The following compounds all show a single line in their 1H NMR spectra. List them as they would appear in an NMR spectrum, e. g. by decreasing chemical shift with the lowest shift to the right.

a. CH4

b. cyclohexane

c. H2C - CH2

d. Benzene

For the provided compounds, by decreasing chemical shift (ppm), the sequence from left to right is Benzene >> Cyclohexane >> Ethane (CH₂-CH₂) >> Methane (CH₄).

Explanation:

¹H-NMR spectrum, roughly, we can say that the more density of electron around the Hydrogen atom, the lower the shift is. So, in this case methane with the simplest structure, only one Carbon atom, does not cause much effect to reduce the density of electron around the hydrogen, so, it is the lowest.

Ethane and cyclohexane looks similar, but cyclohexane with the ring-structure, six carbon atoms, has more effect than ethane with only 02 carbon atoms. Benzene, with the aromatic ring, which has very strong negativity with electron, so it cause the density of electron on the surrounding hydrogen to be the lowest among the four provided compounds.