A compound is usually mixed with Si(CH3)4\text{Si(CH}_3)_4Si(CH3)4 and either CCl4\text{CCl}_4CCl4 or CDCl3\text{CDCl}_3CDCl3 before recording the compound's 1H^1\text{H}1H NMR spectrum.
State why Si(CH3)4\text{Si(CH}_3)_4Si(CH3)4, CCl4\text{CCl}_4CCl4 and CDCl3\text{CDCl}_3CDCl3 are used in 1H^1\text{H}1H NMR spectroscopy. Explain how their properties make them suitable for use in 1H^1\text{H}1H NMR spectroscopy.
Deduce the splitting pattern for each of the peaks given by the H\text{H}H atoms labelled xxx, y y\,y and z z\,z in the 1H^1\text{H}1H NMR spectrum of the compound shown of formula:
CH3xCHyBrCOCH(CH3z)2 \overset{x}{\text{CH}_3}\overset{y}{\text{CH}}\text{BrCO}\overset{}{\text{CH}}(\overset{z}{\text{CH}_3})_2 CH3xCHyBrCOCH(CH3z)2Suggest why it is difficult to use standard chemical shift data tables to predict the chemical shift (δ \delta\,δ value) for the peak given by the H\text{H}H atom labelled yyy.
Two structural isomers of CH3CHBrCOCH(CH3)2\text{CH}_3\text{CHBrCOCH}(\text{CH}_3)_2CH3CHBrCOCH(CH3)2 each have only two singlet peaks in their 1H^1\text{H}1H NMR spectra. In both spectra, the integration ratio for the two peaks is 2:92:92:9.
Deduce the structures of these two isomers.
