Acyclic sugar derivatives show the characteristic carbonyl absorption band centered around 1710-1725 cm-1. This band increases in intensity with temperature and is also sensitive to pH.

thanks Sir Varoujan Yaylayan it is pleasure for me that you have answered. i was worried about that.

May I suggest you to have a look on the attached paper. Zhbankov et al. 1995

Acyclic versus cyclic is linked to shifts at the level of carbone 5 (for pyranose structures).

The acyclic form of a non substituted sugar is a tiny proportion in comparison with the cyclic form, therefore it is quite difficult to detect the CHO vibrations by IR.