Duzlo Traube Rule. DUKLO-DURABE Rule

The presence of hydrophilic and oleophilic (hydrophobic) parts in PAV molecules is a characteristic distinctive feature of their structure. According to the ability to dissociation in aqueous solutions, surfactants are divided into ionogenicand non-ionic.In turn, the ionic surfactants are divided into anionic, cationic and ampholite (amphoteric).

Anionic Peav.dissociated in water to form a surfactant anion. To the surfactant of this type, which constitutes most of the world production of all surfactants, belongs:

a) carboxylic acids and their salts (soaps) of the general formula RCoom (where M is monovalent metal), for example sodium palmitate C 15 H 31 Coona, sodium stearate C 17 H 35 Coona, sodium oleate C 17 H 33 Coona;

b) alkyl sulfates Roso 2 OM;

c) alkylarylsulfonates RARSO 2 OM;

d) substances containing other types of surfactant anions, such as phosphates, thiosulfates, etc.

In acidic media, carboxylic acid salts are transferred to weaklyssorate and low-soluble acids, and in the presence of some cations (calcium, magnesium) form insoluble salts, which sharply reduces the effectiveness of their action as a surfactant, especially deteriorates their detergent action. Alkyl sulfates and alkyl sulfons, which are salts of strong acids, have great advantages in this regard, and therefore can be used in acidic and salt solutions.

Cationic surfactantsdissociate in water to form a surfactant cation. Cationary surfactants include:

a) salts of primary, secondary and tertiary aliphatic and aromatic amines;

b) salts of alkyl-substituted ammonium bases, etc.

Cationic surfactants - the most toxic and least biologically decomposed of all surfactants; They are often used as bactericidal, fungicidal, disinfectants, corrosion inhibitors.

Ampholite Peav.these include two functional groups, one of which has sour, and the other is an authentic, such as carboxyl and amine group. Depending on the pH of the ampholite surfactant environment, anionactive or cationic properties are displayed:

Non-ionic surfactantsdo not dissociate in solutions to ions. The methods of their preparation are based on the reaction of the addition of ethylene oxide to alcohols, carboxylic acids, amines and other connections. For example, the oxyethylated alkylspirts of the "OS" brand are synthesized by reaction:

ROH + NH 2 C-CH 2 ® RO (CH 2 CH 2 O) N H

The polyoxyethylene chain determines the hydrophilic properties of non-ionic surfactants. Changing the length of the polyoxyethylene chain, it is easy to adjust their colloid-chemical properties. These surfactants are used in any media (acid and alkaline), as well as in the presence of soluble salts. The polyoxyethylene esters of alkylphenols of the OP brand have good detergent properties.

The disadvantages of these surfactants include a slow decomposition due to the presence in their composition of the aromatic radical and, as a result, their accumulation in environmental facilities. The non-ionic surfactants with alkyl radicals are capable of biologically degraded quite fully and quickly.

All distinctive surfactants relative to their behavior in water are divided into truly soluble and colloidal.

The first group includes a large class of water soluble in water, organic compounds with a small hydrocarbon radical, such as lower alcohols, phenols, acids and their salts, amines. The substances of this type in the solution are in a molecular-dispersed state up to concentrations corresponding to their saturated solutions and the separation of the system into two solid phases. These substances are used as wetters of foaming agents, hydrophobizers during flotation, dispersants that facilitate the processes of formation of new surfaces, and so on.

Of particular interest are colloidal surfactants. They are primarily understood under the term surfactant. The main distinguishing feature of these substances is the ability to form thermodynamically stable (lyophilic) heterogeneous dispersed systems (associative or micellar colloids). The main properties of colloidal surfactants caused by their widespread use include high surface activity; The ability to spontaneous micelle formation - the formation of lyophilic colloidal solutions at a concentration of the surfactant above a certain value called critical concentration of micelle formation(KKM); The ability to solubilize is a sharp increase in solubility of substances in solutions of colloidal surfactants due to their "implementation" inside the micelles; High ability to stabilize various dispersed systems.

The surface activity of colloidal surfactants depends mainly on the length of the hydrocarbon radical. An increase in the radical length per group -CH 2 leads to an increase in surface activity by approximately 3.2 times ( dUKLO Rule - Traube). This rule is complied mainly for truly soluble surfactants.

For organic media, DUKLO - Traube Rule draws: Surface activity is reduced with an increase in the length of the hydrocarbon radical of the surfactant.

In conclusion, it can be noted that the main quantitative characteristic of the surfactant is the surface activity, which determines their ability to lower the surface tension, cause emulsification, foaming, dispersion and stabilization, wetting and other phenomena.

Adsorption - Phenomenon of spontaneous accumulation of one substance on the surface of another. Substance that is adsorbed called adsorption;the substance on the surface of which adsorption occurs - adsorbent.

Adsorption on the surface of liquids

On the surface of the liquids, particles of substances dissolved in liquids can be admisted. Adsorption accompanies the dissolution process, affecting the distribution of the particles of the dissolved substance between the surface layers of the solvent and its internal volume.

Adsorption on the surface of the liquid can be calculated using the Gibbs equation:

G - the value of specific adsorption, mol / m 2;

C - molar concentration, mol / m 3;

dσ - change in the surface tension corresponding to the change in the concentration of ΔC;

Surface activity.

If with an increase in the substance concentration, the surface tension decreases Δ σ< 0, то его адсорбция Г считается положительной (Г > 0). This means that the concentration of the substance in the surface layer is greater than in the volume of the solution.

If, with an increase in the concentration of the substance, the surface tension on the boundary of the phase separation increases Δ σ\u003e 0, then adsorption is considered negative< 0, это означает, что концентрация вещества в объеме раствора больше, чем в поверхностном слое.

Adsorption of Peav.

Pav - Dimilanses in nature, have polar (hydrophilic) and non-polar (hydrophobic) parts.

For example, soap: from 17 H 35 Coona

the symbol of the non-polar symbol of polar

parts of Part.

Pav is positively adsorbing substances, they include: fats, fatty acids, ketones, alcohols, cholesterol, soaps and other organic compounds. In the dissolution of such substances in water, positive adsorption occurs, accompanied by the accumulation of the substance in the surface layer. The process of exit of the molecules of these substances to the surface is very profitable, because leads to a decrease in surface tension on the border of the phase partition. Paving adsorption scheme:

The ability of the substance to reduce the surface tension on the border of the phase partition is called surface activity.

DUKLO-DURABE Rule

The magnitude of the surface activity of the surfactants of one homologous series of organic compounds depends on the length of the hydrocarbon radical: the lengthening of the surfactant per group -CH 2 increases the surface activity of the substance by 3-3.5 times.

Consider the DUKLO-Traube rule on the example of four representatives of the homologous series of alcohols.

Surface tension isotherm:

Adsorption Piav

In relation to polar water, these substances are electrolytes: inorganic acids, salts, alkali. The dissolution of these substances increases the surface tension, so the pH will be pushed out of the surface layer inside the adsorbent. Such adsorption is called negative. For example: dissolution of KS1 in water is accompanied by a salt dissociation, followed by hydration of the generated ions.

PEA adsorption scheme.

Particularities of the structure of the phase layer surface.

Intermediate phase containing one or more molecular layers

Features:

- inside the volume of pure substance, all forces of intermolecular interaction balanced

- the resultant all forces acting on surface molecules is directed inside the liquid

- Surface phenomena are insignificant if the ratios between body weight and the surface in favor of body weight

- surface phenomena acquire a value when the substance is in a fragmented state or in the form of a subtlest layer (films)

1 cm 3 Arrow 10 -7, S \u003d 6,000 m 2

1mm blood arrow 4 - 5 million erythrocytes; 1l Arrow\u003e 30 MLR cells, S \u003d 1000 m 2

S alveol \u003d 800 -1000 m 2; S capillaries liver \u003d 600 m 2

Surface energy Gibbs

Σ- Surface tension

Reducing Gibbs Energy:

Due to the decrease in surface area (particle enlargement)

By reducing the size of the surface tension (sorption)

403) surface tension

Work performed on the creation of a unit of the surface

Units of Measurement J / M 2

The force acting per unit length of the line limiting the surface of the liquid and directed towards the reduction of this surface

Units of measurement N / m 2

The dependence of the surface tension from the nature of substances, temperature and pressure.

The surface tension of liquids decreases with increasing temperature and near the critical temperature becomes zero. With an increase in pressure, the surface tension on the boundary of the liquid gas decreases, the concentration of molecules in the gas phase increases and the force decreases. Dissolved in-bes can increase, reduce and virtually influence on practical tension of liquids. Surface tension on the border of liquid depends on the nature of the spirps phases. It is the greater, the less the power of molecular interaction between heterogeneous molecules.

Methods for measuring the surface tension of the fluid.

The method of separating the rings from the surface of the liquid

The method of counting the number of drops of a certain amount of fluid under study flowing from the capillary (stalagmometric)

The method of determining the pressure, which is necessary for the separation of the air bubble from the capillary, immersed in the liquid (Rebinder method)

The method of measuring the height of the lift of the fluid in the capillary, the walls of which are well wetted

Distribution of the dissolved substance between the surface layer and the volume of the phase.

three cases of distribution of dissolved in-bes between the surface layer and the volume of the phase are theoretically, 1) is larger than in the volume of the phase.2) of the termination of the termination in the pound layer. Than in the volume of phases.3) of the terminus dissolved in the vo in the pound layer is the same as in the volume of the phases.

Classification of dissolved substances by their influence on the surface tension of the liquid (water).

classification 1) dissolved in-in low tension. Alcohols, K-You.2) Dissolved in-in slightly increases the nat. Neorg k-you, bases, salt.3) dissolved in virtually not changed NAT P-L. Sucrose.

Gibbs equation for the adsorption characteristic of dissolved substances. Analysis of the equation.

R \u003d - (C / RT) * (Δσ / Δc). Mr. adsorption on the p-ra. Δσ / Δc-pov activity in-va.analysis: Δσ / Δc \u003d 0, r \u003d 0. This is a PNV. Δσ / Δc\u003e 0, g<0-поверхностно инактивные в-ва. ∆σ/∆C<0, Г>0-surfactant.

