glucose has no aldehyde(in cyclic structure) but it still reduces tollen's reagent..why????????similar is some some other carbohydrates.

Dear Vikash,

Ag⁺ ions react with OH ^- of aqueous ammonia to produce a brown precipitate of Ag₂O which is dissolved on addition of an excess of aqueous ammonia under the formation of 
[Ag(NH₃)₂]⁺. The silver diamine complex is reduced by glucose to metallic silver. Glucose is oxidized to gluconic acid. 



The Tollens test is important in carbohydrate chemistry, for proof of structure. The test is specific for reducing sugars. Fructose is also capable of reducing Tollens solution, and is thus classified a "reducing sugar". Under basic conditions fructose is converted into glucose. 

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