The formation of bonds is described by SP3 hybridization in the molecule. Type of hybridization of atoms. The angle between connections

Most often there are hybridization SP, SP 2, SP 3 and SP 3 D 2. Each type of hybridization corresponds to a certain spatial structure of the molecules of the substance.

sP-hybridization. This type of hybridization is observed in the formation by a two-link atom due to electrons located on S-orbital and on one P-orbital (one and the same energy level). At the same time, two hybrid q-orbitals are formed, directed in opposite sides at an angle of 180 º (Fig. 22).

Fig. 22. SP-hybridization scheme

During SP-hybridization, linear trichatic molecules of type AV 2 are formed, where a is a central atom, which occurs hybridization, and B - the attached atoms that hybridization does not occur. Such molecules are formed by beryllium, magnesium atoms, as well as carbon atoms in acetylene (C 2 H 2) and in carbon dioxide (CO 2).

Example 5.Explain the chemical bond in the veins 2 molecules and ce the structure and the structure of these molecules.

Decision. Berillia atoms in normal condition do not form chemical bonds, because Do not have unpaired electrons (2S 2). In the excited state (2S 1 2p 1), the electrons are located on different orbital, therefore, in the formation of bonds, SP-hybridization occurs according to the scheme shown in Fig. 22. Two hydrogen or fluorine atoms are attached to two hybrid orbitals, as shown in Fig. 23.

1) 2)

Fig. 23. Scheme of the formation of molecules of veins 2 (1) and ce 2 (2)

The resulting molecules are linear, valence angle 180º.

Example 6. According to experimental data of the CO 2 molecule - linear, and, both bonds of carbon with oxygen are the same in length (0.116 nm) and energy (800 kJ / mol). How are these data explained?

Decision. This data on carbon dioxide molecule explains the next model of its formation.

The carbon atom forms communication in the excited state, at which it has four unpaired electron: 2S 1 2p 3. When forming links, SP-hybridization of orbitals occurs. Hybrid orbitals are directed in a straight line in opposite sides of the nucleus of the atom, and the remaining two pure (non-librid) p-orbitals are perpendicular to each other and to hybrid orbitals. All orbitals (hybrid and non-librid) contain one unpaired electron.

Each oxygen atom having two unpaired electrons on two mutually perpendicular p-orbitals is connected to the carbon atom of S-bond and P-bond: S-bond is formed with the participation of the hybrid orbital carbon, and the P-bond is formed by overlapping clean p-orbitals of carbon atoms and oxygen. The formation of bonds in the CO 2 molecule is shown in Fig. 24.

Fig. 24. Scheme of formation of molecule CO 2

The multiplicity of the bond, equal to two, explains the greater strength of communication, and sp-hybridization is the linear structure of the molecule.

Mixing one S- and two p-orbitals is called sP 2-hybridization. With this hybridization, three equal Q-orbitals are obtained located in one plane at an angle of 120º (Fig. 25).

Fig. 25. SP 2 scheme - hybridization

The molecules of type AB 3 formed with this hybridization are of the form of a flat proper triangle with atoms A in the center and atoms in its vertices. Such hybridization occurs in boron atoms and other elements of the third group and in carbon atoms in a molecule with 2 H 4 and in ion from 3 2-.

Example 7.Explain the formation of chemical bonds in the VN 3 molecule and its structure.

Decision.Experimental studies suggest that in the VN 3 molecule, all three bonds are located in the same plane, the angles between the connections are 120º. This structure of the molecule is explained by the fact that in the atom of boron in the excited state, the valence orbital was mixed, populated with unpaired electrons (2S 1 2p 2) and it forms SP 2-hybrid orbitals. The diagram of the VN 3 molecule is shown in Fig. 26.

Fig. 26. The diagram of the formation of the VN 3 molecule

If one S- and three p-orbitals are involved in hybridization ( sP 3-hybridization), as a result, four hybrid orbitals are formed, directed to the tops of the tetrahedron, i.e. Corner-oriented 109º28 ¢ (~ 109.5º) to each other. The resulting molecules have a tetrahedral structure. The hybridization of this type explains the structure of limit hydrocarbons, carbon compounds with halogens, many silicon compounds, Ammonium cation NH 4 +, etc. The classic example of this hybridization is the methane CH 4 molecule (Fig. 27)

Fig. 27. Scheme of the formation of chemical bonds in the CH 4 molecule

If one S-, three p- and two D-orbitals are involved in hybridization ( sP 3 D 2 - hybridization), then there are six hybrid orbitals, powered by octahedra vertices, i.e. Corner-oriented 90º each other. The resulting molecules have an octahedral structure. The hybridization of this type explains the structure of sulfur compounds, selenium and tellurium with halogens, for example SF 6 and SEF 6, and many complex ions: 2-, 3-, etc. In fig. 28 shows the formation of sulfur hexafluoride molecule.

Fig. 28. SF 6 Molecule Scheme

Chemical bonds with the participation of hybrid orbitals are highly strength. If the S-communication energy formed by the "clean" s-orbitals is taken per unit, then the binding energy at SP-hybridization will be 1.43, with SP 2-hybridization 1.99, with SP 3-hybridization 2.00, and With SP 3 D 2-hybridization 2.92. An increase in the strength of the links is due to a more complete overlapping of hybrid orbitals with non-librid in the formation chemical bond.

In addition to the types of hybridization, in chemical compounds There are hybridization SP 2 D, SP 3 D, SP 3 D 3, SP 3 D 3 and others. With SP 2 D-hybridization of the molecule and ions have a square shape, with SP 3 D-hybridization - the shape of trigonal biiramid and at SP 3 D 3-hybridization - pentagonal biiramid. Other types of hybridization are rare.

Example 8.The equations of two similar reactions are given:

1) CF 4 + 2HF \u003d H 2 CF 6; 2) SIF 4 + 2HF \u003d H 2 SIF 6

Which one is impossible in terms of the education of chemical ties?

Decision. For the formation of H 2 CF 6, SP 3 D 2 is needed, but in the carbon atom, the valence electrons are on the second energy levelwhere there are no D-orbitals. Therefore, the first reaction is in principle impossible. The second reaction is possible, since SP 3 D 2-hybridization in silicon is possible.

b is a torsion angle between planes passing through the top three atoms 1, 2, 3 and 2, 3, 4.

The linear form is characteristic of diatomic molecules. To predict the spatial structure of the polytomic molecule, it is necessary to know not only the length of the communication, but also the values \u200b\u200bof valence and torque angles.

If the molecule consists of three or more atoms, i.e. There are two or more chemical bonds in it, the angles are formed between their directions (up to 180 0)called valence angles(a).

Torsion Angle (B) - dwarbon angle between two planes passing through any dedicated three atoms.

Examples of geometry of molecules are presented in Fig. 4.11.

Consider the effect of hybridization on the geometric shape of molecules.

If we consider that p-orbitals are directed towards a friend at an angle of 90 0, it would be necessary to propose that communication in molecules, for example, H 2 O, NH 3 should also be directed towards each other in direct corners. However, it is not. Moreover, it is often not justified by the experience of the expected non-equality of connections formed at the expense of various orbital. The experimental way is established that if the atom forms several similar links due to electrons of different energy pylons, these bonds turn out to be energetically equivalent.

Fig. 4.11. Geometry Molecules:

(a) - linear; (b) - triangular; (c) - tetrahedral;

(g) - trigonal-biyramidal; (e) - octahedral;

(e) - Pentagonal BiPyramidal

The quantum mechanical theory of the structure of the atom cannot explain this fact, and for carrying out the theory in accordance with the experiment arose a hypothesis. hybridization of orbital .

According to this hypothesis, various orbitals of one atom involved in the formation of S-links are aligned with form and energy. Of several different orbitals, the same number of hybrid orbitals that have the same shape and the same energy are formed. The hybrid orbitals in space around the core are uniformly.

Orbitals can take part in hybridization various shapes. Consider only the hybridization of S- and P-atomic orbitals. The orbital arising from "alignment" of S- and P- orbitals is an inequal control of the "eight" (Fig. 4.12). She is in more than Extracted one way from the kernel than to another. Since the degree of overlapping of valence orbitals in this case is higher, the chemical bond formed by a hybrid orbital should be more durable than formed by conventional S- and P-orbital.

Fig. 4.12. SP-hybrid orbit

Depending on the number of interacting orbitals, a different number of hybrid orbitals is formed in an atom as a result of hybridization. Consequently, the forms of molecules will be different. Consider a number of simple examples.

In the formation of beryllium halide molecules, for example, BECL 2, one S- and one P-electrons appear in the formation of chemical bonds from the central atom appearing during the excitation of an atom:

Such an excitation is justified, if the energy released during the subsequent formation, the energy compensates for the cost of energy to excite the atom (S-electrone crossing per p-orbital).

