14 A hydrocarbon contains 85.7% carbon by mass. Its 'H NMR spectrum shows two signals in the ratio of 3:1. Which compound is consistent with this data? A. O 2-methylprop-1-ene B. O but-1-ene C. O propane D. O propene From the percentage composition the empirical formula is CH2 (so it cannot be propane). The protons in 2- CH3 H2C=C CHE methylprop-1-ene, are in two different chemical environments in the simplest ratio of 3:1. But-1-ene will give four signals in the ratio of 3:2:2:1 and propene three signals in the ratio 3:2:1. 15 Which compound has an IHD different to the other three? A. O C2H7N B. O C2H40 C. O C3H6 D. C2H2C12 C2H7N is fully saturated and has an IHD of 0. The other three compounds all have an IHD of 1. 16 Which compound shows a singlet, a triplet and a quartet splitting pattern for its three signals in its 'H NMR spectrum? A. O propanoic acid, CH3CH2COOH B. O propan-1-ol, CH3CH2CH2OH C. O 1,1-dichloropropane, CH3CH2CHC12 D. O 3-methylbutan-2-one, CH3COCH(CH3)2 The ony two to show a singlet are propanoic acid and 3-methylbutan-2-one as they possess hydrogen atoms in a chemical environment where there are no other hydrogen atoms on adjacent carbon atoms. 3-methylbutan-2- one has a doublet as the two methyl groups are split by a single hydrogen atom. The ethyl group in propanoic acid provides the triplet and quartet. 17 Which will give a peak at M-29 (where M is the mass of the molecular ion peak) in their mass spectrum? I. ethanol, CH3CH2OH II. ethanal, CH3CHO III. ethyl ethanoate, CH3COOCH2CH3 A. O II and III only B. O I, II and III 7/9 ... ... C. O I and III only D. I and II only A peak at M-29 can be due to the fragment caused by the loss of either C2H5 or CHO as both have a relative mass of 29