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8/13/2019 Result Selvi
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CHAPTER-IV
RESULTS AND DISCUSSION
Kinetics of oxidation in absence of monomer
The Kinetics of oxiation of lactic acid (LA) by Ce(IV) in the absence of
monomer was carried out at the temperature 30oC and 350C. The rate of oxidant
consumption (-d[Ce(IV)]/dt) were proportional to [Ce(IV)] , (Table1,Fig1)
.Variation of rates with substrate concentration (Table2,Fig 2) suggested the
formation of 1:1 complex intermediates prior to oxidation.The plots of
(-d [Ce (IV) ]/dt)-1against [LA]-1were linear(Table3,Fig3), with an intercept the
complex formation between the oxidant and the substrate in the redox pair. Double
reciprocal plots of (-d[Ce (IV) / dt)-1 vs[H+]-1 were also found to be linear
(Table4 ,fig4).
The results of oxidation can be accounted for by the following scheme
where Ce (IV) represents the first species of oxidation .
scheme I
K1
LA + H+ -----------LA - H+ .......................(i)
------
K2
LA - H+ + Ce(IV) - ------- Complex(c) ..........(ii)Kr
C R .+ Ce(III) + H+ ......................(iii)
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K0
R. + Ce(IV) Products ....................(iv)
Where, C represents the complex formation between the substrate and the
oxidant.
The two eqilibrium K1and K
2were treated separately so that,
K1
= ([LA - H+]eq
) / ([LA]eq
[H+]) ...........(1)
and
[LA]T
= [LA - H+]eq
+ [LA]eq
........................(2)
From equation(1),
[LA - H+]eq
= K1[LA]
eq[H+]
Introducing this value in equation (2),We get,
[LA]T
= K1
[LA]eq
[H+] + [LA]eq
= [LA]eq
(1 + K1[H+]) ........................(3)
Where [LA]eq
denotes the equilibrium concentration of LA also,
[Ce (IV)]T
= [Ce(IV)]
eq
+ [C] .........................(4)
From the kinetic step (2)
K2= [C] / ([LA - H+]
eq[Ce (IV)]
eq)
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[C] = K2[LA-H+]
eq[Ce (IV)]eq ..........................(5)
Substituting equation (5) in equation(4),
[Ce(IV)]T= [Ce(IV)]
eq+K
2[LA - H+]
eq[Ce (IV)]
eq
= [Ce (IV)]eq
(1+K2[LA - H+]
eq) ..........................(6)
Where [Ce(IV)]eq
represents the equitibrium concentration of ceric ion.
By applying steady-state approximation to the intermediate(R
), the
following expression can be derived from the kinetic scheme-I ,steps(iii) and (iv):
-d[R
] / dt = K0[Ce (IV)]
eq[R
] - Kr[C] = 0
therefore
K0[Ce (IV) ]
eq[R
] = Kr[C]
[R
] = [Kr[C] ) / (K0[Ce (IV)]eq.................................(7)
The rate law for the oxidation could then be derived as follows.
From the Kinetic steps,
-d [Ce (IV) / dt = Kr[C]+K0[Ce(IV)]eq[R
]
=Kr[C]+K0[Ce(IV)]eqKr[C] / (K0[Ce(IV)]eq
)
= 2Kr[C]
From the equation (5),
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-d[Ce(IV)] / dt = 2Kr.K
2[LA-H+]
eq[Ce(IV)]
eq
By using the equation (1),
-d[Ce(IV)] / dt = 2KrK
1K
2[LA]
eq[H+][Ce(IV)]
eq
Applying the equation (3) and (6)
-d[Ce(IV)/dt=(2KrK
1K
2[LA]
T[Ce(IV)]
T[H+]/1+ K
1[H+])x(1+K
2[LA-H+]
eq)
=R0
The above equation explain the dependence of the rate on Ce(IV)
concentration and also variable with substrate concentration.The observation of
Michelis-Menton kineties, i.e.,the formation of a complex between the reactants
allow the oxidation data to be treated according to the method of Line Wearer and
Burk.
