Can you give and explain the mechanism for the reaction between aqueous Sodium Hydroxide (NaOH) and Chloroethane at room temperature? What is a competing reaction which may occur and how would you promote this reaction?

Chlorine is highly electronegative and hence electron withdrawing (briefly ask them what electronegativity is to make sure they're completely comfortable with the concept), so the carbon its directly attached to will be electron deficient . This causes the carbon to have a partially positive charge which will attract nucleophiles. The Hydroxide ion is a good nucleophile due to its negative charge (coulombically attracted to the partial positive charge on the carbon), and hence will attack the electron deficient carbon with its lone pair. The hydroxide oxygen bonds to the carbon, however, carbon cannot have more than 4 bonds, so one other atom will have to leave. Chloride will leave with both the electrons in the C-Cl bond, hence breaking this bond and giving Cl a negative charge. This is because Chlorine is an electronegative atom best able to stabilise this charge by withdrawing electron density close to its nucleus. The product is therefore ethanol. The competing reaction is a Base elimination , it's promoted by high temperatures [if student has knowledge of Gibbs Free energy then carry on explaination in terms of a positive change in entropy effecting delta G to be more negative as temperature increases].