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Home / Issues / № 2, 2014

Chemical sciences

MICROWAVE ACTIVATION IN THE SYNTHESIS OF LOWER ALCOHOL ACETATES
Appazov N.O., Akylbekov N.I., Niyazova D.Zh., Tulepova A.K., Seitova A.A., Shigenova A.S., Omarov E.A., Abilbek Zh.

Acetates of lower alcohols have a strong ester-fruity odor, included in the essential oils of many plants, are used in the food industry as identical to the natural food flavorings, are also used as solvents, paint products, fats, synthetic resins, etc. [1-5].

In the industry acetates obtained from direct esterification reaction of acetic acid with corresponding alcohols in the presence of sulfuric acid (2-13% of the total weight of the reactants) at temperature 110-14000C for 2 hours with the outputs of 60-90% [5-8]. Also known catalytic methods for the synthesis of esters of carboxylic acids, which are carried out by dehydrogenation of alcohols, addition of carboxylic acids, alkenes, carbonylation of alkenes and carbon monoxide, alcohols, etc. [9-11].

Disadvantages of the listed methods of producing carbonic acid esters are the duration of the process, the application of high temperatures and low production yield.

Microwave activation of organic reactions is a dynamically developing method for the synthesis of many compounds, it reduces the duration of the process in a few tens, hundreds, and in some cases thousands of times [12].

Our proposed method of producing acetates of lower alcohols can reduce duration of reaction by tens of times, which save the cost of electro- or thermal energy and accordingly include the production of acetates in the "green" chemistry area.

Synthesis of acetates was performed by direct esterification of acetic acid with lower alcohols (ethanol, isopropanol, isobutanol, isoamyl alcohol) at the microwave irradiation at household microwave oven. Optimum process conditions, such as irradiation power, the duration of the process, the ratio of the total weight of the catalyst reactants and the ratio of reactants has found (Table).

Table - Optimal conditions for the synthesis of lower alcohols acetates

Product

The molar ratio of the reactants

Irradiation power, W

Duration, min

Catalyst, % of total. weight of reactants

Yield of product, %

acetic acid

alcohol

1

ethyl acetate

1

1,5

480

2

1

96,98

2

isopropyl acetate

1

1

900

2

1

96,36

3

isobutyl acetate

1

1

300

3

1

91,41

4

isoamyl acetate

1

1,3

450

3

1

75,70

The reaction products were identified by gas chromatography-mass spectrometer Agilent 7890A/5975C (USA) and IR spectrometer IR-Prestige21 firm Shimadzu (Japan). In the IR spectra the resulting products are observed the characteristic absorption band of the carbonyl group at 1740-1735 cm-1, as in 1243-1053 cm-1 band appear intensive etheric bands due to variations in the C-O-C.

Thus, we have synthesized acetates of lower alcohols direct esterification reaction under microwave irradiation. The optimal synthesis conditions have found. Our proposed method allows to reduce duration of the process of several tens of times, to reduce the content of the catalyst, to increase product yield and eliminate the use of convection heating.



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Bibliographic reference

Appazov N.O., Akylbekov N.I., Niyazova D.Zh., Tulepova A.K., Seitova A.A., Shigenova A.S., Omarov E.A., Abilbek Zh. MICROWAVE ACTIVATION IN THE SYNTHESIS OF LOWER ALCOHOL ACETATES. International Journal Of Applied And Fundamental Research. – 2014. – № 2 –
URL: www.science-sd.com/457-24649 (20.08.2019).