Final answer:
A cyclic hemiacetal with a six-membered ring is referred to as pyranose. This structure forms when certain monosaccharides like glucose undergo a reaction to close the ring, creating a stable six-membered cyclic molecule.
Step-by-step explanation:
A cyclic hemiacetal with a six-membered oxygen-containing ring resulting from the reaction between a carbonyl group and an alcohol group on the same sugar molecule is known as pyranose. This nomenclature is derived from a similar cyclic ether called pyran. In carbohydrates, when the hemiacetal forms between the aldehydic group at the first carbon atom and the hydroxyl group at the fifth carbon atom, the stable six-membered cyclic structure called pyranose is formed. This is commonly seen with monosaccharides such as glucose, which predominately exists as a pyranose ring in solution.