4 Questions
Add 3 ml of Barfoed's reagent, a solution of cupric acetate and acetic acid. Heat the solution in a boiling water bath for 6 minutes. Tube glucose lactose starch observation 4. Bials Test uses concentrated HCl as a dehydrating acid and ______ + traces of ferric chloride as condensation reagent. The test reagent dehydrates pentoses to form furfural. Furfural further reacts with ______ and the iron ion present in the test reagent to produce a bluish or green product, while hexoses yield muddy-brown to grey condensation product. Method: Put 2 ml of a sample solution in a test tube. Add 3 ml of Bial's reagent, a solution of , HCl, and ferric chloride to each tube. Heat the tubes gently in hot water bath. If the color is not obvious, more water can be added to the tube. Tube 1-glucose 2-ribose observation 5. Seliwanoff's Test uses 6M HCl as dehydrating agent and res as condensation reagent. The test reagent dehydrates ketohexoses to form 5-hydroxymethylfurfural. 5-hydroxymethylfurfural further condenses with res______ present in the test reagent to produce a cherry red product within two minutes. Aldohexoses react to form the same product, but do so more slowly giving yellow to faint pink color.
orcinol
Add 3 ml of Barfoed's reagent, a solution of cupric acetate and acetic acid. Heat the solution in a boiling water bath for 6 minutes. Tube glucose lactose starch observation 4. Bials Test uses concentrated ______ as a dehydrating acid and orcinol + traces of ferric chloride as condensation reagent. The test reagent dehydrates pentoses to form furfural. Furfural further reacts with orcinol and the iron ion present in the test reagent to produce a bluish or green product, while hexoses yield muddy-brown to grey condensation product. Method: Put 2 ml of a sample solution in a test tube. Add 3 ml of Bial's reagent, a solution of orcinol, ______, and ______ to each tube. Heat the tubes gently in hot water bath. If the color is not obvious, more water can be added to the tube. Tube 1-glucose 2-ribose observation 5. Seliwanoff's Test uses 6M ______ as dehydrating agent and resorcinol as condensation reagent. The test reagent dehydrates ketohexoses to form 5-hydroxymethylfurfural. 5-hydroxymethylfurfural further condenses with resorcinol present in the test reagent to produce a cherry red product within two minutes. Aldohexoses react to form the same product, but do so more slowly giving yellow to faint pink color.
HCl
Add 3 ml of Barfoed's reagent, a solution of cupric acetate and acetic acid. Heat the solution in a boiling water bath for 6 minutes. Tube glucose lactose starch observation 4. Bials Test uses concentrated HCl as a dehydrating acid and orcinol + traces of ______ as condensation reagent. The test reagent dehydrates pentoses to form furfural. Furfural further reacts with orcinol and the iron ion present in the test reagent to produce a bluish or green product, while hexoses yield muddy-brown to grey condensation product. Method: Put 2 ml of a sample solution in a test tube. Add 3 ml of Bial's reagent, a solution of orcinol, HCl, and ______ to each tube. Heat the tubes gently in hot water bath. If the color is not obvious, more water can be added to the tube. Tube 1-glucose 2-ribose observation 5. Seliwanoff's Test uses 6M HCl as dehydrating agent and resorcinol as condensation reagent. The test reagent dehydrates ketohexoses to form 5-hydroxymethylfurfural. 5-hydroxymethylfurfural further condenses with resorcinol present in the test reagent to produce a cherry red product within two minutes. Aldohexoses react to form the same product, but do so more slowly giving yellow to faint pink color.
ferric chloride
Add 3 ml of Barfoed's reagent, a solution of cupric acetate and acetic acid. Heat the solution in a boiling water bath for 6 minutes. Tube glucose lactose starch observation 4. Bials Test uses concentrated HCl as a dehydrating acid and orcinol + traces of ferric chloride as condensation reagent. The test reagent dehydrates pentoses to form . Furfural further reacts with orcinol and the iron ion present in the test reagent to produce a bluish or green product, while hexoses yield muddy-brown to grey condensation product. Method: Put 2 ml of a sample solution in a test tube. Add 3 ml of Bial's reagent, a solution of orcinol, HCl, and ferric chloride to each tube. Heat the tubes gently in hot water bath. If the color is not obvious, more water can be added to the tube. Tube 1-glucose 2-ribose observation 5. Seliwanoff's Test uses 6M HCl as dehydrating agent and resorcinol as condensation reagent. The test reagent dehydrates ketohexoses to form 5-hydroxymethyl. 5-hydroxymethyl______ further condenses with resorcinol present in the test reagent to produce a cherry red product within two minutes. Aldohexoses react to form the same product, but do so more slowly giving yellow to faint pink color.
furfural
Study Notes
Carbohydrates
- Carbohydrates are the primary source of energy for living things and serve as extracellular structural elements.
- They are defined as polyhydroxy aldehydes or polyhydroxy ketones and have a general formula (CH2O)n.
- D-glucose is used in the human body.
Classification of Carbohydrates
- Simple sugars (monosaccharides) contain one sugar unit.
- Complex sugars can be broken down into smaller sugar units through hydrolysis.
- Disaccharides contain two monosaccharide units, oligosaccharides contain 3-9 units, and polysaccharides contain more than 9 units.
Reducing and Non-Reducing Sugars
- Reducing sugars have an oxygen atom on the anomeric carbon that is not attached to any other structure, allowing them to act as a reducing agent.
- Non-reducing sugars lack this oxygen atom.
Solubility of Sugars
- Monosaccharides and disaccharides can be dissolved freely in water due to its polar nature.
- Polysaccharides have high molecular weights, making them difficult to dissolve in water, resulting in colloidal solutions.
Chemical Properties of Carbohydrates
- Five qualitative tests can be used to identify carbohydrates:
- Molisch test: specific for all carbohydrates, detects the presence of carbohydrates.
- Benedict's test: detects the presence of reducing sugars.
- Barfoed's test: distinguishes between monosaccharides, disaccharides, and polysaccharides.
- Bial's test: distinguishes between pentose and hexose monosaccharides.
- Seliwanoff's test: distinguishes between aldoses and ketoses.
Molisch Test
- Dehydrates pentoses to form furfural and hexoses to form 5-hydroxymethyl furfural.
- Furfural and 5-hydroxymethyl furfural react with α-naphthol to produce a purple ring.
Benedict's Test
- Detects the presence of reducing sugars.
- Reducing sugars are oxidized by copper sulfate to form a carboxylic acid and a reddish precipitate of copper (I) oxide.
Barfoed's Test
- Distinguishes between monosaccharides, disaccharides, and polysaccharides.
- Reducing monosaccharides are oxidized by copper ions to form a carboxylic acid and a reddish precipitate of copper (I) oxide within three minutes.
Bial's Test
- Distinguishes between pentose and hexose monosaccharides.
- Dehydrates pentoses to form furfural, which reacts with orcinol and ferric chloride to produce a bluish or green product.
Seliwanoff's Test
- Distinguishes between aldoses and ketoses.
- Dehydrates ketohexoses to form 5-hydroxymethylfurfural, which reacts with resorcinol to produce a cherry red product within two minutes.
Test your knowledge on the qualitative tests used to identify carbohydrates, the key source of energy for living things. Learn about the structures and classifications of carbohydrates, including simple sugars that end with -ose.
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free
