The pair of optical Isomers which differ in the orientation of H and OH gp only at C1 Carbon atom are called anomers. Difference between two anomers of glucose :

It is a type of Vitamin which contains B₁, B₂, B₆ and B₁₂. It required to release energy from food and to promote healthy skin and muscles. Its deficiency causes beri-beri (Vitamin B₁ ) and Anaemia (Vitamin B₁₂).

(i) Glucose does not give Schiff‘s Test although it contains aldehyde group.
(ii) Glucose does not form crystaline product with NaHSO₃.

The reaction of glucose with HI gives n-hexane and it proves that all sin-carbon-atom are in straight chain.
\(Ho{ CH }_{ 2 }-(CHOH)_{ 4 }-CHO\overset { HI }{ \underset { Heat }{ \longrightarrow } } { CH }_{ 3 }-\underset { n-hezane }{ ({ CH }_{ 2 })_{ 4 } } -{ CH }_{ 3 }\).

Open structure of D-glucose could not explain the following reactions:
(i) Despite having the aldehyde group, glucose does not give Schiffs test and 2, 4-DNP test.
(ii) Glucose does not react with sodium hydrogen sulphite to form addition product.
(iii) The pentaacetate of glucose does not react with hydroxyl amine showing the absence of free -CHO group.
(iv) When glucose is heated with methanol in the presence of dry HCI gas, it forms two isomeric monomethyl derivatives known as \(\alpha \)-D-glucoside(m.p. = 165°C) and \(\beta \)-D-glucoside (m.p = 107°C). Since only one molecule of methanol is used for the formation of methyl glucoside, these must be hemiacetals. 
These results show that glucose does not have open chain form structure.