Chapter IV: Experimental

This Chapter comprises actual experimental work performed to introduce aspects

of Green Chemistry during the conduct of Nitration, Halogenations (Chlorination,

Bromination & Iodination), and Redox reactions. Simple aromatic compounds are

taken as starting material to bring out nuclear substitution (Nitration and

Halogenation) in the light of synthetic aspect while redox reactions are conducted in

the light of analytical aspect

4.1 Nitration of aromatic compounds using NaNO2, p-toluene sulphonic acid, CH3COOH and catalytic amount of KI solution. 4.2 Nuclear Chlorination:

A) Using Bleaching powder solution in NaOH and CH3COOH as solvent. B) Using con. HCl, 6 % H2O2 and 1 % MgCl2 under Thermal condition.

4.3 Bromination using H2O2 and alkali metal bromides in presence of mild acid

H3PO4

4.4 Iodination of m-dinitrobenzene.

4.5 Preparation of Ferrate-

A) From Bleaching powder as a source of available chlorine.

B) Electrochemical synthesis of Ferrate under mild conditions.

4.6 Preparation of 2,4,4,6-tetrabromo-2,5-cyclohexadienone.

4.7 Preparation of 2,3,5,6-tetrabromo-4-methyl-nitrocyclohexa-2,5-dien-1-one.

Step I: Preparation of 4-methyl-2,3,5,6-tetrabromophenol.

Step II: Nitration of 4-methyl-2,3,5,6-tetrabromophenol.

4.8 Preparation of Trans-1,2-Cyclohexanediol from Cyclohexanol

Step I: Conversion of Cyclohexanol to Cyclohexene

Step II: Cyclohexene to trans -1,2-Cyclohexanediol.

4.9 Redox Titration at Room Temperature-Design for energy efficiency.

4.10 Optimum Use of KI in Iodimetric and Iodometric Estimations.

4.11 Regeneration of KI from the spent of Iodimetric and Iodometric Titrations

4.12 Recover and Recycle of CTC. 4.13 Cyclohexanol as a Green solvent to substitute CTC in Partition coefficient of

Iodine Experiment.

4.14 Regeneration of Iodine from Spent using air as a cheap oxidant.

4.1Nitration of aromatic compounds using NaNO2 , p-toluene sulphonic

acid, CH3COOH and catalytic amount of KI solution.

0.600 g substrate + 10 ml CH3COOH + 0.500 g p-TsOH are sonicated for 2

minutes. One drop of KI solution is added as catalyst. 0.500 g NaNO2 powder is added

in small portions to control evolution of HNO2 (It is tested by holding the acidified

starch iodide paper above the solution). Ice water is added and traces of liberated

Iodine are converted to iodides by treatment with pinch of Na2S2O3 powder. The

acid is neutralized by addition of NaHCO3 and reaction mixture is made slightly acidic

with dil. HCl . The product obtained is filtered and purified by recrystalisation.

Sr. No.

Reactant Product Practical Yield

% Yield

M.P. oC

1 p-nitrotoluene 2,4-dinitrotoluene 0.647 81.18 68

2 o-nitrophenol 2,4-dinitrophenol 0.267 49.08 109

3 Acetanilide 4-nitroacetanilide 0.090 11.25 135-140

4 β-naphthol 1-nitro-2-naphthol 0.380 48.25 124

5 Salicylic acid 5-nitrosalicylic acid 0.275 36.66 228

6. Anthranilic acid

2-amino-5-nitrobenzoic acid

0.382 47.92 268 with decomposition

Spectral Analysis-

Some products were identified by taking the IR spectra using JASCO-FTIR-4100 instrument available at the institute and comparing it with SDBS data.

2.4-dinitrophenol [NPNP]: 3107, 3094, 1648, 1599, 1523, 1502, 1423, 1321, 1296,

1248, 1179, 1147, 1107, 906, 858, 835, 740, 684, 632, 582 and 579 cm-1(Peak closely

resemble with SDBS No.2390).

4-nitro acetanilide[NAN-NN] - 3666, 3305, 3266,3063, 2796, 2331, 1900, 1670, 1535,

1490, 1393, 1314, 1260, 1172, 1100, 1006, 825, 751, 692, 506 and 408 cm-1.

1-nitro-2-naphthol [BNNN] - 1667, 1444, 1240, 787 and 676 cm-1(Peak closely

resemble with SDBS No.3434).

5-nitro salicylic acid [SANN]- 3211, 2828, 1692, 1636, 1573, 1516, 1476, 1451, 1423,

1345, 1271, 1208, 1188,1133, 1078, 931, 895, 794, 743, 723, 694 and 637 cm-1.(

Peaks closely resemble with SDBS No. 11070).

2-amino-5-nitro benzoic acid [AANN] - 3288, 3016, 1483, 1445, 1248, 759, 698, 659,

578, 539, 524, 473 and 418 cm-1( SDBS No. 41002- IR spectra is not available).

The H1 NMR spectra of the compound at 400 MHz using DMSO(d6) as a solvent

shows peaks at 7.798, 7.4698, 6.9617,and 6.8977 δ

4.2 Nuclear Chlorination:

Aromatic compounds are chlorinated by following variants.

A) Using Bleaching powder solution in NaOH and CH3COOH as solvent.

Bleaching powder (15 g, Available Chlorine content=21%) is triturated with

minimum amount of water and sufficient amount of 10 % NaOH (60 ml) is added. The

Ca(OH)2 precipitate is allowed to settle. The supernant is filtered once and finally

diluted to give 300 ml solution (5 % bleaching powder (BP) solution in 2 % NaOH).