The presence of unpaired electrons would have to provide two bonds of the beryllium atom with two chlorine atoms (having unpaired 3P electrons), but these bonds would be unequal.

During the cost of small energy, instead of the initial S- and P-orbitals of the beryllium atom, two equivalent SP-orbitals are formed. Hybrid SP-orbitals are elongated (Fig. 4.13, a) in opposite to each other directions (valence angle 180 o). Both energy generations are equivalent.

Since the energy released in the formation of BE-CL bonds is greater than the amount of energy costs to the excitation of the beryllium atom and the hybridization of its 2S- and 2P orbitals, the formation of the BECL 2 molecule is energetically beneficial.

The case considered is called sP-hybridization . Molecules formed with the participation of SP-hybrid orbitals are linear. The simplest example of this kind is a linear acetylene molecule C 2 H 2, formed by the SP-hybrid orbitals of carbon atoms (the remaining p-orbital of carbon atoms of participation in globalization in this case is not taken, but form p-communications).

In the hybridization of one S- and two p- orbitals, three equal SP 2-hybrid orbitals are formed. An example is the formation of a bora trichloride molecule. When excited in the boron atom, three unpaired electron appear:

The orbitals on which these electrons are located are averaged in shape and energy, forming three SP 2-hybrid orbitals, which are at an angle of 120 per friend (Fig. 4.13, b). This angle is optimal: it ensures maximum mutual removal and minimal repulsion energy of three hybrid orbitals, therefore provides minimal system energy.

Thus, molecules formed by SP 2-hybrid orbital are the correct triangle, in the center of which is a central atom (in our case - boron), and in the vertices are the remaining atoms (chlorine). All three connections in the molecule are equivalent.

Examples of molecules with SP 2-hybrid orbital carbon atoms are organic substances: Ethylene C 2 H 4, benzene with 6 H 6, etc. (In these cases, three orbitals of carbon atom are hybridized, and the fourth - participates in the formation of the P-link).

If four orbitals are involved in the formation of hybrid orbitals (for example, in the methane CH 4 molecule), SP 3-hybridization occurs. An excited carbon atom has 4 unpaired electrons (one S- and three P-electrons):

Fig. 4.13. Scheme of the arrangement of orbital at SP- (A), SP 2 - (b) and

sP 3 - hybridization (B)

If all four orbitals take part in hybridization, the four-generated SP 3-hybrid orbitals due to mutual repulsion are oriented towards each other at an angle of 109 o 28 / (Fig. 4.9, B). In this case, carbon atom takes place in the center right tetrahedraAnd in the vertices there are its partners (in the case of methane - hydrogen atoms).

In the nitrogen atom in the external energy level are five electrons:

Modern quantum chemical theory of chemical bond suggests that in the formation of an ammonia molecule NH 3, SP 3-hybridization is subjected to the nitrogen atom. In this case, they are talking about the hybridization of non-electrons, but orbitals, so it can be observed, both in the case of orbitals containing one electron and in the case of orbitals populated by two electrons, or at all free of them. Three atoms of ammonia hydrogen occupy three vertices of the formed tetrahedra from SP 3-hybrid orbital. The fourth Tetrahedron top is engaged in a hybrid electronic cloud that is not involved in the formation of a chemical bond. Since not all vertices of tetrahedra are identical, the valence angle in the ammonia molecule is less than a tetrahedral and equal to 107 0, i.e. The molecule is a slightly distorted tetrahedron (see the trigonal pyramid. 4.10, b).

In the water molecule, the valence corner of the N-O-n is also close to tetrahedral (104.5 0). It is explained by the fact that the orbital atom of the oxygen atom is exposed to SR 3-hybridization, with two SP 3-hybrid orbitals overlap with S-orbitals of two hydrogen atoms, and the two are seated with watered electronic pairs.

Energy characteristics of bonds in halogen hydrogen plants show that even in this case, the orbital atoms of halogens are subject to SP 3-hybridization, and the bond is formed by the hydrogen atom and SP 3-hydride orbital atom of the halogen atom. It seems that there is no need to apply the theory of hybridization for diatomic mole-kul, but the connection in halogen hydrogen has greater durability than the calculation for communication formed by the "clean" p-orbital.

Examples of the influence of the essential electronic pairs of the central atom on the geometry of the molecule are also considered in Fig. 4.14. and in table. 4.3.

