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AS levels Resurrection > C Unit 2.6 Halogenoalkanes Revamp > Flashcards

C Unit 2.6 Halogenoalkanes Revamp Flashcards

1
Q

Define halogenoalkane
(3-way)

A
  • Homologous series (Similar to Alkanes/Alkenes)
  • Which 1/more of H atoms replaced
  • by a halogen
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2
Q

How do we turn a halogenoalkane from saturated to unsaturated compounds?
(+ what it gives us)

A

Undergoing an elimination reaction
+ separating the halogen

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3
Q

How are halogenoalkanes able to undergo an elimination reaction?
(2-way)

A
  • Hydrogen halides are acidic
  • Therefore can be removed using an alkali
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4
Q

What is used to have the halogenoalkane to undergo an elimination reaction?

A

NaOH dissolved in Ethanol

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5
Q

Draw 1-bromopropane converted into propene and HBr

A

Stage is yours y’all

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6
Q

How can halogenoalkanes form more than 1 product when undergoing an elimination reaction?

A

For only unsymmetrical halogenoalkanes

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7
Q

Draw 2-bromobutane and the conversion of 2 products?

A

Stage is yours D:

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8
Q

Define nucleophile
(3-way)

A
  • Atom/group of atoms
  • That has an electron pair
  • That can be donated to an e- deficient centre
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9
Q

The significance of halogenoalkanes having a permanent dipole?
(3-way)

A
  • e- deficient carbons can undergo
  • nucleophilic attack leading to
  • nucleophilic substitution
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10
Q

For any mechanism, what are 4 things that are needed?

A
  1. Lone pairs
  2. Dipoles
  3. Charges
  4. Curly arrows
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11
Q

Draw the mechanism for the nucleophilic substitution of 1-chloropropane by sodium hydroxide

A

All yours.
Also, spectator ion is totally optional but aye, isn’t it nicer to clarify things?

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12
Q

What is the rate of nucleophilic substitution factored on?
(2 things)

A
  • Strength of the carbon-halogen (C-X) bond (bond enthalpy)
  • How strongly they attract electrons? (bond polarity)
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13
Q

Relationship between reactivity, strength of bond, and rate?
(3-way)

A
  • More reactive the halogen,
  • Stronger the bond will be,
  • The longer the reaction will take
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14
Q

Hence, what are the bond strengths of carbon-halogen bonds for the 4 halogens?
(2 points)

A
  • Fluorine strongest (More electronegative)
  • Downwards, iodine the weakest (Least electronegative)
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15
Q

How come the carbon-fluorine bond may get ignored?
(3 points)

A
  • Very strong
  • Greatest polarity
  • May be very unreactive
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16
Q

Hence show rates of reaction from slowest to fastest of halogenoalkanes?

A

RCl > RBr > RI

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17
Q

The purpose of hydrolysing halogenoalkanes?
(Adding water)
(2 things… kinda check up but still serves the purpose)

A
  • Produce alcohols ig? (+ hydroxonium ion)
  • And to test if it’s rlly a halogenoalkane???
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18
Q

Why is nucleophilic substitution slow for hydrolysis of halogenoalkanes?
(2 things)

A
  • Water not very good nucleophile
  • Lacks full negative charge (in comparison to -OH)
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19
Q

Hence, how to speed up nucleophilic substitution for hydrolysis of halogenoalkanes?

A

Use Sodium Hydroxide (NaOH)

20
Q

Then, draw mechanism for the nucleophilic substitution of 1-chloropropane with water

A

Allll yours pal

21
Q

Therefore, the real way to test for halogenoalkanes?
+ brief explanation

A
  • Using silver nitrate (AgNO3)
  • Observing peculiar ppts
22
Q

What would happen if we used just NaOH insteada water against halogenoalkanes?
Hence a counter?

A
  • Interference of results (totally different outcome)
  • Neutralise alkali by addition of nitric acid (NO3)
23
Q

Chloride w/ Ag+ observation?

24
Q

Chloride w/ Ag+ addition of NH3 observation?

A

Ppt dissolves

25
Bromide w/ Ag+ observation?
Cream ppt
26
Bromide w/ Ag+ **addition of NH3** observation? (2-way)
- If NH3 is concentrated - Ppt dissolves (.... otherwise....)
27
Iodide w/ Ag+ observation?
Yellow ppt
28
Iodide w/ Ag+ **addition of NH3** observation?
No change
29
What are CFCs (chlorofluorocarbons)? (2-way)
- Halogenoalkane molecules where - all H atoms replaced with F/C atoms
30
Describe CFCs? (3 points)
- Non-flammable - Not very toxic - Large number of uses
31
Say some uses of CFCs? (At least know one, like ig it's deep)
- Refrigerants - Propellants for aerosols - Generating foamed plastics (e.g. expanded polystyrene/polyurethane foam) - Solvents for dry cleaning/general degreasing purposes - Anaesthetics
32
The big 3 tragedies of CFCs?
- Largely responsible for destroying ozone layer - Contributed to global warming (Not stronger than CO2) - Indirect cause of skin cancer (Ozone holes)
33
What caused CFCs to destroying ozone layer? (5-way)
- At high atmosphere - Carbon-chlorine bonds break giving - Chlorine free radicals - Which destroy ozone layer - 1 ˙Cl destroying 1000s of ozone molecules
34
What are ozone holes? (3-way)
- Marked decreases in concentration of - ozone in the ozone layer above - north and south poles
35
Tragedy of decrease of ozone concentration? (2-way)
- Medium to high energy UV radiation - reached surface of earth
36
What can medium to high energy UV radiation cause? (Likewise to previous y'alls in terms of acknowledging)
- Sunburn - Skin cancers - Eye cataracts - Decreased immune response - Plant damage - Polymer decomposition
37
What was the only truest way to stop ozone destruction by CFCs?
... Prevent release of substance
38
How come C-Cl bond was the main radical attacker than other bonds (C-F/C-H) (2-way)
- More difficult to break C-H/C-F - Hence C-Cl pronounced the **HIGHEST DPS** (main radical)
39
Define reflux? (2-way)
- Heating a reaction mixture to boiling - Process of evaporation and condensation
40
How would we prepare alcohols from halogenoalkanes? (3-way)
- Nucleophilic substitution - w/ Aq sodium hydroxide - when heated to **reflux**
41
Quick alternate method insteada reflux?
Distillation
42
Explain how the reflux works (6 step by steps w/ 1 obviously being 2-way)
- Rxn mixture heated - Liquids evaporate - Vapour rises up through condenser - Condenser has cold-water jacket - which'll cool vapour to a liquid - Dripping back into rxn mixture
43
Ig then a simple summarisation of reflux then? (3-way)
- A continuous process of evaporation and - condensation taking place - without loss of product
44
The least we can do, list the apparatus and chemicals for reflux of halogenoalkanes? (Maybe know one? Or acknowledge, I'm unsure.. hence major check-up)
Apparatus: - Round-bottom flask - Reflux condenser - Heat source (water bath or heating mantle) - Anti-bumping granules (to prevent violent boiling) - Clamps and stand Chemicals: - Halogenoalkane (e.g., 1-bromobutane) - Aqueous sodium hydroxide (NaOH) - Ethanol (as a co-solvent, because NaOH is not very soluble in halogenoalkanes)
45
Almost there
Thank the past self future self

AS levels Resurrection (30 decks)

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