Identification of Unidentified Carbohydrates | Laboratory Report

From the name itself, Sugars are hydrates of carbons that are polar in dynamics. The inspiration of carbohydrates are monosaccharides which are simple sugars because of the low molecular weight. Carbohydrates will be the product of photosynthesis from the condensation of carbon dioxide that will require light and chlorophyll. Carbohydrates have a essential role in the nourishment of organisms since it's the major way to obtain energy. ATP is energy released by crops and it is the needed by your body to function accordingly.

Carbohydrates have different constructions thus it offers particular reactions to various reagents depending on its chemical composition. It can be grouped into monosaccharides, disaccharides and polysaccharides. Monosaccharides could be labeled as polyhrdoxy aldoses or ketoses. These are the simplest glucose that can't be broken down into smaller aggregates. These are aldehydes that contain two or more hydroxyl teams. Disaccharides are two simple sugar that are linked together by way of a glycosidic relationship- an ether bond made from the merging of two hydroxyl groupings between monosaccharides. Polysaccharides, on the other hand, are made of multiple glucose units attached to a group of disaccharides. They can be formed by a glycosidic linkage.


For the identification of the mysterious carbohydrates examples, 1. 00 ml of two undiscovered samples were moved in a test pipe and 1. 00 ml of Molisch reagents was added as well as 1. 00 ml of focused. For each of the assessments- Iodine test, Benedict's test, Barfoed's test, Seliwanoff's test and 2, 4-DNP test, fresh examples were needed for each. Table 1 shows the needed amount of reagent for each test for a qualitative research.

The identity of both unknown samples was then recognized based on the reaction of the given set of carbohydrates.

For the hydrolysis of starch, 50. 00 ml of 5% starch solution was located in a 100 ml beaker. About 5. 00 ml of concentrated sulfuric acid was added. Covering the beaker with aluminium foil, it was then warmed until boiled in a water bathtub. About 1. 00 ml of the test was positioned in two distinct test tubes with the help of 1. 00 ml of iodine reagent to 1 and 1. 00 ml of Benedict's reagent to the other. The sample was heated regularly. With an period of five minutes, 1. 00 ml of the sample was transferred into two individual tees tubes once again and with the help of the iodine and Benedict's reagent until a blue-black precipitate is developed with the iodine reagent and a brick red colorization with the Benedict's reagent.


Color intensity

Table 2 shows the required color change of the carbohydrates upon the addition of certain reagents. Molisch's test is an over-all test for carbohydrates that determines the existence of carbonyl communities, gives off a deep purple colored chemical. The Iodine test produces a blue-black colored complex as a good reaction towards iodine. Benedict's test can determine the personal information of the reducing sugars which results to an orange-rust color. Barfoed's test has the same purpose as Benedict's test for deciding the reducing sugars, but this Barfoed's test produces a good test for lowering monossaccharides only. Seliwanoff's test determines the occurrence of aldoses and ketoses, only the ketoses give off a positive response resulting to a brick red color. The 2 2, 4-dinitrophenylhydrazine or the 2 2. 4-DNP test establishes the reaction of monosaccharides that provides off yellow- dark crystals of osazones that intensifies the colour of the substance.

Molisch's test is an over-all test for carbohydrates. Concentrated sulfuric acid was added creating a deep purple coloured material. The carbohydrate goes through dehydration wherein water was released upon the addition of sulfuric acid. Pentoses and hexoses behave with the sulfuric acid bringing on the positive color change.

For the Iodine test, the only real sweets that reacted was starch. Starch is a polysaccharide- a mixture of amylose and amylopectin. An amylose varieties a helical composition in water. Iodine could easily penetrate through the helical framework, since monosaccharides and disaccharides aren't too small they don't behave with iodine. Upon the penetration of the iodine to the primary of the helix, it produces a blue-black colored substance. When heated up, the blue color disappears because the helical diamond ring of the amylose is disrupted. Iodine is doesn't have the capability to bind itself back again to helix. The blue color earnings when the starch is cooled. The iodine is now able to bind back to the helix.

Benedict's test identifies the reducing sugars, the monosaccharides and the disaccharides. This reagent is a poor oxidizing reagent. Cuprous oxide was converted from cuprous hydroxide. The past determines the existence of the lowering sugar.

Seliwanoff's test differentiates ketoses from aldoses. The ketose produces a brick red color upon the addition of high temperature. Ketose goes through dehydration when diluted in HCl and warmed.

Barfoed's test recognizes the reducing sugars as well, but this test is specific limited to monosaccharides. Carbohydrates exposed to the Barfoed reagent, an assortment of copper acetate and glacial acetic acid, undergoes reduction. The reducing monosaccharide reduces the cupric ions to cuprous ions in acidic medium (4). The cuprous ions made in turn, decrease the colorless phosphomolybdic acid to blue phosphomolybdous acid (4). The positive color change for monosaccharides was exhibited by the deep blue color, as the disaccharide exhibited a light blue color.

The 2, 4- DNP test is an over-all test for sugars. This establishes the occurrence of aldehydes and ketones. The aldoses and ketoses are very similar. The lowering sugars create a positive test.

The personality of starch could be easily distinguished through the iodine test. If the starch is hydrolyzed it can have a positive cause the Benedict's test. The acetal linkages in starch are hydrolyzed in hot aqueous acid (6).

Benedict's test is a good test in discovering the sugar awareness in the urine of a patient diagnosed with diabetes mellitus. The colour of the precipitate offers an approximate percentage of sugars excreted in the urine (4). The colour determines the percentage of sugar within the urine. In case the precipitate is blue, sugars is absent, inexperienced if there are 0-0. 5% sweets, yellowish if 1% sweets, orange if 1. 5% sweets, and red if 2% sugars or even more.

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