Kinetics and mechanism of oxidation of diethyl ether by chloramine-T in acidic medium

Article abstract of DOI:10.1155/2012/957405

The kinetics of oxidation of diethyl ether (DE) with sodium N-chloro-p-toluenesulphonamide (CAT) in hydrochloric acid solution has been studied at (313°K).The reaction rate show a first order dependence on [CAT] and fractional order dependence on each [DE] and [H+] .The variation of ionic strength of the medium has no significant effect on the reaction rate , addition of p-toluenesulphonamide (p-TSA) affects the reaction rate marginally the rate increased with decreasing dielectric constant of the medium , the stochiometry of the reaction was found to be 1:2 and oxidation products were identified , A Michaelis - Menten type mechanism has been suggested to explain the results.The equilibrium and the decomposition constants of CAT - diethyl ether complex have been evaluated. Thermodynamic parameters were computed by studying reaction at temperatures range ( 308 - 323°K) for the rate limiting step and for the observed first order constants by the linear Arrhenius plot. The mechanism proposed and the derived rate law are consistent with observed kinetics.

Full text of DOI:10.1155/2012/957405

ISSN: 0973-4945; CODEN ECJHAO
E-Journal of Chemistry
http://www.ejchem.net
2012, 9(2), 642-649
Kinetics and Mechanism of Oxidation of
Diethyl Ether by Chloramine-T in Acidic Medium
Y. I. HASSAN* and N. H. M. SAEED
Department of Chemistry
College of Education, University of Mosul, Mosul, Iraq
youhassan51@yahoo.com
Received 7 July 2011; Accepted 20 September 2011
Abstract: The kinetics of oxidation of diethyl ether (DE) with
sodium N-chloro-p-toluenesulphonamide (CAT) in hydrochloric
acid solution has been studied at (313oK).The reaction rate show a
first order dependence on [CAT] and fractional order dependence
on each [DE] and [H+] .The variation of ionic strength of the
medium has no significant effect on the reaction rate , addition of
p-toluenesulphonamide (p-TSA) affects the reaction rate
marginally the rate increased with decreasing dielectric constant of
the medium , the stochiometry of the reaction was found to be 1:2
and oxidation products were identified , A Michaelis – Menten
type mechanism has been suggested to explain the results.The
equilibrium and the decomposition constants of CAT – diethyl
ether complex have been evaluated. Thermodynamic parameters
were computed by studying reaction at temperatures range ( 308 –
323oK) for the rate limiting step and for the observed first order
constants by the linear Arrhenius plot. The mechanism proposed
and the derived rate law are consistent with observed kinetics.
Keywords: Oxidation kinetic, Diethyl ether, Chloramine-T, Acidic medium.
Introduction
The versatile nature of aromatic sulphonyl haloaminesis due to their ability to act as sources
of halonium cations, hypohalite species and nitrogen anion which act as both bases and
nucleophilies .Sodium-N-chloro-P-toluenesulphonamide (p-CH3-C6H4SO2NClNa.3H2O),
well known as chloramine-T (CAT, R'NClNa), is a very important member of this class of
compounds and has received a considerable attention as an oxidizing agent for a wide range
of functional groups in both acidic and alkaline media. Generally, Chloramine-T undergoes
a two-electrons change in its reactions ,the products being p-toluenesulphonamide (p-TSA)
and sodium chloride .The redox potential of CAT/RNH2 is pH dependent and decrease with
an increase in pH dependent and decrease with an increase in the pH of the medium ,having
the values of 1.14 at pH 0.65 and 0.5 at pH 121,2. Depending on the pH of the medium CAT

