Halogenoalkanes

• Why is the C-X bond in halogenoalkanes polar?

  Halogens are more electronegative than carbon
• How does electronegativity affect bond polarity in halogenoalkanes?

  Electronegativity decreases down group 7, reducing polarity
• What types of intermolecular forces are present in halogenoalkanes?

  Van der Waals and dipole-dipole attractions
• How does boiling point change with chain length in halogenoalkanes?

  Boiling point increases with chain length
• Why do halogenoalkanes have higher boiling points than alkanes?

  Due to higher masses and polar bonds
• How does reactivity of the C-X bond change down the group?

  Reactivity increases due to weaker bonding
• Why are fluoroalkanes considered unreactive?

  They have a strong C-F bond
• What is the role of a nucleophile in nucleophilic substitution?


  Electron pair donor
• What are common nucleophiles in nucleophilic substitution?

  :OH-, :CN-, NH3
• What happens to the halogen in nucleophilic substitution?

  It is replaced by a new functional group
• How does the rate of nucleophilic substitution change with C-X bond strength?

  Rate increases as C-X bond strength decreases down group
• What is the overall equation for nucleophilic substitution with NaOH?

  R-X + NaOH → R-OH + NaX
• What are the products of nucleophilic substitution reactions?

  Alcohols (OH)

  Nitriles (CN)

  Amines (NH3)
• What are the conditions for the reagents of nucleophilic substitution with NaOH?

  Aqueous and warm
• What are the conditions for the reagents of nucleophilic substitution with KCN?


  Ethanolic and warm
• What are the conditions for the reagents of nucleophilic substitution with NH3?



  Excess ammonia dissolved in ethanol at pressure in a sealed tube
• What are the conditions for the reagents of elimination reaction with KOH?




  Ethanolic and hot
• What is the role of hydroxide ions in elimination reactions?

  Act as a base to remove proton from carbon atom adjacent to one bonded to the halogen
• What is the overall equation for nucleophilic substitution with KCN?

  R-X + KCN -> R-CN + KX
• What is the overall equation for nucleophilic substitution with NH3?

  R-X + 2NH$_3$ -> R-NH$_2$ + NH$_4$X
• What is the overall equation for elimination reaction with KOH?

  R-X + KOH -> R-OH + H2O + KX
• Why is ozone beneficial in the atmosphere?

  Absorbs harmful ultraviolet radiation
• How is ozone formed in the atmosphere?

  Oxygen broken down into 2 oxygen radicals using UV

  $O_2\ \rightarrow\ 2O\cdot$

  Oxygen radical reacts with oxygen molecule to form ozone

  $O\cdot\ +$$\ O_2\ \rightarrow\ O_3$
• What are chlorofluorocarbons (CFCs) and why are they banned?

  Chemicals containing chlorine, fluorine and carbon which contribute to ozone depletion
• How do chlorine atoms contribute to ozone depletion?

  Catalyse decomposition of ozone as they are regenerated
• Write the equations for the process of ozone depletion with chlorine radical

  $Cl\cdot\ +$$\ O_3\ \rightarrow\ ClO\cdot\ +$$\ O_2$

  $ClO\cdot\ +$$\ O_3\ \rightarrow\ 2O_2\ +$$\ Cl\cdot$

  Overall equation: $2O_{3\ }\ \rightarrow\ 3O_2$
• Mechanism for nucleophilic substitution reaction of Xethane with NaOH


  Ethanol

  A) Nucleophile

  B) Arrow 1

  C) Arrow 2

  
• Mechanism for nucleophilic substitution reaction of Xethane with KCN


  Propanenitrile

  A) Nucleophile

  B) Arrow 1

  C) Arrow 2

  D) Arrow 3

  
• Mechanism for nucleophilic substitution reaction of Xethane with NH3

  Ethylamine

  A) Nucleophile

  B) Nucleophile

  C) Arrow 1

  D) Arrow 2

  E) Arrow 3

  F) Arrow 4

  
• Mechanism for elimination reaction of Xethane with KOH

  Hydroxyethene

  A) Nucleophile

  B) Arrow 1

  C) Arrow 2

  D) Arrow 3