0.600 g substance + 15 ml BP solution + 5 ml CH3COOH. The mixture is

sonicated for 15 minutes and then warmed on hot plate for 5 minutes. It is cooled and

neutralized with NaOH and then acidified with concentrated HCl and cooled. The

product is filtered, dried and characterized.

Sr. No.


% Yield M.P. oC

1 Salicylic acid 5-chlorosalicylic acid 0.353 47.06 170

2 p-nitro aniline 2-chloro-4-nitroaniline 0.374 45.93 106

3 m-Cresol - trace < 1 % -

4 p-chlorophenol - Trace < 1 % -

Spectral Analysis-

The products were identified by taking the IR spectra using JASCO-FTIR-4100 instrument available at the institute and comparing it with SDBS data.

2-chloro-4-nitroaniline [CPNA(B)]: 3362, 3223, 2703, 1627, 1588, 1481, 1328, 1309,

1114, 841, 754, 634, 565 and 425 cm-1(Peak closely resemble with SDBS No.3434).

B) Using con. HCl , 6 % H2O2 + 1 % MgCl2 under Thermal condition-

0.600 g of substrate + 10 ml Con. HCl + 5 ml 6 % H2O2 + 2 ml 1 % MgCl2 . The

contents are heated on hot plate for 30 minutes. Evolution of Chlorine is tested by

filter paper strip moistened by acidified KI solution.

Sr. No.


% Yield

M.P. oC

1 Salicylic acid 5-chlorosalicylic acid 0.389 51.86 171

2 p-nitro aniline 2-chloro-4-nitroaniline 0.406 49.86 107

3 Cinnamic acid p-chlorocinnamic acid 0.280 45.45 86-88

4 Benzyl cyanide*

4-chlorophenyl acetic acid 0.524 36.38 105

5. p-nitrobenzoic acid

2-chloro-4-nitrobenzoic acid 0.425 55.80 246-248

* The product was an oily liquid. Hence it was further hydrolyzed by

refluxing with 30 ml 2 N NaOH solutions. It is acidified with con HCl to give solid.

The melting point of solid product is taken.

Spectral Analysis-


5-chlorosalicylic acid [CSA(H)]: 1667, 1444, 1240, 787 and 676 cm-1(Peaks closely

resemble with SDBS No.3434). The H1 NMR spectrum using DMSO(d6) as solvent

and 400 MHz instrument shows peaks at 7.7691, 7.4388 and 6.9271 δ.

p-chlorocinnamic acid [CCA(H)]: 3001, 1727, 1613, 931, 739 and 692 cm-1(Peak

closely resemble with SDBS No.7937).

2-chloro-4-nitroaniline [CPNA(H)]: 3362, 3107, 2707, 1631, 1588, 1481, 1309, 1258,


The H1 NMR spectrum using DMSO(d6) as solvent and 400 MHz instrument shows

peaks at 8.1077, 7.9184, 6.606 and 6.4702 δ.

2-Chloro-4-nitrobenzoic acid[CPNBA(H)]: 3116, 2676, 1696, 1541, 1428, 1350,


4.3 Bromination using H2O2 and alkali metal bromides in presence of mild

acid H3PO4.

0.600 g substrate is transferred to the beaker. 1 g NaBr and 2 ml orthophophoric

acid are added. 10 ml 6 % H2O2 is added drop wise over a period of 10 minutes to

control evolution of Bromine. The contents were sonicated for 10 minutes. Reaction

mixture is diluted with water and the product is separated by filtration.

Sr. No.


% Yield M.P. oC

1 p-nitro aniline 2-bromo-4-nitroaniline 0.901 95.54 104

2 β-naphthol 1-bromo-2-naphthol 0.712 76.64 77

3 Salicylic acid 5-bromosalicylic acid 0.856 90.77 162

4 m-nitro phenol 2-bromo-3-nitrophenol 0.578 61.42 104

5. Acetanilide 4-bromoacetanilide 0.784 82.43 164

Spectral Analysis-


2-bromo-4-nitroaniline [BPNA]: 3370, 3200, 2737, 1623, 1587, 1487, 1299, 1121,

893, 745, 634, 545 and 422 cm-1.

1-bromo-2-naphthol [BBN]: 3288, 1670, 1603, 1500, 1434, 1348, 1283, 1237, 1145, 986, 930, 862, 813, 762, 723 and 645 cm-1 (Peak closely resemble with SDBS No. 6608).

5-bromosalicylic acid [BSA]: 3058, 2714, 1664, 1596, 1454, 1440, 1229, 877. 832,

659, 528.and 472 cm-1(Peak closely resemble with SDBS No. 1758 ). The H1 NMR

spectrum using DMSO(d6) as solvent and 400 MHz instrument shows peaks at

7.8923, 7.5827 and 6.9019 δ.

2-bromo-3-nitro phenol [BMNP]: 3389, 3083, 1698, 1573, 1509, 1407, 1232, 1169,

899, 876, 742, 721 and 593 cm-1( Peaks closely resemble with SDBS No. 16699).

4-bromoacetanilide [BAN]: 3286, 3195, 3065, 2993, 2929, 1671, 1604, 1393, 1313, 1292, 1172, 1114, 1072, 1042, 823 and 541( Peaks closely resemble with SDBS No. 35309 ).

4.4 Iodination of m-dinitrobenzene.

Preparation of Iodine solution :-

2.540 g I2 crystals are transferred to 50 ml water containing 16.600 g KI

contents are sonicated and finally diluted to 120 ml to give I2 solution.

