Is pyranose a 5-membered or 6-membered ring? Many times we get the structure of pyranose wrong. It so happens that we confuse pyranose with pyrrole which is a five-membered ring.Also, the word pyranose sounds like"pentose"so we end up drawing a five-membered ring.
But instead of what it seems, pyranose has a six membered ring structure with 5 carbons and one oxygen as shown below:
The name pyranose is derived from pyran (structure below). Pyran has two double bonds in its structure. But, pyranose (structure above) does not have any double bonds in it.