AdobeReader allows you to view and print pdf documents (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
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
ChemSketch v.12.01 (Russian version)
Russian version absolutely free program for drawing chemical structures. It has a user-friendly interface consisting of two windows: "Structure" and "Figure". The first window is for depicting structures, the second is for drawing chemical reactions and various schemes. The program contains a very handy table of radicals, templates of 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 a 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:
The chemical formula editor for xumuk.ru was written in 20 days in the actionscript 2 language. The first raw version was created in 5 days, and then we worked on convenience, embodying completely crazy ideas 😃 For example, automatic attachment and rotation of chemical bonds, splitting elements into independent parts, and even own language markup for creating new elements.
Quick creation of chemical formulas
With a few collaborative ideas in the editor, you can create simple structures very quickly. For example, this picture was just created in 1 minute, and I did not draw from memory, but sketched:
Editor Features
- Objects can be immediately dragged to the "stage"
(in other editors, you need to click on the object, and then click in Right place scenes). - To rotate an object, just point at it with the mouse and turn the mouse wheel (at the bottom, for control, the degree of rotation is indicated, the step is 3 °)
(in other editors, either there are rotation buttons, and this is already a few unnecessary movements, or you can’t twist at all). - Objects are attached to each other by edges or vertices (if you rotate the shape at the same time, it will rotate relative to the attached vertex)
(no analogues). - Simple text objects (C, CH, etc.) can be immediately taken and dragged to the desired location on the scene.
- Complex objects of type C 6 H 5 and chains are created simply - from a text string; then they can be moved, and they also cling to the vertices.
Pictures are optionally stored on the server. Pictures are saved static, so be careful when creating them - it will be impossible to edit them. On the other hand, it's not so scary, because you can draw the entire connection again in a matter of minutes, and at the same time fill your hand and train your head 😃 Just kidding 😃
Comments
interesting implementation
Alexander
Interesting thing, this editor
A good thing to quickly sketch chem. formula
(I found it by chance, tomorrow a friend of mine in chemistry should do
I'm not a chemist, but
There were 2 questions
1) How to adjust the size of elements?
(for example, the main thing is the font size)
2) Auto-positioning of elements into nodes seemed to me
"not too centered", ie. with some error
(relative to visual centers of letters)
which, upon closer examination, may disturb
picky teacher.
This is all, of course, Subjective opinion, but if it occurs
the question of finalizing the editor, I would recommend paying attention to the scalability of elements and the background grid
for ease of placement
1) The size of all elements is constant. If you need more or less, there is a solution: resize the browser window and make a printscreen. As for the font, for most formulas its relative size is optimal.
2) The positioning of the font elements really doesn't match their actual centers (or vertices). If this is very critical, then you will have to "finish" the final picture in Photoshop, for example.
In general, this editor is designed for simpler cases. For term papers, diplomas and any other printed works, it is better to use a full-fledged vector editor (I can’t advise something specific) or draw formulas in Word (but this, by the way, is not difficult :-).
The things you listed are from the category of prettiness, but it would really be nice to finish them. So far, we are collecting suggestions, comments, and when enough of them accumulate, we will start working on the next version of the editor.
In substances, atoms are connected to each other in a certain sequence, and there are certain angles between pairs of atoms (between chemical bonds). All this is necessary for the characterization of substances, since their physical and Chemical properties. Information about the geometry of bonds in substances is partially (sometimes completely) reflected in the structural formulas.
In structural formulas, the bond between atoms is represented by a bar. For example:
The chemical formula of water is H2O, and the structural formula is H-O-H,
The chemical formula of sodium peroxide is Na2O2, and the structural formula is Na-O-O-Na,
The chemical formula of nitrous acid is HNO2, and the structural formula is H-O-N=O.
When depicting structural formulas, dashes usually show the stoichiometric valency of the elements. Structural formulas based on stoichiometric valences are sometimes called graphic.Such structural formulas carry information about the composition and arrangement of atoms, but do not contain correct information about the chemical bonds between atoms.
