[kimchi521]

why glyceraldehyde does not have cyclic form? while tetroses with only one more carbon atom form a ring readily.

[Schrödinger]

Glyceraldyhyde is a 3 carbon chain. If you attempt to form a ring using the OH on the 2nd carbon, you will get a 3-membered ring, which is highly strained.

Moreover, formation of the ring is improbable due to the orientation of the OH group...its quite far away from the 1st carbon.

See http://en.wikipedia.org/wiki/Glyceraldehyde for structure.