Structure hydrogen bond We will analyze with you interaction Water molecules among themselves.

Water molecule is dipolem. This is explained by the fact that atom hydrogenassociated with more electric negative Element oxygenhaving, experiencing disadvantage electrons And therefore is able to interact With an oxygen atom, another water molecule.

As a result interaction arises hydrogen communications (Fig. 2.1):

2.1. The mechanism of the formation of hydrogen bond between water molecules

This is explained by atom hydrogenassociated with more electric negative Element having various electronic couple (nitrogen, oxygen, fluorine, etc.) is experiencing disadvantage electrons and therefore can interact with virtual pair of electrons another electronegative atom this same or other molecules.

As a result, it also arises hydrogen Communicationwhich is graphically designated three dots (Fig.):

Fig. 2.2. The mechanism for the formation of hydrogen bond between the proton ( . δ + ) and more electronegative sulfur atoms (:S. δ - ), oxygen (:O. δ - ) and nitrogen (:N. δ - )

This connection is significant weaker other chemical connections ( energy Her Education 10-40 kJ / mol), and, mainly, is determined by electrostatic and donor-acceptor interactions.

Hydrogen bond can be like intramolecular, so I. intermolecular.

2.1.4. Hydrophobic interactions

Before considering nature hydrophobic interaction, it is necessary to introduce the concept " hydrophilic " and " hydrophobic " Functional group.

Groups that can form hydrogen bonds with water molecules are called hydrophilic.

These groups include polar Groups: amino group (-NH 2 ) , carboxyl(- Coool), carbonyl group(- Cho.) I. sulfgidrile Group ( - Sh).

Usually, hydrophilic Connections Good soluble in water. !!! This is due to the fact that the polar groups are able to form hydrogen bonds with water molecules .

Appearance Such connections are accompanied energy release, therefore, there is a tendency to maximum increase in contact surface charged groups and water ( Fig. 2.3):

Fig. 2.3. The mechanism of formation of hydrophobic and hydrophilic interactions

Molecules or parts of molecules, unable to form hydrogen bonds with water are called hydrophobic groups.

These groups include alkyl and aromatic radicals that notolar and do not bear Electric charge.

Hydrophobic groups – badly or not at all soluble in water.

This is explained by atoms and group of Atomsincluded hydrophobic Groups are electrophetraland therefore) can not form hydrogen ties with water.

!!! Hydrophobic interactions arise as a result of contact between non-polar radicals, unable to break the hydrogen bonds between water molecules.

As a result water molecules Ostive on surface hydrophilic molecules ( Fig. 2.3).

2.1.5. Van der Waals interaction.

In molecules there are also quite weak and short-range attraction forces between electrically neutral atoms and functional groups.

These are the so-called van der Waals interaction.

They are due electrostatic interaction between negatively charged electrons one Atom and a positively charged core other Atom.

As the nuclei of atoms shielded surrounding their own electricians from nuclei of adjacent atoms, then arising between different atoms van der Waalsy interaction quite nearby.

All these types of interactions Take part in formation, maintaining and stabilization spatial structure ( conformations) protein molecules ( Fig. 2.4.):

Fig. 2.4. Education mechanism covalent ties and weak non-virulent interactions:1 - Electric static interactions;2 - hydrogen bonds;3 - hydrophobic interactions,4 - disulfide connections

Forces that contribute the formation of the spatial structure of proteins and holding it in a stable stateare very weak forces. The energy of these forces on 2-3 The order is less than the energy of covalent bonds. They act between individual atoms and groups of atoms.

However, a huge number of atoms in biopolymers (proteins) molecules leads to the fact that the total energy of these weak interactions becomes comparable to covalent bonds.

Water molecules are interconnected by hydrogen bonds, the distance between the oxygen and hydrogen atoms is 96 pm, and between two hydrogen - 150 PM. In the solid state, the oxygen atom participates in the formation of two hydrogen bonds with adjacent water molecules. In this case, individual H 2 O molecules come into contact with each other with a different poles. Thus, layers are formed in which each molecule is associated with three molecules of its layer and one of the neighboring. As a result, the crystalline structure of ice consists of hexagon "tubes" interconnected, like beesh cells.