Kinetics and Mechanism of Oxidation of Diethyl Ether 346
furnishes different types of reactive species in solution , such as
N-chloro-p-
toluenesulphonamide
(R'NHCl,monochloramine-T,
where
R=P-CH3C6H4SO2),
+
dichloramine-T (R'NCl2), HOCl and possibly H2O+CL and RNH2 Cl in acid solution and
R'NCl - and OCl- in alkaline medium .Free chlorine has also been detected in medium in the
presence of chloride ion3. Although this reagent has been widely ulitized for the quantitative
determination of a large number of inorganic and organic compoundsin solution4,5, only a
few kinetic studies have been carried out .Mention may be made about the oxidation of
hydrogen peroxide6, P-cresols7,8 ,phenols9, aldehyde10, ketones11, aldoses12,13, primary14 and
secondary alcohols15, α-hydroxy acid16 ,formic acid17, furan-2-carboxic acid18, amino acid19,20
,
aniline21, toluene22, acetanilide23 catecholamines24, sulphoxides25,26, cyanide27 and thiocynat28
by CAT.
Diethyl ether is widely used as a solvent, a reaction medium and to avery low extent as
reactant. It can be oxidize to acetic acid with sodium bromate29. The present work is an
attempt to find out the nature of reacting species and to explore the mechanistic pathway
involved in the oxidation of diethyl ether, since, such study has not previously been (fully)
explored.
Experimental
Diethyl ethers (fluka) of spectrophotoscopic grade used as recived. Chloramine-T was
prepared as reported in the literature (30) and purified by the method of Morris et al31. An
aqueous solution of CAT was standaraized by iodometric method and preservedin brown
bottles to prevent its photo chemical deterioration .All other reagents were of Analar grade
and used as supplied. The ionic strength of the system was kept at a high value by using
sodium perchlorate.
Kinetic measurements
The reaction was carried out in glass stoppered pyress boiling tubes, under pseudo –first
order condition by keeping diethyl ether concentration large in comparison with
[CAT].Appropriate amounts of diethyl ether, hydrochloric acid sodium perchlorate
solutions,and water (to keep the total volume constant for all runs)were taken in the
tubeand thermostated at 40 OC for the thermal equilibrium. A desired amount of
thermostated CAT at the same temperature was rapidly added to the mixture in the bolling
tube. The progress of the reaction was followed by with drwawing a measured samples
at various time intervals to the quenched solution (5% potassium iodide , 2M sulphuric
acid) and water in a volumetricacid. The liberated iodine was estimated spectrophoto-
metrically at 353 nm. The course of reaction was studied for at least two half –lives.The
pseudo –first order rate constant calculated from the slope of the plots of [CAT] vs. time,
were reproducible within ±3%.
Stoichiometry
Varying ratios of CAT to diethyl ether in the presence of 0.2M HCl, ethanol and water were
equilibrated at 313Ko for 24 h. Estimation of residual oxidant showed that 2 mole of CAT is
consumed per mole of dietyl ether .The stoichiometry obtained can be represented as:
H+
CH3CH2OCH2CH3 + 2R'NClNa + H2O
CH3COOH + CH3CH2OH
+ 2R'NH2 + 2Na+ + 2Cl-
(1)
p-Toluenesulphonamide among the reaction products was detected by paper
chromatography. Benzyl alchohol satutrated with water was used as the solvent with
0.5% vaniline in 1%HCl solution in ethanol as spray reagent (RF=0.905)32,33. The acetic