Iodination of m-DNB-

0.612 g m-DNB is dissolved in 10 ml CH3COOH. 10 ml Iodine solution is added

to above solution and 1 ml 2 N HClO4 solution is added as a catalyst. The contents are

heated for 30 minutes at 60 0 C. The supernant is decanted, neutralized with NaOH

solution and cooled. The product is separated by filtration.

M.P = 89 oC

Practical Yield =0.136

% Yield = 12.69

*Iodination of m-nitrophenol and 2,4-dinitrochlorobenzene is also tried but the

product s are not obtained.

4.5 Preparation of Ferrate-

A) From Bleaching powder as a source of available chlorine-

10.0 g bleaching powder (Available chlorine content- 21 %) is triturated with 1 M

KOH solution to form a paste. Sufficient amount of KOH solution is added to

precipitate Ca+2. It is filtered. The filtrate is cooled up to 5 0 C. Ferric nitrate (2.0 g) is

added. The solution is stirred. (More amount of solid KOH is to be added to

precipitate the potassium ferrate). However the solution is tested qualitatively for

presence of FeO4 -2.

𝑖𝑖) 𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴 𝑠𝑠𝐴𝐴𝑠𝑠𝑠𝑠𝑠𝑠𝑖𝑖𝐴𝐴𝑠𝑠 + 𝐶𝐶2𝐻𝐻5𝑂𝑂𝐻𝐻 → 𝐸𝐸𝐸𝐸𝐸𝐸𝐴𝐴𝐸𝐸𝐴𝐴𝐴𝐴𝑠𝑠𝐸𝐸𝐴𝐴𝑠𝑠𝐸𝐸𝐴𝐴 𝐴𝐴𝐸𝐸 𝐶𝐶𝑂𝑂2.

𝑖𝑖𝑖𝑖) 𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴 𝑠𝑠𝐴𝐴𝑠𝑠𝑠𝑠𝑠𝑠𝑖𝑖𝐴𝐴𝑠𝑠 + Ba(NO3)2

= 𝑅𝑅𝐴𝐴𝑅𝑅𝑅𝑅𝑖𝑖𝑠𝑠ℎ 𝐴𝐴𝐸𝐸𝐴𝐴𝑏𝑏𝑠𝑠 𝑝𝑝𝐸𝐸𝐴𝐴𝐸𝐸𝑖𝑖𝑝𝑝𝑖𝑖𝑠𝑠𝑝𝑝𝑠𝑠𝐴𝐴

𝑖𝑖𝑖𝑖𝑖𝑖) 𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴 𝑠𝑠𝐴𝐴𝑠𝑠𝑠𝑠𝑠𝑠𝑖𝑖𝐴𝐴𝑠𝑠 + 1: 1 NH3 Solution = formation of Fe(OH)3 precipitate

B) Electrochemical synthesis of Ferrate under mild conditions-

Ferrate was prepared by electrochemical method using electrodes of iron nails

and 6 M NaOH. The method is time consuming. Hence attempts are made to prepare

ferrate using less concentrated NaOH and improve the rate of formation of ferrate by

suitable catalyst. Efforts are made to characterize it.

Material Used-

2 N NaOH solution: - 80 g NaOH is dissolved in 200 ml distilled water and finally

diluted to 1000 ml using volumetric flask.

1000 ppm Hydroquinone solution: - 100 mg Hydroquinone is transferred to the

volumetric flask. 10 ml 2 N NaOH solution is added to dissolve it. The solution is

diluted to 100 ml with distilled water. It is 100 ppm solution of Hydroquinone.

12 V D. C. Power Supply: - A D.C. Power Supply with facility for tapping 500 mA

current at 2,4,6,8,10 & 12 V is used as current source.

Electrodes: - The cathode and anode are made from soft iron wire( Binding wire). The

anode is isolated by covering it with a cotton bag.

Procedure- 150 ml 2 N NaOH is transferred to 250 ml beaker. The soft iron

electrodes are immersed into the solution and current is passed by gradually raising the

potential. At 10 V applied voltage bubbling of gases started due to electrode reactions.

The solution becomes colored after passage of current for 1 hr.

In the other set, the process is initiated by adding 5 ml hydroquinone solution to

150 ml 2 N NaOH and current is passed at 10 V. The solution becomes coloured in

shorter time. The electrolysis is continued for 2 hr and stopped as there is heating of

the medium. The electrodes are removed and the solution is subjected for

spectrophotometric analysis using diluted Hydroquinone solution as the blank. It

shows spectrum as shown in figure.

It is also tested qualitatively for presence of FeO42- species as follows.

𝑖𝑖) 𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴 𝑠𝑠𝐴𝐴𝑠𝑠𝑠𝑠𝑠𝑠𝑖𝑖𝐴𝐴𝑠𝑠 + 𝐶𝐶2𝐻𝐻5𝑂𝑂𝐻𝐻 → 𝐸𝐸𝐸𝐸𝐸𝐸𝐴𝐴𝐸𝐸𝐴𝐴𝐴𝐴𝑠𝑠𝐸𝐸𝐴𝐴𝑠𝑠𝐸𝐸𝐴𝐴 𝐴𝐴𝐸𝐸 𝐶𝐶𝑂𝑂2.

𝑖𝑖𝑖𝑖) 𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴 𝑠𝑠𝐴𝐴𝑠𝑠𝑠𝑠𝑠𝑠𝑖𝑖𝐴𝐴𝑠𝑠 + Ba(NO3)2

= 𝑅𝑅𝐴𝐴𝑅𝑅𝑅𝑅𝑖𝑖𝑠𝑠ℎ 𝐴𝐴𝐸𝐸𝐴𝐴𝑏𝑏𝑠𝑠 𝑝𝑝𝐸𝐸𝐴𝐴𝐸𝐸𝑖𝑖𝑝𝑝𝑖𝑖𝑠𝑠𝑝𝑝𝑠𝑠𝐴𝐴

𝑖𝑖𝑖𝑖𝑖𝑖) 𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴 𝑠𝑠𝐴𝐴𝑠𝑠𝑠𝑠𝑠𝑠𝑖𝑖𝐴𝐴𝑠𝑠 + 1: 1 NH3 Solution = formation of Fe(OH)3 precipitate

Findings-

1) The solution does not show expected λmax of 510 nm. However it undergoes all

qualitative test of FeO42- . It might contain Fe(V) species.

2) Hydroquinone facilitates the formation of ferrate like species in shorter time and using 2 M NaOH.

4.6 Preparation of 2,4,4,6-tetrabromo-2,5-cyclohexadienone.

One gram phenol is dissolved in 20 ml distilled water using sonication for 1

minute. 3.0 g NaBr and 2.0 g NaBrO3 are added to the solution. The contents are

stirred using Magnetic stirrer. 10 ml con HCl is added drop wise to control liberation

of free Bromine (Tested by holding filter paper strip moistened by acidified KI

solution). A white product of 2,4,6,-tribromophenol is obtained. Now 5 ml of 6 %

H2O2 and trace amount of NaNO2 are added to the solution. The product turns light

yellow in shorter time.

Br

BrBr

Br

OOH

Br

Br

Br

OH

NaBr/NaBrO3

Con. HClH2O2

NaNO2 (Catalytic)

The product is filtered on suction pump. It is washed twice with ample amount

of water and air dried to give 4.130 g. The dried product (3.0 g) is subjected to further

re-crystallization using CHCl3 as solvent. Anhydrous Na2SO4 is used to dry

Chloroform layer and it is concentrated over electrical hot plate. The concentrate is

transferred to watch glass and air blown to give crystalline light yellow product .

Melting Point = 125 0C.

Practical Yield = 2.630 g

% Yield = 94.72 %

The IR Specta of the product is recorded using JASCO FTIR-4100 Instrument and

KBr as Standard.

The peaks are-3071, 2916, 2850, 2718, 2683, 1691, 1556, 1455, 1408, 1381, 1344,

1320, 1265, 1174, 1119, 059, 909, 857, 703 and 598 cm-1 (The peaks closely

resemble with SDBS No. 19952).

The H1 NMR Spectrum(400 MHz) of the sample is taken from SAIF, Punjab

University, Chandigarh (India). It shows characteristic peak at 5.90 δ .

*X*

4.7 Preparation of 2,3,5,6-tetrabromo-4-methyl-nitrocyclohexa-2,5-

dien-1-one.

Step I: Preparation of 4-methyl-2,3,5,6-tetrabromophenol-

2.5 ml p-Cresol is transferred to the 100 ml conical flask. Mixture of 5 ml CTC

and 20 ml CHCl3 is poured into the conical flask. Ball of Steel wool (500 mg) is

dumped. 5 ml liquid Bromine(density 3.12 g/ml) is added by means of Pasture pipette

over a period of 30 minutes. Vigorous exothermic reaction with liberation of dense

white fumes is observed. The reaction is further controlled by addition of NaHCO3

powder and placing the flask in crushed ice. The reaction is quenched by addition of

water after 30 minutes. The product is filtered at suction pump. It is washed with

distilled water twice and air dried.

OH

CH3

OH

Br

Br

Br

Br

CH3

Br2/Fe/CTCCHCl3 / icebath

Melting Point- 196 0C

Practical Yield - The yield of Perbromomethyllphenol is 9.893 g.

% Yield = 96.86

Spectral Study – IR Spectra was recorded using JASCO FTIR-4100 instrument

available at the Research Institute and KBr standard.

It shows peaks as -3416, 2924, 2854, 2365, 1551, 1526, 1455, 1440, 1267,

1205, 1094, 817 and 562 cm-1.


University, Chandigarh (India). It shows peak at 2.3561 δ.

Step II: Nitration of 4-methyl-2,3,5,6-tetrabromophenol-

Perbromoalkylphenol (2.0 g) is transferred to beaker. 10 ml glacial CH3COOH

and a small crystal of Cu (NO3)2 are added. The contents are sonicated for one

minute and cooled up to 5 0C. Con.HNO3 (2 ml) is added drop wise with the help of

Pasteur pipette (The temperature is kept below 10 0C). The contents turn yellow on

sonication just for 2 minutes. These are further stirred for 20 minutes to ensure

complete nitration.

O

Br

NO2H3C

Br

Br

Br

HNO3 /AcOH

Cu(NO3)2 / Sonicate

OH

Br

Br

Br

Br

CH3

Practical Yield- 1.605 g.

% Yield: 72.88

Spectral Study - IR Spectra was recorded using JASCO FTIR-4100 instrument

available at the Research Institute and KBr standard.

It shows peaks as -3675, 3648, 2931, 2766, 1672, 1557, 1386, 1251, 1040, 971,

611, 577, 512 and 411 cm-1.


University, Chandigarh (India). It shows intense peak at 1.6809 δ.

M.P. - Decomposes at 80 0C.

4.8 Preparation of Trans -1, 2- Cyclohexanediol from Cyclohexanol

Step I: Conversion of Cyclohexanol to Cyclohexene

OH

Toluene/Con.H2SO4

Reflux

0.2 ml toluene is added to the R.B. flask containing 2.0 ml con. H2SO4. It is

warmed on water bath to generate p-toluene sulphonic acid(PTSA) in-situ. 4 ml

cyclohexanol is added. Hickman still is placed in between flask and water condenser

and the contents are refluxed over water bath. Cyclohexene gets collected in the collar

of Hickman still. Its boiling point is determined separately.

B. P. 82 oC Practical Yield 2.8 ml

% Yield = 72.04

Step II: Cyclohexene to trans -1, 2-Cyclohexanediol

p_TSA/H2O2/Reflux

NaOH/Heat

OH

OH

2 ml Cyclohexene is added to the 50 ml R.B. flask followed by 5 ml 6 % H2O2.

The contents are sonicated for 5 minutes. Excess of H2O2 is destroyed by Na2SO3 and

NaOH is added to neutralize PTSA as it forms azeotropic mixture with the product.

Water is evaporated. Product is separated from the dry mass by sublimation.

Practical Yield= 1.120 g % Yield = 48.80

M.P. = 102 o C.

*X*

4.9 Redox Titration at Room Temperature- Design for Energy Efficiency.

The titration of Oxalic acid against KMnO4 is a part of Higher Secondary and

Undergraduate Chemistry Practical Course in Pune University region and in other

states also. The oxalate solution(oxalic acid or sodium oxalate) is titrated with KMnO4

in acidic medium. However it requires preheating of oxalate solution up to 60 oC so

that the reaction become autocatalytic. Lot of heat energy in the form of LPG is

consumed during the laboratory work. Oxalic acid is titrated against Potassium

permanganate at room temperature with the intervention of enzyme Oxalate oxidase.

The enzyme is derived from Banana Peel in the form of water extract and is used as

such. To boost the activity, 100 ppm solution of FeSO4.7H2O, CuSO4.5H2O,

MnSO4.7H2O and (NH4)2MoO4 were used. Its activity is boosted by few drops of 100

ppm Ammonium Molybdate solution. Similarly the reaction is further coupled with

peroxidase enzyme derived from Potato extract as oxalate oxidase reacts on oxalic

acid to liberate H2O2 which further enzymatically decomposed by peroxidase enzyme.

Findings-

The Oxalic acid can be titrated with potassium permanganate solution without

preheating by intervention of oxalate oxidase and peroxidase and 100 ppm solution of

ammonium molybdate.

Paper Published

Gujarathi D.B. Bholane K.P. & Kale K.A. “Enzymes Catalyzed Titration of Oxalic

Acid with Potassium permanganate at Room Temperature”,

ChemistryEducation,Vol.No.2,Oct.Dec.1995, p.65-67

4.10 Optimum Use of KI in Iodimetric and Iodometric Estimations

In India, particularly at our college, I have completed UGC sponsored Minor

Research Project entitled “Economic Use of Chemicals at Undergraduate

Chemistry Practical w.r.t. Iodimetry and Iodometry”. The chemicals and reagents

should be optimally and efficiently used to ensure economy and reduce pollution load.

Stoichiometric amount of KI should be used. Hence modifications in procedure are

suggested (Table 1 ). Accordingly, BOS in Chemistry, University of Pune has

issued Circular (Ref. No. CBS/1457dt.27/05/1999) to modify procedures.

Table 1:- Amount of 10% KI solution required to be added in Iodometric titrations

Sr. No

Experiment ml of 10% KI required

Usual procedure

Theoretically required

Modified procedure

1 Estimation of Cu (II) from Copper sulphate solution

a) Standardization of Na2S2O3 soln.

b) Estimation of Cu (II)

20.0 25.0

4.2 8.3

5.0 10.0

2 Estimation of aniline a) Blank Titration b) Back Titration

20.0 20.0

4.1 1.6 to 4.1

5.0 5.0

3 % available Chlorine in Bleaching powder sample

10.0 5.6 6.0

4 Partition Coefficient of Iodine between water and CTC**

a) Titration of organic layer b) Titration of aqueous layer

25.0 5.0

2.0 0.02

2.0 1.0

5 Estimation of Cu (II) in Brass a) Standardization of Na2S2O3

soln. b) Estimation of Cu (II)

20.0 20.0

4.2 2.3

5.0 3.0

6 Determination of Iodine value of oil a) Blank Titration b) Back Titration

10.0 10.0

1.6 <1.6

2.0 2.0

There is net saving of KI consumed in laboratories. The people have adopted the findings and procedures in Practical Books which are followed by Undergraduate and Postgraduate students of Pune University, are also modified by the respective authors.

4.11 Regeneration of KI from the spent of Iodimetric and Iodometric

Titrations

The laboratory spent consists of unreacted Potassium iodide and Sodium iodide

formed during titration of liberated Iodine and Sodium thiosulphate. Appreciable

amount of iodides are present in the spent. It is just thrown away. It causes soil and

water pollution. The iodides are costly. Hence attempts are made to recover iodine

from such laboratory spent.

a) The spent formed during iodometric titration is collected. Different oxidants

are considered and their ability to oxidize iodide is determined by considering the

reaction stoichiometric ratios(Table 4.11.1)

Table 4.11.1-different Oxidants and their Capacity to oxidize iodides.

Sr. No. Oxidant Mol. Wt. Amount of Iodine

liberated per gram

(Theoretically)

1 KMnO4 158 4.0189

2 K2Cr2O7 294 2.590

3 MnO2 87 2.919

4 KBrO3 167 4.560

5 KIO3 214 3.560

6 CaCl(OCl) 127 2.000

7 H2O2 34 7.469

Considering the cost, shelf life, residues formed after the oxidation of iodides etc,

it seems that KMnO4 is convenient and cheap. Hence Iodine is regenerated from the

spent using KMnO4 .

