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SUGAR FROM SAWDUST

 

The name of the carbohydrates received in error. It happened in the middle of the last century. Then believed that the molecule of any sugary substance corresponds to the formulam(H2O)n. All the then known carbohydrates fit under this measure, and the formula of glucose With6H12O6 wrote With6(H2O)6.

But later they were discovered and such sugar, which turned out to be the exception to the rule. Thus, an explicit representative of carbohydrates rhamnose (it also gives the reaction of MOLISA) is a formula With6H12O5. Although the inaccuracy in the name of a class of compounds was evident, the term "carbohydrate" has become so familiar that it did not change. However, these days many chemists prefer another name is "sugar".

One of the sugars we will try to get from sawdust by hydrolysis, i.e. the decomposition of water. This is a very common chemical process. Sawdust and other wood wastes contain carbohydrate cellulose). From her hydrolysis plants prepare glucose, which you can then use in different ways; most often it is fermented into alcohol starting material for many chemical syntheses. Large and independent branch of the chemical industry is called hydrolysis industry,

Before playing the hydrolysis of wood, let us try to understand what is its essence, and this will be easier to start of with sawdust, and with cucumbers and Luchenok.

Wash cucumber, grate it on a grater and squeeze the juice. The juice can be filtered, but not necessarily.

Prepare in vitro copper hydroxide cu(OH)2. To do this, add 2-3 drops of copper sulfate solution to 0.5-1 ml of sodium hydroxide solution. To the resulting precipitate, add equal amount of cucumber juice and shake the test tube. The precipitate will dissolve, you get a blue solution. This reaction is characteristic of polyhydric alcohols, i.e. alcohols containing multiple hydroxyl groups.

Now heat until boiling (or put in boiling water) tube obtained a blue solution. It will first turn yellow, then turns orange, and after cooling will drop a red precipitate of copper oxide Cu2O. This reaction is characteristic of another class of organic compounds - aldehydes. So, in cucumber juice contains a substance representing the aldehyde and alcohol at the same time. This substance is glucose, which in structure is uldehitusest. Thanks to her cucumber sweet taste.

You can probably guess that this experience does not have to put it with the juice of a cucumber. He is good with other sweet juice - grape, carrot, Apple, pear, are available to experience and free cucumber water, which is sold in perfume shops. And, of course, just glucose tablets.

Now the second prior experience: the saccharification sliver.

Prepare a solution of sulfuric acid to one volume of water hcl one volume of concentrated sulfuric acid (in any case, do not pour water into acid!). In a test tube with a solution of lower luchinku and heat the solution to boiling. Lucinka this charred, but the experience is not hurt.

After heating, remove luchinku, put it into another test tube with 1-2 ml of water and boil. In both test tubes now have glucose. You can verify this by adding to the solutions of two-three drops of copper sulphate, and then caustic soda will be familiar blue color. If the solution to boil, fall out, as we expected, a red precipitate of copper oxide Cu2O. so, glucose is detected.

The fact that our lucinka acharyas, and is the result of hydrolysis of cellulose and its share in the wood accounts for about 50%). As with the hydrolysis of starch, sulfuric acid in this process is not consumed, it plays the role of a catalyst.

Finally, we come to the main experience that was promised in the title: getting sugar from sawdust.

In a porcelain Cup pour 2-3 tablespoons of wood chips and soak them with water. Add a little water and an equal amount of previously prepared solution of sulfuric acid (1:1), the liquid slurry mix well. Cover and place in oven gas stove (or in a Russian stove) for about an hour, or a little less.

Then remove the Cup, add water to the top and stir. Filter the solution and neutralize the filtrate by adding crushed chalk or lime water until, until it stopped bubbling carbon dioxide. About the end of the neutralization can also be judged, feeling the liquid litmus test or one of the self-made indicators. No need to drop the indicator directly in the reaction mass. You should take a sample, just 2-3 drops, and put it on a glass plate or in a small test tube.

The contents of the Cup, pour in a bottle of milk, shake the liquid and let stand several hours. The calcium sulfate formed during the neutralization of the acid settles to the bottom, and the top will remain the glucose solution. Carefully pour it into a clean Cup (preferably on a glass rod and filter.

Remained in the final operation the evaporation of water in a water bath. After her bottom remain light yellow crystals of glucose. They can taste, but the product is not clean.

We have now completed four operations: boiling sawdust with a solution of sulfuric acid, neutralizing the acid, filtration and evaporation. Exactly and receive glucose on hydrolysis plants, only, of course, not in porcelain cups.

And another industrial process, we can play without much difficulty: turn one sugar in the other two.

When storing homemade jams often is candy. This is because sugar is crystallized from the syrup. With jam, which is sold in the store, this problem happens much less frequently. The fact that canning plants, except beet or cane sugar sucrose (C12H 22O11, use other sweeteners, such as invert sugar. What is inversion of sugar and where it leads, you will learn from the following experience.

Pour into a test tube or a glass of 10-20 g weak sugar solution and add a few drops of dilute hydrochloric acid. Then heat the solution in a boiling water bath for ten or fifteen minutes, and then neutralise the acid, preferably magnesium carbonate MgCO3 . Pharmacies sell so-called white magnesia, the matter is somewhat more complex structure; it is also a good. At least you can take and drinking a soda, NaHCO3, but then the solution will remain salt, which with sugar as it is not in harmony...

When you stopped bubbling of carbon dioxide, allow the liquid to settle. Just in case, check the indicator, whether or not there was kind of balanced out the acid. Drain the pooled liquid and try its taste: it will seem less sweet than the original solution (for comparison, leave some of the original sugar solution).

In the finished solution is almost no sucrose, but there are two new substances, glucose and fructose. This process is called inversion of sugar, and the resulting mixture is invert sugar.

And here's what's interesting: apparently the reaction does not detect. And color, and volume, and the reaction of the environment remain the same. Do not stand out no gases, no precipitation. Nevertheless, the reaction proceeds only to detect the desired optical devices. Sugar - optically active substances: a beam of polarized light passing through the solution, changes the polarization direction. They say that sugar rotate the plane of polarization in one direction or another, and at a definite angle. Now, sucrose rotates the plane of polarization to the right, and glucose and fructose, the products of its hydrolysis,left. Hence the word "inversion" (Latin for "curl").

But, because of optical instruments at our disposal no, let's try to verify by chemicals that are taken sugar and in fact has undergone changes. To the source and obtained the solutions of sugars, add a few drops of a solution of methylene blue (you can take the blue fountain pen ink) and a bit of a weak solution of any alkali. Heat researched solutions in a water bath. In vitro with normal sugar no changes will occur, but the contents of the test tubes with invert sugar becomes almost colorless.

Invert sugar is much less than normal, prone to crystallization. If you care to evaporate on a water bath his solution, you get a thick syrup that looks somewhat like honey. After cooling, it is not crystallized.

By the way, the beloved honey three quarters consists of the same carbohydrates as invert sugar,glucose and fructose. Artificial honey also make on the basis of invert sugar. Of course, our syrup from honey is different, and significantly - mainly the lack of smell. But if to it to add a bit of honey, this disadvantage can be partly overcome.

But why not prepare at home more recrystallizes syrup to cook on it jam? Alas, full clean of foreign substances is difficult, and there is no guarantee that it will be able to finish. Anyway, isn't worth the risk.

O. Holguín. "Experiments without explosions"
M., "Chemistry", 1986

 

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