Which carbon atoms of glucose, numbered from 1 to 6 forms a hemiacetal structure between -CHO and -OH groups.?

Step-by-step solution

In the open-chain structure of glucose, the aldehyde group (-CHO) is present at C-1. The cyclic hemiacetal structure is formed by the intramolecular nucleophilic addition of the -OH group at C-5 to the -CHO group at C-1. This results in the formation of a stable six-membered pyranose ring. Thus, the -OH group at C-5 is involved in the hemiacetal formation. Answer: C-5