Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Organic chem > 3.3 Halogenoalkanes > Flashcards

3.3 Halogenoalkanes Flashcards

1
Q

Why are halogenoalkanes more reactive than alkanes?

A

Presence of a polar bond (carbon - halogen bond)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are 3 uses of halogenoalkanes?

A
  • refrigerants
  • solvents
  • pharmaceuticals
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

KEY DEFINITION: nucleophile

A

An electron pair donor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

KEY DEFINITION: hydrolysis

A

The breaking of a bond using water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are the conditions needed for halogenoalkanes to react with aqueous hydroxides (hydrolysis)?

A
  • warm
  • aqueous
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are the products when halogenoalkanes react with aqueous hydroxides?

A
  • Alcohols
  • halide ion
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What if formed when halogenoalkanes react with CN?

A

Nitriles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are the conditions needed for halogenoalkanes to react with CN?

A
  • warm
  • ethanolic (in ethanol)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How does CN change the halogenoalkane?

A

It increases the length of the carbon chain

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is formed when halogenoalkanes react with excess ammonia?

A

Amines

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are the conditions needed for halogenoalkanes to react with excess ammonia?

A
  • warm in a sealed tube
  • ethanol solvent
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the general equation for the reaction between halogenoalkanes and aqueous hydroxides?

A

R-X + (OH-)&raquo_space; R-OH + (X-)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is the general equation for the reaction between halogenoalkanes and CN?

A

R-X + KCN&raquo_space; R-CN + KX

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the general equation for the reaction between halogenoalkanes and ammonia?

A

R-X + 2NH3&raquo_space; R-NH2 + NH4X

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Give a method to test for the relative rates of hydrolysis of the halogenoalkanes:

A
  • warm 1-chloro, 1-bromo and 1-iodobutane to 60”C with aqueous silver nitrate
  • use ethanol as a mutual solvent
  • time how long it takes for the halide precipitate to form to calculate the rate of reaction
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are 3 ways to ensure a fair test?

A
  • use equal amounts (in mol) of each halogenoalkane
  • use halogenoalkanes with the same chain lengths
  • use a water bath to ensure a constant temperature
17
Q

What is the relative rate of hydrolysis for halogenoalkanes?

A

Iodoalkane > bromoalkane > chloroalkane

18
Q

Why do iodoalkanes have the fastest rate of hydrolysis?

A
  • The C-I bond has the lowest enthalpy (240KJmol)
  • so it is the easiest C-halogen bond to break
19
Q

Why can this reaction not be used for 1-flourobutane?

A
  • the reaction would be slower than with Cl
  • AgF is soluble
20
Q

KEY DEFINITION: elimination

A

A reaction in which an atom or group of atoms is removed from a reactant

21
Q

What is produced in an elimination reaction with a halogenoalkane?

A
  • alkene
  • H2O
  • NaX
22
Q

What are the conditions for an elimination reaction with a halogenoalkane?

A

Hot and ethanolic

23
Q

Compare the conditions for substitution and elimination reactions:

A

SUBSTITUTION: warm, aqueous sodium hydroxide

ELIMINATION: reflux, hot ethanolic hydroxide

24
Q

Compare the major products of substitution and elimination reactions:

A

SUBSTITUTION: alcohol
ELIMINATION: alkene (s)

25
Compare the role of OH- in substitution and elimination reactions:
SUBSTITUTION: nucleophile ELIMINATION: base
26
What are 2 uses of CFC's and what properties make them suitable?
Uses: solvents, refrigerants Properties: non-toxic, low reactivity
27
Why is the ozone layer beneficial for life on earth?
It absorbs harmful UV radiation from the sun that can cause skin cancer
28
What is the equation that shows the formation of ozone?
O2 + O. >> O3
29
What is the problem with CFC's?
* they do not break down easily * the rise up to the upper atmosphere and break down to form chlorine radicals * chlorine radicals catalyse the breakdown of ozone
30
What are the propagation steps for the breakdown of ozone?
1) O3 + Cl. >> O2 + ClO. 2) O3 + ClO. >> 2O2 + Cl.
31
What is the overall equation for the breakdown of ozone?
2O3 >> 3O2
32
What are some alternative organo-halogen compounds?
* HFC's (hydrofluorocarbons) * e.g. CH2F2 or CHF3
33
Why do halogenoalkanes take part in nucleophilic substitution reactions?
The carbon is electron deficient (delta +)
34
What happens in nucleophilic substitution?
* the nucleophile donates a pair of electrons to the C+ atom to form a new bond * the C-X bond breaks by heterolytic fission and a halide ion is formed
35
What happens in the elimination reaction?
* the halogen atom is always removed * the H atom from an adjacent C atom is removed * a double bond forms between the 2 C atoms (forms alkene)

Organic chem (6 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions