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CAIE A-Level Chemistry 22.2.4 Identifying Fragment Ions

Practise assigning simple fragment-ion formulae and using diagnostic peaks to distinguish organic structures.

Syllabus
2028–2030
Course
Chemistry 9701
Level
AS

Exam points

  • propose a positively charged fragment whose atom totals and nominal mass match the m/e peak
  • show the bond cleavage that could generate fragments such as C4H9+ while conserving the remaining atoms
  • use presence or absence of diagnostic peaks such as m/e 41, 43 or 57 to select between isomers

22.2.4—Suggest the identity of molecules formed question 1

[Maximum number: 1]

Fig. 4.1 shows a possible synthesis of propene, C3H6\mathrm{C}_{3} \mathrm{H}_{6}.

Fig. 4.1

Fig. 4.1

Under different conditions, two molecules of propene can combine to form compounds X and Y.

Figure for Question 22.2.4—Suggest the identity of molecules formed question 1 — CAIE A-Level Chemistry AS

Fig. 4.2 shows the mass spectrum of either compound X or compound Y.

Fig. 4.2

Fig. 4.2

Identify which of X and Y gives this mass spectrum.
Give one reason for your answer, referring to the fragmentation pattern.

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