Mechanisms

Question 1

Addition reactions

Answer 1

Two or more molecules react together to form a single molecule

Question 2

Ethene + Bromine molecule

Answer 2

1,2 dibromoethane

Question 3

Ethene + Chlorine molecule

Answer 3

1,2 dichloroethane

Question 4

Ethene + hydrogen chloride

Answer 4

Chloroethane

Question 5

Ethene +H2O

Answer 5

Ethanol

Question 6

Function of 1,2 dibromoethane

Answer 6

Used as fumingant for treating logs against termites and beetles

Question 7

Function of 1,2 dichloroethane

Answer 7

To manufacture chloroethane

To make polyvinyl chloride

Question 8

Function of chloroethane

Answer 8

Used in dentistry to identify a ‘dead tooth’

Question 9

Function of ethanol

Answer 9

Used as an industrial solvent and fuel

Question 10

Step 1: Mechanism of the Reaction between Ethene and Bromine

Answer 10

Br molecule become polarised as they come closer to the carbon carbon double bond of an ethene molecule. (One molecule is delta positive and the other is delta neg)This is because its a region of high concentration of negative charge.

Question 11

Step 2: Mechanism of the Reaction Between Ethene and Bromine

Answer 11

The polarization becomes so great it splits the Br molecule with one becoming positively charged and the other becoming negatively charged. This is called a heterolytic fission. This also create free radical bromine

Question 12

Step 3: Mechanisms of the Reaction Between Ethene and Bromine

Answer 12

The Br+ will want to regain its two electrons by attacking the ethene molecule carbon carbon double bond and creating a covalent bond with one of the carbon atoms. This leaves positvely charged carbon atom and its now called a carbonium ion.

Question 13

Step 4: Mechanisms of the Reaction Between Ethene and Bromine

Answer 13

The Br- ion attacks the carbonium ion this is called the ion addition. This results in the prodution of 1,2 dibromoethane

Question 14

Evidence for the mechanism of the reaction between Ethene and Bromine

Answer 14

When ethene reacts with bromine in water that contains sodium chloride in solution 1-bromo-2chloroethane and 2-bromoerhanol is produced this shows carbonium ion is present

Question 15

Elimination Reaction

Answer 15

A small moleule os removed from a larger molecule to leave a double bond in the larger molecule

Question 16

Example of an elimination reaction

Answer 16

Ethanol -Al2O3-> Ethene + H2O

Question 17

Substitution reaction

Answer 17

A chemical reaction in which an atom or group of atoms in a molecule is replaced by another atom or group of atoms

Question 18

Mechanism

Answer 18

The detailed step by step description of how the overall reactoon occurs

Question 19

Step 1: Mechanisms of the Reaction between Methane and Chlorine

Answer 19

With the presence of a UV light its energy is enough to break the weak van der waals forces between these molecules. This created chlorine free radicals. Since the electrons are equally shared after the split its called a homolytic fission

Question 20

Step 2: Mechanisms of the reaction Between Methane and Chlorine

Answer 20

One of the chlorine free radicals attacks the methane molecule to form a methyl free radical. Since the chlorine free radical has produced a methyl free radical this is called propagation

Question 21

Step 3: Mechanisms of the Reaction Between Methane and Chlorine

Answer 21

The other chlorine free radical attacks the methyl free radical and forms chloromethane. The chlorine atoms produced in step 3 can cause a chain reaction

Question 22

Chain reaction

Answer 22

A reaction that continues on and on because a product from one step of the reaction is a reactant for another step of the reaction

Question 23

Step 4: Mechanisms of the Reaction Between Ethene and Chlorine

Answer 23

In order to stop the chain reactions two chlorine free radicals can combine to make Chlorine molecule. A chlorine free radical and methyl free radical can combine to make chloromethane. Two methyl free radicals combine to make ethane

Question 24

Evidence of the Reaction Between Ethene and Chlorine

Answer 24

Reaction takes place in UV light. Suggests Cl2 has broken to make chlorine free radical.
Ethane is a product. Only evident if two methyl free radicals are present
Adding free radicals like tetramethyl lead speeds up a reaction. Only free radicals reacting to other radicals encourages chain reaction