Chemical editor ChemSketch from the ACD/Labs software package of the Canadian company “Advanced Chemistry Development” for functionality is not inferior to the ChemDraw editor and even surpasses it in some ways. Unlike ChemDraw (60 megabytes of memory), ChemSketch only takes up about 20 megabytes of disk space. It is also important that documents created using ChemSketch occupy a small volume - only a few kilobytes. This chemical editor is more focused on working with organic formulas of medium complexity (there is a big library ready-made formulas), but it is also convenient to compose in it chemical formulas inorganic substances. It can be used to optimize molecules in three-dimensional space, calculate distances and bond angles between atoms in a molecular structure, and much more.
Based on these ideas, A. M. Butlerov developed principles for constructing graphic formulas chemical substances. To do this, you need to know the valency of each element, which is depicted in the figure as the corresponding number of lines. Using this rule, it is easy to establish whether the existence of a substance with a certain formula is possible or impossible. So, there is a connection called methane and having the formula CH 4. A compound with the formula CH 5 is impossible, since carbon no longer has a free valency for the fifth hydrogen.
Let us first consider the principles of the structure of the most simply constructed organic compounds. They are called hydrocarbons, since they contain only carbon and hydrogen atoms (Fig. 138). The simplest of these is the aforementioned methane, which has only one carbon atom. Let's add another similar atom to it and see what the molecule of a substance called ethane Each carbon atom has one valency occupied by its fellow carbon atom. Now we need to fill the remaining valencies with hydrogen. Each atom has three free valence bonds left, to which we will add one hydrogen atom. The resulting substance has the formula C 2 H 6 . Let's add another carbon atom to it.
Rice. 138. Complete and abbreviated structural formulas of organic compounds
Now we see that the average atom has only two free valences left. We will add a hydrogen atom to them. And to the outer carbon atoms we will add, as before, three hydrogen atoms. We get propane– a compound with the formula C 3 H 8. This chain can be continued, obtaining more and more new hydrocarbons.
But carbon atoms do not necessarily have to be arranged in a linear order in a molecule. Let's say we want to add another carbon atom to propane. It turns out that this can be done in two ways: attach it to either the outermost or middle carbon atom of propane. In the first case we get butane with the formula C 4 H 10. In the second case, the general, so-called empirical, formula will be the same, but the image in the picture, called structural formula, will look different. And the name of the substance will be slightly different: not butane, but isobutane
Substances that have the same empirical but different structural formulas are called isomers, and the ability of a substance to exist in the form of various isomers is isomerism. For example, we eat various substances having the same formula C 6 H 12 O 6, but they have different structural formulas and are different names: glucose, fructose or galactose.
The hydrocarbons that we have considered are called saturated hydrocarbons. In them, all carbon atoms are connected to each other by a single bond. But since the carbon atom is tetravalent and has four valence electrons, theoretically it can form double, triple and even quadruple bonds. Quadruple bonds between carbon atoms do not exist in nature, triple bonds are rare, but double bonds are present in many organic substances, including hydrocarbons. Compounds in which there are double or triple bonds between carbon atoms are called unlimited or unsaturated hydrocarbons. Let us again take a hydrocarbon molecule containing two carbon atoms, but connect them using a double bond (see Fig. 138). We see that now each carbon atom has two free bonds left, to each of which it can attach one hydrogen atom. The resulting compound has the formula C 2 H 4 and is called ethylene. Ethylene, unlike ethane, has fewer hydrogen atoms for the same number of carbon atoms. Therefore, hydrocarbons that have a double bond are called unsaturated in the sense that they are not saturated with hydrogen.
DEFINITION
Structural formula is a chemical formula that reflects how atoms are bonded within a molecule.
It has two varieties: planar (2D) and spatial (3D) (Fig. 1). When depicting a structural formula, intramolecular bonds are usually denoted by dashes (primes).
Rice. 1. Structural formula ethyl alcohol: a) planar; b) spatial.
Planar structural formulas can be depicted in different ways. Highlight brief a graphic formula in which the bonds of atoms with hydrogen are not indicated:
CH 3 - CH 2 - OH
a skeletal graphic formula, which is most often used when depicting the structure of organic compounds; it not only does not indicate the bonds of carbon with hydrogen, but also does not indicate the bonds connecting carbon atoms to each other and other atoms:
for organic compounds of the aromatic series, special structural formulas are used, depicting the benzene ring in the form of a hexagon:
EXAMPLE 1
EXAMPLE 2
| Exercise | Indicate the molecular and structural formulas of magnesium sulfate and calculate molecular weight this connection. |
| Answer | The molecular formula of magnesium sulfate is MgSO 4. It shows that the composition of this molecule includes one magnesium atom (Ar = 24 amu), one sulfur atom (Ar = 32 amu) and four oxygen atoms (Ar = 16 amu. m.). Using the chemical formula, you can calculate the molecular weight of magnesium sulfate: Mr(MgSO 4) = Ar(Mg) + Ar(S) + 4×Ar(O); |
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Here you can draw chemical formulas online, write reactions and much more. The changes you make on this page are not saved anywhere, so you need to export the resulting chemical structure (reaction) to one of the formats: SMILES, MOL, SVG and others (the button in the second row, under “i”)
Here you can also create a chemical formula, write a reaction and much more, including radicals, charges, and so on. This editor supports more formats that can be downloaded immediately after you've drawn. It can import from other file formats.
Remember that the changes you make on this page are not saved anywhere, so you need to export the resulting chemical structure (reaction) to one of the formats of chemical structures or pictures (click on the floppy disk)
In this on-line chemical formula editor, you can also draw chemical formulas. Its interface is quite old and may not be suitable for everyone, but it can export to many formats. In any case, chemists are not spoiled by beautiful application interfaces :)
Reminders that you made on this page are not saved anywhere, so you need to export the resulting chemical structure (reaction) to one of the formats of chemical structures or pictures (there is an "Export" button)
AdobeReader allows you to view and print documents in pdf format (full-color e-books, magazines...). The software product is freely distributed by Adobe. Has a multilingual interface.
interface: multilingual
download: http://www.adobe.com/products/acrobat/readstep2_allversions.html
DjVuReader is a program for viewing files in djvu format (electronic books).
terms of use: free FreeWare
interface: Russian
size: 1.75 MB
download: djvreader.zip
Russian version absolutely free program, designed for drawing chemical structures. It has a convenient interface consisting of two windows: “Structure” and “Drawing”. The first window is for depicting structures, the second is for drawing chemical reactions And various schemes. The program contains a very convenient table of radicals, templates for rings, chains and functional groups and other tools. In many respects, the program is not inferior to ChemDraw and ISIS/Draw; it can save files in both formats - ChemDraw Document (*.cdx) and ISIS/Draw Sketch (*.skc). In addition to ChemSketch, the installation package also includes 3D Viewer, a program that allows you to create three-dimensional models of molecules.
terms of use: free FreeWare
developer: http://www.acdlabs.com
interface: Russian
size: 34.9 MB
download:
