Deduce two features you would expect to observe in its mass spectrum.

Predict two features you would expect to observe in its infrared (IR) spectrum.

peaks at (m/z =) 62 and 64 / two molecular ion peaks;

height ratio of molecular ion peaks is 3 :1;

peak at (m/z =) 27 (due to loss of Cl);

Accept peaks at 63/65 (¹³C)/peak(s) resulting from ¹³C / peaks at 61/63 (loss of H)/peak(s) resulting from loss of H / peaks at 48/50 (loss of CH₂)/peak(s) resulting from loss of CH₂/ 35/37 Cl⁺ as an alternative to final marking point.

absorption at 600 – 800 (\({\text{c}}{{\text{m}}^{ - 1}}\) C–Cl);

absorption at 1610 – 1680 (\({\text{c}}{{\text{m}}^{ - 1}}\) >C=C<);

absorption at 2850 – 3100 (\({\text{c}}{{\text{m}}^{ - 1}}\) C–H);

The first and second marking points were rarely scored as most students did not recall that chlorine exists as a mixture of isotopes. The most common molecular ion peak stated was 62.5 instead of both 62 and 64. A common incorrect response in this question was to suggest fragmentation at the double bond with the production of the CH₂ fragment. The identification of possible IR absorption bands and the effect of IR radiation being absorbed by molecules was well done by most candidates. It was clear that most candidates understood that bond stretching/bending occurred when IR radiation is absorbed but there were fewer correct references to the change in bond polarity which was required for the second mark.

The first and second marking points were rarely scored as most students did not recall that chlorine exists as a mixture of isotopes. The most common molecular ion peak stated was 62.5 instead of both 62 and 64. A common incorrect response in this question was to suggest fragmentation at the double bond with the production of the CH₂ fragment. The identification of possible IR absorption bands and the effect of IR radiation being absorbed by molecules was well done by most candidates. It was clear that most candidates understood that bond stretching/bending occurred when IR radiation is absorbed but there were fewer correct references to the change in bond polarity which was required for the second mark.