ข้อความ 8วิจารณ์ผลการทดลองคาร์โบไฮเ

ข้อความ 8


วิจารณ์ผลการทดลองคาร์โบไฮเดรต

The Molisch Test
Shows positive test for:
All carbohydrates. Monosaccharides give a rapid positive test. Disaccharides and polysaccharides react slower.
Reactions:
The test reagent dehydrates pentoses to form furfural (top reaction) and dehydrates hexoses to form 5-hydroxymethyl furfural (bottom reaction). The furfurals further react with -naphthol present in the test reagent to produce a purple product (reaction not shown).

How to perform the test:
Two ml of a sample solution is placed in a test tube. Two drops of the Molisch reagent (a solution of -napthol in 95% ethanol) is added. The solution is then poured slowly into a tube containing two ml of concentrated sulfuric acid so that two layers form.

A positive test is indicated by:
The formation of a purple product at the interface of the two layers.

a negative test (left) and a positive test (right)


Barfoed's Test
Shows positive test for:
Reducing monosaccharides
Reactions:
Reducing monosaccharides are oxidized by the copper ion in solution to form a carboxylic acid and a reddish precipitate of copper (I) oxide within three minutes. Reducing disaccharides undergo the same reaction, but do so at a slower rate.

How to perform the test:
One ml of a sample solution is placed in a test tube. Three ml of Barfoed's reagent (a solution of cupric acetate and acetic acid) is added. The solution is then heated in a boiling water bath for three minutes.

A positive test is indicated by:
The formation of a reddish precipitate within three minutes.

a negative test (left) and a positive test (right)






Iodine/Potassium Iodide Test

Shows positive test for:
Starch

Reactions:
Iodine complexes with starch to form a blue-black product. Note that other polysaccharides may give other colors including blue or red.

How to perform the test:
Two ml of a sample solution is placed in a test tube. Two drops of iodine/potassium iodide solution and one ml of water are added.

A positive test is indicated by:
The formation of a blue-black complex.

a negative test (left) and a positive test (right)



Benedict's Test
Shows positive test for:
Reducing sugars

Reactions:
Reducing sugars are oxidized by the copper ion in solution to form a carboxylic acid and a reddish precipitate of copper (I) oxide.

How to perform the test:
One ml of a sample solution is placed in a test tube. Two ml of Benedict's reagent (a solution of sodium citrate and sodium carbonate mixed with a solution of copper sulfate) is added. The solution is then heated in a boiling water bath for three minutes.

A positive test is indicated by:
The formation of a reddish precipitate within three minutes.
A negative test (left) and a positive test (right)



Seliwanoff's Test
Shows positive test for:
Ketoses
Reactions:
The test reagent dehydrates ketohexoses to form 5-hydroxymethylfurfural. 5-hydroxymethylfurfural further reacts with resorcinol present in the test reagent to produce a red product within two minutes (reaction not shown). Aldohexoses react to form the same product, but do so more slowly.

How to perform the test:
One half ml of a sample solution is placed in a test tube. Two ml of Seliwanoff's reagent (a solution of resorcinol and HCl) is added. The solution is then heated in a boiling water bath for two minutes.

A positive test is indicated by:
The formation of a red product.
A negative test (left) and a positive test (right)


Bial's Test
Shows positive test for:
Pentoses

Reactions:
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 product (reaction not shown).

How to perform the test:
Two ml of a sample solution is placed in a test tube. Two ml of Bial's reagent (a solution of orcinol, HCl and ferric chloride) is added. The solution is then heated gently in a Bunsen Burner or hot water bath. If the color is not obvious, more water can be added to the tube.

A positive test is indicated by:
The formation of a bluish product. All other colors indicate a negative result for pentoses. Note that hexoses generally react to form green, red, or brown products.

ผลลัพธ์ (อังกฤษ) 1:

Text 8Critics of the carbohydrate trials. The Molisch Test Shows positive test for: All carbohydrates. Monosaccharides give a rapid positive test. Disaccharides and polysaccharides react slower. Reactions: The test reagent dehydrates pentoses to form furfural (top reaction) and dehydrates hexoses to form 5-hydroxymethyl furfural (bottom reaction). The furfurals further react with -naphthol present in the test reagent to produce a purple product (reaction not shown). How to perform the test: Two ml of a sample solution is placed in a test tube. Two drops of the Molisch reagent (a solution of -napthol in 95% ethanol) is added. The solution is then poured slowly into a tube containing two ml of concentrated sulfuric acid so that two layers form. A positive test is indicated by: The formation of a purple product at the interface of the two layers. a negative test (left) and a positive test (right) Barfoed's Test Shows positive test for: Reducing monosaccharides Reactions: Reducing monosaccharides are oxidized by the copper ion in solution to form a carboxylic acid and a reddish precipitate of copper (I) oxide within three minutes. Reducing disaccharides undergo the same reaction, but do so at a slower rate. How to perform the test: One ml of a sample solution is placed in a test tube. Three ml of Barfoed's reagent (a solution of cupric acetate and acetic acid) is added. The solution is then heated in a boiling water bath for three minutes. A positive test is indicated by: The formation of a reddish precipitate within three minutes. a negative test (left) and a positive test (right) Iodine/Potassium Iodide Test Shows positive test for: Starch Reactions: Iodine complexes with starch to form a blue-black product. Note that other polysaccharides may give other colors including blue or red. How to perform the test: Two ml of a sample solution is placed in a test tube. Two drops of iodine/potassium iodide solution and one ml of water are added. A positive test is indicated by: The formation of a blue-black complex. a negative test (left) and a positive test (right) Benedict's Test Shows positive test for: Reducing sugars Reactions: Reducing sugars are oxidized by the copper ion in solution to form a carboxylic acid and a reddish precipitate of copper (I) oxide. How to perform the test: One ml of a sample solution is placed in a test tube. Two ml of Benedict's reagent (a solution of sodium citrate and sodium carbonate mixed with a solution of copper sulfate) is added. The solution is then heated in a boiling water bath for three minutes. A positive test is indicated by: The formation of a reddish precipitate within three minutes. A negative test (left) and a positive test (right) Seliwanoff's Test Shows positive test for: Ketoses Reactions: The test reagent dehydrates ketohexoses to form 5-hydroxymethylfurfural. 5-hydroxymethylfurfural further reacts with resorcinol present in the test reagent to produce a red product within two minutes (reaction not shown). Aldohexoses react to form the same product, but do so more slowly. How to perform the test: One half ml of a sample solution is placed in a test tube. Two ml of Seliwanoff's reagent (a solution of resorcinol and HCl) is added. The solution is then heated in a boiling water bath for two minutes. A positive test is indicated by: The formation of a red product. A negative test (left) and a positive test (right) Bial's Test Shows positive test for: Pentoses Reactions: 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 product (reaction not shown). How to perform the test: Two ml of a sample solution is placed in a test tube. Two ml of Bial's reagent (a solution of orcinol, HCl and ferric chloride) is added. The solution is then heated gently in a Bunsen Burner or hot water bath. If the color is not obvious, more water can be added to the tube. A positive test is indicated by: The formation of a bluish product. All other colors indicate a negative result for pentoses. Note that hexoses generally react to form green, red, or brown products.

