Choline Peroxydisulfate - ACS Publications - American Chemical

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Choline peroxydisulfate: Environmental friendly biodegradable oxidizing TSIL for selective and rapid oxidation of alcohols Balu Laxman Gadilohar, Haribhau Shantaram Kumbhar, and Ganapati S. Shankarling Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/ie5032919 • Publication Date (Web): 10 Nov 2014 Downloaded from http://pubs.acs.org on November 13, 2014

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Industrial & Engineering Chemistry Research

Choline peroxydisulfate: Environmental friendly biodegradable oxidizing TSIL for selective and rapid oxidation of alcohols

Solvent free, 70°C, 0.5 hr

ChPS

15 examples 80-93% yield 96% Energy saving

a

Bio TSIL Easily Biodegradable R.T. Biodegradable Effluent Choline chloride

Persulfate

ACS Paragon Plus Environment


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Choline peroxydisulfate: Environmental friendly biodegradable oxidizing TSIL for selective and rapid oxidation of alcohols Balu L. Gadilohar, Haribhau S. Kumbhar, Ganapati S. Shankarling* Department of Dyestuff Technology, Institute of Chemical Technology, N.P.Marg, Matunga, Mumbai, 400 019, India. KEYWORDS: Biodegradable; TSIL; oxidizing ionic liquid.

ABSTRACT: Choline and peroxydisulfate based environmentally benign biodegradable oxidizing task specific ionic liquid (TSIL) Choline Peroxydisulfate (ChPS) was synthesized, characterized, and evaluated its oxidizing property for selective oxidation of alcohols to aldehydes/ketones under solvent free mild reaction condition without over oxidation to acid. FT-IR spectra establish ionic structure of ChPS. The present ChPS compared with metal (NH4+, K+) peroxydisulfate and other oxidizing agents, oxidation occurs in short reaction time, with good to excellent yields. Physicochemical properties, such as density, thermal stability, viscosity, cyclic voltametry

and

solubility

in

common

solvents

were

determined. Biodegradability prediction using BIOWIN and BOD5 test, antimicrobial activity test and energy calculations shows excellent performance of choline peroxydisulfate, as an effective oxidant.


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1. Introduction Ionic liquids (ILs) are important class of green media and have gained overwhelming interest over the past years in organic synthesis owing to their unique physical and chemical properties. ILs comprise entirely of ions11. Many ILs however, are precarious environmental contaminants2 and the development of alternative ILs from components that are inexpensive, non-toxic towards the environment and which are biodegradable, is the need of the hour to overcome these drawbacks. Properties of ILs such as density, melting point, viscosity, thermal stability and solubility in water or solvents can be fine tuned by changing either the anion or cation. Recent development in ionic liquid research provides another route for achieving TSIL, i.e. by metathesis reaction, in which functional group is covalently tethered to cation or anion3. In past few decades selective oxidation of alcohols to carbonyl compounds is an important aspect in industrial production of many drugs, vitamins, and fragrances4. An oxidation is one of the important reactions, thus finding a new oxidizing agent is always desirable5. Classical reagents containing metals, such as chromium (VI) and manganese (VII) derivatives and halides, such as O-iodoxybenzoic acid6, IBX-tetrabutylammonium bromide7 have been introduced as oxidizing agent, which are expensive, perilous and generate huge amounts of heavy metal wastes. Persulfate (peroxydisulfate) has gain more attraction as an oxidant which is used in oxidation of contaminants8. It is a strong oxidizing agent (E0 = 2.01V), selectively reactive, and relatively stable at room temperature. The use of peroxydisulfate9 has several advantages like its stability, nontoxic nature, low cost, weakly pollutant, in addition to this it is also easy and safe to handle. There are several peroxydisulfate based oxidizing reagents that have been introduced such as K2S2O8, K2S2O8 in



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bronsted

acid

peroxydisulfate12,

ionic

liquids10,

polymer

TEMPO/K2S2O8/I211,

supported

benzyltriphenylphosphonium

peroxydisulfate13,

peroxydisulfate14 and imidazolium peroxydisulfate15 etc.

