What is glucose? Obtaining glucose and its properties

Glucose translated from Greek means "sweet." In nature, in large quantities, it occurs in the juices of berries and fruits, including grape juice, which is why the people have the name "wine sugar".

History of the discovery

Glucose was discovered in the early XIX century by an English physician, chemist and philosopher William Prout. This substance became widely known after Henri Braccone extracted it from sawdust in 1819.

Physical properties

Glucose is a colorless crystalline powder of sweet taste. It is readily soluble in water, concentrated sulfuric acid, zinc chloride and Schweizer reagent.

The structure of the molecule

Like all monosaccharides, glucose is a hetero-functional compound (the molecule contains several hydroxyl and one carboxyl group). In the case of glucose, the carboxyl group is aldehyde.

The general formula for glucose is C6H12O6. The molecules of this substance have a cyclic structure and two spatial isomers of alpha and beta forms. In the solid state, the alpha form predominates almost 100%. In solution, the beta-form is more stable (it occupies about 60%). Glucose is the final product of the hydrolysis of all poly- and disaccharides, that is, the production of glucose occurs in an overwhelming number of cases precisely in this way.

Preparation of a substance

In nature, glucose is formed in plants as a result of photosynthesis. Consider industrial and laboratory methods of obtaining glucose. In the laboratory, this substance is the result of aldol condensation. In industry, the most common way is to obtain glucose from starch.

Starch is a polysaccharide whose mono-parts are glucose molecules. That is, to obtain it, the polysaccharide must be decomposed into a mono-part. How is this process carried out?

The production of glucose from starch begins with the starch being placed in a container of water and mixed (starch milk). Another container of water is brought to a boil. It should be noted that boiling water should be twice as much as starch milk. In order for the reaction to obtain glucose to the end, a catalyst is needed. In this case, it acts hydrochloric or sulfuric acid. The calculated amount is added to a container of boiling water. Then starch milk is slowly poured. In this process it is very important not to get a paste, if it is still formed, it is necessary to continue boiling until it disappears completely. On average, boiling takes an hour and a half. In order to be sure that the starch is completely hydrolyzed, a qualitative reaction must be made. Iodine is added to the selected sample. If the liquid gets a blue color, then hydrolysis is not finished, but if it becomes brown or reddish brown, then there is no starch in the solution. But in this solution there is not only glucose, it was obtained with the help of a catalyst, which means that the acid also has a place to be. How to remove acid? The answer is simple: with neutralization, pure chalk and finely chopped porcelain.

Neutralization is checked with a litmus test. Next, the resulting solution is filtered. The case for small: the resulting colorless liquid should be evaporated. The formed crystals are our final result. Now consider the production of glucose from starch (reaction).

The Chemical Essence of the Process

This equation of obtaining glucose is presented to the intermediate product - maltose. Maltose is a disaccharide consisting of two glucose molecules. It is evident that the methods for obtaining glucose from starch and from maltose are the same. That is, in the continuation of the reaction, we can put the following equation.

In conclusion, it is necessary to summarize the necessary conditions for obtaining glucose from starch was successful.

The necessary conditions

• Catalyst (hydrochloric or sulfuric acid);
• Temperature (not less than 100 degrees);
• Pressure (enough atmospheric, but increasing pressure speeds up the process).

This method is the simplest, with a great yield of the final product and minimal energy costs. But he is not the only one. The production of glucose is also carried out from cellulose.

Preparation from cellulose

The essence of the process is almost entirely consistent with the previous reaction.

The production of glucose (formula) from cellulose is given. In fact, this process is much more complicated and energy-intensive. So, the product that comes into reaction is the waste from the wood processing industry, ground to the fraction, the particle size in which is 1.1 - 1.6 mm. This product is treated first with acetic acid, then hydrogen peroxide, then with sulfuric acid at a temperature of not less than 110 degrees and hydromodule 5. The duration of this process is 3-5 hours. Then, for two hours, hydrolysis with sulfuric acid at room temperature and a hydro module 4-5 passes. Then, water dilution and inversion occur for approximately one and a half hours.