Structural formula is a graphic image chemical structure molecules of a substance, which shows the order of bonding of atoms, their geometric arrangement. In addition, it clearly shows the valency of the atoms included in its composition.
For the correct writing of the structural formula of one or another chemical you must know and understand well what the ability of atoms to form a certain number of electron pairs with other atoms is. After all, it is valency that will help you draw chemical bonds. For example, given the molecular formula of ammonia NH3. You must write a structural formula. Keep in mind that hydrogen is always monovalent, so its atoms cannot be bonded to each other, therefore, they will be bonded to nitrogen.
To write structural formulas correctly organic compounds, repeat the main provisions of the theory of A.M. Butlerov, according to which there are isomers - substances with the same elemental composition, but with different chemical properties. For example, isobutane and butane. Their molecular formula is the same: C4H10, but the structural ones are different.
In a linear formula, each atom is written separately, so such an image takes up a lot of space. However, when drawing up a structural formula, you can specify the total number of hydrogen atoms for each carbon atom. And between neighboring carbons, draw chemical bonds in the form of lines.
Start writing isomers with a hydrocarbon of a normal structure, that is, with an unbranched chain of carbon atoms. Then reduce by one carbon atom, which is attached to another, internal carbon. Having exhausted all the options for writing isomers with a given chain length, reduce it by one more carbon atom. And again attach it to the inner carbon atom of the chain. For example, the structural formulas of n-pentane, isopentane, tetramethylmethane. Thus, a hydrocarbon molecular formula C5H12 has three isomers. Learn more about the phenomena of isomerism and homology in the following articles!
One of the most important tasks in chemistry is the correct compilation of chemical formulas. A chemical formula is a written representation of the composition of a chemical substance using the Latin designation of the element and indices. For correct compilation formulas, we will definitely need the periodic table and knowledge of simple rules. They are quite simple and even children can remember them.
How to write chemical formulas
The main concept in the preparation of chemical formulas is "valence". Valency is the property of one element to hold a certain number of atoms in a compound. The valency of a chemical element can be viewed in the periodic table, and you also need to remember and be able to apply simple general rules.
- The valence of a metal is always equal to the group number, provided that it is in the main subgroup. For example, potassium has a valence of 1, and calcium has a valence of 2.
- Non-metals are a little more difficult. A non-metal can have a higher and a lower valency. The highest valency is equal to the group number. The lowest valency can be determined by subtracting the element's group number from eight. When combined with metals, non-metals always have a lower valence. Oxygen always has a valence of 2.
- In the combination of two non-metals, the chemical element that is located to the right and above in the periodic table has the lowest valency. However, fluorine always has a valence of 1.
- And one more important rule when placing odds! The total number of valences of one element must always be equal to the total number of valences of another element!
Let's consolidate the knowledge gained on the example of a compound of lithium and nitrogen. The lithium metal has a valence of 1. The non-metal nitrogen is located in the 5th group and has a higher valence of 5 and a lower one of 3. As we already know, in compounds with metals, non-metals always have a lower valence, so nitrogen in this case will have a valency of three. We arrange the coefficients and get the desired formula: Li 3 N.
So, quite simply, we learned how to make chemical formulas! And for better memory algorithm for compiling formulas, we have prepared its graphical representation.
Well, to complete our acquaintance with alcohols, I will give another formula of another well-known substance - cholesterol. Not everyone knows that it is a monohydric alcohol!
|`/`\\`|<`|w>`\`/|<`/w$color(red)HO$color()>\/`|0/`|/\<`|w>|_q_q_q<-dH>:a_q|0<|dH>`/<`|wH>`\|dH; #a_(A-72)<_(A-120,d+)>-/-/<->`\
I marked the hydroxyl group in it in red.