Thus, the compliance of the theory of hybridization by experimental studies (for example, data on the energy of chemical bonds) confirms the importance of the concept of hybridization itself. The hybridization is determined by the chemical and crystal chemical structure of substances, and, therefore, their chemical properties.

Fig. 4.14. The effect of vapor electronic pairs (e) of the central atom on the spatial configuration of molecules:

(a) - tetrahedron; (b) - trigonal pyramid; (B) - angular form;

(g) - trigonal biiramid; (e) - distorted tetrahedron; (e) - T-form; (g) - linear form; (h) - octahedron; (and) - tetragonal pyramid; (K) - Square

Table 4.3.

Number of electronic pairs of central atom

and spatial configuration of ABN molecules

Number of electronic pairs of atom a	The location of electronic par	The number of binding par	Number of vulnerable par	Geometric shape and composition of the molecule *	Examples
	Linear			Linear AV 2.	Beh 2, BECL 2
	Triangular			Flat triangle AV 3 Angle AB 2 E	BF 3 SNCL 2
	Tetrahedral			Tetrahedron AB 4 Trigonal Pyramid AB 3 E Angle AB 2 E 2	CCL 4, CH 4 H 3 N, NF 3 H 2 O, OF 2
	Trigonal Bipira Midal			Trigonal Bipiramid AB 5 Wrong Tetrahedron AB 4 E T-shaped AB 3 E 2 Linear AB 2 E 3	PCL 5 SF 4 CLF 3 XEF 2, IF
	Octahedral			Oktahedron AV 6 Square Pyramid AB 5 E Flat Square AB 4 E 2	SF 6, SIF IF 5, SBF XEF 4, ICL
	Pentagonal BiPi-Ramidal			Pentagonal Bipiramid AV 7 Wrong octahedron AB 6 E	IF 7 XEF 6

* E is a vapor electron pair.

Hybridization - Alignment (mixing) of atomic orbitals ( s. and r) with the formation of new atomic orbitals called hybrid orbitals.

Atomic orbital. - This is a function that describes the density of the electronic cloud at each point of the space around the atom kernel. Electronic cloud is a space area in which an electron can be detected with a high probability

SP-hybridization

It occurs when mixing one S and one p-orbitals. Two equivalent sp-atomic orbitals are formed, located linearly at an angle of 180 degrees and directed into different directions from the kernel of the central atom. The two remaining non-mentioned P-orbitals are located in mutually perpendicular planes and are involved in the formation of π-bonds, or are engaged in the vulnerable pairs of electrons.

SP2 hybridization

SP2 hybridization

It occurs when mixing one S- and two P-orbitals. Three hybrid orbitals are formed with axes located in the same plane and directed to the vertices of the triangle at an angle of 120 degrees. The non-liberal P-atomic orbital is perpendicular to the plane and, as a rule, participates in the formation of π-links

The table shows examples of compliance with the most common types of hybridization and the geometric structure of molecules under the assumption that all hybrid orbitals participate in the formation of chemical bonds (there are no vapor electronic pairs)

Type of hybridization	Number of hybrid orbitals	Geometry	Structure	Examples
		Linear		BEF 2, CO 2, NO 2 +
sp. 2		Triangular		BF 3, NO 3 -, CO 3 2-
sp. 3		Tetrahedrical		CH 4, CLO 4 -, SO 4 2-, NH 4 +
dSP. 2		Flat-shed		Ni (CO) 4, 2-
sp. 3 d.		Hexahedrical
sp. 3 d. 2 , d. 2 sp. 3		Octahedrical		SF 6, FE (CN) 6 3-, COF 6 3-

4. Electrovalent, covalent, donor-acceptor, hydrogen bonds. Electronic structure Σ and π communication. The main characteristics of a covalent bond: communication energy, length, valence angle, polarity, polarizability.

If there is an electrostatic interaction between two atoms or two groups of atoms, leading to a strong attraction and the formation of a chemical bond, then such a connection is called electrovalent or heteropolar.

Covalent communication chemical bond formed by overlapping a pair of valence electronic clouds. Compound communication Electronic clouds are called a common electronic pair.

Donor-acceptor communication - This is a chemical bond between two atoms or a group of atoms, carried out by a vapor pair of electrons of one atom (donor) and the free level of the other atom (acceptor). This relationship differs from the covalent bond with the origin of electron communication.

Hydrogen communications - This type of chemical interaction of atoms in a molecule is characterized by the fact that a hydrogen atom has already been tied to a covalent tie with other atoms.

Σ Communication is the first and more durable bond, which is formed when overlapping electronic clouds in the direction of direct connecting the centers of atoms.

σ Communication is the usual covalent bonds of carbon atoms with hydrogen atoms. Molecules of limit carbon contain only σ communications.

π Communication is a less durable bond, which is formed when the electronic plane is overlapped by the nuclear atoms

The electrons π and σ communications lose their belonging to a specific atom.

Features σ and π communications: 1) The rotation of carbon atoms in the molecule is possible if they are connected by σ bond 2) the appearance of π communication deprives the carbon atom in the molecule in free rotation.

Communication length this is the distance between the centers of the associated atoms.

Valence corner this is the angle between two bonds having a common atom.

Energy connection energy released in the formation of chemical. communication and its strength characterized

Polarity Communications is due to the uneven distribution of electron density due to differences in the electrical negativeness of atoms. On this basis, covalent ties are divided into non-polar and polar. Polarizability Communications is expressed in displacement of electrons communications under the influence of an external electric field, including a different reacting particle. Polarizability is determined by electron mobility. The polarity and polarizability of covalent bonds determines the reactivity of molecules with respect to polar reagents.

5. ion connection (electrosal) - Very durable chemical bonds formed between atoms with a large difference of electrical negotiations, in which the total electron pair passes mainly to the atom with greater electronegitability. Covalent bond - arises due to the socialization of the electronic pair by means of an exchange mechanism when each of the interacting atoms supplies one electron. Donoro Acceptor bond (coordination) Chemical bond between two atoms or a group of atoms, carried out by a vapor pair of electrons of one atom (donor) and free orbital of the other atom (acceptor). For example NH4 for the occurrence of hydrogen bonds, it is important that atoms have atoms in the molecules of substances Hydrogen associated with small but electronegative atoms, for example: O, N, F. It creates a noticeable partial positive charge on hydrogen atoms. On the other hand, it is important that electronegative atoms have insolent electronic pairs. When the hydrogen is depleted by electrons of one molecule (acceptor) interacts with a different electronic pair on an N, O or F atom of another molecule (donor), then there is a link similar to the polar covalent. In the formation of a covalent bond in organic compound molecules, a general electron pair populates binding molecular orbitals with lower energy. Depending on the form of the MO - σ-MO or π-MO - the bonds are referred to σ- or p-type. σ-bond is a covalent bond formed by overlapping S-, P- and hybrid JSC along the axis connecting the kernel of the binding atoms (i.e., with axial overlapping of JSC). π-Communication is a covalent bond arising from the lateral overlapping of non-librid R-AO. Such overlapping occurs outside the straight line connecting the kernels of atoms.
π-bonds arise between atoms already connected by σ-bond (at the same time double and triple covalent bonds are formed). π-bond is weaker than σ-bond due to the less complete overlapping of the R-AO. The different structure of σ- and π-molecular orbitals determines the characteristic features of σ- and π-bonds. 1.σ-link is stronger than π-bond. This is due to a more efficient axial overlapping of AO in the formation of σ-mo and finding σ-electrons between the nuclei. 2. By σ-bonds, intramolecular rotation of atoms is possible, since the form σ-MO allows such a rotation without breaking the connection (cm. Picture bottom)). The rotation of the double (σ + π) of the connection is impossible without a π-communication break! 3. Electrons on π-Mo, being outside the interstitial space, have greater mobility compared to σ electrons. Therefore, the polarizability of π-bond is significantly higher than σ-bonds.

The characteristic properties of a covalent bond - focus, saturation, polarity, polarizability - determine chemical and physical properties connections.

The focus of the communication is due to the molecular structure of the substance and geometric shape Their molecules. Corners between two connections are called valence.

Saturability - the ability of atoms to form a limited number of covalent bonds. The number of connections formed by an atom is limited by the number of its external atomic orbitals.

The polarity of the communication is due to the uneven distribution of electron density due to differences in the electrical negativeness of atoms. Under this feature, covalent bonds are divided into non-polar and polar (non-polar - ductomic molecule consists of identical atoms (H 2, CL 2, N 2) and the electronic clouds of each atom are distributed symmetrically relative to these atoms; polar - ductomic molecule consists of atoms of different chemical elements , and the general electronic cloud shifts towards one of the atoms, thereby forming an asymmetry of the distribution of the electric charge in the molecule, the generation of the molecule).

