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Section 16. Chemistry
Mahmudova Feruza Ahmadzhanovna, assistant of Tashkent Chemical-Institute of Technology Umarova Muattar Bahtiyarovna, senior teacher of Tashkent Institute of Chemistry and Technology
Maksumova Aytura Sitdikovna, professor of Tashkent Chemical-Institute of Technology E-mail: feruza_ahmadjonovna @mail.ru
ETHERIFICATION OF METACRYLIC ACID BY OLEFINES
Abstract: The process of synthesis of methacrylic unsaturated ester is studied. The reaction of esterification of methacrylic acid with isomeres of liquid olefins has been studied in the presence of an acid catalyst in a temperature range of40-60 °C. The influence of the length of the hydrocarbon chain of olefins on the yield of the final product has been shown.
Keywords: olefins, esterification, methacrylic acid, catalyst, inhibitor.
Literary sources in recent years show that unsaturated esters are the obj ect of research by many scientists. Owing to the presence of several reaction centers, these compounds can be the starting objects for the preparation on their basis of a number of substances possessing a complex of valuable properties.
Of the general methods for the preparation of esters can be indicated as the following: 1) the reaction of esterification of acids with alcohols; 2) reaction of esterification of alcohols with acid anhydrides or acid chlorides; 3) a interesterification reaction; 4) the reaction of esterification of carboxylic acids with olefins, etc. The esterification of carboxylic acids directly by olefins instead of alcohol has the following advantages:
a) the stage of obtaining alcohols from olefins is removed;
b) there is no need to allocate water; c) for a large excess of olefin with respect to the acid, it is possible to obtain a high purity ether, etc. [1, 172]. Most of the research in this area relates to esters based on acrylic and methacrylic acids.
To obtain p-chlorophenyl methacrylate, the authors used the methacrylic acid esterification (MAA) reaction with p-chlorophenol in the presence of a mixture of sulfuric and boric acids [2, 236-241]. The researchers showed that the esterification of MAC with p-chlorophenol does not occur with the catalysis only of sulfuric or boric acids, but occurs with the catalytic action of the H2SO4-H3BO3 system, based on the intermediate formation of tri-chlorophenyl borate.
The authors synthesized methacrylic ethers of cyclic and O, S, N-containing heterocyclic acetylenic alcohols [3, 237241]. The influence of the structure and the ratio of reagents, the nature of the catalyst, the temperature on the kinetics of the reaction, and the conditions for the synthesis of esters have been determined.
Literature sources practically do not provide data on the processes of esterification of methacrylic acid with liquid olefins, the study of which is of undoubted interest for the purpose of producing reactive monomers.
Experimental part
To conduct the studies, liquid olefins were separated from the C6-C7 fractions by the rectification method; 2-meth-yl-1-pentene (clear liquid, boiling point 62.1 °C, density at 20 °C0.66798 g/cm3); 2-ethyl-1-pentene (clear liquid, boiling point 62.1 °C, density at 20 °C0.66798 g/cm3); hexene-1 (clear liquid, boiling point 62.1 °C, density at 20 °C0.66798 g/cm3); methacrylic acid (TU2431-027-55856863-2003).
Esterification of methacrylic acid with liquid olefins has been carried out in a three-necked round-bottom flask fitted with a thermometer, a separatory funnel and a mechanical stirring device. The flask has been immersed in a "WITEG" thermostat filled with distilled water (temperature error of+0.1 °C).
The process of carrying out the experiment is as follows. The calculated amount of methacrylic acid, hydroquinone,
acid catalyst was loaded into the flask. While stirring at room temperature, olefins were added dropwise. The resulting reaction mixture was stirred for 10-11 hours at a temperature of 60 °C. After completion of the reaction, the catalyst was separated by treatment with a 10% alkali solution. The ether extract was washed with distilled water and the mixture was distilled in vacuum to isolate the desired product. Synthesized esters are colorless liquids, readily soluble in organic solvents.
IR spectra of the initial reagents and the synthesized esters were recorded on a Fourier spectrophotometer "SISTEM-200" on KBr.
Results and discussion
Synthesis of unsaturated methacrylic esters was carried out by esterification of methacrylic acid with the corresponding olefins (2-methyl-1-pentene, 2-ethyl-1-pentene, 1-hexene) according to the following scheme:
H2C
H3C-C 3 I
C=O I
O
,O
CH2=C—CH2-CH2-CH3+ CH2-C—c
CH3
CH3
xOH
H+
ch3—c—ch2- ch^- ch3
I
CH3
CH2=C—CH^CH^CH3 + CH^C—C.
