Editing Reducing sugar (section)

==Characterization==
Several [[qualitative organic analysis|qualitative tests]] are used to detect the presence of reducing sugars. Two of them use solutions of [[cupric|copper(II)]] ions: [[Benedict's reagent]] (Cu<sup>2+</sup> in aqueous sodium citrate) and [[Fehling's solution]] (Cu<sup>2+</sup> in aqueous sodium tartrate).<ref name=Klein>{{cite book |last1=Klein |first1=David.  |date=2012 |title=Organic Chemistry |edition=First |publisher=John Wiley & Sons |page=1159 |isbn=978-0471756149}}</ref> The reducing sugar reduces the [[copper|copper(II)]] ions in these test solutions to copper(I), which then forms a brick red [[copper(I) oxide]] precipitate. Reducing sugars can also be detected with the addition of [[Tollen's reagent]], which consist of silver ions (Ag<sup>+</sup>) in aqueous ammonia.<ref name=Klein/> When Tollen's reagent is added to an aldehyde, it precipitates silver metal, often forming a silver mirror on clean glassware.<ref name=Campbell/>

[[3,5-dinitrosalicylic acid]] is another test reagent, one that allows quantitative detection. It reacts with a reducing sugar to form [[3-amino-5-nitrosalicylic acid]], which can be measured by [[spectrophotometry]] to determine the amount of reducing sugar that was present.<ref>{{cite journal |last1=Leung |first1=David W. M. |last2=Thorpe |first2=Trevor A. |date=April 1984 |title=Interference by edta and calcium ions of the 3,5-dinitrosalicylate reducing sugar assay |journal=Phytochemistry |publisher=Pergamon Press  |volume=23 |issue=12 |pages=2949–2950 |doi=10.1016/0031-9422(84)83048-4  |bibcode=1984PChem..23.2949L |issn=0031-9422 }}</ref>

Some sugars, such as sucrose, do not react with any of the reducing-sugar test solutions. However, a non-reducing sugar can be [[Hydrolysis#Polysaccharides|hydrolyzed]] using dilute [[hydrochloric acid]]. After hydrolysis and neutralization of the acid, the product may be a reducing sugar that gives normal reactions with the test solutions.

All carbohydrates are converted to aldehydes and respond positively in [[Molisch's test]]. But the test has a faster rate when it comes to monosaccharides.