Organic Chemistry II: Carbonyl Chemistry (Edexcel A Level Chemistry): Exam Questions

This question is about redox reactions.

Name the ion with formula . Include the relevant oxidation number.

State what happens to a reducing agent during a reaction, in terms of oxidation number and electrons.

Identify the species that is the strongest reducing agent from the list of standard electrode potentials in the Data Booklet.

Manganese(IV) oxide, MnO₂, and manganate(VII) ions, MnO₄^–, react in alkaline solution to form manganate(VI) ions, MnO₄^2–.

i) Write the ionic equation for this reaction.

State symbols are not required.

(2)

ii) Give a reason why this reaction is not disproportionation.

(1)

Sodium tetrahydridoborate(III), NaBH₄, is used in organic chemistry. It is an alternative reagent to lithium tetrahydridoaluminate(III) for the reduction of carbonyl compounds.

i) Draw a dot-and-cross diagram of the BH₄^– ion.

Use crosses (×) for the boron electrons, dots (•) for the hydrogen electrons and triangles () for the additional electron forming the negative ion.

(1)

ii) The BH₄^– ions reduce carbonyl compounds to alcohols in aqueous solution.

Complete the mechanism for the reduction of propanone to propan-2-ol by adding curly arrows, and any relevant lone pairs and dipoles.

(4)