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tetrabutylammonium

Disappointingly, most oxidants

have several limitations such as, solubility problem, hygroscopicity, poor selectivity & purity, low to moderate yields, long reaction time, harsh reaction conditions and use of hazardous solvents. Therefore, there is a need for environmentally benign reaction conditions, which leads to new eco-benign reaction procedures that save energy and preserve green reaction procedure. Choline chloride is a naturally occurring biocompatible compound which is non hazardous if it is released back to nature as choline16. It is readily available in bulk at low cost and it is non-toxic and biodegradable17, 30. Abbott et al.18 published a series of studies on the low melting point of deep eutectic liquid system. Especially, Choline based ILs19 played significant role in various organic reactions as a catalyst or substitute for conventional solvents. Considering the scope of choline chloride based ionic liquids in organic synthesis20 herein, we report first time biocompatible, environmentally benign ChPS monohydrate TSIL (Fig. 1) and its use in efficient and highly selective oxidation of primary and secondary alcohols to the corresponding carbonyl compounds under solvent free condition, without further oxidation to acids with good to excellent yields (Scheme 1).

Fig. 1 Choline peroxydisulfate (ChPS)


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Scheme 1 Oxidation of alcohols using Choline peroxydisulfate. 2. Experimental : 2.1 Materials and method Choline Chloride, potassium peroxydisulfate (99.0%) and all substrate of benzyl alcohol derivatives were purchased from SDFCL. Reagents were used as received without further puriﬁcation. All solvents were purchased from commercial sources and were distilled prior to use. All melting points/boiling points are uncorrected and are presented in degrees Celsius. FT-IR spectra were recorded as solid or liquid on a Bomem Hartmann and Braun MB-Series FT-IR spectrometer. 1H & 13C NMR spectra were recorded on Varian 400 MHz mercury plus spectrometer, and chemical shifts are expressed in δ ppm using TMS as an internal standard. Mass spectral data were obtained using a micromass - Q - TOF (YA105) spectrometer. Elemental analysis was performed with Thermo Finnigan, FLASH EA 1112 series instrument. The thermal stability of the ionic liquid was investigated with a TG/DTA851 thermogravometric analyzer at a heating rate of 10°C/min with nitrogen as the purge gas. Viscosity of the ionic liquid was measured with a Brookfield RVF (Rheotec) rotating viscometer. Cyclic voltammogram obtained using PGSTAT 350N electrochemical workstation loaded with GPES software. A three-electrode electrochemical cell was used for the cyclic voltametric experiments. The three-electrode system consisting of a platinum rod as working electrode (1 mm diameter), glassy carbon as counter electrode and a SCE as



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reference electrode were used. GC–MS analysis was done on a Hewlett Packard GCD-1800 MS system. Conductivity measurement carried out using Equip-Tronics. Density measurement was carried using specific gravity bottle with respect to water. ESI-MS was carried out using Varian Inc, USA, 410 Prostar Binary LC with 500 MS IT PDA Detectors. 2.4 Typical Procedure for Choline peroxydisulfate (ChPS•H2O) preparation {2-hydroxy-N, N, N-trimethyl ethanaminium peroxydisulfate [NMe3CH2CH2OH] 2[S2O8] } ChPS•H2O prepared by the reaction of Choline chloride (0.1 mol) with K2S2O8 (0.055 mol) in acetone (100 mL). The mixture was stirred for 24 h at room temperature and then filtered to remove KCl. Acetone wash given to KCl, to get entrapped IL in it. The solvent was evaporated under reduced pressure to obtain a light yellow liquid, which was further dried under high vacuum for 4-5h and store at 0-5°C. Yield 88%. Silver nitrate test was carried out to detect halide ion present in ChPS, by dissolving it in Millipore water, which found to be negative. Light yellow viscous liquid. M.P (Tm) = -6°C, 1H NMR (400 MHz, CDCl3): δ/ppm: 3.30 (9H, s, 3xCH3-N), 3.58 (2H, br s, CH2-N), 4.06 (2H, br s, CH2-O); 13C NMR (100 MHz, DMSOd6): δ/ppm: 53.26 ((CH3)3N), 55.33(CH2-O), 66.99(CH2-N); IR: ν˜ = 3337, 1479, 1261, 1082, 1044, 952, 682 cm-1. Calc (ChPS•H2O) C, 28.70; H, 7.23; N, 6.69; found C 28.82, H 7.72, N 6.26. ESI-MS (ChPS•H2O) M+ for NMe3CH2CH2OH = 104.17; S2O8 = 194.9 2.5 Procedure for oxidation of alcohols using ChPS•H2O In a 25 mL flask mixture of various benzyl alcohols (0.005 mol) and Choline peroxydisulfate (0.01 mol) were charged at room temperature (RT). The reaction mixture was heated at 70°C for 0.5 hr. The completion of the reaction was monitored by TLC using 10% ethyl acetate in


