Substitution Reactions of Haloalkanes

Question 1

What type of bond is the covalent C-X bond in a haloalkane?

Answer 1

Polar bond

Question 2

What is a nuclephile?

Answer 2

A chemical species which donates a pair of electrons in the formation of a new covalent bond- an electron pair donor

Question 3

Show the mechanism for the nucleophilic substitution of chloromethane with aqueous sodium hydroxide

Answer 3

• A curly arrow from lone pair on OH^- to Carbon atom of C-Cl bond
• A dipole shown on Carbon (slightly positive) and Cl (slightly negative) AND a curly arrow from C-Cl bond to the Cl atom
• Correct organic alcohol product and Cl^-

Question 4

Show the mechanism for the nucleophilic substitution of chloromethane with water

Answer 4

• A curly arrow from lone pair on O in H₂O to Carbon atom of C-Cl bond
• A dipole shown on Carbon (slightly positive) and Cl (slightly negative), a dipole on the O (slightly negative) and H’s (slightly positive) in water AND a curly arrow from C-Cl bond to the Cl atom
• Correct organic alcohol product and HCl

Question 5

What is a reagent?

Answer 5

A compound or substance used to start a chemical reaction

Question 6

What is the reagent in the hydrolysis/nucleophillic addition of haloalkanes?

Answer 6

With aqueous hydroxide solution = aqueous hydroxide solution

With water= water

Question 7

What are the conditions for the nucleophillic substituion/hydrolysis of haloalkanes?

Answer 7

• Aqueous hydroxide solution*
• Ethanol*
• Heat under reflux

1- OR WATER if that is the nucleophile*
2- when aqueous hydroxide is the nucleophile as it increaes its solubility in water*

Question 8

What colour is the silver chloride precipitate?

Answer 8

White

Question 9

What colour is the silver bromide precipitate?

Answer 9

Cream

Question 10

What colour is the silver iodide precipitate?

Answer 10

Yellow

Question 11

Which C-X bond hydrolyses the fastest?

Answer 11

C-I bond

Question 12

Which C-X bond hydrolyses the slowest?

Answer 12

C-F bond

Question 13

Explain the trend in the rates of hydrolysis of primary haloalkanes

Answer 13

• The weaker the C-X bond the faster the rate of reaction.
• The C-I bond is weaker than the C-F bond and so it hydrolyses faster.

Question 14

What is the equation for the formation of silver chloride?

Answer 14

Cl^-_(aq) + Ag⁺_(aq) → AgCl_(s)

Question 15

What is the equation for the formation of silver bromide?

Answer 15

Br^-_(aq) + Ag⁺_(aq) → AgBr_(s)

Question 16

What is the equation for the formation of silver iodide?

Answer 16

I^-_(aq) + Ag⁺_(aq) → AgI_(s)

Question 17

What solution do you react with haloalkanes to form a precipitate

Answer 17

Aqueous silver nitrate solution