According to computer simulation, with a tube diameter of 1.35 nm and pressure in 40000 atmospheres, hydrogen bonds were twisted, leading to the formation of a twin-wall helix. The inner wall of this structure is twisted in four spiral, and the external consists of four double spirals, similar to the structure of the DNA molecule.

The last fact imposes an imprint not only to the evolution of our ideas about the water, but also the evolution of early life and the DNA molecule itself. If we assume that in the era of the birth of life, cryolitic clay rocks had the shape of nanotubes, the question arises - could the water that was sorbed into them to serve as a structural basis - a matrix for DNA synthesis and reading information? It is possible why the spiral structure of DNA repeats the spiral structure of water in nanotubes. According to the NEW Scientist magazine, now our foreign colleagues will be confirmed to confirm the existence of such macromolecules of water in real experimental conditions using infrared spectroscopy and neutron scattering spectroscopy.

Such studies of the Ice nanocrystals were held in 2007, Mikelidez from the Center for Nanotechnology in London and Morgenshtern from the University. Leibnia in Hanover (Fig. 36). They cooled water vapor over the surface of the metal plate, located at a temperature of 5 degrees Kelvin. Soon with the help of a scanning tunnel microscope on the plate, hexamer was observed (six interconnected water molecules) - the smallest snowflake. This is the smallest of possible ice clusters. Scientists also observed clusters containing seven, eight and nine molecules.

Fig . 36. The water hexamera image obtained by the scanning tunnel microscope the size of the hexamera in the diameter is about 1 nm. Photo London Center for Nanotechnology

Development of technology that allowed to obtain the image of water hexamera - in itself an important scientific achievement. To observe, it was necessary to reduce the sensing current to a minimum, which made it possible to prevent weak bonds between the individual water molecules from the destruction due to the observation process. In addition, the theoretical approaches of quantum mechanics were used in the work. An integrated approach gave impressive results.

Unlike crystalline ice, where, between all water molecules, the energy of communication is the same, in nanoclusters there are alternation of strong and weak bonds (and corresponding distances) between individual molecules. Important results were also obtained on the ability of water molecules to the distribution of hydrogen bonds and to their connection with the metal surface.

Theoretical analyzes of oppar, experiments of Miller, Fox, and others. It is indisputable that organic molecules from inorganic can be structured in nature. The main source of energy in their experiments is heat. In nature, this is solar radiation and magma energy. Another very significant conclusion is that the birth of life can occur in an alkaline environment. In all cases there is self-organization of the living.

In the XIX century Palate noted that in the inanimate nature of the molecule is symmetrical. And in the wilderness there is a mirror asymmetry of molecules. Proteins consist of left-hand amino acids. This property is determined by the rotation of the molecule of the plane of the light polarization. How to explain the phenomenon?

Perhaps the presence of asymmetry in organic molecules was manifested when the open system preceding the biosphere was in an extremely non-equilibrium critical condition.

An accelerated evolutionary transition occurred, which is a characteristic feature of self-organization. An example of such a state is experiments, where the aqueous molecules resemble DNA in nanotrubs. The transition from symmetric molecules of inanimate nature to asymmetric biomolecules could occur at the initial stage of chemical evolution as self-organization of matter. Prof. Antonov proved that water is also an open system and exchanges energy and substance with the environment (prof. Antonov, 1992).

Such extreme conditions are observed with volcanic activities, discharges in the atmosphere of young land. Mineral water interacting with calcium carbonate, as well as sea water, is a favorable spectrum to preserve self-organizing structures. The effect of Kiryan in laboratory creates a selective discharge that allows you to observe the radiation of light by atoms or molecules. With Miller experiments, non-equilibrium extreme conditions with a gas discharge are also created.

