The Haloalkanes

HideShow resource information
What happens with alkanes in the presence of UV lights?
react with chlorine to form a micture of products with the halogens substituting hydrogen atoms
1 of 49
What is the overall equation of the synthesis of chloroalkanes?
CH4 + CL2 ---> CH3CL +HCL
2 of 49
What is the mechanism for this reaction called?
Free radical substitution
3 of 49
what are the three steps involved?
Initiation, propagation and Termination
4 of 49
What is a condition for initiation?
UV light
5 of 49
What does the UV light do?
it supplies energy to break the CL-CL bond. It is broken in preference to others as it is the weakest
6 of 49
What is the process called where the bond has broken?
homolytic fission
7 of 49
What does this reaction form?
Free radicals
8 of 49
What do free radicals not have?
a charge
9 of 49
What is the definition of a free radical?
a reactive species which possess an unpaired electron
10 of 49
What is the first stage of propagation?
CH4 + CL- --> HCL + .CH3
11 of 49
What are chlorine free radicals?
very reactive and remove an H from the methane leaving methyl
12 of 49
What happens with the methyl free radicals?
It reacts with a cl2 molecule to produce the main product and another cl free radical
13 of 49
what do all propagation steps have in the reactants and the products?
free radical
14 of 49
What is the second stage of propagation?
.CH3 +CL2 ---> CH3CL +CL-
15 of 49
As the free radical is regenerated what can it do? in what?
It can react with several more alkane molecules in a chain reaction
16 of 49
Why is step termination called termination?
Collisions of two free radicals does not generate further free radicals: so thechains is terminated
17 of 49
What is one reaction in termination?
.CH3 + CL- -----> CH3Cl
18 of 49
What is the second equation?
.CH3 + .CH3 ------> CH3CH3
19 of 49
What is CH3CCL3 used as?
the solvent in dry cleaning
20 of 49
What does the naturally occuring ozone layer in the upper atmosphere do?
It filiters out much of the sun's harmful UV radiation
21 of 49
What is the definition of a nucelophile?
Electron pair donator eg: OH-, NH3 and CN-
22 of 49
What do the curly arrows show?
it shows the movement of two electrons
23 of 49
What does the rate of substitution depend on?
the strength of the C-X bond
24 of 49
What does this mean?
The weaker the bond, the easier it is t break and the faster the reaction
25 of 49
What is hydrolysis defined as?
The splitting of a molecule by a reaction with water
26 of 49
what is water and what can it do?
It is a poor nucleophile but it can react slowly with halo-alkanes in a substitution reaction
27 of 49
What does a precipitation formation mean?
The quicker the precipitate is formed, the faster the substitution rection and the more reactive the haloalkane
28 of 49
What does this substitution reaction depend on?
The strength of the C-X bond
29 of 49
What is formed in a nucleophilic reaction with aqueous hydroxide ions?
Change in functional group haloalkane ----> alchohol
30 of 49
What is the reagant in this reaction?
potassium or sodium hydroxide
31 of 49
What conditions are needed?
In aqueous solution
32 of 49
What is the mechanism?
Nucleophilic substitution
33 of 49
What is the type of reagent?
Nucleophile, OH-
34 of 49
Why are aqueous conditions needed?
If the solvent is changed to ethanol an elimination reaction ccours
35 of 49
What is happening in nucleophilic substitution with CN ions?
Change in functional group: haloalkane to nitrile
36 of 49
What is the reagent in the reaction?
KCN dissolved in ethanol
37 of 49
What are the conditions?
heating under reflux
38 of 49
What is the mechanism?
nucleophilic substitution
39 of 49
What is the type of reagent?
Nucleophile, CN-
40 of 49
What is the change in functional group in nucleophilic substitution with ammonia?
Haloalkane to amine
41 of 49
What is the reagent?
NH3 dissolved in ehtanol
42 of 49
What are the conditions?
heating under pressure
43 of 49
What happens between the haloalkane and the amines formed?
further substitution reactions
44 of 49
What does this lead to?
A lower yield of the amine
45 of 49
How can this be minimised?
Using excess ammonia
46 of 49
What do the chlorine free radicals do in the ozone layer?
they catalse the decomposition because they are regenerated
47 of 49
What is the fist equation in the ozone layer?
Cl. +O3 -----> ClO. +O2
48 of 49
What is the second equation?
CLO. + O3 -----> 2O2 +CL.
49 of 49

Other cards in this set

Card 2

Front

What is the overall equation of the synthesis of chloroalkanes?

Back

CH4 + CL2 ---> CH3CL +HCL

Card 3

Front

What is the mechanism for this reaction called?

Back

Preview of the front of card 3

Card 4

Front

what are the three steps involved?

Back

Preview of the front of card 4

Card 5

Front

What is a condition for initiation?

Back

Preview of the front of card 5
View more cards

Comments

No comments have yet been made

Similar Chemistry resources:

See all Chemistry resources »See all Organic chemistry resources »