Halogenoalkanes

Question 1

What is the general formula?

Answer 1

CnH2n+1X where X is the halogen

Question 2

Are they polar?

Answer 2

the C-X bond is polar, (Cδ+-Xδ-) the halogen is more electronegative than carbon

Question 3

Are they soluble?

Answer 3

the polar bonds are not polar enough to make them soluble in water mix with hydrocarbons - can be used as cleaning fluids to remove oily strains

Question 4

How does their boiling point change?

Answer 4

• increases with increased chain length
• increases going down the halogen group
• decreases with increased branching

Question 5

What are the two factors that dermine how quickly the C-X bond reacts?

Answer 5

polarity and enthalpy of the bond

Question 6

What is a nucleophile?

Answer 6

a nucleophile is a electron pair donor

Question 7

How does nuclephillic addition occur in the C-X bond?

Answer 7

C is partially positive - electron deficit react with electron pair donors C-F would be most reactive as F is the most electronegative halogen

Question 8

How do bond enthalpys change going down the group?

Answer 8

bonds get weaker going down group F is the smallest atom and the shared electrons are strongly attracted to the nucelus the shared electrons become further and further away going down the group - more shielding

Question 9

Write the two propagation steps in the conversion of CHF2CH3 into CF3CH3

Answer 9

CHF₂CH₃ + •F → •CF₂CH₃ + FH

•CF₂CH₃ + F₂ → CF₃CH₃ + •F