| Date | May 2016 | Marks available | 2 | Reference code | 16M.2.hl.TZ0.5 |
| Level | HL | Paper | 2 | Time zone | TZ0 |
| Command term | Deduce | Question number | 5 | Adapted from | N/A |
Question
Compound A and compound B are hydrocarbons.
(i) State the term that is used to describe molecules that are related to each other in the same way as compound A and compound B.
(ii) Suggest a chemical test to distinguish between compound A and compound B, giving the observation you would expect for each.
Test:
Observation with A:
Observation with B:
Outline how you could use the IR spectra of compounds A and B and section 26 of the data booklet to identify them.
Two signals occur in the 1H NMR spectrum of compound A. Deduce their expected chemical shift and their splitting pattern, using section 27 of the data booklet.
Markscheme
(i)
«structural/functional» isomer«s»
(ii)
Test:
«react with» bromine/Br2 «in the dark»
OR
«react with» bromine water/Br2 (aq) «in the dark»
A: from yellow/orange/brown to colourless AND B: colour remains/slowly decolourized
Accept other correct reagents, such as manganate(VII) or iodine solutions, and descriptions of the corresponding changes observed.
Accept “decolourized” for A and “not decolourized/unchanged” for B.
Do not accept “clear/transparent” instead of “colourless”.
compound A would absorb at 1620–1680«cm−1»
Accept any value in range 1620 – 1680 cm−1.
Signal 1/2 2/1
Chemical shift/ ppm 0.9 - 1.0 AND 4.5 - 6.0
Splitting pattern singlet AND singlet
Accept 0.9 to 2.0 for the first signal as the C=C affects the CH3 shift (actually 1.7).
Accept “none/no splitting” for both splitting patterns
Award [1 max] for the correct deduction (both shift and splitting) of signal 1 or 2.