Thus the above equation can be written as follows:
(2KrK1K2 [LA]T[Ce(IV)]T[H+])
-d[Ce(IV)]/dt =
(1+K1[H+])(1+K 2K 1[LA]eq[H
+])
(2KrK1K2[LA]T[Ce(IV)]T[H+])
=(1+K1K2[LA]T[H
+])/(1+K1[H+])
(2KrK1K2[LA]T[Ce(IV)]T[H+])
=
(1+K1[H+]+ K1K2[LA]T[H
+])
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Taking reciprocal rate in given by,
(-d[Ce(IV)]/dt)-1=1/(2KrK1
K2[LA]
T[Ce(IV)]
T[H+])+1/(2K
rK
2[LA]
T[Ce(IV)]
T)
+ 1/(2Kr[Ce(IV)]
T) ................................(8)
This equation explains the linear plot of(-d[Ce(IV)]/dt)-1 vs[H+]-1,
(-d[Ce(IV)]/dt)-1 vs[LA]-1
Equation (8) explain the dependence of rate on[Ce(IV)].
Thus Kr could be evaluated from the plots of (-d[Ce(IV)]/dt)-1 vs [LA]-1
from the intercepts of the plots of(-d[Ce(IV)]/dt)-1vs[H+])-1, K2could be evaluated
The value of K1can be determined from the slope of the plots of (-d[Ce(IV)]/dt)-1
vs [H+]-1by knowing the values of krand k
2. The calculated data are listed in Table
5. The thermodynamic parameters calculated for the reaction are also listed in the
same table.
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Table 1
[LA] = 0.2 mol.dm-3
= 1.1 mol.dm-3
[H2SO4] = 5 mol. dm-3
Temperature = 300C & 35
0C.
[Ce(IV)] mol. dm-3
10
-7
[-d [Ce(IV)]/dt] mol. dm-3
. sec-1
300C 350C
0.00314 6.9079 5.3289
0.00418 7.6974 7.5
0.00523 8.2895 8.8816
0.00627 8.8816 10.8553
0.00732 10.0658 12.2368
0.00783 10.8553 12.3434
Table 2
[Ce(IV)] = 0.0209 mol.dm-3
= 1.1 mol.dm-3
[H2SO4] = 5 mol. dm-3
Temperature = 300C & 35
0C.
[LA] mol. dm-310- [-d [Ce(IV)]/dt] mol. dm- . Sec-
30 C 35 C
0.02 14.013 14.605
0.03 15.395 15.395
0.04 15.987 16.9740.05 16.579 17.961
0.055 17.566 19.145
0.06 17.961 20.132
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[Ce(IV)] mol. dm-3
Fig.1 Variation of Oxidant
[LA] mol. dm-3
Fig.2 Variation of Reductant
0
2
4
6
8
10
12
14
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08
0
5
10
15
20
25
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07
10-7[-d[Ce(IV)]/dt]mol.dm-3.S
ec-1
35oC
30oC
10-7
[-d[Ce(IV)]/dt]
mol.dm
-3.
Sec
-1
35oC
30oC
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Table 3
[Ce(IV)] = 0.0209 mol.dm-3
= 1.1 mol.dm-3
[H2SO4] = 5 mol. dm-3
Temperature = 300C & 35
0C.
[LA]-1(mol. dm-3)-1 10 [-d [Ce(IV)]/dt]
-
mol. dm
-
. Sec
-
30
0C 35
0C
50 0.7136 0.6847
33.33 0.6496 0.6496
25 0.6255 0.5891
20 0.6032 0.5568
16.67 0.5693 0.5223
14.29 0.5568 0.4967
Table 4
[Ce(IV)] = 0.0209 mol.dm-3 = 1.1 mol.dm-3
[LA] = 0.2 mol. dm-3
Temperature = 300C & 35
0C.
