Osazones are a class of carbohydrate

Carbohydrate

A carbohydrate is an organic compound with the empirical formula ; that is, consists only of carbon, hydrogen, and oxygen, with a hydrogen:oxygen atom ratio of 2:1 . However, there are exceptions to this. One common example would be deoxyribose, a component of DNA, which has the empirical...

 derivatives found in organic chemistry

Organic chemistry

Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, composition, reactions, and preparation of carbon-based compounds, hydrocarbons, and their derivatives...

 formed when sugar

Sugar

Sugar is a class of edible crystalline carbohydrates, mainly sucrose, lactose, and fructose, characterized by a sweet flavor.Sucrose in its refined form primarily comes from sugar cane and sugar beet...

s are reacted with phenylhydrazine

Phenylhydrazine

Phenylhydrazine is the chemical compound with the formula C6H5NHNH2. Organic chemists abbreviate the compound as PhNHNH2.- Chemical properties :...

  . The famous German

Germany

Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

 chemist

Chemist

A chemist is a scientist trained in the study of chemistry. Chemists study the composition of matter and its properties such as density and acidity. Chemists carefully describe the properties they study in terms of quantities, with detail on the level of molecules and their component atoms...

 Emil Fischer

Emil Fischer

Emil Fischer may refer to:* Emil Fischer , German dramatic basso* Franz Joseph Emil Fischer , German chemist, worked with oil and coal* Hermann Emil Fischer , German Nobel laureate in chemistry...

 developed and used the reaction to identify sugars whose stereochemistry

Stereochemistry

Stereochemistry, a subdiscipline of chemistry, involves the study of the relative spatial arrangement of atoms within molecules. An important branch of stereochemistry is the study of chiral molecules....

 differed by only one chiral carbon

Chirality (chemistry)

A chiral molecule is a type of molecule that lacks an internal plane of symmetry and thus has a non-superimposable mirror image. The feature that is most often the cause of chirality in molecules is the presence of an asymmetric carbon atom....

. The reaction involves formation of a pair of phenylhydrazone

Hydrazone

Hydrazones are a class of organic compounds with the structure R1R2C=NNH2. They are related to ketones and aldehydes by the replacement of the oxygen with the NNH2 functional group...

 functionalities, concomitant with the oxidation of the hydroxymethylene group adjacent to the formyl center. The reaction can be used to identify monosaccharides.
It involves two reactions. Firstly glucose with phenylhydrazine gives us glucosephenylhydrazone by elimination of a water molecule from the functional group.The next step involves reaction of one mole of glucosephenylhydrazone with two moles of phenylhydrazine

Phenylhydrazine

Phenylhydrazine is the chemical compound with the formula C6H5NHNH2. Organic chemists abbreviate the compound as PhNHNH2.- Chemical properties :...

 (excess). First phenylhydrazine

Phenylhydrazine

Phenylhydrazine is the chemical compound with the formula C6H5NHNH2. Organic chemists abbreviate the compound as PhNHNH2.- Chemical properties :...

 is involved in oxidizing the alpha carbon to a carbonyl group, and the second phenylhydrazine

Phenylhydrazine

Phenylhydrazine is the chemical compound with the formula C6H5NHNH2. Organic chemists abbreviate the compound as PhNHNH2.- Chemical properties :...

involves in removal of one water molecule with the formyl group of that oxidized carbon and forming the similar carbon nitrogen bond. The alpha carbon is attacked here because its more reactive than the others.They are highly coloured and crystalline compounds and can be easily detected.
Glucose gives broomstick shaped crystals with this whereas maltose gives sunflower shaped crystals.