Nucleophilic substitution in halogenoalkanes

Question 1

What do nucleophiles attack and form bonds with?

Answer 1

positively or partially positively charged carbon atoms

Question 2

What is a nucleophile?

Answer 2

A lone electron pair donor

Question 3

What things tend to be a nucleophile?`

Answer 3

A negatively charged ion or a an atom with a delta negative charge.

Question 4

How does the nucleophile create a bond with carbon?

Answer 4

Carbon atoms are electron deficient and so the nucleophile donates a pair of electrons and swaps places with the halogen in order to create a covalent bond.

Question 5

What are the names of the three common nucleophiles?

Answer 5

• Hydroxide ion
• Ammonia
• Cyanide ion

Question 6

What is the formula for the hydroxide ion?

Answer 6

^-:OH

Question 7

What is the formula for ammonia?

Answer 7

:NH₃

Question 8

What is the formula for the cyanide ion?

Answer 8

^-:CN

Question 9

How would you represent a halogen?

Answer 9

X

Question 10

How would you represent any negatively charged nucleophile?

Answer 10

:Nu^-

Question 11

Draw the general equation for nucleophilic substitution

Answer 11

Check pg 208

Question 12

Draw a curly arrow representing the movement of a pair of electrons

Answer 12

Question 13

Draw a curly arrow representing the movement of a single electron

Answer 13

Question 14

Draw the general mechanism for nucleophilic substitution, along with the curly arrows and partial charges

Answer 14

check pg 208

Question 15

The diagram below shows the electron pair in the C-X bond moving to the halogen atom (X). What does the halogen atom become?

Answer 15

A halide ion

Question 16

What is the halide ion called?

Answer 16

The leaving group

Question 17

What does the rate of substitution depend on?

Answer 17

The halogen

Question 18

Which of the halogens is unreactive?

Answer 18

Flourine

Question 19

Why are flouro-compounds unreactive?

Answer 19

Because of the strength of the C-F bond

Question 20

The rate of reaction increases going….(up or down the halogen group)?

Answer 20

Down the halogen group

Question 21

Why dies the rate of reaction increase going down the halogen group?

Answer 21

because the strength of the C-X bond decreases.

Question 22

The reaction of halogenoalkanes and the hydroxide ion is very slow in room temperature. What can be done to speed up the rate of reaction?

Answer 22

Warm the mixture

Question 23

Halogenoalkanes do not mix with water. So what is used instead as a solvent in which both the halogenoalkane and the hydroxide ion can both mix.

Answer 23

Ethanol

Question 24

Name the reaction between a halogenoalkane and hydroxide ion in ethanol

Answer 24

Hydrolysis

Question 25

Write the general formula between a halogenoalkane and a hydroxide ion

Answer 25

R-X + OH^- → ROH + X^-

Question 26

What is the functional group ROH that is formed?

Answer 26

An alcohol

Question 27

Write the formula for the reaction of bromoethane and and a hydroxide ion

Answer 27

C₂H₅Br + OH^- → C₂H₅OH + Br

Question 28

Draw the mechanism for the reaction of bromoethane and and a hydroxide ion

Answer 28

Check pg 209

Question 29

Describe the conditions for the reaction of a halogenoalkane and the cyanide ion

Answer 29

Warm and in a alcoholic solution

Question 30

What is produced in the reaction between a halogenoalkane and the cyanide ion?

Answer 30

A nitrile

Question 31

Draw the mechanism for the reaction of a halogenoalkane and a cyanide ion

Answer 31

Check pg 209

Question 32

Describe the conditions for the reaction of a halogenoalkane and ammonia

Answer 32

In ethanol and under pressure

Question 33

What is produced in the reaction between a halogenoalkane andammonia?

Answer 33

an amine

Question 34

Write out the formula for the reaction of a halogenoalkane and ammonia

Answer 34

R-X + 2NH₃ → RNH₂ + NH₄X

Question 35

Draw the mechanism for the reaction of a halogenalkane and ammonia

Answer 35

Check pg 210

Question 36

Why does the reaction of a halogeonalkane and ammonia have a third step?

Answer 36

Because ammonia is a neutral nucleophile a H⁺ must be lost to form a neutral product, called amine.