Methods of quantitative determination

Having considered all methods of obtaining glucose, it is necessary to study methods for its quantification. There are situations when only a solution containing glucose should participate in the process, that is, the process of evaporation of the liquid before obtaining crystals is unnecessary. Then the question arises, how to determine what concentration of a given substance in the solution. The resulting amount of glucose in the solution is determined by spectrophotometric, polarimetric and chromatographic methods. There is also a more specific method of determination - enzymatic (with the enzyme glucosidase). In this case, the count is already the products of the action of this enzyme.

Application of glucose

In medicine, glucose is used in intoxication (this can be both food poisoning and the activity of the infection). In this case, the glucose solution is administered intravenously with a dropper. This means that in pharmacy, glucose is a universal antioxidant. Also, this substance plays a minor role in the detection and diagnosis of diabetes mellitus. Here, glucose acts as a stress test.

In the food industry and cooking, glucose takes a very important place. Separately, it should be noted the role of glucose in winemaking, beer and brewing. This is a method such as obtaining ethanol by fermenting glucose. Let us consider this process in detail.

Getting alcohol

The technology of obtaining alcohol has two stages: fermentation and distillation. Fermentation, in turn, is carried out with the help of bacteria. In biotechnology, cultures of microorganisms have long been excreted, which allow obtaining the maximum yield of alcohol at the minimum time spent. In everyday life, ordinary dining yeast can be used as reaction assistants.

First of all, glucose is diluted in water. In the other tank, the microorganisms used are diluted. Further, the resulting liquids are mixed, shaken and placed in a container with a gas outlet tube. This tube is connected to one more (U-shaped). In the middle of the second tube, lime water is poured. The end of the tube is closed with a rubber stopper with a hollow glass rod having a drawn end.

This container is placed in a thermostat at a temperature of 25-27 degrees for four days. In the tube with calcareous water, there will be a cloudiness, which indicates the entry into the reaction with it of carbon dioxide. As soon as carbon dioxide ceases to stand out, fermentation can be considered finished. Then follows the distillation stage. In the laboratory for the distillation of alcohol, use reflux coolers - appliances in which cold water flows through the outer wall, thereby cooling the gas formed and transferring it back to the liquid.

At this stage, the liquid that is in our tank should be heated to 85-90 degrees. Thus, alcohol will evaporate, the water will not be brought to a boil.

Mechanism of obtaining alcohol

Consider the preparation of alcohol from glucose in the reaction equation: C6H12O6 = 2C2H5OH + 2CO2.

So, it can be noted that the mechanism for obtaining ethanol from glucose is very simple. Moreover, it has been known to mankind for many centuries, and has been practically perfected.

The value of glucose in human life

So, having a definite idea of this substance, its physical and chemical properties, use in various industries, we can conclude that such a glucose. Getting it from polysaccharides already gives an understanding that, being the main component of all sugars, glucose is an indispensable source of energy for a person. As a result of metabolism, adenosine triphosphoric acid is formed from this substance, which is converted into a unit of energy.

But not all of the glucose that enters the human body goes to replenish energy. In the waking state, a person turns only 50 percent of the glucose obtained into ATP. The rest is converted to glycogen and accumulates in the liver. Glycogen over time is destroyed, thereby regulating the level of sugar in the blood. Quantitatively the content of this substance in the body is a direct indicator of his health. The hormonal functioning of all systems depends on the amount of sugar in the blood. Therefore, it is worth remembering that excessive use of this substance can lead to serious consequences.

Glucose at first glance is a simple and understandable substance. Even from the point of view of chemistry, its molecules have a fairly simple structure, and chemical properties are understandable and familiar in everyday life. But, despite this, glucose is of great importance both for the person himself and for all spheres of his life activity.