The mass spectrum of iodoethane, \({{\text{C}}_{\text{2}}}{{\text{H}}_{\text{5}}}{\text{I}}\), shows three prominent peaks with m/z values of 156, 127 and 29. Identify the ions responsible for each of these three prominent peaks.

Bromine contains two isotopes, \(^{{\text{79}}}{\text{Br}}\) and \(^{{\text{81}}}{\text{Br}}\), in approximately equal amounts. Predict the m/z values of the prominent peaks in the mass spectrum of bromoethane, \({{\text{C}}_{\text{2}}}{{\text{H}}_{\text{5}}}{\text{Br}}\).

\({{\text{C}}_2}{{\text{H}}_5}{{\text{I}}^ + }\);

\({{\text{I}}^ + }\) and \({{\text{C}}_2}{\text{H}}_5^ + \);

Penalize once only if the + sign is missing.

108 and 110;

79 and 81;

29;

Part (a), identification of the ions, was answered well by most candidates. Few missed charge or used incorrect charge on the ions e.g. \({{\text{I}}^ - }\). For part (b), most scored the point for 29. Prominent peaks values for bromine isotopes proved to be a little more challenging for the candidates, many gave average values of 109 and 80 as other answers.

Part (a), identification of the ions, was answered well by most candidates. Few missed charge or used incorrect charge on the ions e.g. \({{\text{I}}^ - }\). For part (b), most scored the point for 29. Prominent peaks values for bromine isotopes proved to be a little more challenging for the candidates, many gave average values of 109 and 80 as other answers.