The polarizability of communication is expressed in the displacement of electrons of communication under the influence of an external electric field, including another reacting particle. Polarizability is determined by electron mobility. The polarity and polarizability of covalent bonds determines the reactivity of molecules with respect to polar reagents.

6.Namenclature It is a rules system that allows you to give an unambiguous name to each individual connection. For medicine, knowledge of the general rules of the nomenclature is of particular importance, since the names of numerous drugs are being built in accordance with them. Currently generally accepted systematic Nomenclature of Jupak(IUPAC - International Union of Theoretical and Applied Chemistry) *.

However, still persisted and widely used (especially in medicine) trivial(ordinary) and semi -rial names used even before the construction of the substance becomes known. In these names, natural sources can be reflected and methods for obtaining, especially noticeable properties and applications. For example, lactose (milk sugar) is isolated from milk (from lat. lactum- Milk), palmitic acid - from palm oil, peyrogradic acid obtained with a pyrolysis of grape acid, in the name of glycerin reflected its sweet taste (from Greek. glykys- Sweet).

Trivial names especially often have natural compounds - amino acids, carbohydrates, alkaloids, steroids. The use of some rooted trivial and semi -rial names is allowed by the rules of Jew. These names include, for example, "glycerin" and the names of many widely known aromatic hydrocarbons and their derivatives.

Rational nomenclature of limit hydrocarbons

Unlike trivial names are based on the structure of molecules. The names of the complex structures are fought from the names of the blocks of the radicals associated with the main novels the most important node of the molecule along this nomenclature of alkanes are considered as derivatives of methane in which hydrogen atoms are substituted with appropriate radicals. The selection of methane carbon is arbitrary therefore 1 can have several names. According to this nomenclature, alkens are considered as derivatives of ethylene and alkina-acetylene.

7. Homology of organic compoundsor the law of homologues - It is that substances of one-meter function and the same structure, differing from each other. by Its atomic composition of NCN 2 is consistent and in all their others. The character, and the difference in their physical behavior increases or changes correctly as the difference increases in the composition determined by the number of N groups of CH 2. Such chemicals. Similar compounds form so ordinary. a homological manner, the atomic composition of all members of which it is possible to express a general formula based on the composition of a group of a number and number of carbon atoms; Organic substances of the same name type of alkane only.

Isomers compounds having the same composition but a different structure and properties.

8. Nucleophandflax and electrophopandlinen reagginge.nTU. The reactants participating in reacts are divided into nucleophilic and electrophile. Nucleophilic reagents, or nucleophiles, provide their pairslelectrons on the formation of a new bond and displace from the RX molecule a leaving group (x) with a pair of electrons that have formed an old connection, for example:

(where R is an organic radical).

Neglofils include negatively charged ions (HAL -, OR, CN -, NO 2 -, OR -, RS -, NH 2 -, RCOO - etc.), neutral molecules with a free pair of electrons (for example, N 2 , NH3, R 3 N, R 2 S, R 3 P, ROH, RCOOH), and metalloorganic. Connections R - ME with a sufficiently polarized relationship C - ME +, i.e. capable of being donors of R -. Reactions involving nucleophiles (nucleophilic substitution) are characteristic mainly for aliphatic compounds, such as hydrolysis (it -, H 2 O), alcoholiz (RO -, ROH), acidoliz (RCOO, RCON), amination (NH - 2, NH 3 , RNH 2, etc.), cyanization (CN -), etc.

Electrophilic reagents, or electricifications, in the formation of a new communication serve as an electron pair acceptors and displacing the leaving group as a positively charged particle. Electrophilas include positively charged ions (for example, H +, NO 2 +), neutral molecules with an electronic deficiency, for example SO 3, and strongly polarized molecules (CH 3 SO - BR +, etc.), and polarization is particularly effectively achieved by complex formation with coefficients Lewis (HAL + - HAL - · A, R + - CL - · A, RCO + - CL - · A, where A \u003d A1C1 3, SBCl 5, BF 3, etc.). The reactions involving electrophils (electrophile substitution) include the most important reactions for the aeromatic hydrocarbons (for example, nitration, halogenation, sulfonation, Freidel - Krafts reaction):

(E + \u003d HAL +, NO + 2, RCO +, R +, etc.)

In certain systems, the reaction with the participation of nucleophiles is carried out in an aromatic series, and reactions involving electrophils - in aliphatic (most often in a number of metal organic compounds).

