Chemistry 9701 · AS & A Level · Hydrocarbons

Hydrocarbons — practice question

P, Q and R each possess the molecular formula $\text{C}_3\text{H}_6\text{O}$. All three are structural isomers of one another. In both P and Q, an oxygen atom is attached directly to a carbon atom that is $sp^2$ hybridised. In R, the oxygen atom is attached directly to a carbon atom that is $sp^3$ hybridised.
(a(i))[2]

Explain what is meant by structural isomers.

(a(ii))[2]

Explain how $sp^2$ and $sp^3$ hybridisation can happen in carbon atoms.

(a(iii))[2]

State the bond angles usually linked with each type of hybridisation in carbon atoms.

(b(i))[1]

R has two different functional groups, one of which is an alkene group. R reacts with cold, dilute, acidified manganate(VII) ions to produce propane-1,2,3-triol. Give the displayed formula of R.

(b(ii))[2]

State the reaction type and what you would observe when R reacts with bromine water.

(b(iii))[1]

Draw the structure of the product formed when R reacts with bromine water.

(b(iv))[1]

Identify the gaseous product formed when R reacts with hot, concentrated, acidified manganate(VII) ions.

(c(i))[2]

P and Q ($\text{C}_3\text{H}_6\text{O}$) each form an orange precipitate with 2,4-DNPH. Only Q gives a yellow precipitate with alkaline aqueous iodine. Name P and Q.

(c(ii))[1]

Identify the yellow precipitate formed by the reaction of Q with alkaline aqueous iodine.

(d(i))[2]

P and Q each react with hydrogen cyanide to form a single product. The product from P exists as a pair of optical isomers. The product from Q does not show optical isomerism. Explain the meaning of the term optical isomers.

(d(ii))[3]

Ethanal, $\text{CH}_3\text{CHO}$, also reacts with hydrogen cyanide. The product of this reaction is $\text{CH}_3\text{CH(OH)CN}$. Draw the mechanism of this reaction. Include all necessary charges, dipoles, lone pairs and curly arrows.

(ii)[3]

Ethanal, $\text{CH}_3\text{CHO}$, also reacts with hydrogen cyanide. The product of this reaction is $\text{CH}_3\text{CH(OH)CN}$. Draw the mechanism of this reaction. Include all necessary charges, dipoles, lone pairs and curly arrows.

Worked solution & mark scheme

This 22-mark question has a full step-by-step worked solution and mark scheme. One marking point: Same molecular formula / same count of atoms of each element

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