C Unit 2.6 Halogenoalkanes

Question 1

What is a halogenoalkane?

Answer 1

• A homologous series
• In which one/or more of the hydrogen atoms
• Have been replaced by a halogen

Question 2

Explain a halogenoalkane undergoing an elimination reaction

Answer 2

Hydrogen halides are acidic ∴ can be removed using an alkali
Dissolving NaOH in ethanol will avoid a substitution reaction
(halogen replaced with an OH group - apparently that’s 2.5)

Question 3

How do i show u 1-bromoprone converted into propene and hydrogen bromide

Answer 3

Meh, i’ll state the chemical formula ig?

C₃H₇Br + NaOH (in ethanol) -> C₃H₆ + HBr

From saturated to unsaturated
(do i needa know this?)

Question 4

Show unsymmetrical halogenoalkanes forming into more than one product when undergoing an elimination reaction

Answer 4

Chemical formula state D:

Bro idk, if this is helpful lowkey, I’ll think about writing it ig (will forget)

Question 5

What is a nucleophile?

Answer 5

Has an electron pair that can be donated to an electron deficient centre

Question 6

How do C-X (carbon halogen bonds) able to undergo necleophilic attack?

Answer 6

• They’re polar and have a permanent dipole
• Electron-deficient carbons can undergo
• Nucleophilic attack leading to substitution

Question 7

What should be included within nucleophilic substitution diagram?

Answer 7

• Lone pairs
• Dipoles
• Charges
• Curly arrows

Question 8

How to draw nucleophilic substitution???

Answer 8

This is so bad….

1. C₂H₅X (X = random halogen)
2. Curly arrow from OH ion pointing towards the C connected to X
   - Show O as lone pair within OH and the negative charge
   - Show C has delta positive and X has delta negative
3. Show curly arrow from bond between C-X and X
4. Results:
   C₂H₅OH + X^-
   - Show X as lone pair with negative charge

Question 9

Can u draw nucleophilic substitution for other halogenalkenes?

Answer 9

Heck yea

Question 10

Describe the rate of nucleophilic substitution towards carbon-halogens

Answer 10

• Rate increases down the group
• The more reactive the halogen
• The stronger the bond
• The longer the reaction will take

Question 11

Show me rates of reaction between 3 halogenoalkanes in terms of nucleophilic substitution

Answer 11

Slowest
RCl
RBr
RI
Fastest

Question 12

How to test for halogenalkanes?

Answer 12

• Add water (hydrolysis)
• Add silver nitrate (AgNO₃)

Question 13

Draw mechanism for nucleophilic substitution of 1-chloroproane with water

Answer 13

Ehhhh, wait

Question 14

How is the nucleophilic substitution with water very slow?

Answer 14

• Water not good nucleophile
• Lacks full negative charge [of, say, a hydroxide ion]

Question 15

How would u speed up nucleophilic substitution with water?

Answer 15

Add sodium hydroxide (NaOH)

Question 16

If u use sodium hydroxide for nucleophilic substitution, what should u also add and why?

Answer 16

Nitric acid, sodium hydroxide would interfere with the results of the test

Question 17

Chlorine with Ag₊?

Answer 17

White ppt

Question 18

Bromide with Ag₊

Answer 18

Cream ppt

Question 19

Iodide with Ag₊

Answer 19

Yellow ppt

Question 20

Chlorine’s “ppt” with NH₃

Answer 20

Ppt dissolves

Question 21

Bromide’s “ppt” with NH₃

Answer 21

Ppt dissolves **if concentrated NH₃

Question 22

Iodide’s “ppt” with NH₃

Answer 22

No change

Question 23

What are CFCs (chlorofluorocarbons)?

Answer 23

Halogenoalkane molecules where all of the hydrogen atoms have been replaced with fluorine and chlorine atoms

Question 24

What were CFC’s used for?

Answer 24

1. Refrigerants
2. Propellants - aerosols
3. Generating foamed plastics - expanded polystyrene/polyurethane foam
4. Solves - dry cleaning
5. General degreasing purposes
6. Anaesthetics

Question 25

How were CFCs dangerous?

Answer 25

Responsible for destroying ozone layer
- At high atmosphere, carbon-chlorine bonds break
- Gives chlorine free radicals
- They destroy ozone
- In addition, causes global warming
- Can cause skin cancer (should know why ¬.¬)

Question 26

What are ozone holes?

Answer 26

Area of decreases concentration of ozone in ozone layer (particularly at the poles)
In addition, cuz cycle of ozone formation and decomposition absorbs medium and high energy UV radiation, decrease in ozone concentration causes more of this radiation to reach the surface of the earth

Question 27

What can medium to high energy UV radiation cause?

Answer 27

• Sunburn
• Skin cancers
• Eye cataracts
• Decreased immune response
• Plant damage
• Polymer decomposition

Question 28

What was the way of stopping ozone destruction by CFCs?

Answer 28

Prevent the releasing of the substances

Question 29

Which is the main radical damaging the ozone in the atmosphere and why?

Answer 29

Chlorine Cl^. radical from chlorine-carbon bond
It’s the weakest in a CFC
Easily broken by UV radiation

Question 30

What’s the experiment to carry out nucleophilic substitution?

Answer 30

Reflux experiment

Question 31

What is reflux?

Answer 31

Heating a reaction mixture to boiling. A process of evaporation and condensation

Question 32

Describe reflux experiment

Answer 32

• Reaction mixture heated
• Liquids evaporate
• Vapour rises up through condenser
• Condenser has a cold-water jacket
• That’ll cool the vapour back to a liquid
• This’ll drip back into the reaction mixture
• A continuous process of evaporation and condensation will take place without loss of product

Question 33

Course, there’s more for this yano of this “reflux experiment” so u be careful now

Answer 33

….

Question 34

Everything

Answer 34

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