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Tollens' test for aldehyde: left side positive (silver mirror), right side negative Ball-and-stick model of the diamminesilver(I) complex. 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.
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Formic acid (HCO 2 H) also gives a positive Fehling's test result, as it does with Tollens' (eponymous for Bernhard Christian Gottfried Tollens (1841 – 1918)) test and Benedict's solution also. The positive tests are consistent with it being readily oxidizable to carbon dioxide. The solution cannot differentiate between benzaldehyde and acetone.
A positive test is signalled by the formation of a yellow, orange or red precipitate of the dinitrophenylhydrazone. Aromatic carbonyls give red precipitates whereas aliphatic carbonyls give more yellow color. [2] The reaction between DNPH and a generic ketone to form a hydrazone is shown below:
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).
In propositional logic, modus tollens (/ ˈ m oʊ d ə s ˈ t ɒ l ɛ n z /) (MT), also known as modus tollendo tollens (Latin for "mode that by denying denies") [2] and denying the consequent, [3] is a deductive argument form and a rule of inference. Modus tollens is a mixed hypothetical syllogism that takes the form of "If P, then Q. Not Q ...
All monosaccharide ketoses are reducing sugars, because they can tautomerize into aldoses via an enediol intermediate, and the resulting aldehyde group can be oxidised, for example in the Tollens' test or Benedict's test. [3] Ketoses that are bound into glycosides, for example in the case of the fructose moiety of sucrose, are nonreducing ...
Modus ponens is a mixed hypothetical syllogism and is closely related to another valid form of argument, modus tollens. Both have apparently similar but invalid forms: affirming the consequent and denying the antecedent. Constructive dilemma is the disjunctive version of modus ponens. The history of modus ponens goes back to antiquity. [4]