I Opaynich, V Dutka, Ya Kovalsky - Surface pressure of monomolecular layers and reactivity of diacyl peroxides - страница 1

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ВІСНИК ЛЬВІВ. УН-ТУ VISNYK LVIV UNIV.

Серія хім. 2008. Bun. 49. Ч. 2. С. 212-216    Ser. Khim. 2008. No 49. Part 2. P. 212-216

УДК 661.729.541.-183.3

SURFACE PRESSURE OF MONOMOLECULAR LAYERS AND REACTIVITY OF DIACYL PEROXIDES

I. Opaynich1, V. Dutka1, Ya. Kovalsky2

1Ivan Franko National University of Lviv, Kyryla & Mefodiya Str., 6, 79005 Lviv, Ukraine е-mail: vdutka @ ukr.net

2National University "Lviv Polytechnica", S. Bandera Str., 12, 79013 Lviv, Ukraine e-mail: yakovalskyi@mail.ru

Surface pressure of diacylic diperoxides monolayer on water-air phase interface was studied. It was shown that solvent which was used for monolayer formation influences the quantity of boundary area (Sm) of diperoxide. Decomposition rate constants of peroxides in different solvents and responsible value Sm of diacylic diperoxides monolayer were compared.

Key words: diperoxides, rate constants, surface pressure, monolayer.

Monomolecular layers obtained with small quantities of insoluble organic peroxides on the surface of liquid may be considered as a limiting case of adsorption when the solubility of surfactant is so low that may be neglected. The behavior of the organic peroxides layers on the surface of water is similar to adsorptions phenomena on the solid surface. It was noted that the proteins monomolecular layers have self-organization possibility. Protein systems can be perspective for the nanomaterials construction [1]. Polyaniline layers and their derivatives [2-3] investigation gave the possibility to obtain organized ensemble for using them in electronic devices.

Studying the monomolecular layers of organic peroxides at the liquid-gas interface gives possibility to estimate the reactivity initiators of radical processes in heterogeneous polymerizations. At the same time, there is possibility to determine the structure of monomolecular layers and flexibility of polymeric peroxides [4]. Polymeric diperoxides initiators have a series of preferences over the traditional monoinitiators. That is why the information about their behavior in the interface allows to these types of compounds effective utilizing.

In the present work the isotherms of organic peroxides surface pressure on the water surface were investigated. Among that the thermodestruction rates of investigated compounds in organic medium were studied.

Diacylic diperoxides were synthesized with the well-known methods by the reaction of respective chlorine anhydride with diperoxyacids in acetone in the presence of pyridine [5]. After the synthesis we clearned peroxides by water using and drying. After the recrystallization the active oxygen content was determined as shown in [6]. The diperoxides

© Opaynich I., Dutka V., Kovalsky Ya., 2008

SURFACE PRESSURE OF MONOMOLECULAR LAYERS ...

213

with 99.0% purity of prime products were used in the both kinetic and surface pressure of monolayers experiments. The rate of the peroxide compounds thermal decomposition was determinated like in [4]. The values of the surface pressures of monolayers were measured on the vertical bowl on the water-air interface. The experiment was carried out for mono­layer compression velocity 0.1-10-2 m/s. The monolayer on the bidistilled water surface was compressed by the Teflon barrier. All experiments were carried out at the temperature 25° C.

In this work the symmetric diacylic peroxides with the general formula were synthesized:

O O O о

Some physico-chemical parameters of obtained diperoxide compounds are represented in the Table 1. Synthesized diacylic diperoxides and one molecule in mono-layer interface optimal geometric structure AM1 which may occupy area (Sa) were calcu­lated by semi-empirical method (Fig. 1).

Fig.1. Optimized structure of diacetyldipersebacenat

In the Table 1 the effective constants (k) of thermal diperoxides decomposition in ethyl acetate at 353 K and this process energy of activation (Ea) are represented. For mono­layer surface peroxides pressure investigations with different size and rigidity of radicals R1 and R2 were chosen.

Table 1

Physical-chemical parameters of the diperoxides

Peroxide

R1

R2

T °С

M, g/mol

k-10-5,s-1

Ea, kJ/ mol

Sa, A2

DP-1

СН3-

-(Сщ4-

68.0

262

15.3

124.8

16

DP-2

СщСщ4-

-(Сщ4-

46.0

374

23.5

119.5

35

DP-3

СщСщ8-

п-С<Нг

69.0

506

23.6

116.0

32

DP-4

СщСщ8-

-(Сщ4-

71.0

486

24.7

124.2

43

DP-5

0CH3C6H4-

-(Сщ4-

88

416

18.4

121.0

28

The isotherms of surface pressure of diacetyl diperoxiadipinate (DP-1), dicaproyl diperoxiadipinate (DP-2) and dicaproyl diperoxiphtalat (DP-3) are shown in Fig. 2. Structure of organic peroxides monomolecular layers influences the surface of water with toluene using as solvent.

AREA PER MOLECULE (A2)

Fig. 2. The isotherms of surface pressure of DP-1 (7), DP-2 (2), DP-3 (3). Solvent: toluene

The obtained results show that on the water surface both DP-1 and DP-3 form the condensed monolayers [7]. In this case the structure of peroxide effects the character of sur­face pressure isotherms (Fig. 2). Qn the basis of the obtained results we can conclude that hydrophilic peroxide groups stay in the plane of interface, and the ended radicals Ri may be situated both in the plane of the interface and maybe orientated on side of gas phase under the some pressure value. The diperoxide DP-1 is characterized not by the big size radical R1 and not big rigidity of the central radical R2, that is why the monolayer, which is formed by this peroxide on the surface will not be able to make important deformations, in contrast to monolayer formed by the DP-2. The DP-3 diperoxide characterized by the flat central radical, however from the surface pressure isotherms we can conclude that the ended radicals are oriented in the side of gas phase from the start of manolayer formation. The ended R1 in DP-2 may be situated on the plane of interface with low deformations and be oriented in the side of the gas phase with the strong mololayer pressing. The numerical values of the investigated peroxides areas (Sm) extrapolated on zero pressure are in correlation with values Sa calculated by the quantum-chemistry method.

