Mild oxidizing agents such as bromine water, silver oxide, sodium hypobromite etc. oxidize glucose to gluconic acid converting -CHO group to -COOH group.
Reducing sugars are easily oxidized to give carboxylic acid.
carbohydrates (having C=O) can be oxidised to carboxylic acids.
Such carbohydrates are classified as reducing sugars based on Benedicts or Fehlings tests
Aldoses (as they come from aldehydes)are readily oxidised.
In order for oxidation to occur, the cyclic form must first ring-open to give the reactive aldehyde.
Ketoses can also be reducing sugars because they can transform to (by tautomerisation) aldoses via an enediol.
Wednesday, January 23, 2008
IIT JEE Revision Carbohydrates - Reduction
Reaction type: Nucleophilic Addition
The C=O groups in open chain forms of carbohydrates can be reduced to alcohols by sodium borohydride, NaBH4, or catalytic hydrogenation (H2, Ni, EtOH/H2O).
The products are known as "alditols"
LiAlH4 is usually not suitable because of its incompatibility with the polar solvents.
Aldehydes, i.e. aldoses, are reduced to primary alcohols.
Ketones, i.e. ketoses, are reduced to secondary alcohols.
The C=O groups in open chain forms of carbohydrates can be reduced to alcohols by sodium borohydride, NaBH4, or catalytic hydrogenation (H2, Ni, EtOH/H2O).
The products are known as "alditols"
LiAlH4 is usually not suitable because of its incompatibility with the polar solvents.
Aldehydes, i.e. aldoses, are reduced to primary alcohols.
Ketones, i.e. ketoses, are reduced to secondary alcohols.
IIT JEE Revision Glycoside Formation
The open form of D-glucose (and many other sugars) can cyclize to form hemiacetals.
Under acidic conditions the hemiacetal form of glucose can react with other alcohols to give acetals known as glycosides. These are widely distributed in nature.
When a hemiacetal joins with an alcohol with the elimination of a water molecule, an acetal is formed.
eg. monosaccharides can be converted to glycosides by treatment with alcohols.
Under acidic conditions the hemiacetal form of glucose can react with other alcohols to give acetals known as glycosides. These are widely distributed in nature.
When a hemiacetal joins with an alcohol with the elimination of a water molecule, an acetal is formed.
eg. monosaccharides can be converted to glycosides by treatment with alcohols.
IIT JEE Revision Hydrolysis of Sucrose
Sucrose is hdyrolysed by concentrated alcoholic solution of hydrochloric acid.
The hydrolysis is carried out at about 323 K by heating on a water bath for about two hours.
Hydrolysis gives glucose and fructose
C12H22O11 --> C6H12O6 + C6H12O6
Glucose and fructose both have the same molecular formula.
Glucose being almost insoluble in alcohol crystallises on colling while fructose being comparatively more soluble remains in the solution
The hydrolysis is carried out at about 323 K by heating on a water bath for about two hours.
Hydrolysis gives glucose and fructose
C12H22O11 --> C6H12O6 + C6H12O6
Glucose and fructose both have the same molecular formula.
Glucose being almost insoluble in alcohol crystallises on colling while fructose being comparatively more soluble remains in the solution
IIT JEE Revision Ch. 32 Amino Acids and Peptides Core Point
Amino acids and peptides:
General structure (only primary structure for peptides) and
physical properties.
------------
Chapter Core Points
amino acids are organic compounds containing both an amino group (NH2) and carboxylic group (COOH). They are represented by the general formula:
R
|
C-COOH
|
NH2
amino acids contain an amino group attached to alpha carbon of a carboxylic acid.
Amino acids are the basic units of proteins.
There are twenty amino acids commonly found in proteins.
Except Glycine all other amino acids contain asymmetric carbon atom next to the carboxylic acid.
Peptide linkage: The condensation of two amino acids with the eliminatin of H2O (H from NH2 and OH from the acid side produces CO-NH linkage, which in protein chemistry is known as peptide linkage.
General structure (only primary structure for peptides) and
physical properties.
------------
Chapter Core Points
amino acids are organic compounds containing both an amino group (NH2) and carboxylic group (COOH). They are represented by the general formula:
R
|
C-COOH
|
NH2
amino acids contain an amino group attached to alpha carbon of a carboxylic acid.
Amino acids are the basic units of proteins.
There are twenty amino acids commonly found in proteins.
Except Glycine all other amino acids contain asymmetric carbon atom next to the carboxylic acid.
Peptide linkage: The condensation of two amino acids with the eliminatin of H2O (H from NH2 and OH from the acid side produces CO-NH linkage, which in protein chemistry is known as peptide linkage.
IIT JEE Revision Amino Acids
Amino acids are organic compounds containing both an amino group (NH2) and carboxylic group (COOH). They are represented by the general formula:
R
|
C-COOH
|
NH2
Essential amino acids
These amino acids are required by the body but are not made by our bodies. hence they must be supplied in diets.
Valine
Leucine
Isoleucine
Phenylalanine
Methionine
Trptophan
threonine
Lysine
Agrinine
R
|
C-COOH
|
NH2
Essential amino acids
These amino acids are required by the body but are not made by our bodies. hence they must be supplied in diets.
Valine
Leucine
Isoleucine
Phenylalanine
Methionine
Trptophan
threonine
Lysine
Agrinine
IIT JEE Revision Amino Acids Zwitterion
This is a doubly charged ion.
The pH of the solution at which the species becomes zwitterion is known as isoelectric point.
The pH of the solution at which the species becomes zwitterion is known as isoelectric point.
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