Deduce the structural formulas of the two possible isomers.

Mass spectra A and B of the two isomers are given.

Explain which spectrum is produced by each compound using section 28 of the data booklet.

State the type of bond fission that takes place in a S_N1 reaction.

State the type of solvent most suitable for the reaction.

Draw the structure of the intermediate formed stating its shape.

Suggest, giving a reason, the percentage of each isomer from the S_N1 reaction.

Nitrobenzene, C₆H₅NO₂, can be converted to phenylamine via a two-stage reaction.

In the first stage, nitrobenzene is reduced with tin in an acidic solution to form an intermediate ion and tin(II) ions. In the second stage, the intermediate ion is converted to phenylamine in the presence of hydroxide ions.

Formulate the equation for each stage of the reaction.

Accept condensed formulas.

[2 marks]

A:

CH₃CH₂COCH₂CH₃ AND «peak at» 29 due to

(CH₃CH₂)⁺/(C₂H₅)⁺/(M – CH₃CH₂CO)⁺

OR

CH₃CH₂COCH₂CH₃ AND «peak at» 57 due to

(CH₃CH₂CO)⁺/(M – CH₃CH₂)⁺/(M – C₂H₅)⁺

B:

CH₃COCH₂CH₂CH₃ AND «peak at» 43 due to

(CH₃CH₂CH₂)⁺/(CH₃CO)⁺/(C₂H₃O)⁺/(M – CH₃CO)⁺

Penalize missing “+” sign once only.

Accept “CH₃COCH₂CH₂CH₃ by elimination since fragment CH₃CO is not listed” for M2.

[2 marks]

heterolytic/heterolysis

[1 mark]

polar protic

[1 mark]

Shape: triangular/trigonal planar

[2 marks]

«around» 50% «each»

OR

similar/equal percentages

nucleophile can attack from either side «of the planar carbocation»

Accept “racemic mixture/racemate” for M1.

[2 marks]

Stage one:

C₆H₅NO₂(l) + 3Sn(s) + 7H⁺(aq) → C₆H₅NH₃⁺(aq) + 3Sn²⁺(aq) + 2H₂O(l)

Stage two:

C₆H₅NH₃⁺(aq) + OH^–(aq) → C₆H₅NH₂(l) + H₂O(l)

[2 marks]