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hexane as eluent. After completion of reaction mixture was cooled and extracted with ethyl acetate and the TSIL layer was separated as thick liquid at bottom of flask. The ethyl acetate layer was washed with water, dried (anhyd. Na2SO4) and concentrated. The residue was chromatographed on silica gel column and eluted with hexane: ethyl acetate (9:1), to afford pure various aldehydes and ketones (80-93%). All products were identified by GC–MS. The results of oxidation of variety of alcohols are summarized in Table 7. Selected spectral data Benzaldehyde (Table7, Entry 1) 1H NMR (CDCl3, 400 MHz) δ/ppm 7.46-7.54 (2H, m, aromatic H), 7.60-7.64 (1H, m, aromatic H), 7.85-7.88 (2H, m, aromatic H), 10.0 (1H, s, CHO); GC-MS (EI, 70 eV) m/z (%): 106 (M+, 85), 105 (100), 77 (54). 4-Chlorobenzaldehyde (Table 7, Entry 4). 1H NMR (CDCl3, 400 MHz) δ/ppm 7.59-7.65 (2H, m, aromatic H), 7.70-7.72 (2H, m, aromatic H), 9.94 (1H, s, CHO); GC-MS (EI, 70 eV) m/z (%): 140 (M+, 87), 139 (100), 111 (58), 75 (40). Acetophenone (Table 7, Entry 6). 1H NMR (CDCl3, 400 MHz) δ/ppm 2.58 (3H, s, CH3CO), 7.42-7.46 (2H, m, aromatic H), 7.52-7.56 (1H, m, aromatic H), 7.92-7.95 (2H, m, aromatic H); GC-MS (EI, 70 eV) m/z (%): 120 (M+, 32), 105 (100), 77 (73). Benzophenone (Table 7, Entry 12).1H NMR (CDCl3, 400 MHz) δ/ppm 7.45-7.48 (4H, m, aromatic H), 7.55-7.59 (2H, m, aromatic H), 7.78-7.80 (4H, m, aromatic H); GC-MS (EI, 70 eV) m/z (%): 182 (M+, 52), 105 (100), 77 (68), 51 (23).



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3. Results and discussion With this fact in mind, and as a continuation to develop and study application of new ILs, in this work we present the synthesis and study of physico-chemical properties of an efficient, metal free and halogen free biodegradable oxidant TSIL ChPS•H2O 3.1 TSIL preparation and characterization Choline persulfate / peroxydisulfate (ChPS•H2O) was synthesized by the metathesis/ion exchange reaction of the choline chloride with potassium peroxydisulfate in acetone at RT. The by-product, KCl, is insoluble in acetone and spontaneously separated from the reaction system as a precipitate, which also promoted the formation of yellow colour viscous liquid and led to higher yields (Scheme 2).

Scheme 2 Choline peroxydisulfate synthesis TSIL was characterized by 1H-NMR,

13

C-NMR, IR, Mass spectroscopy and CHN analysis.

The FTIR spectrum of TSIL shows characteristic band at 1255, 1044, 677 cm-1 (S2O8)2- and several other bands at 3363, 1479, 1134, 1082 and 952 cm-1 which are due to C-H stretching and rocking vibration of the Cholinium ion and alkyl chain. Comparative IR spectra show presence of cholinium ion and peroxydisulfate anion bands in TSIL. These observations indicate that TSIL has been successfully prepared (See Fig. 2)


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Fig. 2 FT-IR spectra overlay of Potassium peroxydisulfate (___), Choline chloride (___) and Choline peroxydisulfate (___) Table 6 demonstrate synthesis of benzaldehyde as model compounds using other peroxydisulfate such as, ammonium peroxydisulfate and potassium peroxydisulfate. The yield using choline peroxydisulfate shows significant improvement in comparison to ammonium peroxydisulfate and potassium peroxydisulfate. After completion of reaction ChPS•H2O will dissociate as cholinium ion (NMe3CH2CH2OH)+ and bisulphate/hydrogen sulphate ion (HSO4-) or sulphate (SO4--) and is expected not to accumulate in the soil without any environmental hazards. But in case of use of other metal oxidant or halogenated oxidant, generation of large amounts of residual effluents subsequently leads to its treatment to minimize their environmental impact, whereas it cannot be seen in case of ChPS•H2O. Thus the use of novel choline based oxidizing TSIL can be the best alternative for oxidation of alcohols.