carboxylic acids
Any winemaker knows that wine must be kept out of the air. Otherwise it will sour. But chemists know the reason - if you add one more oxygen atom to alcohol, you get an acid.Let's look at the formulas of acids that are obtained from alcohols already familiar to us:
| Substance | Skeletal formula | Gross formula | ||
|---|---|---|---|---|
| Methanoic acid (formic acid) |
H/C`|O|\OH | HCOOH | O//\OH | |
| Ethanoic acid (acetic acid) |
H-C-C\O-H; H|#C|H | CH3-COOH | /`|O|\OH | |
| propanoic acid (methylacetic acid) |
H-C-C-C\O-H; H|#2|H; H|#3|H | CH3-CH2-COOH | \/`|O|\OH | |
| Butanoic acid (butyric acid) |
H-C-C-C-C\O-H; H|#2|H; H|#3|H; H|#4|H | CH3-CH2-CH2-COOH | /\/`|O|\OH | |
| Generalized formula | (R)-C\O-H | (R)-COOH or (R)-CO2H | (R)/`|O|\OH |
A distinctive feature of organic acids is the presence of a carboxyl group (COOH), which gives such substances acidic properties.
Everyone who has tried vinegar knows that it is very sour. The reason for this is the presence of acetic acid in it. Typically, table vinegar contains 3 to 15% acetic acid, with the rest (mostly) water. Eating undiluted acetic acid is life-threatening.
Carboxylic acids may have several carboxyl groups. In this case they are called: dibasic, tripartite etc...
Food products contain many other organic acids. Here are just a few of them:
The name of these acids corresponds to those food products in which they are contained. By the way, note that there are acids here that also have a hydroxyl group characteristic of alcohols. Such substances are called hydroxycarboxylic acids(or hydroxy acids).
Below each of the acids is signed, specifying the name of the group of organic substances to which it belongs.
Radicals
Radicals are another concept that has influenced chemical formulas. The word itself is probably known to everyone, but in chemistry, radicals have nothing to do with politicians, rebels and other citizens with an active position.
Here they are just fragments of molecules. And now we will figure out what is their peculiarity and get acquainted with a new way of writing chemical formulas.
Above in the text, generalized formulas have already been mentioned several times: alcohols - (R) -OH and carboxylic acids - (R) -COOH. Let me remind you that -OH and -COOH are functional groups. But R is the radical. No wonder it is depicted in the form of the letter R.
More specifically, a univalent radical is a part of a molecule devoid of one hydrogen atom. Well, if you take away two hydrogen atoms, you get a divalent radical.
Radicals in chemistry have their own names. Some of them even received Latin designations, similar to the designations of the elements. And besides, sometimes radicals in formulas can be indicated in an abbreviated form, more reminiscent of gross formulas.
All this is shown in the following table.
| Name | Structural formula | Designation | Short Formula | alcohol example | ||
|---|---|---|---|---|---|---|
| Methyl | CH3-() | Me | CH3 | (Me)-OH | CH3OH | |
| Ethyl | CH3-CH2-() | Et | C2H5 | (Et)-OH | C2H5OH | |
| Propil | CH3-CH2-CH2-() | Pr | C3H7 | (Pr)-OH | C3H7OH | |
| Isopropyl | H3C\CH(*`/H3C*)-() | i-Pr | C3H7 | (i-Pr)-OH | (CH3)2CHOH | |
| Phenyl | `/`=`\//-\\-{} | Ph | C6H5 | (Ph)-OH | C6H5OH | |
I think that everything is clear here. I just want to draw your attention to the column that gives examples of alcohols. Some radicals are written in a form that resembles an empirical formula, but the functional group is written separately. For example, CH3-CH2-OH is converted to C2H5OH.
And for branched chains like isopropyl, constructions with brackets are used.
There is another phenomenon free radicals. These are radicals that for some reason separated from functional groups. In this case, one of the rules with which we began the study of formulas is violated: the number of chemical bonds no longer corresponds to the valency of one of the atoms. Well, or you can say that one of the links becomes open from one end. Free radicals usually live a short time, because the molecules tend to return to a stable state.
Introduction to nitrogen. Amines
I propose to get acquainted with another element that is part of many organic compounds. This nitrogen.
It is denoted by the Latin letter N and has a valency of three.
