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Showing posts with label PRACTICAL ORGANIC. Show all posts
Showing posts with label PRACTICAL ORGANIC. Show all posts

Tuesday, February 4, 2020

Both glucose and fructose are reducing sugars but sucrose is non-reducing in nature. Why?


Glucose and fructose are reducing sugars as they reduce Fehling's solution and Tollen's reagent. In aqueous solution these saccharides containing hemiacetal or hemiketals exist in equilibrium with a small amount of open chain aIdehyde or alpha-hydroxy ketonic form. When treated with the above said reagents the open chain form is oxidised. As the open chain form is consumed with some reagent, the equilibrium gets disturbed and more of open chain aldehyde or alpha-hydroxy ketone is formed and thus reduction of these reagents keeps on going. On the other hand sucrose is a non reducing sugar because it does not reduce these reagents. This is due to the reason that the reducing groups present in the constituting monosaccharide units are not free and are involved in the formation of glycosidic linkages. 

Related Questions:

Wednesday, January 29, 2020

What is Dunstan's test , How can it use for test Glycerol ?

When phenolphthalein is added to dilute cold solution of borax, a pink colour is produced. When glycerol is mixed in it, in cold, the colour disappears, but on heating colour reappears. It is a characteristic test of glycerol. This test is called Dunstan's test.

Related Questions:

Both glucose and fructose are reducing sugars but sucrose is non-reducing in nature. Why?
Fructose contains a keto group, yet it reduces Fehling solution and Tollen's reagent. Why ?
What is Dunstan's test , How can it use for test Glycerol ?
What is luca's reagent and where is luca's reagent uses ?
What is Victory-Meyer's test and how can distinction between 1°, 2° and 3° alcohols by this ?
Benzaldehyde gives a positive test with Tollen's reagent but not with Benedict's and Fehling's solution. Comment why?
Aromatic amines are lesser basic than aliphatic amines.why ?
Which are the compounds gives positive Tollen's test?
What is Tollen's reagent?
What is Carbylamine test or Isocyanide test ?
What is Hinsberg's reagent and where Hinsberg's test use?
N-Ethyl-N-methyl propanamine does not show optical activity why?


Fructose contains a keto group, yet it reduces Fehling solution and Tollen's reagent. Why ?



Fructose although contains a ketone group yet it acts as a reducing sugar. This is explained by the formation of glucose from fructose by enolisation. Enolisation results in the formation of glucose from fructose and vice versa. (Lobry de Bruyn Van Ekenstein rearrangement).

Tuesday, January 28, 2020

What is lucas reagent and where is lucas reagent uses ?

Anhydrous zinc chloride and concentrate HCl is known as Lucas reagent and it is use for distinguish between primary, secondary and tertiary alcohols:



Related Questions:

Both glucose and fructose are reducing sugars but sucrose is non-reducing in nature. Why?
Fructose contains a keto group, yet it reduces Fehling solution and Tollen's reagent. Why ?
What is Dunstan's test , How can it use for test Glycerol ?
What is luca's reagent and where is luca's reagent uses ?
What is Victory-Meyer's test and how can distinction between 1°, 2° and 3° alcohols by this ?
Benzaldehyde gives a positive test with Tollen's reagent but not with Benedict's and Fehling's solution. Comment why?
Aromatic amines are lesser basic than aliphatic amines.why ?
Which are the compounds gives positive Tollen's test?
What is Tollen's reagent?
What is Carbylamine test or Isocyanide test ?
What is Hinsberg's reagent and where Hinsberg's test use?
N-Ethyl-N-methyl propanamine does not show optical activity why?

What is Victory-Meyer's test and how can distinction between 1°, 2° and 3° alcohols by this ?

Victory- Meyer's test use for distinction of 1°, 2° and 3° alcohols which include a series of reagent as given below :



Benzaldehyde gives a positive test with Tollen's reagent but not with Benedict's and Fehling's solution. Comment why?

Benedict's solution (Cu+2 citric acid + base) and Fehling's solution (Cu+2  tartaric acid + base) are weaker oxidising agents than Tollen's reagent [Ag(NH3)2]+, they oxidise alipharic aldehydes only, but are not capable of oxidising aromatic aldehydes.

Related Questions:

Both glucose and fructose are reducing sugars but sucrose is non-reducing in nature. Why?
Fructose contains a keto group, yet it reduces Fehling solution and Tollen's reagent. Why ?
What is Dunstan's test , How can it use for test Glycerol ?
What is luca's reagent and where is luca's reagent uses ?
What is Victory-Meyer's test and how can distinction between 1°, 2° and 3° alcohols by this ?
Benzaldehyde gives a positive test with Tollen's reagent but not with Benedict's and Fehling's solution. Comment why?
Aromatic amines are lesser basic than aliphatic amines.why ?
Which are the compounds gives positive Tollen's test?
What is Tollen's reagent?
What is Carbylamine test or Isocyanide test ?
What is Hinsberg's reagent and where Hinsberg's test use?
N-Ethyl-N-methyl propanamine does not show optical activity why?

Aromatic amines are lesser basic than aliphatic amines.why ?


Aliphatic amines are more basic in nature than aromatic amines because In aliphatic amines the electron density around N atom increases due to - I effect of alky  group and thus chance for proton attack also Increases.
On the other hand in aromatic amines the electron density around N atom decreases due to withdrawing nature of aromatic ring hence thus chance for proton attack on nitrogen atom decreases.

Related Questions:

Both glucose and fructose are reducing sugars but sucrose is non-reducing in nature. Why?
Fructose contains a keto group, yet it reduces Fehling solution and Tollen's reagent. Why ?
What is Dunstan's test , How can it use for test Glycerol ?
What is luca's reagent and where is luca's reagent uses ?
What is Victory-Meyer's test and how can distinction between 1°, 2° and 3° alcohols by this ?
Benzaldehyde gives a positive test with Tollen's reagent but not with Benedict's and Fehling's solution. Comment why?
Aromatic amines are lesser basic than aliphatic amines.why ?
Which are the compounds gives positive Tollen's test?
What is Tollen's reagent?
What is Carbylamine test or Isocyanide test ?
What is Hinsberg's reagent and where Hinsberg's test use?
N-Ethyl-N-methyl propanamine does not show optical activity why?