The iodide is oxidized to Iodine by using KMnO4.

𝑲𝑲𝑲𝑲𝑲𝑲𝑶𝑶𝟒𝟒 + 𝟏𝟏𝟏𝟏𝑰𝑰− + 𝟏𝟏𝟏𝟏𝟏𝟏𝟏𝟏𝟏𝟏 → 𝟐𝟐𝑲𝑲𝟏𝟏𝟏𝟏 + 𝟐𝟐𝑲𝑲𝑲𝑲𝟏𝟏𝟏𝟏𝟐𝟐 + 𝟏𝟏𝟏𝟏𝟏𝟏𝟏𝟏− + 𝟓𝟓𝑰𝑰𝟐𝟐

b) The Extraction of the generated Iodine – As Carbon tetrachloride(CTC) is the best

solvent for Iodine and the same is routinely used in laboratories for preparing the

solution of Iodine, it is extracted in CCl4. The extractor assembly comprises of Iodine

Regenerator, condenser and collection flask which are interconnected by Teflon

tubing. The spent is poured into the regenerator and KMnO4 solution is added in

portions. The collector flask containing CTC is heated using electric heating mentle

and the vapors enter into the regenerator and iodine get extracted. The bottom layer

consists of iodine solution. It can be drawn out or sent to collector flak through cock

Q.

c) Conversion of I2 to KI -

𝑰𝑰𝟐𝟐 + 𝑲𝑲𝑶𝑶𝟏𝟏 → 𝑲𝑲𝑰𝑰 + 𝑲𝑲𝑶𝑶𝑰𝑰 + 𝟏𝟏𝟐𝟐𝑶𝑶

𝑲𝑲𝑶𝑶𝑰𝑰 𝑺𝑺𝑺𝑺𝑺𝑺𝑺𝑺𝑰𝑰𝑺𝑺𝟏𝟏𝑺𝑺.

→ 𝑲𝑲𝑰𝑰 + 𝑶𝑶𝟐𝟐

The potassium iodide solution can be reused for iodometric estimation.

Paper Published-

Gujarathi D.B. Research J. Chemistry and Environment, Vol.4(1), 2000,.77.(6)

4.12 Recover and Recycle of CTC

Carbon tetrachloride is non-inflammable and possesses high solvency power.

Hence it is consumed in variety of industries. However, it is one of the dangerous

environmental and health hazard. CTC evaporates and rises beyond 15 Km in the

atmosphere. It destroys Ozone. Each single chlorine atom of CTC destroys 105

molecules of Ozone in its lifespan of 25-30 years. Thus CTC is a potential

environmental hazard. To protect Ozone layer, 191 countries including India have

signed 'Montreal Protocol' to phase out (production and consumption of) CTC and

other ODS. Government of India has instituted supply controls on CTC from 2009.

However in academic laboratories, CTC is being used during the conduct

practical. Collectively the amount of CTC consumed is considerable and poses

environmental hazard.

I had developed and practiced the ‘Recover and Recycle of CTC’ concept

practiced at our college during the conduct of experiment entitled “Partition

coefficient of Iodine between water and CTC ” causing saving of about 2.5 to 3.0 L

CTC every year since A.Y. 2004-05. The details are summarized below.

Attempts made by Sangamner College :

As a part of Practical Chemistry curriculum, the S.Y.B.Sc. students have to

perform the experiment entitled, 'Determination of Partition Coefficient of Iodine

between Water and CTC'. Usually the effluent is just thrown into the sink. Realizing

the hazardous potential of CTC, Recover and Recycle of CTC has been initiated by

myself. The details are as follow.

Participants : S.Y.B.Sc. Chemistry students.

Orientation : Students are exposed to

1. Aspects of Green Chemistry

2. Environmental hazards posed by CTC.

Appeal : The students are requested to collect the effluent in a

container.

Recovering CTC : The laboratory attendants are trained to separate the CTC

from aqueous layer of effluent by using separating funnel.

Recycling : The collected CTC is added to saturated solution of

Iodine in CTC. It is used for next Batch.

The students honestly followed the instructions. As a result, the college is

able to cut off the consumption of CTC to some extent (Table 2) and thereby able to

save the environment.

Table 2: Extent of Ozone protected from its decomposition by CTC

Academic Year

No. of Students

Amount of CTC required

in ml

Amount of CTC used

in ml

Net saving by Recover and recycle

in ml

Number of moles of CTC

moles

Number of moles of Ozone conserved X 104

2004-05 124 3000 2000 1000 10.39 8.312

2005-06 96 2500 1500 1000 10.39 8.312

2006-07 87 2250 1500 750 7.79 6.232

2007-08 78 2000 1200 800 8.31 6.642

2008-09 70 1750 1000 750 7.79 6.232

2009-10 76 1900 1600 300 3.12 2.496

2010-11 63 1600 900 700 7.27 5.816

2011-12 80 2000 1330 670 6.94 5.552

Each molecule of CTC contains four Chlorine atoms and possesses average life

of 25 years. On an average each molecule of CTC could be able to decompose 8000

molecules of Ozone per year.

Recommendations :-

Though environmentally hazardous, we have to use chemicals in an act of

teaching and learning,. However one is able to protect the environment by following

the principles of Green Chemistry like -making judicious and optimum use of

chemicals, recover and recycle of toxic chemical like CTC. It does not require huge

financial investment but the desire to protect the environment and extension of

knowledge.

References:-

1. Circular No. CBS/1457 dated 27-05-1999, University of Pune. 2. Practical Chemistry for S.Y.B.Sc., Manali Publication, Pune, June 2003. 3. 'CTC Phase Out-2009', Sampada, September 2008, p.28.

