Question: I am studying spin-spin coupling theory in NMR. Below is an exercise from Mcmurry's organic chemistry.

[![cyclohexanol](https://i.stack.imgur.com/zacXW.png)](https://i.stack.imgur.com/zacXW.png)

The textbook says that \* stands for chiral center. But is it true? When I searched for it some said that there is no chiral center in cyclohexanol. Then, Aren't this hydrogens enantiotopic?

Answer: 
The substitution of one of the two hydrogens leads to the *cis* or the *trans* isomer of the disubstituted cyclohexane. Thus, they are certainly diastereotopic.

Perhaps, what confused you, as well me in a previous answer focused on 1,3-cyclohexandiol, is that substitution with an OH group leads to two diastereoisomers one of which consists of a couple of enantiomers (the other is the *meso* form).

A prochiral H on a stereogenic center does not imply its enantiotopic character. The obtained diastereoisomers can be optically active in fact, but not enantiomers.
Cyclohexanol does not have a chiral carbon but hydrogen atoms are diasteotopic because the substitution for one of the two hydrogen atoms (in alternate fashion) would give diastereomers, as the $\ce{C-1}$ carbon of cyclohexanol will now become either chiral (for C-2 and C-3 H-substitution) or will have specific cis or trans geometry(for C-4 H-substitution).

The enantiotopic hydrogen word is used only when one of the hydrogen replacement generates an enantiomer with only one chiral carbon (at the site of hydrogen replacement).