The structure of molecules and properties of surfactants.

sV-VA: limited soluble

Have a smaller surface tension than liquids

Sharply change the surface properties of fluid

Structure: DIFIS - Different areas of the molecule are characterized by a different ratio of solvent

Hydrophobic properties: hydrocarbon radical

Hydrophilic properties: OH, NH 2, SO 3 H

Classification of surfactants, examples.

Molecular or non-ionic - alcohols, bile, protein substances

Ionic anionactive - soaps, sulfonic acids and their salts, carboxylic acids

Ionic cationic - organic nitrogen-containing bases and salts

The influence of the nature of the surfactant on their surface activity. Rule Dukelo - Traube.

Elimination of the chain on the radical - CH 2 - increases the ability of fatty acids to adsorption by 3.2 times

Applicable for dilute solutions and for temperatures close to room, because Desorption increases with increasing temperature

As part of its molecule. According to this rule, with an increase in the length of the hydrocarbon radical by one group Cη 2, the surface activity of the substance increases by an average of 3.2 times.

Surface activity depends on the structure of Pav molecules; The latter usually consist of a polar part (groups with a large dipole moment) and non-polar part (aliphatic or aromatic radicals). In the boundaries of the homologous series of organic substances, the concentration required to reduce the surface tension of the aqueous solution to a certain level is reduced by 3-3.5 times with an increase in carbon radical by one -Cη 2-group.

The rule was formulated by I. Traube (it.)russian In 1891, as a result of its experiments conducted on solutions of sets of substances (carboxylic acids, ethers, alcohols, ketones) in water. The previous studies of E. Ducloh though were close in spirit to the work of Traube, but did not offer any clear dependence of the concentration, therefore, in foreign literature, the rule only the name of the traube. . The thermodynamic interpretation of the Traube rule was given in 1917 by I. Langmur.

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As already noted, the molecules of surfactants (surfactant) capable of adsorbing on the border of the solution gas should be diliophores, i.e. have a polar and non-polar part.

The polar part of the surfactant molecules can be groups with a fairly large dipole moment: --on, - it, -nn 2, - SN, -CN, -NO 2.-CNS,

SNO, -SO 3 N.

The non-polar part of the surfactant molecule is usually aliphatic or aromatic radicals. The length of the hydrocarbon radical strongly affects the surface activity of the molecule.

DUKLO, and then a traube, studying the surface tension of aqueous solutions of a homologous series of limiting fatty acids, found that the surface activity of these substances on the border of the solution-air is greater than the larger the length of the hydrocarbon radical. Moreover, when lengthening the hydrocarbon radical on one - CH 2 - the surface activity increases by 3-3.5 times (by an average of 3.2 times). This situation has become known as dUKLO-DURABE Rule .

Other wording it It comes down to the following: with an increase in fatty acid chain in arithmetic progression, surfactivity increases in geometric progression.

What is the reason (physical meaning) of such a dependence set first Dukelo, and then, in a more general form, Traube? It lies in the fact that with an increase in the chain length, the solubility of fatty acid is reduced and thereby increases its molecules to move from the volume into the surface layer. For example, oil acid is mixed with water in all respects, Valerian gives only a 4 percent solution, all other fatty acids, with a larger molecular weight, soluble in water to an even less.

The Dukell-Traube rule, as was then established, is observed not only for fatty acids, but also for other surfactants forming homologous rows, alcohols, amines, etc. Ethooretical (thermodynamic) justification was given by Langmur.

With the introduction of surfactants to the water, almost non-radically hydrocarbon chains are pushing water molecules, embedded in its structure. The accomplishment of this requires the accomplishment of work, against molecular forces, since the interaction between water molecules is significantly larger than between water molecules and surfactant molecules. The reverse process - the yield of the surfactant molecules on the interfacial surface with the orientation of the hydrocarbon chains into the non-polar phase of the gas - it is spontaneously with a decrease in the energy of Gibbs system and the "winnings" of adsorption. The longer the hydrocarbon radical, the greater the number of water molecules, it discovers and the greater the desire of the surveillance molecules to the output to the surface, i.e. Moreover, their adsorption and adsorption work. The operation of adsorption when lengthening the chain on one link - CH 2 increases on the same value, which leads to an increase in the adsorption equilibrium constant (adsorption coefficient K) in the same number of times (3.2 times at 20 ° C) . This in turn leads to an increase in surface activity at ~ 3.2 times.

It should be noted that with this wording, the DUKLO-Traube rule is observed only for aqueous solutions and for temperatures close to room.

For solutions of the same surfactant in non-polar solvents, the DUKLO-Traube rule refers: with an increase in the length of the hydrocarbon radical, the solubility of the surfactant increases and they tend to move from the surface layer into the solution.

At higher temperatures, the average multiplier3.2 decreases, striving at the limit to one: with an increase in temperature, the surface activity as a result of desorption of molecules falls and the difference between the surface activity of the homologous series is smoothed.