Question 22M.2.hl.TZ2.8d(iv)
| Date | May 2022 | Marks available | [Maximum mark: 2] | Reference code | 22M.2.hl.TZ2.8d(iv) |
| Level | hl | Paper | 2 | Time zone | TZ2 |
| Command term | Suggest | Question number | d(iv) | Adapted from | N/A |
Carbon forms many compounds.
Suggest two differences in the 1H NMR of but-2-ene and the organic product from (d)(ii).
[2]
ALTERNATIVE 1: Any two of:
but-2-ene: 2 signals AND product: 4 signals ✔
but-2-ene: «area ratio» 3:1/6:2 AND product: «area ratio» 3:3:2:1 ✔
product: «has signal at» 3.5-4.4 ppm «and but-2-ene: does not» ✔
but-2-ene: «has signal at» 4.5-6.0 ppm «and product: does not» ✔
ALTERNATIVE 2:
but-2-ene: doublet AND quartet/multiplet/4 ✔
product: doublet AND triplet AND quintet/5/multiplet AND sextet/6/multiplet ✔
Accept “product «has signal at» 1.3–1.4 ppm «and but-2-ene: does not»”.
A considerable number of students (40%) got at least 1 mark here, but marks were low (average mark 0.9/2). Common errors were predicting 3 peaks, rather than 4 for 2 -bromobutane and vague / unspecific answers, such as ‘different shifts’ or ‘different intensities’. It is surprising that more did not use H NMR data from the booklet; they were not directed to the section as is generally done in this type of question to allow for more general answers regarding all information that can be obtained from an H NMR spectrum.