Kirlyanaya Aura. - the plasma glow of the electrical discharge is observed on the surface of the objects in the variable electric field of the high frequency of 10-100 kHz, in which the surface tension occurs between the electrode and the object under study from 5 to 30 square meters. The Kiryan Effect is observed like a lightning or static discharge on any biological, organic objects, as well as in inorganic samples of various nature.

To visualize Kirlian aura on the electrode, a high variable voltage with high frequency is served - from 1 to 40 kilovolt at 200-15000 Hertz. Another electrode serves the object itself. Both electrodes are separated by an insulator and a thin layer of air whose molecules are subjected to dissociation under the action of a strong magnetic field arising between the electrode and the object. In this layer of air, which is between the object and the electrode, there are three processes.

The first process is the ionization and formation of atomic nitrogen.

The second process is the ionization of air molecules and the formation of ionic current - the corona discharge between the object and the electrode. The shape of the crown of the glow, its density, etc. Determined by their own electromagnetic radiation of the object.

The third process is the transition of electrons from the lowest to higher energy levels and back. At the same time, the transition of electrons occurs radiation of a quanta of light. The magnitude of the electron transition depends on its own electromagnetic field of the object under study. Therefore, at various points of the field surrounding the object, the electrons receive different impulses, i.e. retell on different energy levels, which leads to the emission of the light quanta different lengths and energy. The latter are recorded by a human eye or color photographic as a different colors, which, depending on the object, can aback the crown of the glow in various colors. These three processes in their totality give the overall picture of the Kirlyan effect, which allows you to study the electromagnetic field of the object. The effect of Kirlyan is thus associated with a bioelectric aura of a live object.

The presence of essential electronic pairs in H 2 o molecules in oxygen atoms and positively charged hydrogen atoms leads to a completely special interaction between molecules called a hydrogen bond (see Figure). Unlike all those already familiar to us chemical bond This connection is intermolecular.

The hydrogen bond (in the figure it is denoted by the dotted line) occurs when the hydrogen-depleted electrons interacts with the electrons of a single water molecule with a different electron pair of an oxygen atom of a different water molecule.

Hydrogen bond is a special case intermolecular connections. It is believed that it is due to the main electrostatic forces. For the occurrence of hydrogen bonds, it is necessary that in the molecule there was one or more hydrogen atoms associated with small, but electronegative atoms, for example: O, N, F. It is important that these electronegative atoms have vulnerable electronic couples. Therefore, hydrogen bonds are characteristic of such substances such as Water H 2 O, Ammonia NH 3, HF fluoride. For example, HF molecules are interconnected by hydrogen bonds, which are shown in the figure by dotted lines:

Hydrogen bonds Approximately 20 times less durable than covalent, but it is they who cause water to be liquid or ice (and not gas) under normal conditions. Hydrogen bonds are destroyed only when liquid water goes into pairs.

At temperatures above 0 ° C (but below the boiling point), water no longer has such an ordered intermolecular structure, as shown in the figure. Therefore, in liquid water, the molecules are interconnected only into separate units from several molecules. These aggregates can move freely with each other, forming a moving fluid. But when the temperature decreases, the ordering is becoming more and more, and the aggregates are increasingly larger. Finally, ice is formed, which has exactly an ordered structure that is shown in the figure.

Topic: Basic classes of inorganic compounds. Classification of inorganic substances

Lecture Plan:

1. Basic classes of inorganic compounds.
2. Basis. Chemical properties.
3. Oxides. Their types chemical properties.
4. Acids. Classification and their chemical properties.
5. Salt. Classification and their chemical properties.

Simple substances. Molecules consist of atoms of one species (atoms of one element). In chemical reactions can not be detected with the formation of other substances.

Sophisticated substances (or chemical compounds). Molecules consist of atoms of different types (atoms of various chemical elements). Chemical reactions decompose with the formation of several other substances.

There is no sharp boundary between metals and non-metals, because there is simple substancesShowing dual properties.