Papers presented-

1) Gujarathi D.B. ’Conducting Chemistry Practical in Green Chemistry Sense’-

Presented at National Seminar on Green Chemistry held at Mudhoji College,

Phaltan, Maharashtra ( India) on 31st July-1st Aug.2004.

2) Gujarathi D.B. “Best Practices Implemented at Sangamner College” –

Presented at State Level Seminar on TQM and Best Practices in Higher

Education held at Dada Patil Mahavidyalaya, Karjat, Maharashtra (India) on

16th & 17th December 2005.

3) Gujarathi D.B. 'Environmental Protection – A Sustainable Activity Run by

Stakeholders of Chemistry Department, Sangamner College' in National

Conference on 'Role of Youth in Environmental Protection' held at S.N.Arts,

D.J.M. Commerce & B.N. Sarda Science College, Sangamner,

Maharashtra(India) on 5th & 6th February 2010.

4.13 Cyclohexanol as a Green solvent to substitute CTC in Partition

coefficient of Iodine Experiments

CTC is dangerous devil as it destroys the Ozone layer. Each single chlorine atom

of CTC destroys 105 molecules of ozone in its life span of 25-30 years1. Hence the

use of CTC has been banned as per Montreal Protocol. Yet in academic laboratories,

CTC is being used to perform the undergraduate chemistry experiment. The scenario

may change if suitable solvents are tested to take place of CTC. Hence an attempt is

made to check the usefulness of Cyclohexanol in determination of partition coefficient

of Iodine between water & Cyclohexanol and to replace CTC.

Chemicals-

1. Saturated solution of Iodine in Cyclohexanol is prepared by adding 5.020 g

Iodine crystals in 50 ml Cyclohexanol and the contents are vigorously stirred.

2. Sodium Thiosulphate solution(0.1 N)- 24.8 g Na2S2O3 is dissolved in 100 ml

water and finally diluted to 1000 ml to give 0.1 N solution.

3. Sodium Thiosulphate solution(0.01 N)- 100 ml 0.1 N Na2S2O3 solution is

diluted to 1000 ml using distilled water to give 0.01 N solution.

Experimental-

a) Determination of solubility of Iodine in Cyclohexanol-

• Different volumes of Iodine solution are titrated against 0.1 N Na2S2O3

solution and hence the concentration of solution is determined (Table 1).

Table 1: For solubility of Iodine in Cyclohexanol

I2 solution in Cyclohexanol 5.0 6.0 7.0 8.0

ml of 0.1 N Na2S2O3 16.0 19.2 23.1 26.5

b) Determination of Partition coefficient of Iodine between water and Cyclohexanol

• Five sets are prepared by using different amounts of Iodine solution, cyclohexanol, water and solid NaCl as shown in Table 2.

Table 2 -Five sets with different composition

Set I2 in Cyclohexanol

ml

Cyclohexanol

ml

Water

ml

NaCl

g

I 03 12 100 2.0

II 06 09 100 2.0

III 09 06 100 2.0

IV 06 09 100 5.0

V 09 06 100 5.0

• The solutions are shaken for 30 minutes to establish equilibrium between

the aqueous layer and cyclohexanol layer for Iodine.

• 25 ml aqueous layer of each set is titrated against 0.01 N Na2S2O3

solution while 1ml cyclohexanol layer is titrated against 0.1 N Na2S2O3

solution.( 2 ml of 5 % KI solution is added to each prior to titration to

facilitate reaction with aqueous Na2S2O3 solution).

• The readings are recorded in Table 3.

Calculation-

1000 𝑚𝑚1 1𝑁𝑁 𝑁𝑁𝑝𝑝2𝑆𝑆2𝑂𝑂3 𝑠𝑠𝐴𝐴𝑠𝑠𝑠𝑠𝑠𝑠𝑖𝑖𝐴𝐴𝑠𝑠 ≡ 127 𝑔𝑔 𝐼𝐼𝐴𝐴𝑅𝑅𝑖𝑖𝑠𝑠𝐴𝐴.

∴ 1 𝑚𝑚𝑠𝑠 1 𝑁𝑁 𝑁𝑁𝑝𝑝2𝑆𝑆2𝑂𝑂3 𝑠𝑠𝐴𝐴𝑠𝑠𝑠𝑠𝑠𝑠𝑖𝑖𝐴𝐴𝑠𝑠 ≡ 127 𝑚𝑚𝑔𝑔

𝐴𝐴𝑠𝑠 5 𝑚𝑚𝑠𝑠 𝐼𝐼2 𝑠𝑠𝐴𝐴𝑠𝑠𝑠𝑠𝑠𝑠𝑖𝑖𝐴𝐴𝑠𝑠 𝐸𝐸𝐴𝐴𝑠𝑠𝑠𝑠𝑠𝑠𝑚𝑚𝐴𝐴𝑠𝑠 16.0 𝑚𝑚𝑠𝑠 0.1 𝑁𝑁 𝑁𝑁𝑝𝑝2𝑆𝑆2𝑂𝑂3 𝑠𝑠𝐴𝐴𝑠𝑠𝑠𝑠𝑠𝑠𝑖𝑖𝐴𝐴𝑠𝑠.

∴ It contains 16× 12.7 = 203.2 𝑚𝑚𝑔𝑔 𝐼𝐼𝐴𝐴𝑅𝑅𝑖𝑖𝑠𝑠𝐴𝐴 .

