this?

A

(see page 3 in the chemrevise revision guide)

Further substitution reactions can occur between the halogenoalkane and the amines formed leading to a lower yield of the amine. Using excess ammonia helps minimise this.

29
Q

When halogenoalkanes undergo an elimination reaction with alcoholic hydroxide ions what is the change in the functional group (like what product does it form)

A

(see page 4 in the chemrevise revision guide)

30
Q

When a halogenoalkane reacts with ammonia, what are the:

  • conditions
  • the reagent
  • the mechanism
  • the type of reagent
A

(see page 4 in the chemrevise revision guide)

31
Q

Draw the overall equation for when 1-bromopropane reacts with KOH.

Draw the mechanism for this reaction, giving the name of the mechanism.

A

(see page 4 in the chemrevise revision guide)

32
Q 
Which performs which type of reaction:
- Aqueous
- Alcoholic
performing
- Elimination
- Substiution
A

Aqueous : substitution

Alcoholic : elimination

33
Q

read bottom of page 4 in the chemrevise revision guide.

A

understand?

34
Q

Describe an elimination reaction in words.

A

The removal of small molecule (often water) from the organic molecule.

35
Q

What are the uses of choroalkanes and chlorofluoroalkanes? Why have they now stopped being used?

A

Chloroalkanes and chlorofluoroalkanes can be used as solvents.
CH3CCl3 was used as the solvent in dry cleaning.
Many of these uses have now been stopped due to the toxicity of halogenoalkanes and also their detrimental effect on the atmosphere.

36
Q

What are some uses of halogenoalkanes?

A

Halogenoalkanes have also been used as refrigerants, pesticides and aerosol propellants.

37
Q

Give an entire explanation of ozone depletion. Including equations.

A

(see page 5 in the chemrevise revision guide)

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