344 Y. I. HASSAN
acid produced was identified by conversion to hydro –oximic acid derivative34 which
give violate color with ferric ion .or formation of deep-red coloration on reaction with
practically neutral or basic solution of ferric chloride35.
Results and Discussion
The kinetics of oxidation of diethyl ether (DE), by chloramine-T was investigated at several
initial concentration of reactants in acid medium.
Effect of varying reactant concentration
At constant acid concentration with the substrate in excess ,plots of log [CAT] vs. time were
linear (r >0.9954), indicating a first –order rate dependence of rate on [CAT] .The pseudo –
first-order rate constant (k ') are given in Table 1. The values of k ' increase with substrate
concentration . Plot of log k' vs. log [DE] gives a straight line (r=0.9931) with slope of
(0.52) indicating a fractional –order dependence on the substrate concentration .
Effect of varying [H+]
The reaction rate will increase with increase in [H+], Table 1. A plot of log k' vs. log [H] was
linear (r=0.9960%) with slope of (0.53), thus indicating a fractional –order dependence on
the [H+]
Effect of varying ionic strength on p-Toluenesulphonamide
Variation of ionic strength of the medium (0.125-0.625 M) by adding concentrated solution
of sodium perchlorate, has no significant effect on the reaction rate. Also addition of p-
toluenesulphonamide (p-TSA) affected the reaction rate marginally Table 2.
Effect of changing the solvent composition
The first-order rate constant k' was affected by variation of methanol in the methanol-water
content or the reaction mixture with [methanol]=20,30,40,50,and 60% ,104 k ' sec-1 values
were 3.071 ,5.374, 8.061, 9.212 and 13.434 respectivly. A plot of log k' vs. 1/D (dielectric
constant values were taken from literature35) gives a straight line (r=0.9884) with a positive
slope.
Effect of temperature
Kinetics were studied at different temperatures (308-323Ko) under varying substrate
concentrations (0.48-2.41M). Plots of log k' versus log [DE] were linear (r>0.9570) with
slopes (0.563,0.528, 0.503,0.503 and 0.511) at 308,313,318,323, and 328 Ko for each of
[DE],respectively ,indicating fractional –order dependence on substrate .The rate constant
of the slow step (k3) was obtained from the intercept of the linear plot 1/k' versus 1/[DE].
(r=0.9852). From the linear Arrhenius plot of log k' versus 1/T (r=0.9980) the activation
energy and other thermodynamic parameters for composite and reaction for the rate limiting
step were evaluated. These values are given in Table 3.

Kinetics and Mechanism of Oxidation of Diethyl Ether 346
Table 1. Effect of varying of chloramine-T, diethyl ether, and hydrogen ion concentration
on the reaction rate.
103[CAT] M
1.50
[DE] M
0.96
0.96
0.96
0.96
0.96
0.48
0.96
1.45
1.93
2.41
0.96
0.96
0.96
0.96
0.96
10[H+] M
3.0
3.0
3.0
3.0
3.0
3.0
3.0
3.0
3.0
3.0
2
104k' Sec-1
3.071
3.070
2.986
2.986
3.081
2.303
3.071
3.455
3.838
4.606
2.508
2.850
3.071
3.372
3.629
104ka
1.75
2.00
2.25
2.50
1.50
1.50
1.50
1.50
1.50
1.50
1.50
1.50
1.50
1.50
3.393
3.138
2.839
3.154
2.895
5.848
5.909
5.785
5.857
5.876
2.5
3
3.5
4
T= 313 K0 in (1:5) ethanol: water(v/v) ,μ=0.5 M. Note. a k=k'/[DE or H+]n ,where n is slope of the
plot log k' vs log [DE or H+] k has the units of Lh mol-n sec-1.
Table 2. Effect of varying ionic strength and [P-TSA] on the reaction rate.
[NaClO4] M
0.125
104 k' Sec-1
3.071
103[P-TSA] M
1.25
104 k' Sec-1
3.000
0.250
3.062
2.50
2.851
0.375
3.079
3.75
2.590
0.500
3.075
5.00
2.412
0.625
3.071
6.25
2.374
T= 313K ,[DE]=0.96 M ,[CAT]=0.001 M in (1:5) ethanol :water (v/v) and μ=0.25 M while varying
[P-TSA].
Table 3. Effect of temperature on the reaction rate and activation parameters.
Temperature K0 104 k' Sec-1
104 k3 Sec-1
Activation Parameters
308
313
318
323
328
2.00
3.07
3.84
4.61
5.20
(6.83)
(7.89)
(15.15)
(19.60)
(43.48)
Ea , KJ mol-1 84.955 (77.22)
∆H≠, KJ mol-1 82.309± 0.084 (74.575±0.083)
∆S≠, JK-1mol-1-47.766±1.844 (-65.156±178)
∆G≠, K J mol-197.509±0.884 (95.305±1.07)
10-10 A ,sec-1 5.822±1.275 (0.7205±0.1301)
μ=0.25 M , (1:5) ethanol :water(v/v) ,[CAT]=0.001M ,[DE]=0.96 M ,[H+]=0.3 M and Note. values
in parenthesis are the decomposition constant and activation parameters limiting step.
Chloramine-T behaves like a strong electrolyte in aqueous solution and dissociates
according to equation (2). The anion picks up a proton in acid solutions to give the free acid
has not been isolated there is an experimental evidence for its formation in acid solution
.It undergoes disproportionation giving rise to p-toluenesulphonamide and dichloramine-T
,equation(4). Dichloramine-T and the free acid hydrolyse to give hypochlorus acid , HOCl
,[equation (5) and (6)]. Hypochlorous acid produce can be ionize according to equation (7).