ผลลัพธ์ (อังกฤษ) 2:

Text 8


reviews the results of carbohydrate

The Molisch Test
Shows positive Test for:
All carbohydrates. Monosaccharides give a Rapid positive Test. Disaccharides and polysaccharides React slower.
Reactions:
The Test reagent dehydrates pentoses to form furfural (top Reaction) and dehydrates hexoses to form. 5-hydroxymethyl furfural (bottom Reaction). The further Furfurals React with -naphthol present in the Test reagent to Produce a product Purple (Reaction not shown).

How to Perform the Test:
Two ml sample of a Test Solution is Placed in a tube. . Two drops of the Molisch reagent (a 95% Solution of -napthol in ethanol) is added. The Solution is then poured Slowly Into a tube containing sulfuric acid so that Two ml of Concentrated Two layers form.

A positive Test is indicated by:.
the Formation of a Purple product at the interface of the Two layers.

a negative Test (left) and a positive Test (Right)


Barfoed's Test
Shows positive Test for:
Reducing monosaccharides
Reactions:
Reducing monosaccharides are oxidized by the Copper ion in Solution to form. a carboxylic acid and a reddish precipitate of Copper (I) oxide Within Three minutes. Reducing disaccharides undergo the Same Reaction, but do so at a slower rate.

How to Perform the Test:
One ml of a sample Solution is Placed in a Test tube. . Three ml of Barfoed's reagent (a Solution of cupric acetate and acetic acid) is added. The Solution is then heated in a Boiling Water bath for Three minutes.

A positive Test is indicated by:
The Formation of a reddish precipitate Within Three minutes.

a negative Test (left) and a positive Test (Right)






Iodine / Potassium Iodide Test

Shows positive Test for:
Starch

Reactions:
Iodine complexes with starch to form a blue-Black product. Note that Other polysaccharides May give Other colors including blue or Red. .

How to Perform the Test:
Two ml of a sample Solution is Placed in a Test tube. Two drops of Iodine / potassium iodide Solution and one ml of Water are added.

A positive Test is indicated by:
The Formation of a blue-Black. Complex.

a negative Test (left) and a positive Test (Right)



Benedict's Test
Shows positive Test for:
Reducing sugars

Reactions:
Reducing sugars are oxidized by the Copper ion in Solution to form a carboxylic acid and a reddish precipitate of Copper (I). oxide.

How to Perform the Test:
One ml of a sample Solution is Placed in a Test tube. Two ml of Benedict's reagent (a Solution of Sodium citrate and Sodium carbonate mixed with a Solution of Copper sulfate) is added. The Solution is then. heated in a Boiling Water bath for Three minutes.

A positive Test is indicated by:
The Formation of a reddish precipitate Within Three minutes.
A negative Test (left) and a positive Test (Right)



Seliwanoff's Test
Shows positive Test for:
Ketoses
Reactions:.
The test reagent dehydrates ketohexoses to form 5-hydroxymethylfurfural. 5-hydroxymethylfurfural further reacts with resorcinol present in the test reagent to produce a red product within two minutes (reaction not shown). Aldohexoses react to form the same product, but do so more slowly. .

How to Perform the Test:
One Half ml of a sample Solution is Placed in a Test tube. Two ml of Seliwanoff's reagent (a Solution of resorcinol and HCl) is added. The Solution is then heated in a Boiling Water bath for Two minutes. .

A positive Test is indicated by:
The Formation of a Red product.
A negative Test (left) and a positive Test (Right)


Bial's Test
Shows positive Test for:
pentoses

Reactions:
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 product (Reaction not shown).

How to Perform the Test:
Two ml of a sample Solution is Placed in a Test tube. Two ml of Bial's reagent (a Solution of. Orcinol, HCl and ferric chloride) is added. The Solution is then heated gently in a Bunsen Burner or hot Water bath. If the Color is not Obvious, more Water Can be added to the tube.

A positive Test is indicated by:
The Formation. of a bluish product. All other colors indicate a negative result for pentoses. Note that hexoses generally react to form green, red, or brown products.