O
CH^CH3
CH3
OH
CH2=CH-CH^CH^CH3 + CH^C—C,
CH3
O
H+
H2C 2II
H3C-C
C=O I
0
1
■»- CH3— C— CH^CH^CH3
I
CH^CH2
H2C
H3C-C
H+
C=O I
0
1
■>■ CH3-CH—CH^CH^CH3
OH
The structure of synthesized complex unsaturated ethers is confirmed by IR spectra (table).
Table 1. - IR spectra of methacrylic esters of olefins CH2=C(CH3) COO-R
№ R IR-spectra
c=c c=o c-o-c
1. CH3—C—CH2—CH2—CH3 CH3 1638 1728 1295
2. CH3—C—CH2—CH2—CH3 CH2—CH3 1646 1730 1280
3. —CH-CH2—CH2—CH2—CH3 CH3 1637 1729 1290
The IR spectroscopic data showed that new absorption bands appear in the spectra of esters, corresponding to the frequencies of the stretching vibrations at C = O and C = C in the regions 1728, 1730, 1729, 1638, 1640, 1637 cm-1.
The influence of the nature of the olefin, the ratio of the initial reagents and the concentration of the catalyst on the
Figure 1. The dependence of the ester yield on time in the esterification reaction of MAC with 2-methyl-1-pentene. The ratio of MAC: olefin = 4, catalyst p-toluenesulfonic acid, [Inh] = 0.5 mg/eq. T, oC = 1-40; 2-50; 3-60
yield of the final product has been studied. The esterification reaction was carried out in bulk, i.e. without solvent. As a homogeneous acidic esterification catalyst, sulfuric acid, p-toluenesulfonic acid was used. In the presence of these catalysts, the esterification reaction rate increases sharply with increasing temperature (Figure 1, 2).
P,% 100-
80604020-
120
240
360
480
600 Time, m
Figure 2. Dependence of the ester yield on time in the reaction of esterification of MAC with 2-methyl-1-pentene. The ratio of MAC: olefin = 4; catalyst, H2SO4, [Inh] = 0.5 mg/eq. T, oC = 1-40; 2-50; 3-60
P,%
1004
80 604020
120
240
360
480
600 Time, m
Figure 3. Dependence of the yield of esterification of methacrylic acid esterification with 2-methyl-1-pentene at different molar ratio of reagents: 1-1: 1; 2-2: 1; 3-3: 1. T = 60 °C; catalyst p-toluenesulfonic acid, [Inh] = 0.5 mg/eq
As can be seen from (Figure 1, 2) sulfuric acid is inferior in catalytic activity. The results of esterification of methacrylic acid with olefins at different ratios of the initial reagents are shown in (Figure 3).
From the data obtained, it follows that to achieve a high yield of ether, no less than threefold excess of methacrylic acid is required. Under these conditions, the yields of the ester based on methacrylic acid and 2-methyl-1 pentene are 80-82%.
Conclusions
1. A method for the preparation of esters by the reaction of methacrylic acid esterification with liquid olefins has been studied. The influence of the temperature and nature of olefins on the esterification process has been studied.
2. It has been found that the rate of reaction and the yield of the final product depends on the structure of the olefin used. Thus, in the esterification of 2-methyl-1-pentene with methacrylic acid, the greatest yield of the ester is formed.
References:
1. Дьячкова Т. П., Орехов В. С., Субочева М. Ю., Воякина Н. В. Химическая технология органических веществ. Учебное пособие. - Тамбов: Изд-во Тамб. Гос. Техн. Ун-та. 2007. - Ч. 1.- 172 с.
2. Кобякова Н. К., Макарова И. Ю., Протасов А. А., Червякова Г. Н. Особенности получения п-хлорфенилметакрилата методом этерификации // Химия, химические и биотехнологии. Труды Нижегородского государственного технического университета им Р. Е. Алексеева, - № 3(100). 2013.- С. 236-241.
3. Гилажов Е. Г., Абилхайров А. И. Синтез мономеров на основе циклических и гетероциклических ацетиленовых спиртов // Вестник КазНу серия химическая,- № 1. 2012.- С. 237-241.