343 Y. I. HASSAN
hypochlorus acidinium ion (H2O+Cl) and protonated monochloramine-T (R'N+H2Cl) have
also been detected in acid medium through equation (8) and equation (9), respectively.


(2)

R' NCINa R' NCI Na
R' NCI H R' NHCI

(3)


(4)

2 R' NHCI R' NCI2  RNH2

(5)

R' NCI2  H2O R' NHCI2  HOCI

(6)

R' NHCI2  H2O RNH2  HOCI
_

(7)

HOCI H  OCI
HOCI H  CI_ H2O  CI2

(8)

R' NHCI H R' NH2CI

(9)

rate=d[CAT]/dt=k3[X]
(10)
Therefore the possible reactive species in acidified chloramine-T solutions are R'NHCl,
R'NCl2, HOCl, Cl2, and probably (RNH+2Cl and H2O+CL). If RNCl2 were to be the reactive
species then the rate predicats a second –order dependence of rate on CAT but
experimentally clear first –order plots were obtained for disappearance of CAT. Equation (6)
indicates that the hydrolysis is slight and if HOCl is involved a first –order retardation of
rate by the added P-toluenesulphonamide is expected. However ,no such effect was observed
.first –approximation calculations by Bishop and Jennings(36)on 0.05 M solution of CAT
have shown that the concentration of RNHCl and HOCl are 10-2 and 10-7M ,respectively ;at
PH < 3. Under the present experimental conditions (0.2-0.4 M H+), it is quite likely that
R'NHCl is the oxidizing species variation of ionic strength of medium or addition of the
reaction product. P-toluenesulphonamide, have virtually no effect on the rate. Bearing these
facts in mind, the following scheme 1 has been proposed;
Scheme 1
In scheme 1, DE represent the substrare, X and X' represents the complex intermediate
species whose structures are shown in scheme 2, where a details plausible mechanism of
oxidation of DE with CAT in HCl medium is illustrated.
From the slow step of scheme 1,
d[CAT] k3[X]
(10)
rate
dt
If [CAT]t is the total effective concentration of CAT, then
[CAT]t =[R'NCl-] + [R'NHCl] + [X]
(11)
By substituting for [R'NCl] and [R'NHCl] from step (i) and (ii) in scheme 1,
respectively, in to equation (11) and solving for [X], one obtains;

Kinetics and Mechanism of Oxidation of Diethyl Ether 346
[X]
[X]
(12)
(13)
[CAT] 

[X]
t
K1K2[DE][H] K2[DE]
K1K2[DE][H ][CAT]t
1 K1[H ]  K1K2[DE][H ]
[X]
Substituting equation (13) in equation (10), the following , rate law can be obtained;
K1K2k3[DE][H ][CAT]t
d[CAT]t
(14)
rate

1 K1[H ] K1K2[DE][H ]
dt
Rate law (14) is in good agreement with the experimental results ,where in a first –order
dependence of rate on [CAT] , a fractional order dependence on both [DE] and [H+] have
'
been observed .Since rate =k1 [CAT]t , equation (14) can be transformed in to equations (15-
17)
K1K2k3[DE][H ]
1 K1[H ]  K1K2[DE][H ]
k’
(15)
k'
1
k
1
1
1
(16)
(17)