Let's see what substances are obtained if nitrogen is added to familiar hydrocarbons:
| Substance | Expanded structural formula | Simplified structural formula | Skeletal formula | Gross formula |
|---|---|---|---|---|
| Aminomethane (methylamine) |
H-C-N\H;H|#C|H | CH3-NH2 | \NH2 | |
| Aminoethane (ethylamine) |
H-C-C-N\H;H|#C|H;H|#3|H | CH3-CH2-NH2 | /\NH2 | |
| Dimethylamine | H-C-N<`|H>-C-H; H|#-3|H; H|#2|H | $L(1.3)H/N<_(A80,w+)CH3>\dCH3 | /N<_(y-.5)H>\ | |
| Aminobenzene (Aniline) |
H\N|C\\C|C<\H>`//C<|H>`\C<`/H>`||C<`\H>/ | NH2|C\\CH|CH`//C<_(y.5)H>`\HC`||HC/ | NH2|\|`/`\`|/_o | |
| Triethylamine | $slope(45)H-C-C/N\C-C-H;H|#2|H; H|#3|H; H|#5|H;H|#6|H; #N`|C<`-H><-H>`|C<`-H><-H>`|H | CH3-CH2-N<`|CH2-CH3>-CH2-CH3 | \/N<`|/>\| |
As you probably guessed from the names, all these substances are combined under the common name amines. The functional group ()-NH2 is called amino group. Here are some general formulas for amines:
In general, there are no special innovations here. If these formulas are clear to you, then you can safely engage in further study of organic chemistry using some textbook or the Internet.
But I would like to talk more about formulas in inorganic chemistry. You will see how easy it will be to understand them after studying the structure of organic molecules.
Rational formulas
It should not be concluded that inorganic chemistry is simpler than organic. Certainly, inorganic molecules usually look much simpler because they don't tend to form complex structures like hydrocarbons. But on the other hand, one has to study more than a hundred elements that make up the periodic table. And these elements tend to combine according to their chemical properties, but with numerous exceptions.
So, I won't say any of this. The topic of my article is chemical formulas. And with them, everything is relatively simple.
The most commonly used in inorganic chemistry are rational formulas. And now we will figure out how they differ from those already familiar to us.
First, let's get acquainted with another element - calcium. This is also a very common item.
It is designated Ca and has a valency of two. Let's see what compounds it forms with carbon, oxygen and hydrogen known to us.
| Substance | Structural formula | rational formula | Gross formula |
|---|---|---|---|
| calcium oxide | Ca=O | CaO | |
| calcium hydroxide | H-O-Ca-O-H | Ca(OH)2 | |
| Calcium carbonate | $slope(45)Ca`/O\C|O`|/O`\#1 | CaCO3 | |
| Calcium bicarbonate | HO/`|O|\O/Ca\O/`|O|\OH | Ca(HCO3)2 | |
| Carbonic acid | H|O\C|O`|/O`|H | H2CO3 |
At first glance, one can see that the rational formula is something in between the structural and gross formulas. But so far it is not very clear how they are obtained. To understand the meaning of these formulas, you need to consider the chemical reactions in which substances participate.
Calcium in its purest form is a soft white metal. It does not occur in nature. But it is quite possible to buy it in a chemical store. It is usually stored in special jars without air access. Because it reacts with oxygen in air. In fact, that is why it does not occur in nature.
So, the reaction of calcium with oxygen:
2Ca + O2 -> 2CaO
The number 2 before the formula of a substance means that 2 molecules are involved in the reaction.
Calcium oxide is formed from calcium and oxygen. This substance also does not occur in nature because it reacts with water:
CaO + H2O -> Ca(OH2)
It turns out calcium hydroxide. If you look closely at its structural formula (in the previous table), you can see that it is formed by one calcium atom and two hydroxyl groups, with which we are already familiar.
These are the laws of chemistry: if a hydroxyl group is attached to organic matter, it turns out alcohol, and if to a metal, then hydroxide.