𝑆𝑆𝐴𝐴𝑠𝑠𝑠𝑠𝐴𝐴𝑖𝑖𝑠𝑠𝑖𝑖𝑠𝑠𝑆𝑆 𝐴𝐴𝐸𝐸 𝐼𝐼𝐴𝐴𝑅𝑅𝑖𝑖𝑠𝑠𝐴𝐴 = 203.2 × 20 = 4064 𝑚𝑚𝑔𝑔

= 4.064 𝑔𝑔 / 100 𝑚𝑚𝑠𝑠

Table 3: For Partition Coefficient of Iodine between Water and cyclohexanol.

Set 0.01N Na2S2O3 required by 25 ml aq. layer ml

0.1N Na2S2O3 required by 2 ml Cyclohexanol Layer

ml

Conc. of Iodine in aq. Layer C1 x10-4

M

Conc. of Iodine in Cyclohexanol layer C2 x10-2

M

C1 / C2

x10-3 I 0.8 1.52 1.6 03.80 4.210 II 1.7 3.10 3.4 07.75 4.387 III 2.4 4.50 4.8 11.25 4.266 IV 1.5 4.20 3.0 10.50 2.857 V 1.75 4.92 3.5 12.30 2.845

Calculations for C1 –

𝐴𝐴𝐴𝐴𝑠𝑠𝐴𝐴𝐴𝐴𝑠𝑠𝑠𝑠 𝐿𝐿𝑝𝑝𝑆𝑆𝐴𝐴𝐸𝐸 𝑉𝑉𝑠𝑠 𝑁𝑁𝑝𝑝2𝑆𝑆2𝑂𝑂3

𝑁𝑁1 × 𝑉𝑉1 = 𝑁𝑁2 × 𝑉𝑉2

𝑁𝑁1 = 𝑁𝑁2 × 𝑉𝑉2 × 1𝑉𝑉1�

∴ 𝐶𝐶1 = 𝑁𝑁1 × 12�

Calculation for Cyclohexanol-

𝑁𝑁1 × 𝑉𝑉1 = 𝑁𝑁2 × 𝑉𝑉2

𝑁𝑁2 = 𝑁𝑁1 × 𝑉𝑉1 × 1𝑉𝑉2�

∴ 𝐶𝐶2 = 𝑁𝑁2 × 12�

1) From burette readings in Table 1, solubility of Iodine in cyclohexanol is

4.064 g/100 ml which is greater than its solubility in CTC.

2) Partition coefficient of Iodine between water and Cyclohexanol is 4.287x10-3.

It is smaller than partition coefficient of Iodine in water and CTC.

3) It further decreases with the addition of electrolyte such as NaCl.

4) Cyclohexanol is the best substitute for CTC as far as the partitioning of Iodine is

concerned.

Paper Published-

Gujarathi D.B., Bharati K.T., Pokharkar R.D., 'Cyclohexanol- A Green Solvent To

Substitute CTC in Partition Coefficient of Iodine Experiment', PDFARDIJ [PRINT]

2012, 4(5); (P) 33 –36.

4.14 Regeneration of Iodine from Spent using a Cheap Oxidant

A) Preparation of Laboratory Spent containing iodides-

260 ml 0.1 N I2 solution is titrated against 0.1 N (approximate) Na2S2O3

solution to give 560 ml effluent. The iodide content is calculated and is found to be

5.864 mg/ml.

B) Set up for Regeneration of Iodine from Spent-

1) 1,2,3,4 & 5 ml catalyst solution is transferred to each of the stopper bottle

numbered 1 to 5 respectively which contain 20 ml effluent and 40 ml 0.5 N HCl.

2) 5 ml Cyclohexanol is added to each bottle and air is bubbled for 5 minute through

the solution of each bottle by means of fish aquarium pump at low rate (Table 1).

3) 10 ml of aqueous layer is titrated against 0.01 N Na2S2O3 solution while all the

separated organic layer is titrated against o.1 N Na2S2O3. The observations are

summarized in Table 2.

4) To ensure that the time interval (5 minute) for which air is bubbled through the

solution is sufficient, one set is repeated and air is bubbled for 10 minutes and amount

of iodide oxidized and extracted into Cyclohexanol is estimated by titration of aqueous

layer and organic layer against respective Na2S2O3 solution.

5) Table 2 indicates % of Iodine regenerated through oxidation of Iodide and extracted

from each set of spent solution and the average % extraction is calculated.

Table 1 : To study effect of catalyst concentration on regeneration of Iodine

Sr. No.

Amount of effluent

Amount of 0.5 N HCl

Amount of Catalyst

Amount of Cyclohexanol

1 20 ml 40 ml 1 ml 5 ml 2 20 ml 40 ml 2 ml 5 ml 3 20 ml 40 ml 3 ml 5 ml 4 20 ml 40 ml 4 ml 5 ml 5 20 ml 40 ml 5 ml 5 ml

Regeneration of Iodine form Spent using air and catalyst

Air Bubbling through Spent Addition of Catalyst Solution

Extraction of Liberated Iodine in Cyclohexanol Upper Layer of Iodine in

Cyclohexanol

Table 2 : % of Iodine regenerated & extracted in Cyclohexanol

Sr. No.

10 ml aq. layer against 0.01 N

Na2S2O3

All org. layer against 0.1 N

Na2S2O3

% Iodine regenerated & extracted

1 1.5 7.0 75.84

2 1.3 8.5 92.10

3 1.1 8.0 86.67

4 1.0 8.3 89.92

5 1.1 8.0 86.67

Average % Extraction

86.24

1. Iodide is catalytically and quantitatively oxidized by air to Iodine.

2. It is extracted in Cyclohexanol and average % extraction is 86.24 .

*Paper Communicated to PDFARDIJ [PRINT].

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