Video Transcript
The incomplete reaction scheme
below shows the synthesis of propanol from chloropropane. Which of the following reactants
and conditions will result in the above reaction? (A) HCl and heat, (B) KOH and ZnCl2
catalyst, (C) sodium metal and heat, (D) H2SO4 and ice, or (E) KOH and heat.
Halogenoalkanes are compounds that
contain a halogen atom covalently bonded to an alkyl group. The carbon–halogen bond tends to be
polar and breaks when interacting with a hydroxide group.
The figure shown describes the
structure of a simple halogenoalkane molecule. One example of a halogenoalkane is
the molecule with the chemical formula CH3CH2Cl. In a carbon–chlorine bond, the
electron density is higher in the halogen atom and lower on the covalently bonded
carbon atom. In the presence of hydroxide ions,
carbon–halogen bond breaks and the electrons of a hydroxide group react with the
electron-deficient carbon atom.
We can see that in this process,
the product of the reaction is an alcohol molecule. These reactions tend to be
relatively slow at room temperature. And chemists often use high
temperatures in order to speed reactions up. In the example above, to get an
alcohol, a mixture of potassium hydroxide and alkyl halide would be stirred and
heated. Remember that OH− exists as a salt,
where potassium is a counter ion that is not involved in the reaction. As in the previous example, the
carbon–chlorine bond breaks when it’s added to a mixture with hydroxide ions and
heat.
And now with this information, we
can revisit the question. The incomplete reaction scheme
below shows the synthesis of propanol from chloropropane. Which of the following reactants
and conditions will result in the above reaction? And the correct answer is (E), KOH
and heat.