But calcium hydroxide is not found in nature due to the presence of carbon dioxide in the air. I think that everyone has heard about this gas. It is formed during the breathing of people and animals, the combustion of coal and petroleum products, during fires and volcanic eruptions. Therefore, it is always present in the air. But it also dissolves quite well in water, forming carbonic acid:
CO2 + H2O<=>H2CO3
Sign<=>indicates that the reaction can proceed in both directions under the same conditions.
Thus, calcium hydroxide dissolved in water reacts with carbonic acid and turns into poorly soluble calcium carbonate:
Ca(OH)2 + H2CO3 -> CaCO3"|v" + 2H2O
The down arrow means that the substance precipitates as a result of the reaction.
Upon further contact of calcium carbonate with carbon dioxide in the presence of water, a reversible reaction occurs to form an acid salt - calcium bicarbonate, which is highly soluble in water.
CaCO3 + CO2 + H2O<=>Ca(HCO3)2
This process affects the hardness of the water. As the temperature rises, the bicarbonate turns back into carbonate. Therefore, in regions with hard water, scale forms in kettles.
Chalk, limestone, marble, tuff and many other minerals are largely composed of calcium carbonate. It is also found in corals, mollusk shells, animal bones, etc...
But if calcium carbonate is heated on a very high heat, it will turn into calcium oxide and carbon dioxide.
This short story about the calcium cycle in nature should explain why rational formulas are needed. So, rational formulas are written in such a way that functional groups are visible. In our case, this is:
Besides, individual elements- Ca, H, O (in oxides) - are also independent groups.ions
I think it's time to get acquainted with ions. This word is probably familiar to everyone. And after studying the functional groups, it doesn’t cost us anything to figure out what these ions are.
In general, the nature of chemical bonds is usually that some elements donate electrons while others receive them. Electrons are particles with a negative charge. An element with a full set of electrons has zero charge. If he gave an electron, then its charge becomes positive, and if he accepted it, then it becomes negative. For example, hydrogen has only one electron, which it gives up quite easily, turning into a positive ion. For this, there is a special record in chemical formulas:
H2O<=>H^+ + OH^-
Here we see that as a result electrolytic dissociation water breaks down into a positively charged hydrogen ion and a negatively charged OH group. The OH^- ion is called hydroxide ion. It should not be confused with the hydroxyl group, which is not an ion, but part of a molecule. The + or - sign in the upper right corner shows the charge of the ion.
But carbonic acid never exists as an independent substance. In fact, it is a mixture of hydrogen ions and carbonate ions (or bicarbonate ions):
H2CO3 = H^+ + HCO3^-<=>2H^+ + CO3^2-
The carbonate ion has a charge of 2-. This means that two electrons have joined it.
Negatively charged ions are called anions. Usually these include acidic residues.
Positively charged ions cations. Most often it is hydrogen and metals.
And here you can probably fully understand the meaning of rational formulas. The cation is written in them first, and then the anion. Even if the formula does not contain any charges.
You probably already guess that ions can be described not only by rational formulas. Here is the skeletal formula of the bicarbonate anion:
Here, the charge is indicated directly next to the oxygen atom, which received an extra electron, and therefore lost one line. Simply put, each extra electron reduces the number of chemical bonds depicted in the structural formula. On the other hand, if some node of the structural formula has a + sign, then it has an additional wand. As always, this fact needs to be demonstrated with an example. But among the substances familiar to us, there is not a single cation that would consist of several atoms.
And such a substance is ammonia. His water solution often called ammonia and is part of any first aid kit. Ammonia is a compound of hydrogen and nitrogen and has the rational formula NH3. Consider chemical reaction, which occurs when ammonia is dissolved in water:
NH3 + H2O<=>NH4^+ + OH^-
The same, but using structural formulas:
H|N<`/H>\H + H-O-H<=>H|N^+<_(A75,w+)H><_(A15,d+)H>`/H + O`^-# -H
On the right side we see two ions. They were formed as a result of the fact that one hydrogen atom moved from a water molecule to an ammonia molecule. But this atom moved without its electron. The anion is already familiar to us - it is the hydroxide ion. And the cation is called ammonium. It exhibits properties similar to metals. For example, it can combine with an acid residue. The substance formed by the combination of ammonium with a carbonate anion is called ammonium carbonate: (NH4)2CO3.
