NMR is used to help identify the product of nearly every reaction run in the laboratory. For example, we said in Section 8.5 that hydroboration–oxidation of alkenes occurs with non-Markovnikov regiochemistry to yield the less highly substituted alcohol. With the help of NMR, we can now prove this statement. Does hydroboration–oxidation of methylenecyclohexane yield cyclohexylmethanol or 1-methylcyclohexanol? The 1 H NMR spectrum of the reaction product is shown in Figure \(\PageIndex{1}\)a. The spectrum shows a two-proton peak at 3.40 δ , indicating that the product has a –CH 2 – group bonded to an electronegative oxygen atom (–CH 2 OH). Furthermore, the spectrum shows no large three-proton singlet absorption near 1 δ , where we would expect the signal of a quaternary –CH 3 group to appear. (Figure \(\PageIndex{1}\)b) gives the spectrum of 1-methylcyclohexanol, the alternative product.) Thus, it’s clear that cyclohexylmethanol is the reaction product. Exercise \(\PageIndex{1}\) How could you use 1 H NMR to determine the regiochemistry of electrophilic addition to alkenes? For example, does addition of HCl to 1-methylcyclohexene yield 1-chloro-1-methylcyclohexane or 1-chloro-2-methylcyclohexane? Answer 1-Chloro-1-methylcyclohexane has a singlet methyl absorption.