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
Q

How do CFCs break the ozone layer down?

A

Free radical substitution

26
Q

Write an equation for the overall decomposition of

ozone into oxygen (O2)

A

2O3→ 3O2