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Tollens' reagent (chemical formula ()) is a chemical reagent used to distinguish between aldehydes and ketones along with some alpha-hydroxy ketones which can tautomerize into aldehydes. The reagent consists of a solution of silver nitrate , ammonium hydroxide and some sodium hydroxide (to maintain a basic pH of the reagent solution).
Reagents are "substances or compounds that are added to a system in order to bring about a chemical reaction or are added to see if a reaction occurs." [1] Some reagents are just a single element. However, most processes require reagents made of chemical compounds. Some of the most common ones used widely for specific reactive functions are ...
Unable to resist the call of his former professor Wöhler, Tollens returned to Göttingen in 1872 and there he remained in various positions until he died in 1918. It was during this final time in Göttingen that he started his work on carbohydrates, which yielded structures of several sugars, the Tollens' reagent, and most of his publications.
Brady's reagent or Borche's reagent, is prepared by dissolving DNPH in a solution containing methanol and some concentrated sulfuric acid. This solution is used to detect ketones and aldehydes . A positive test is signalled by the formation of a yellow, orange or red precipitate of the dinitrophenylhydrazone.
In organic chemistry, Fehling's solution is a chemical reagent used to differentiate between water-soluble carbohydrate and ketone (>C=O) functional groups, and as a test for reducing sugars and non-reducing sugars, supplementary to the Tollens' reagent test. The test was developed by German chemist Hermann von Fehling in 1849. [1]
Phloroglucinol is a reagent of the Tollens' test for pentoses. This test relies on reaction of the furfural with phloroglucinol to produce a colored compound with high molar absorptivity. [26] A solution of hydrochloric acid and phloroglucinol is also used for the detection of lignin (Wiesner test).
An oligosaccharide has both a reducing and a non-reducing end. The reducing end of an oligosaccharide is the monosaccharide residue with hemiacetal functionality, thereby capable of reducing the Tollens’ reagent, while the non-reducing end is the monosaccharide residue in acetal form, thus incapable of reducing the Tollens’ reagent. [2]
It is soluble in ammonia solution, producing active compound of Tollens' reagent. A slurry of Ag 2 O is readily attacked by acids: Ag 2 O + 2 HX → 2 AgX + H 2. where HX = HF, HCl, HBr, HI, or CF 3 COOH. It will also react with solutions of alkali chlorides to precipitate silver chloride, leaving a solution of the corresponding alkali hydroxide.