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A Level Chemistry - Organic Chemistry > 3.3.3 Halogenoalkanes > Flashcards

3.3.3 Halogenoalkanes Flashcards

1
Q

What is a nucleophile

A

It is a chemical species that donates an electron pair to form a chemical bond

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2
Q

Which nucleophiles do you need to know the substitution reactions with

A

OH-
CN-
NH3

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3
Q

is a carbon halogen bond polar or non-polar

A

polar

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4
Q

why are carbon halogen bonds polar
and charges

A

halogens are more electronegative than carbon, and electrons are closer to halogens
the halogen is negative, and the carbon is positive

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5
Q

What colour precipitate does chlorine form

A

White

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6
Q

What colour precipitate does bromine form

A

Cream

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7
Q

What colour precipitate does iodine form

A

Yellow

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8
Q

What is the most common halogenalkanes

A

Chlorofluorocarbons

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9
Q

Uses of CFCs

A

Refrigerators
Solvents for dry cleaning

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10
Q

Why do CFCs have many uses

A

Due to their chemical inertness they are non-flammable & non-toxic

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11
Q

How do CFCs cause the destruction of the ozone layer (3 steps)

A

CFCs absorb lots of UV radiation in upper atmosphere
CFC are broken down by UV light causing formation of chlorine radicals
The radicals react with ozone and break the layer down

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12
Q

Do paper flash cards for mechanisms

A

Do it

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13
Q

What is used in elimination reaction
Heated under ….. with…..

A

Reflux
Sodium/potassium hydroxide dissolved in ethanol

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14
Q

In elimination the hydroxide is acting as a. + why

A

Base
It is excepting a proton

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15
Q

Equation to show how chlorine catalyses decomposition of the atmosphere

A

CCl3F + he —> *CCl2F + *Cl

Cl* + O3 —-> ClO* + O2
ClO* + O3 ——> 2O2 + Cl*

*cl + *Cl —Cl2

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16
Q

Why do halogenalkanes have a high boiling point ( than alkanes)

A

They have Van deer Waals forces but because polarity of carbon halogen bond there are also permanent dipole dipole forces

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17
Q

As we go down group 7 the boiling point of halogenalkanes ….. and why

A

Increases
Number of electrons increases this means greater Van deer Waals forces

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18
Q

Halogenalkanes are soluble/insoluble + why

A

Insoluble can’t form hydrogen bonds

They are soluble in non polar

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19
Q

Elimination hydroxide ion conditions why

A

Solution of hydroxide ions

Ethanol to solubilise the haloalkane so it can react with aqueous hydroxide ions

Heat under reflux increase rate of reaction

(Halogenalkanes insoluble in water so would not react with the dissolved hydroxide ions)

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20
Q

What type of reaction is nucleophilic substitution with hydroxide ion

A

Hydrolysis

21
Q

What happens during the rate of hydrolysis practical

A

The water reacts with the halogenalkanes by nucleophilic substitution and the halide ion is released
Halide ion reacts with silver ion to form precipitate

22
Q

Order of reactions for hydrolysis of hydrogenalkanes practical + why

A

Iodine then bromine then chlorine

The bond enthalpy increases lots of energy needed longer time

23
Q

Why when doing nucleophilic substitution do we use an excess of ammonia

A

The product amine still has a lone pair of electrons on the nitrogen
so it can act as a nucleophile and react with haloalkane
Excess ammonia more likely to react with haloalkane

24
Q

What reactions should happen in the ozone layer without CFCs

A

O2 —> *O + *O (UV light needed)
O2 + *O —> O3

25
Q

Define free radical

A

Any species with an unpaired electron

26
Q

Give two equations to show how chlorine radicals catalyse the decomposition of the ozone

A

Cl* + O3 —> ClO* + O2
ClO* + O3 —> Cl* + 2O2

27
Q

What determine reactivity of halgeonalkanes

A

Bond enthalpy

28
Q

Halogenalkanes get more reactive going …

A

Down the group

29
Q

Why is water used rather than hydroxide ion

A

Hydroxide ions would react with silver to form insoluble silver hydroxide

30
Q

What are the 3 steps for makinga cyclohexene

A

Distillation
Seperation
Purification

31
Q

Why are anti-bumping granules used

A

To prevent bubbling

32
Q

What do we use to heat a round bottom flask in the distillation step

A

Heating mantle

33
Q

Why do we use a heating mantle and not a bunsen burner

A

Cyclohexanol is flammable

34
Q

How to purify when making cyclohexene

A

Add anhydrous CaCl2. This dehydrating agent will remove any aqueous substance. Invert and leave

35
Q

How are alcohol produced

A

Hydration alkenes

36
Q

Conditions for hydration of alkenes

A

Use steam and acid catalysts
Temperature 300 and 60 atm

37
Q

Is fermentation endo or exothermic

A

Exothermic

38
Q

Advantages of biofeuls

A

Renewable
Carbon neutral

39
Q

Disadvantages biofeuls

A

Expensive
Takes up land that could be used for farming

40
Q

What is used for oxidation of alchols +more info

A

Acidified potassium dichromate
Turns from orange to green

41
Q

What are primary acids oxidised to

A

Aldehydes then carboxylic acids

42
Q

What a secondary oxidised to

A

Ketones

43
Q

What are teritary alcohols oxidised to

A

Nothing

44
Q

How do we oxidise alcohols

A

Distillation then reflux

45
Q

In the industrial process of making an alcohol from an Alkene is a catalysts used

A

Yes
Acid catalyst E.g. phosphoric acid

46
Q

Role of ammonia in nucleophilic substitution

A

Nucleophile
Then a base

47
Q

Hydroxide ion acts as x2 in which

A

Elimination = base
Substitution = nucleophilic

48
Q

In chlorofluorocarbons which bind is easier to break and why

A

C-cl lower bond enthalpy

49
Q

Overall equation destruction of ozone

A

2O3 —> 3O2

A Level Chemistry - Organic Chemistry (6 decks)

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