6.3 - Halogenoalkanes And Alcohols

Question 1

Which elements are we looking at?

Answer 1

Halogens , Group 7 elements… F, Cl, Br, I, At

Question 2

What are dihalogenoalkanes?

Answer 2

compounds where atleast one hydrogen in the alkane chain has been replaced by a halgen

Question 3

Primary, secondary and tertiary?

Answer 3

You work out the stability of the compound; primary is week as it only has one methyl group, tertiary is strong as it has 3 methyl groups.

Question 4

Fact about the carbon-halogen bond?

Answer 4

it’s polar as the halogen is always more electronegative

Question 5

What is a nucleophile?

Answer 5

Electron donating, electron rich

Question 6

What is an electrophile?

Answer 6

Electron pair acceptor, electron defficient

Question 7

What does the nucleophile do?

Answer 7

Replaces the halogen atom in the halogenoalkane, forming a compound with a different functional group

Question 8

What happens during the hydrolysis of halogenoalkanes?

Answer 8

The halogen atom is replaced by the hydroxide ion

Question 9

What is nucleophillic attack?

Answer 9

Hydroxide ion attacks the electron defficient carbon with its lone pair of electrons

Question 10

How does the carbon- halogen bond break?

Answer 10

Heterolytic fission?

Question 11

Substitution reactions, with water?

Answer 11

Halide is replaced with OH group, producing an alcohol, this is a hydrolysis reaction.

Question 12

Substitution reactions, with aqueous potassium hydroxide?

Answer 12

Another way to produce alcohols - very quick

Halide is replaced with OH group

Question 13

Substitution reactions, with potassium cyanide?

Answer 13

Halide is replaced with CN group, which increases the carbon chain length and forms a nitrile
This is carried out under reflux with potassium cyanide in ethanol

Question 14

Substitution reactions, with ammonia?

Answer 14

Halide is replaced with NH2 group, producing an amine
Ethanol is used
Ammonium salt is also produced

Question 15

Elimination reactions, with ethanolic potassium hydroxide?

Answer 15

Produces an alkene
Heated under reflux
hydroxide ion acts as a base

Question 16

Carbo-cations?

Answer 16

the stability of the carbocation formed, effects the products of a reaction! primary (1 methyl group- very weak) quaternary ( 4 methyl groups- very strong)

Question 17

Are halogenalkanes soluble in water?

Answer 17

No, as C-H bonds are non polar they need to dissolve in ethanol which is also non polar

Question 18

do halogenalkanes have a polar bond? why?

Answer 18

Yes, as the halogen has a higher electronegativity than carbon

Question 19

When do their boiling points increase?

Answer 19

Further down group 7

When the carbon chain length increases

Question 20

which halogen bond is most polar?

Answer 20

C-F bond, as fluorine is most electronegative

Question 21

which halogen has the lowest bond enthalpy?

Answer 21

Iodine, therefore the C-I bond is the most reactive

Question 22

Examples of nucleophiles?

Answer 22

OH-, CN-

Question 23

What is nucleophilic substitution?

Answer 23

a reaction where a nucleophile donates a lone pair of electrons

Question 24

what is formed in the elimination reactions of halogenalkanes?

Answer 24

an alkene, water and halogen ion