[ostudent]

Compound 1 is shown.

Question: Consider the cyclic form of the sugar from which Compound 1 is derived. Can this sugar be classified as a hemiacetal?

My thought process:
1. A hemiacetal means that I am looking for an OH and OR attached to carbon 1.
2. That isn't present.
3. This is not a hemiacetal.

However, the answer is that the sugar from which compound 1 is derived IS in fact a hemiacetal. I assume this means the Br would originally be an OH. How can I backtrack to that logic?

Best regards, and thank you for your input.

[hollytara]

Compound 1 isn't a hemiacetal - but then it isn't a sugar.  It has been protected (protecting groups) and activated for reaction.  But what about the sugar they started with to make compound 1?  Is THAT a hemiacetal?  that is what is being asked.

[hollytara]

PS - the activation is that they react the OH with HBr to make the bromide.