Here is the reaction equation for the interaction of ammonium with a carbonate anion, written in the form of structural formulas:
2H|N^+<`/H><_(A75,w+)H>_(A15,d+)H + O^-\C|O`|/O^-<=>H|N^+<`/H><_(A75,w+)H>_(A15,d+)H`|0O^-\C|O`|/O^-|0H_(A-15,d-)N^+<_(A105,w+)H><\H>`|H
But in this form, the reaction equation is given for demonstration purposes. Usually equations use rational formulas:
2NH4^+ + CO3^2-<=>(NH4)2CO3
Hill system
So, we can assume that we have already studied the structural and rational formulas. But there is another issue worth considering in more detail. What is the difference between gross formulas and rational ones?
We know why the rational formula for carbonic acid is written H2CO3 and not otherwise. (Two hydrogen cations come first, followed by the carbonate anion.) But why is the gross formula written as CH2O3?
In principle, the rational formula of carbonic acid may well be considered a true formula, because there are no repeating elements in it. Unlike NH4OH or Ca(OH)2 .
But an additional rule is often applied to gross formulas, which determines the order of the elements. The rule is pretty simple: put carbon first, then hydrogen, and then the rest of the elements in alphabetical order.
So CH2O3 comes out - carbon, hydrogen, oxygen. This is called the Hill system. It is used in almost all chemical reference books. And in this article too.
A little about the easyChem system
Instead of concluding, I would like to talk about the easyChem system. It is designed so that all those formulas that we discussed here can be easily inserted into the text. Actually, all the formulas in this article are drawn using easyChem.
Why do we need any system for the derivation of formulas? The thing is that the standard way to display information in Internet browsers is Hypertext Markup Language (HTML). It is focused on text processing.
Rational and gross formulas can be depicted with the help of text. Even some simplified structural formulas can also be written in text, for example alcohol CH3-CH2-OH. Although for this you would have to use this notation in HTML: CH 3-CH 2-OH.
This of course creates some difficulties, but you can put up with them. But how to represent the structural formula? In principle, one can use a monospaced font:
H H | | H-C-C-O-H | | H H It certainly doesn't look very nice, but it's also feasible.
The real problem arises when trying to represent benzene rings and when using skeletal formulas. There is no other way but to connect the bitmap. Rasters are stored in separate files. Browsers can include gif, png or jpeg images.
To create such files, a graphical editor is required. For example, Photoshop. But I have been familiar with Photoshop for more than 10 years and I can say for sure that it is very poorly suited for depicting chemical formulas.
Molecular editors are much better at this task. But at in large numbers formulas, each of which is stored in a separate file, it is quite easy to get confused in them.
For example, the number of formulas in this article is . They are displayed in the form of graphic images (the rest using HTML tools).
easyChem allows you to store all formulas directly in an HTML document in text form. I think it's very convenient.
In addition, the gross formulas in this article are calculated automatically. Because easyChem works in two stages: first, the textual description is converted into an information structure (graph), and then various actions can be performed with this structure. Among them are the following functions: calculation molecular weight, converting to a gross formula, checking for the possibility of output as text, graphic and text rendering.
Thus, for the preparation of this article, I used only a text editor. Moreover, I did not have to think which of the formulas would be graphical and which would be textual.
Here are some examples that reveal the secret of article text preparation: Descriptions from the left column are automatically converted into formulas in the second column.
In the first line, the description of the rational formula is very similar to the displayed result. The only difference is that the numeric coefficients are output as interlinear.
In the second line, the expanded formula is given as three separate strings, separated by a symbol; I think it's easy to see that a text description is a lot like what would be required to draw a formula with a pencil on paper.
The third line demonstrates the use of slanted lines using the characters \ and /. The ` (backtick) sign means that the line is drawn from right to left (or from bottom to top).
There is much more detailed documentation on using the easyChem system here.
On this, let me finish the article and wish you good luck in studying chemistry.
