Some compounds with different molecular formulas have the same relative molecular mass to the nearest whole number.
A dicarboxylic acid has a relative molecular mass of 146, to the nearest whole number. Deduce the molecular formula of the acid.
A student dissolved some of the dicarboxylic acid in water and made up the solution to 250 cm3 in a volumetric flask. In a titration, a 25.0 cm3 sample of the acid solution needed 24.40 cm3 of 0.120 mol dm-3 sodium hydroxide solution for neutralisation. Calculate the mass, in g, of the dicarboxylic acid used. Give your answer to the appropriate number of significant figures.
Compounds with molecular formula C8H18O2\text{C}_8\text{H}_{18}\text{O}_2C8H18O2 also have a relative molecular mass of 146 to the nearest whole number. These include the diol octane-1,8-diol:
HO−CH2−CH2−CH2−CH2−CH2−CH2−CH2−CH2−OH \text{HO}-\text{CH}_2-\text{CH}_2-\text{CH}_2-\text{CH}_2-\text{CH}_2-\text{CH}_2-\text{CH}_2-\text{CH}_2-\text{OH} HO−CH2−CH2−CH2−CH2−CH2−CH2−CH2−CH2−OHDeduce the number of peaks in the 1H^1\text{H}1H NMR spectrum of this diol.
Draw or state the structure of a different diol also with molecular formula C8H18O2\text{C}_8\text{H}_{18}\text{O}_2C8H18O2 that has a 1H^1\text{H}1H NMR spectrum that consists of three singlet peaks.
State why the dicarboxylic acid can be distinguished from the two diols by high-resolution mass spectrometry using electrospray ionisation.