K1K2k3[DE][H ]
K2k3[DE] k3
1
1
1
1
1}
k3

{
K1[H ]
k
K2k3[DE]
Based on equations (16) and (17), plots of 1/k' versus 1/[DE] and 1/k' versus 1/[H+]
were linear (r>0.9910) (Figure 1) .from the intercepts and slopes of these plots values of
formation constant k3 calculated and found to be K1=1.34 mol.dm-3, K2=2.06 dm.mol-1 and
*
k3=7.886 10-3 sec-1 at 313 Ko respectively. Since the rate was fractional –order in [DE]0,
Michaelis –Menten37 kinetics were adopted to study the effect of [DE]0 on the rate at
different temperatures (308-3430k) by plotting 1/k' versus 1/[DE]0 .Using the calculated k3
and the observed rate constants k' values, activation parameters were evaluated from linear
Arrhenuis plot of 1/k' versus 1/T. the values are recorded in Table 3.
y=1814x+1268
y=478.1x+ 1610
1/[H+]
1/[DE]
Figure 1. plot of 1/ko versus 1/[H+]and 1/[DE]; [CAT]=0.001 M; μ=0.25 M;
Temperature=313Ko.

346 Y. I. HASSAN
K1
R\NCl-
R\NHCl
(i)
H
K2
Cl NHR\
CH2CH3
(ii) CH3CH2
O
O
Cl
N
H
R\
CH3CH2
O
CH2CH3
(X)
H
k3
-R\NH
CH3CH2
Cl NHR\
CH2CH3
CH3
C
H
O
Cl
CH2CH3
(iii)
(X\)
(X)
-HCl
H
H
C
CH3
C
O
O
CH3
O
CH2CH3
CH2CH3
O
H
-H+
H
H
H
CH3
C
H
R\
RNH
Cl
O
O
CH2CH3
N
H
CH3
C
O
CH2CH3
Cl
H
H
OH
-R\NH
CH3
CH3
C
-HCl
O
O
C
H
O
CH2CH3
O
CH2CH3
Cl
2R\NH- +2H+
( R = CH3C6H5SO2
2RNH2
(iv)
)
Scheme 2
The propose mechanism and the derived rate law are supported by the experimental data
and findings ;there is a good agreement between them indicating the consistency and the
correctness of the proposed Schemes and the derived rate law ,except that for (K1) value
,which may be due to variation of experimental condition .The reaction rate is un altered by
the variation of ionic strength of the medium .Addition of the reaction product P-TSA
affects the reaction rate marginally showing that it is not involved in a pre –equilibrium. A
change in the solvent composition by varying the methanol content in methanol –water
affects the reaction rate which has been describe in detail by frost and pearson38, laidler39
and Amis40. For the limiting case of zero angle of approach between two dipoles or an ion-
dipole system , Amis(40) has shown that a plot of log k' versus 1/D gives a straight line, with
a negative ion and a dipole or between two dipoles ,whiles a positive results for a positive
ion –dipole interaction. The latter concept agrees with the present investigation where a
positive ion may be involved in the rate determining step (which extended to the transition –
state) of the proposed mechanism. The propose mechanism is also supported by the
moderate ∆H≠ and ∆G≠ values and by the high negative value of ∆S≠ which indicate that the
transition state is more ordered than the reactants.
Conclusion
Oxidation of diethyl ether with chloramine-T in HCl medium has been studied .the
stoichiometry of oxidation diethyl ether with CAT in acid medium is found to be 1:2. The
oxidation product identified was ethyl acetate .The active oxidizing species involved in acid
medium is CH3C6H4SO2NHCl .Activation parameters calculated from Arrhenius plot the
observed results supported the proposed mechanism and derived rate law.

