Halogen Derivatives

Question 1

Definition of nucleophiles

Answer 1

Nucleophiles are electron rich species that forms a bond by donating a lone pair of electrons to an electron deficient species.

Question 2

What are the reasons where in SN2 mechanism, the nucleophile does a backside attack on the carbocation?

Answer 2

• Like charges repel (in the case if OH- or CN- etc.)
• Large halogen impedes the approach of nucleophile.

Question 3

Things to take note when drawing the SN2 mechanism

Answer 3

-partial charges
-3D configuration (backside attack and inversion of config)
-full arrow start from lone pair ends on C
-full arrow start from bond pair ends on X
-check overall charge of transition state based on charge of nucleophile.

Question 4

Properties of fluorohalogenoalkanes

Answer 4

• inert and stable (C-F bond very strong)
• non flammable (no C-H bonds)
  -non toxic
  -odourless
• good organic solvents

Question 5

Uses of fluorohalogenoalkanes

Answer 5

• refrigerants
• cleaning agents
• aerosol propellants
• fire retardants

Question 6

Environmental concern of CFCs

Answer 6

• CFCs are inert and non biodegradable
• They are able to absorb ultraviolet light which causes C-Cl bonds to break homolytically and release Cl free radicals
• These Cl radicals deplete the ozone layer by attacking ozone molecules in ozone layer, converting them into O2 molecules.
• Ozone depletion endangers us from UV radiation which can cause skin cancer in human and widespread failure in crops cultivation.