Bebeto tollens' reagent

Tollens reagent

1. Tollens’ reagent, reaction and application Seminar by, Bebeto G Nair 199305 2 nd M.Sc Analytical Chemistry

2. Tollens reagent Discovered by German chemist Bernhard Tollens Presence of an Aldehyde or alpha-hydroxy ketone functional groups  It is a colorless, basic, mild oxidizing agent and aqueous solution containing silver ions coordinated to ammonia, forming a diaminesilver (I) complex [Ag(NH 3 ) 2 ] + . Tollens' reagent itself is reduced to metallic silver. Since Tollens’ Reagent has a relatively short shelf life, the reagent is not commercially sold. 199305 Tollens’ Reagent 09/04/2021

3. Preparation Step 1:  Aqueous silver nitrate is mixed with aqueous sodium hydroxide. Silver ions in the presence of hydroxide ions come out of solution as a brown precipitate of silver(l) oxide, Ag 2 O (s). Step 2:  Aqueous ammonia is added drop-wise until the precipitated silver oxide completely dissolves. This precipitate dissolves in aqueous ammonia forming the diamine silver (l) ion, [Ag(NH 3 ) 2 ] + 199305 Tollens’ Reagent 09/04/2021

4. Another method of preparation Aqueous ammonia can be added directly to silver nitrate solution. At first ammonia will induce formation of solid silver oxide But with additional ammonia, this solid precipitate dissolve to give a clear solution of diamine silver (l) coordinated complex , [Ag(NH 3 ) 2 ] + Filter this reagent before use to prevent false positive results. 199305 Tollens’ Reagent 09/04/2021

5. Application Qualitative organic analysis Tollens' reagent gives a negative test for most ketones, with  α- hydroxy ketone being one exception (e.g. - hydroxy acetone) . Tollens' reagent gives a positive test for the p resence of an Aldehyde 199305 Tollens’ Reagent 09/04/2021

6. Mechanism for reaction of Tollens' reagent with aldehydes https://chemistry.stackexchange.com/questions/13918/mechanism-for-reaction-of-tollens-reagent-with-aldehydes 199305 09/04/2021

7. Glucose gives silver mirror test with Tollens' reagent. It is due to the presence of an aldehydic group  (−CHO) . https://www.toppr.com/ask/en-in/question/glucose-gives-silver-mirror-with-tollens-reagent-it-shows-the/ 199305 Tollens’ Reagent 09/04/2021

8. 2. Staining Fontana-Masson Stain : It is a silver stain technique Detection of melanin, argentaffin and lipofuscin in tissue sections By the reduction of Silver nitrate to metallic Silver. 199305 Tollens’ Reagent 09/04/2021

9. 3. Silver mirroring Application of silver mirror to glassware Inside of insulated vaccum flask, high quality mirror, Telescope mirrors https://byjus.com/chemistry/tollens-test/ 199305 Tollens’ Reagent 09/04/2021

10. References   Tollens, B. (1882).  " Ueber ammon-alkalische Silberlösung als Reagens auf Aldehyd “ -   doi : 10.1002/cber.18820150243 .   http://library.med.utah.edu/WebPath/HISTHTML/MANUALS/FONTANA.PDF http://www.chemguide.co.uk/organicprops/carbonyls/oxidation.html   Oshitna , K.; Tollens, B. (1901). " Ueber Spectral- reactionen des Methylfurfurols ". Ber. Dtsch . Chem. Ges .  34 : 1425. Hart, M. (1992). Manual of scientific glassblowing. St. Helens, Merseyside [England]: British Society of Scientific Glassblowers.  ISBN   0-9518216-0-1 . N. Chitvoranund1; S. Jiemsirilers ; D.P. Kashima (2013). "Effects of surface treatments on adhesion of silver film on glass substrate fabricated by electroless plating". Journal of the Australian Ceramic Society.  49 : 62–69. C. Heber D. (February 1911).  "Methods of Silvering Mirrors“ -   doi : 10.1086/122040 . Svehla , G.; Vogel, Arthur Anton (1996). Vogel's Qualitative Inorganic Analysis. New York: Longman.  ISBN   0-582-21866-7 . https://www.toppr.com/ask/en-in/question/glucose-gives-silver-mirror-with-tollens-reagent-it-shows-the/ https://byjus.com/chemistry/tollens-test/ https://www.chemistrylearner.com/tollens-test.html#:~:text=Tollens'%20test%2C%20also%20known%20as,)%20%5B1%2D4%5D . https://chemistry.stackexchange.com/questions/13918/mechanism-for-reaction-of-tollens-reagent-with-aldehydes https://www.chemistrylearner.com/tollens-test.html#:~:text=Tollens'%20test%2C%20also%20known%20as,)%20%5B1%2D4%5D.

11. Thank You