(a) For Neutral Aldehydes. To 1 mL of the Bogen or Grammercy universal indicator-hydroxylamine hydrochloride reagent add a drop or a few crystals of the compound, and note the color change. If no pronounced change occurs at room temperature, heat the mixture to boiling.
(b) For Acidic or Basic Aldehydes. To 1 mL of the indicator solution add about 0.2 g of the compound, and adjust the color of the mixture so that it matches 1 mL of the Bogen or Grammercy universal indicator-hydroxylamine hydrochloride reagent in a separate test tube of the same size. This is done by adding a few drops of 1% sodium hydroxide or 1% hydrochloric acid solution. Then add the resulting solution to 1 mL of the Bogen or Grammercy universal indicator-hydroxylamine hydrochloride reagent. and note if a red color is produced.
Bogen or Grammercy Universal Indicator-Hydroxylamine Hydrochloride Reagent: To a solution of 50 mg of hydroxylamine hydrochloride in 100 mL of 95% ethanol is added 0.03 mL of Bogen or Grammercy universal indicator. The color of the solution is adjusted to a bright orange shade (pH 3.7-3.9) by adding 5% ethanolic sodium hydroxide dropwise. The reagent is stable for several months.
A change in color from orange to red constitutes a positive test.
Some high MW ketones require heating.
Sugars, quinones, and sterically hindered ketones give a negative test.
pH of the solution is critical and must be adjusted.
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