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3.2 Biodegradability prediction and evaluation of Choline chloride and Peroxydisulfate using BIOWIN and BOD5 test of ChPS•H2O Evaluation of hazardous ionic liquids has now become an essential area of research and many groups have reported toxicity, ecotoxicity and biodegradation studies on ionic liquids21. The toxicity of ionic liquids has been evaluated using microorganisms as well as software22. Probably, the most widely used software based on the group contribution approach is the Biodegradation Probability Program (BIOWIN), developed by the SRC on behalf of the US EPA23. The software, which is freely downloadable,24 estimates the probability of rapid aerobic biodegradation of an organic chemical in the presence of mixed populations of environmental microorganisms. BIOWIN has been used previously in international journals for predicting biodegradability of premanufacture notice (PMN) chemical substances25. The probability of rapid aerobic biodegradation of choline chloride and peroxydisulfate has been predicted using above software (Table 1), which conclude that, choline chloride is readily biodegradable (as per Biowin model no 1-6, 8) while peroxydisulfate also biodegrade rapidly (as per Biowin model no 1, 2 and 7). From this we can predict, that ChPS•H2O prepared form choline chloride and potassium peroxydisulfate will also be biodegradable, KCl being a by-product. Thus ChPS•H2O can be used in oxidation reaction in industrial scale as no toxic effluent will be released.


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Table 1 Biodegradation prediction of choline chloride and potassium peroxydisulfate using Biowin software26 Entry

Model

Choline Chloride

Potassium peroxydisulfate

1

Biowin1

Biodegrades Fast

Biodegrades Fast

2

Biowin2

Biodegrades Fast

Biodegrades Fast

3

Biowin3

Weeks

Weeks

4

Biowin4

Days

Days-Weeks

5

Biowin5

Biodegrades Fast

Does not Biodegrades Fast

6

Biowin6

Biodegrades Fast


7

Biowin7


Biodegrades Fast

8

Ready Biodegradability Prediction

Yes

No

3.3 Biodegradability of ChPS•H2O using BOD5 Test (APHA 5210B) To support above biodegradability prediction using BIOWIN, we performed aerobic biodegradability test of the ChPS•H2O by the closed bottle test for 5 days (BOD5) 5210 B as per APHA guidelines26. In which ChPS•H2O was added to aerobic aqueous media inoculated with waste water microorganisms, and the depletion of dissolved O2 was determined after 5 days. The biodegradability was defined as a ratio of biological oxygen demand to practical chemical oxygen demand. If it founds >0.5 refers to easily biodegradable, 0.4-0.5 average biodegradable, 0.2-0.4 slowly biodegradable, less polar>non polar), miscibility of ChPS•H2O also gets decreases. This solvent property formulates this TSIL as a best medium for various chemical reactions. The solubility of the said TSIL in water was found to be excellent in comparison with potassium peroxydisulfate, ammonium peroxydisulfate, and sodium peroxydisulfate. Thermal Properties The thermal behaviour of the ionic liquid was done by thermogravimetry analysis (TGA) measurements. Thermograms of ChPS showed decomposition temperature (Td) at 300°C. The slight decreases at 100°C, which correspond to the release of oxygen of TSIL. TSIL showed a weight loss (10.5%) from 101 to 200°C is due to the decomposition of the peroxydisulfate anion, ensuing in the release of oxygen as shown in Fig. 3. Further weight loss and degradation that occur between 201°C and 360°C may be attributed to the decomposition of the cholinium and sulphate ions, Hiroyuki Ohno; et.al reported decomposition temperature (Td) of a series of choline salts was 184–224°C31. In common, for oxidants such as peroxydisulfate TSIL, a lower decomposition temperature means a high reactivity. Thus, the lower decomposition temperature of TSIL containing peroxydisulfate shows high reactivity.



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Fig. 3 Thermogravometric analysis of synthesized ChPS•H2O Viscosity The viscosity of ionic liquids is similar to that of oils, about 1-3 orders of magnitude greater than those of common molecular solvents32 and their viscosities range from 10 cP to about 500 cP at room temperature. One of the limitations of ILs is their high viscosity, than water (0.89 cP at 25°C), this is particularly important in the area of electrochemistry since this significantly lowers the conductivity and mobility of the ions.

Comparing viscosity of

common imidazolium based ionic liquid (

Choline Peroxydisulfate - ACS Publications - American Chemical

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