Kinetics and Mechanism of Oxidation of Diethyl Ether 346
References
1.
2.
3.
4.
Murthy.A R V and Rao.V R S, Proc Indian Acad Sci., 1952, 69, 35.
Cambell M M and Johnson.G, Chem Rev., 1978. 78, 65.
Rao.V.R.S, Venkappayya.D and Aravamudan.G, Talanta, 1970, 17, 770.
KolthoffI.M and Belcher R, "Volumetric Analysis" Vol.3, Interscience, New York,
1975, P639.
5.
6.
7.
8.
9.
Jennings V J, CRC Crit Rev Anal Chem., 1964, 407.
Coull J, Hope H B and Gouguell.B, J Am Chem Soc., 1935, 57, 1489.
Pryde L R and Soper F G, J Chem Soc., 1931, 1510.
Higuchi T and Hussain A, J Chem Soc., 1967, B, 549.
Balasubramania.V and Thiagarajain.V, Int J Chem Kinet., 1975, 7, 605.
10. Agrawal M C and Mushran S P, Naturfrosch., 1972, B27, 401.
11. Bose A K, Sanehi R and Mushran S P, J Indian Chem Soc., 1973, 50,197 .
12. Agrawal M C and Mushran S P, J Chem Soc Perken Trans II, 1973, 762.
13. Rangappa K S, Manjunathaswamy H, Ragharendra M P and Gowda D C,
Carbohydrate Reseach., 1998,307,253.
14. Mahadevappa D S and Naidu H M K, Aust J Chem., 1974, 27, 1203; 1975, 28, 899.
15. Natarajam M M and Thaiagarajan V, J Chem Soc Perken Trans., 1975, II, 1590.
16. Mushran S P, Agrawal M C and Prased B, J Chem Soc., 1971, 1712 .
17. Hassan Y I, Aziz L A and AL-Joraycee A A, J Edec.and Sci., 1989, 9, 73.
18. Hassan Y I and AL-Hatim A A, Mutah J Res Stud., 1995, 5, 19.
19. Bose A K, Mehrotra R M and Mushran S P, Indian J Chem., II,1973,896.
20. Mahadevappa D S, Rangappa K S, Gowda M M and Gowda B T, J Phys Chem.,
1981, 85,3 651, Int.J.Chem.Kinet.1981, 14,1183, J Chem Soc Perkin Trans II,39,
(1985) and Ref. (13) there in.
21. Ramanujam V M S and Trieff N M, J Chem Soc Perken Trans., II, 1975, 1590.
22. Radhakrishhnaamurti P S, Pati S C and Dev B R, Int J Chem Kinet., 1982, 14.
23.. Hassan Y I and Saeed N H M, J Educt Scince, 2008, 21,9, Saeed N H M,
M.Sc.Thesis, University of Mosul ,Mosul,Iraq, (2006).
24. Puttaswamy, Jadadeesh R V and Vaz N, Europ J Chem.,.2005, 3, 326.
25. Mahadevappa D S, Jadhav M B and Naidu H M K, Int J Chem Kinet., 1979, 11.261.
26. Jadhav M B, Naidu H M K and Mahadevappa D S, J Indian Chem Soc., 1980, 57,
693.
27. Mahadevappa D S and Gowda B T, Indian J Chem., 1979, 17, 484.
28. Ahmed M S, Gowda B T and Mahadevappa D S, Indain J Chem., 1980, 19, 650.
29. Metsger L and Bittner S, Tetrahedron, 2000, 51, 1905.
30. Vogel A I, "Text Book of practical organic chemistry" 4th ed. Longman press,
London, U.K.P, 1978, 651.
31. Morris J C, Salazar J A and Wineman M A, Am Chem Soc., 1948, 70, 2036.
32. Soloway S and Lipshits A, Anal Chem., 1952, 24, 898.
33. Gowda N M M and Mahadevappa D S, Talanta, 1970, 24, 470.
34. Cheronis N D and Entrikim J B, "Identification of organic compounds" See Ed.,
1966, John Wikey and Sons ,New York ,U.S.A.
35. Vogel A I, "A Text-Book of Macro and Semimicro qualitative Inorganic Analysis" 4th
Ed., Longmans, London, U.K, 1965.
36. Gkerlof A and Amer J, Chem Soc., 1932, 54, 4125.
37. Bishop E and Jennings V J, Talanta, 1958, 1, 197.
38. Forst A A and Pearson R G "Kinetics and mechanism" 2nd Ed., Wiley, New York
U.S.A, 1961.
39. Laidler K J, "Reaction Kinetics"Progamon, 1962, New York, U.S.A, 1962.
40. Amis E S, Anal Chem., 1955, 27, 1672.

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http://www.hindawi.com
Hindawi Publishing Corporation
http://www.hindawi.com
Hindawi Publishing Corporation
http://www.hindawi.com
Volume 2014
Volume 2014
Volume 2014
Volume 2014
Volume 2014