53. Interaction of oxo compounds with metallorganic (ketone or aldehyde plus metal)

Reactions are widely used to produce alcohols. In addition to the formaldehyde of Grignar reagent (R-MGX), the primary alcohol is formed, another aldehyde of secondary, and rituitful alcohols

sP 3-hybridization is characteristic of carbon compounds. As a result of the hybridization of one S-orbital and three

p-orbitals are formed by four hybrid SP 3 -Orbital, aimed at the tops of the tetrahedron with an angle between the orbitals of 109.5 oh. Hybridization is manifested in the complete equivalence of bonds of carbon atom with other atoms in compounds, for example, in CH 4, CCl 4, C (CH 3) 4, etc.

Fig.5 SP 3-hybridization

If all hybrid orbitals are associated with the same atoms, then the relationships do not differ from each other. In other cases there are small deviations from standard valence angles. For example, in the water molecule H 2 O oxygen - SP 3-Gybrid, is located in the center of the wrong tetrahedron, the tops of which "look" two hydrogen atoms and two vapor pairs of electrons (Fig. 2). The shape of the angular molecule, if you look through atom centers. The horn valence corner is 105 o, which is quite close to the theoretical value of 109 o.

Fig.6. SP 3-hybridization of oxygen and nitrogen atoms in molecules A) H 2 O and B) NCl 3.

If it had not been hybridization ("alignment" o-H connections), HOH valence angle would be 90 °, because hydrogen atoms would be attached to two mutually perpendicular p-orbitals. In this case, our world would probably look completely different.

The theory of hybridization explains the geometry of the ammonia molecule. As a result of the hybridization of 2s and three 2P nitrogen orbital, Four hybrid orbitals SP 3 are formed. The configuration of the molecule is a distorted tetrahedron, in which three hybrid orbitals participate in the formation of a chemical bond, and the fourth with a pair of electrons - no. Corners of each n-H connections Not equal to 90 o as in the pyramid, but are not equal to 109.5 o, corresponding to the tetrahedra.

Fig.7. SP 3 - hybridization in ammonia molecule

In the interaction of ammonia with a hydrogen ion as a result of donor-acceptor interaction, ammonium ion is formed, the configuration of which is a tetrahedron.

Hybridization also explains the difference between the corner between the O-H bonds in the angular molecule of water. As a result of the hybridization of 2S and three 2P oxygen orbital, SP 3 hybrid orbitals are formed, of which only two are involved in the formation of a chemical bond, which leads to distortion of an angle corresponding to the tetrahedra.

Fig.8. SP 3-hybridization in water molecule

In hybridization, not only S and R-, but also D- and F-orbitals may be included.

With SP 3 D 2-hybridization, 6 equal clouds are formed. It is observed in such compounds as 4-, 4-. At the same time, the molecule has an octahedron configuration:

Fig. nined 2 SP 3-hybridization in ion 4-

Presentations on hybridization make it possible to understand such features of the structure of molecules that cannot be explained in another way.

The hybridization of atomic orbitals (AO) leads to a displacement of the electron cloud in the direction of education with other atoms. As a result, the area of \u200b\u200boverlapping hybrid orbitals turns out to be greater than for pure orbital and the strength of communication increases.

End of work -

This topic belongs to the section:

Chemical bond. Types of interaction of molecules

For molecular systems as for multielectronic atoms, an accurate solution of the SD Dinger equation is impossible. Approximate solutions are achieved. There are two ways to explain the character of a covalent bond. Method of valence.

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All the themes of this section:

Chemical bond. Types of interaction of molecules
Chemical bond is a combination of forces between atoms, forming stable systems: molecules, ions, radicals. None of the known interactions - electric, magnetic or gravitations

The reason for the formation of a chemical bond - a decrease in the total energy of the system
Fig. 1 The dependence of the potential energy E of the system of two hydrogen atoms from the ground

The main provisions of the MWS
1) a covalent chemical bond is formed by two electrons with oppositely directed spins, and this electron pair belongs to two atoms. 2) covalent bond all the stronger

Chemical Communication Education Mechanisms
In the valence method, the exchange and donor-acceptor mechanisms for the formation of chemical bond are distinguished. Exchangeable mechanism. To the exchange mechanism of chemical education

Donor-acceptor mechanism
The donor-acceptor mechanism is the formation of a covalent bond due to the two-electron cloud of one atom (donor) and the free orbital of the other (acceptor). Examples of chemical education

Valence
The valence is the property of the atom of this element to attach or substitute a certain number of atoms of another element. The measure of valence is the number of covalent bonds that form an atom. At this

