Halolkanes Flashcards

1
Q

What happens to the boiling points as you go down the group?

A

The boiling point increases with mass

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2
Q

What is the solubility of haloalkanes?

A

They are soluble in organic solvents, but not in water because they are not polar enough and don’t exhibit hydrogen bonding

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3
Q

What is the theory behind their nucleophilic substitution?

A

Halogens have a greater electronegativity than carbon.
A dipole is induced in the C-X bond and it becomes polar.
The carbon is then open to attack from nucleophiles.

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4
Q

What does nucleophilic mean?

A

positive liking

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5
Q

What are 3 examples of nucleophiles?

A

OH-, CN-,NH3 and H2O

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6
Q

Advantages of CFC’s

A

low reactivity, volatility, non-toxicity

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7
Q

Problems with CFC’s

A

They break up in the atmosphere to form free radicals, which catalyse ozone decomposition.

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8
Q

Solutions to CFC’s

A

Using HCFC’s

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9
Q

Do halogenoalkanes have a polar bond?why?

A

Yes polar, as halogen has a higher electronegativity than C ( halogen is δ-, carbon is δ+)

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10
Q

Which intermolecular forces do they have? why?

A

Permanent dipole-dipole and van der Waals forces of attraction C-X bond polarity creates permanent dipoles

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11
Q

When would they have higher boiling points?

A

Increase Carbon chain length

Halogen further down group 7

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12
Q

How would the mass of a haloalkane compare with the mass of an alkane of the same chain length?

A

Greater as mass of halogen > mass of H

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13
Q

What is the most important factor in determining their

reactivity?

A

Carbon-halogen bond enthalpy

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14
Q

What would bond polarity suggest the order of reactivity would be?

A

C-F would be most reactive as most polar bond

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15
Q

What would bond enthalpies suggest the order of reactivity would be?

A

C-I would be most reactive as lowest bond

enthalpy

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16
Q

What are the conditions/reactants needed for the elimination reaction of
haloalkanes?

A

NaOH or KOH dissolved in ethanol (no water
present)
Heated

17
Q

What is formed in the
elimination reaction of
haloalkanes?

A

An alkene, water and halogen ion

18
Q

How do you test for

haloalkanes? What is the result?

A
Add NaOH (aq) and warm, acidify with HNO3, add AgNO3
(aq)
Result: precipitate of AgX (for Cl=white, for
Br=cream, for I=yellow)
19
Q

How are haloalkanes formed from alkanes?

A

Free radical substitution

20
Q

What is the 1st stage of free radical substitution?

A

Initiation - breaking halogen bond to form free radicals

21
Q

What is the 2nd stage of free radical substitution?

A

chain part of the reaction where products are formed but free radical remains

22
Q

What is the 3rd stage of free radical substitution?

A

free radicals removed, stable products formed

23
Q

What are the conditions needed for the formation of a free radical chlorine atom?

A

Presence of UV light

24
Q

What is the ozone layer’s function?

A

protects the earth from harmful exposure to too many UV rays

25
How do CFCs break the ozone layer down?
Free radical substitution
26
Write an equation for the overall decomposition of | ozone into oxygen (O2)
2O3→ 3O2