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Chemistry AS 2015-16 > 3.3 Haloalkanes > Flashcards

3.3 Haloalkanes Flashcards

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1
Q

Are haloalkanes or alkanes more reactive?

A

Haloalkanes are more reactive than alkanes.

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2
Q

What uses of haloalkanes are there?

A

Many uses e.g refrigerators, solvents and in pharmaceuticals.

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3
Q

Can all haloalkanes be used without limitations?

A

The use of haloalkanes has, had to be restricted.

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4
Q

Name one restricted group of haloalkanes and why it is restricted.

A

One restricted group are CFCs due to their affect on the atmosphere.

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5
Q

What type of bonds do haloalkanes contain?

A

Haloalkanes contain polar bonds.

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6
Q

What are the nucleophiles for substitution reactions?

A

The nucleophiles for the substitution reactions are OH–, CN– and NH3.

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7
Q

In elimination what do reagents act as?

A

A base

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8
Q

In nucleophilic substitution what do reagents act as?

A

A nucleophile

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9
Q

How does bond enthalpy affect the nucleophilic substitution reaction?

A

The higher the bond enthalpy of the bond between the carbon-halogen, the slower the nucleophilic substitution reaction.

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10
Q

What must haloalkanes contain?

A

Haloalkanes must contain at least one halogen which replaces a hydrogen atom.

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11
Q

Name 4 Mechanisms

A

Free radical substitution, electrophilic addition, nucleophilic substitution and elimination

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12
Q

What causes C-Cl bonds in CFCs to break (releasing Cl atoms) when in the atmosphere?

A

UV light

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13
Q

What effect do Cl atoms have on the atmosphere?

A

They catalyse the decomposition of ozone, contributing to holes in the ozone layer

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14
Q

Describe the conditions for elimination with OH-

A

Concentrated NaOH, high temperature, pure ethanol for the solvent and the use of a tertiary haloalkane

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15
Q

Describe the conditions for substitution with OH-

A

Use a primary haloalkane, dilute NaOH, low temperature (warm)

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16
Q

What is the name of the product formed in a substitution reaction with cyanide ions?

A

Nitrile

17
Q

What is different about the carbon chain of the product when compared to the initial carbon chain in a substitution reaction with CN- ions?

A

The product has one more carbon in the chain

18
Q

What are the stages of a mechanism?

A

Initiation, propagation and termination

19
Q

What is formed in an elimination reaction with OH- ions?

A

An alkene

20
Q

What is formed in a substitution reaction with OH- ions?

A

An alcohol

21
Q

What happens in an elimination reaction?

A

one hydrogen atom and one halogen atom are removed from neighbouring carbon atoms in the molecules and a double bond forms between the two carbons

22
Q

What conditions are required for substitution reactions?

A

Base: low concentration of OH- ions Solvent: water + ethanol Temperature: low

23
Q

What conditions are required for elimination reactions?

A

Base: high concentration of OH- ions Solvent: ethanol Temperature: high

24
Q

Which type of reaction (substitution or elimination) favours primary/ secondary/ tertiary haloalkanes?

A

-Primary favours substitution -Secondary favours neither -Tertiary favours elimination

25
Q

What are nucleophiles?

A

Atom with a lone pair of electrons that carries a negative charge, these are attracted by the slightly positively charged carbon atoms

26
Q

What essential condition is required to produce free radicals?

A

UV light

27
Q

What is the overall equation to display the braking down of our ozone?

A

2O3 —-> 3O2

28
Q

What role is the OH- ion in an elimination reaction?

A

A base

29
Q

What role is the OH- ion in substitution reaction?

A

A nucleophile

30
Q

What happens during a substitution reactions?

A

a halogen atom is exchanged for another atom or group of atoms in the halogenalkane

Chemistry AS 2015-16 (18 decks)

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