Question

31.

A clear and colourless sample of a pure liquid hydrocarbon is mixed with a limited amount of hydrochloric acid in the absence of UV light. The resulting solution is found to be electrically conductive.      

Identify the species that would have to be present, of those available in this reaction, to cause electrical conductivity, then determine if the hydrocarbon was saturated or unsaturated.

Answer 1

The reaction between Hydrochloric acid and hydrocarbon as follows...

alkenes + HCl = Alkyl Halide ( here Chloride)

The alkenes react with gaseous hydrochloric acid  at room temperature. If the alkene is also a gas, you can simply mix the gases. If the alkene is a liquid, It can be made to bubble the hydrogen halide through the liquid.

The electrical conductivity arises because of the dipole dipole moment.

with water the haloalkanes shows electrolyte activity due to

(CH₃)₃CCl + H₂O (aq) gives rise to  (CH₃)₃C⁺ +    Cl^-

The In the above case the hydrocarbon has to be unsaturated so that the chlorine atom can add to the double bond.

The alkyl halides are only slightly soluble in water. For a halogenoalkane to dissolve in water it has to break attractions between the halogenoalkane molecules (van der Waals dispersion and dipole-dipole interactions) and break the hydrogen bonds between water molecules.

the carbon-halogen bond breaking to give positive and negative ions. The ion with the positively charged carbon atom then reacts with something either fully or slightly negatively charged..so the solvent that is needed for dispersion is water.