Qn the isotherms for DP-4 the region of semi-isobaric compression is observed. The appearance of this region is connected with the changing of ended radicals R1 of molecule orientation. The benzene rings presence in the ends of diperoxides molecules (DP-5) and in central part (DP-3) leads to the condensed monolayers formation [8].

The results of solvent studying on the surface pressure isotherms (DP-2) are shown on fig. 3 As the obtained data indicate the solvent used for the infliction have the sufficient effect on the form and values of extrapolated magnitudes of diperoxide area in the monolayer. In the polyperoxide case the correlation between general rates constants of Q-Q group decomposition in solution and occupy area the elementary link in monolayer formed from the respective solvent was found [4].

SURFACE PRESSURE QF MQNQMQLECULAR LAYERS ...

215

0 40 80 120 160

AREA PER MOLECULE (A2)

Fig. 3. The isotherms of surface pressure of DP-2. Solvent: 7 - benzene; 2 - toluene; 3 - xylene; 4 - acetone; 5 - butan-2-one; 6 - dioxane; 7 - ethylacetate; 8 - butylacetate; 9 - cyclohexane; 70 - CHCl3; 77 - chlorbenzene; 72 - ethylbenzene; 73 - CCl4

The thermal decomposition rates constants (k) are determined for 353 K in the different solvents for DP-4 and the corresponding values of the area occupied by diperoxide molecule in monolayer (Sm) extrapolated on zero pressure are listed in Table 2.

Table 2

The values of area per molecule (Sm) of DP-2 in monolayer and rate of thermal decomposition (k) peroxide in solvents

Solvent

dioxane

benzene

acetone

toluene

ethylacetate

CCl4

CHCl3

 

23.0

26.0

33.0

43.0

48.0

68.0

72.0

k 105, s-1

37.2

19.4

31.9

17.4

24.7

10.4

24.8

As it should be seen from presented results there is no correlation between these parameters in contrast to polymer analogs of diperoxides [4]. The given fact may indicate that the reactivity of Q-Q group in the case of diperoxide molecules basically depends on the solvent nature a while the role of molecules conformation in this case is insignificant.

1. Ямполъская Г.П., Левачев СМ., Харлов А.Е., Фадеев А.С., Измайлова В.Н. Мономолекулярные слои белков и перспективы конструирования наномате-риалов на их основе // Вестн. Москов. ун-та. Сер. 2. Химия. 2001. Т. 42. № 5. С. 355-362.

2. Dabke R.B., Dhanabalan A., Major S., Talwar S.S., Lal R., Contractor A.Q. Electrochemistry of polyaniline Langmur-Blodgett films // Thin Solid Films. 1988. Vol. 335. P. 203-208.

3. Ram M.K., Adami M., Sartore M., Salerno M., Paddeu S., Nicolini C. Comparative studies on Langmuir-Schaefer films of polyanilines // Synthetic Metals. 1999.

Vol. 100. P. 249-259.

4. Дутка В., Опайнич І. Реакційна здатність і поверхневий тиск моношарів діациль-них поліпероксидів // Вісн. Львів. ун-ту. Сер. хім. 2005. Вип. 46. С. 234-236.

5. Дутка В.С., Панкевич Р.В., Ковалъсъкий Я.П. Реакции индуцированного распада диацильных пероксидов // Укр. хим. журнал. 1988. Т. 54. № 4. С. 429-433.

6. Антоновский В.Л., Бузланова М.М. Аналитическая химия органических пероксидов. М.: Химия, 1978. С. 308.

7. Адамсон А. Физическая химия поверхностей. М.: Мир, 1979. C. 568.

8. Дутка В., Опайнич І. Поверхневий тиск моношарів діацильних пероксидів // Вісн. Львів. ун-ту. Сер. хім. 2006. Вип. 47. С. 312-316.

ПОВЕРХНЕВИЙ ТИСК МОНОМОЛЕКУЛЯРНИХ ПЛІВОК ТА РЕАКЦІЙНА ЗДАТНІСТЬ ДІАЦИЛЬНИХ ДИПЕРОКСИДІВ

І. Опайнич1, В. Дутка1, Я. Ковальський2

7 Лъвгвсъкий нацюналъний університет імені Івана Франка, вул. Кирила і Мефодія, 6, 79005 Лъвів, Україна е-mail: vdutka @ ukr.net

2Нацюналънийутверситет "Лъвівсъка політехніка", вул. С. Бандери, 72, 79073 Лъвів, Україна e-mail: yakovalskyi@mail.ru

Досліджено поверхневий тиск моношарів діацильних дипероксидів на межі поділу фаз вода-повітря. Показано, що розчинник, який використовували для формування моношару, впливає на величину площі дипероксиду на межі розділу фаз. Проведено порівняння констант швидкост термолзу дипероксид в у рзних розчинниках з в дпов дними величинами площ молекули в моношар .

Ключові слова: дипероксиди, швидкість розкладання, поверхневий тиск, моношар.

Стаття надійшла до редколегії 01.11.2007 Прийнята до друку 03.01.2008

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I Opaynich, V Dutka, Ya Kovalsky - Surface pressure of monomolecular layers and reactivity of diacyl peroxides