SP- hybridization
SP-hybridization occurs, for example, in the formation of halides BE, Zn, CO and HG (II). In the valence, all metals halides contain at the corresponding energy level S and P-Nesar

Method of molecular orbitals
The Sun method is widely used by chemists. As part of this method, a large and complex molecule is considered as consisting of separate two-center and two-electron connections. It is assumed that electrons

Polarity of communication
Between different atoms, a clean covalent bond may manifest itself if electronegativity (EO) of atoms is the same. Such molecules are electrosymmetric, i.e. "Centers of gravity" of positive charges I

Hydrogen communications
Hydrogen bond is a special type of chemical bond. It is known that hydrogen compounds with strongly electronegative non-metals, such as F, O, N, have anomalous high temperatures boiling

Communication energy
The energy characteristic of the chemical bond is important. In the formation of a chemical bond, the total energy of the system (molecules) is less than the energy of the components (atoms), i.e. E (AB)<Е(А)+

Strength increases with a decrease in communication length
Metal communication occurs as a result of partial delocalization of valence electrons, which are quite freely moving in the lattice of metals, electrostatically interacting with

sP-hybridization occurs, for example, in the formation of halides BE, Zn, CO and HG (II). In the valence, all metals halides contain at the corresponding energy level S and p-unpaired electrons. When the molecule is formed, one S- and one p-orbital form two hybrid SP-orbitals at an angle of 180 o.

Fig. 3. SP-hybrid orbitals

Experimental data show that all BE, ZN, CD and HG (II) halides are linear and both bonds have the same length.

sP 2 -Hypebridization

As a result of the hybridization of one S-orbital and two p-orbitals, three hybrid SP 2 are formed, located in the same plane at an angle of 120 per friend. Such, for example, the configuration of the BF 3 molecule:

Fig.4.sP 2 -Hypebridization

sP 3-hybridization

sP 3-hybridization is characteristic of carbon compounds. As a result of the hybridization of one S-orbital and three

p-orbitals are formed by four hybrid SP 3 -Orbital, aimed at the tops of the tetrahedron with an angle between the orbitals of 109.5 oh. Hybridization is manifested in the complete equivalence of bonds of carbon atom with other atoms in compounds, for example, in CH 4, CCl 4, C (CH 3) 4, etc.

Fig.5 SP 3-hybridization

If all hybrid orbitals are associated with the same atoms, then the relationships do not differ from each other. In other cases there are small deviations from standard valence angles. For example, in the water molecule H 2 O oxygen - SP 3-Gybrid, is located in the center of the wrong tetrahedron, the tops of which "look" two hydrogen atoms and two vapor pairs of electrons (Fig. 2). The shape of the angular molecule, if you look through atom centers. The horn valence corner is 105 o, which is quite close to the theoretical value of 109 o.

Fig.6. SP 3-hybridization of oxygen and nitrogen atoms in molecules A) H 2 O and B) NCl 3.

If there were no hybridization ("alignments" of O-H bonds), the hOH valence angle would be equal to 90 °, because hydrogen atoms would be attached to two mutually perpendicular p-orbitals. In this case, our world would probably look completely different.

The theory of hybridization explains the geometry of the ammonia molecule. As a result of the hybridization of 2s and three 2P nitrogen orbital, Four hybrid orbitals SP 3 are formed. The configuration of the molecule is a distorted tetrahedron, in which three hybrid orbitals participate in the formation of a chemical bond, and the fourth with a pair of electrons - no. The angles between the N-H bonds are not equal to 90 o as in the pyramid, but are not equal to 109.5 o, corresponding to the tetrahedra.

Fig.7. SP 3 - hybridization in ammonia molecule

In the interaction of ammonia with a hydrogen ion as a result of donor-acceptor interaction, ammonium ion is formed, the configuration of which is a tetrahedron.

Hybridization also explains the difference between the corner between the O-H bonds in the angular molecule of water. As a result of the hybridization of 2S and three 2P oxygen orbital, SP 3 hybrid orbitals are formed, of which only two are involved in the formation of a chemical bond, which leads to distortion of an angle corresponding to the tetrahedra.

Fig.8. SP 3-hybridization in water molecule

In hybridization, not only S and R-, but also D- and F-orbitals may be included.

With SP 3 D 2-hybridization, 6 equal clouds are formed. It is observed in such compounds as 4-, 4-. At the same time, the molecule has an octahedron configuration.