Schiff test

Schiff s reagent analy chem An aqueous solution of rosaniline and sulfurous add used in the Schiff test. shifs re,a-(3nt ... 

Schiff test analychem A test for aldehydes by using an aqueous solution of rosaniline... 

Formaldehyde is commonly detected by the Schiff test (above), and confirmed by the formation of a dimethyl derivative with a mp of I89°C. 

Schiff Test. Add 1 drop (30 mg) of the unknown to 1 mL of Schiff s reagent. A magenta color will appear within 10 min with aldehydes. Compare the color of your unknown with that of a known aldehyde. 

The typical aldehyde reactions of D-(-H)-glucose—osazone formation, and perhaps reduction of Tollens and Fehling s reagents—are presumably due to a small amount of open-chain compound, which is replenished as fast as it is consumed. The concentration of this open-chain structure is, however, too low (less than 0.5%) for certain easily reversible aldehyde reactions like bisulfite addition and the Schiff test. 

Tollen s test, described previously, can be used to distinguish between the aldehyde and -the ether. Also, oxime formation with hydroxylamine, and Schiff test with the fuchsin-aldehyde reagent to fom a characteristic magenta color can be used. 

Therefore, to distinguish between n-propyl ether and diethyl acetal, one can add acid to both compounds and then perform either Tollen s test or Schiff test both tests are described in previous problems. The appearance of a silver mirror can identify it as acetaldehyde, that is, the compound is diethyl acetal. 

To distinguish between dioxane and trioxane, one can decyclize trioxane back into formaldehydes by adding acid and heating and then perform the Tollen s test or Schiff test. 

The evidence from the Schiff test that aldehydes are produced in the lipid droplets of ordinary formalin-fixed tissues, as cited in Section V.2, certainly suggests that aldehydes are present. The questions of importance here are (1) whether or not detectable quantities of ketonic lipids are present as weU, and (2) whether the methods of handling the tissues and reagents can be performed in such a way as to avoid the production of aldehydes from tissue lipids. 

The carbohydrates failed to undergo certain reactions that were typical of aldehydes. Although the hexoses and pentoses were readily oxidized at C-1 under mild alkaline conditions, they did not give a positive result with the Schiff test (reaction with basic fuchsin), and they did not form bisulfite addition products, reactions that are typical of aldehydes. The cyanohydrin and phenylhydrazine reactions also went much more slowly than they did for other a-hydroxy aldehydes. 

Gives some of the tests for acetaldehyde, but more feebly e.g., it restores the colour to SchifF s reagent, gives a yellow resin with NaOH, and responds to the nitroprusside test. With ammoniacal AgN03, it gives a silver minor only after 2 -3 minutes warming. It does not give the iodoform reaction. 

Solution in aqueous NaaCOa reduces silver nitrate (Schiff s test). 

Schiff s test. Dissolve about o i g. of uric acid in NsjCOj solution and pour some of this solution on to a filter-paper which has been moistened with AgNO solution a black stain of metallic silver results. 

An alternative procedure for the above test is as follows. Mix 2-3 ml. of 2 per cent, aqueous paraperiodic acid solution with 1 drop of dilute sulphuric acid (ca. 2 5N) and add 20-30 mg. of the compound. Shake the mixture for 5 minutes, and then pass sulphur dioxide through the solution until it acquires a pale yellow colour (to remove the excess of periodic acid and also iodic acid formed in the reaction). Add 1-2 ml. of Schiff s reagent (Section 111,70) the production of a violet colour constitutes a positive test. 

Liquid Fabric Softeners. The principal functions of fabric softeners are to minimize the problem of static electricity and to keep fabrics soft (see Antistatic agents). In these laundry additives, the fragrance must reinforce the sense of softness that is the desired result of their use. Most fabric softeners have a pH of about 3.5, which limits the materials that can be used in the fragrances. For example, acetals cannot be used because they break down and cause malodor problems in addition, there is the likelihood of discoloration from Schiff bases, oakmoss extracts, and some specialty chemicals. Testing of fragrance materials in product bases should take place under accelerated aging conditions (eg, 40°C in plastic bottles) to check for odor stabiUty and discoloration. 

A solution of magenta decolourised by sulphur dioxide becomes violet on the addition of a drop of aldehyde (Schiff . Prepare a weak solution of magenta by dissolving a crystal in half a test-tube of water and bubbling in sulphur dioxide until the colour disappears. Now add a few drops of aldehyde. 

PS(180)1909>, or from its derived Schiff base (Equation 81) <2004JHC281> the same is true of the examples 264-266 in Scheme 64 <2000FA109>. The latter have been tested as antifungal agents. 

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