[H2SO4]-1
(mol. dm-3
)-1
106[-d [Ce(IV)]/dt]-1mol. dm-3. Sec-1
30 C 35 C
20 1.2992 1.1783
3.33 1.1259 1.1014
1.818 1.034 1.0555
1.25 0.9559 0.9744
0.952 0.8587 0.9212
0.769 0.7795 0.8587
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[LA]-1(mol. dm-3)-1
Fig.3 Variation of Reductant
[H2SO4]-1(mol. dm-3)-1
Fig.4 Variation of H2SO4
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0 10 20 30 40 50 60
0
0.2
0.4
0.6
0.8
1
1.2
1.4
0 5 10 15 20 25
35oC
30oC
35oC
30oC
10
6[
-d[Ce(IV)]/dt]-1mol.
dm
-3.
10
6[
-d[Ce(IV)]/dt]-1
mol.dm
-3.
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Table 5
Rate and thermodynamic parameters for the oxiation of lactic acid in the
absence of monomer
Temperature Kr K
1 K
2 K
a H S
K s-1 dm3.mol-1 dm3.mol-1 KJ.mol-1 KJ.mol-1 J.mol-1k-1
303
308
Oxidation in the presence of monomer
Where the oxidation of lactic acid by Ce(IV) was carried out in dilute
sulphuric acid medium in the presence of monomer it was observed that the rates
of disapperance of ceric ion were directly proportional to [Ce(IV)]. The plots of
rate versus ceric ion concentration were linear (Table6, Fig5). The rate were
variable with substrate conentration (Table7, Fig6). The order with respect to
monomer concentration was found to be unity as sum from the linear plots of rates
versus monomer concentration (Table8, Fig7) which means that, under the present
experimental conditions ceric ions were involved in a M+ Ce(IV)- type initiation
reaction. The plots of (-d[Ce(IV)]/dt)1against [LA]-1were linear with intercept on
the ordinate as shown in the (Table9, Fig8) The plots of(-d[Ce(IV)/dt) -1 vs [H+]
were linear with respect on the rate axis (Table10, Fig 9).
For methyl methacrylate the intercepts of the lines on the y-axis,may arise
due to an one of the following reasons.
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(a)A side reaction involving oxidation of the monomer by ceric ion.
(b) A side reaction involving oxidation of the impurities in the monomer by
ceric ion.The possibility of oxidation of the impurities in the monomer by ceric ion
receives some support from the evidences in the literature , where impurities
present in the polymerization system have been shown to affect the determination
of reaction rates.We therefore conclude that the initiation takes place by a direct
reaction between the monomer and ceric ion.This may probably involves an
electron transfer from the ceric ion to the monmer, producing a radical ion of the
type CH2=CHX,which in similar to the one proposed by bawn and sharp4 in theoxidation of olefins by cobaltic ion. The direct dependence of the rate on monomer
concentration has also been observed in the studies with ceric-reducing agent redox
system..
The above results of oxidation in the presence of monomer can be
accounted for the following scheme.
scheme-II
KCe (IV) + LA complex c ............................(i)
Kr
C R. +Ce(III) + H+ ........................(ii)
R. + Ce(IV) products ........................(iii)
Ki
Ce (IV) +M M
+ Ce(III) .......................(iv)Applying steady state approximation to the intermediate R., the following
expression can be derived for the oxidation in the presence of monomer.
-d[Ce(IV)]/dt=Kr[C]+K
0[Ce(IV)]
eq[R]+K
i[M][Ce(IV)]
eq............(9)
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substituting the value of[R
] from equation (7) in to equation(9),
-d[Ce(IV)]/dt=K
r[C]+K
0[Ce(IV)]
eq
(Kr[C]]/K0[Ce(IV)]
eq
)+Ki[M][Ce(IV)]
eq
=2Kr[C]+K
i[M][Ce(IV)]
eq
Introducing the value of[C] from equation(5)
-d[Ce(IV)]/dt=2KrK
2[LA - H+]
eq[Ce(IV)]
eq+K
i[M][Ce(IV)]
eq...........(10)
substituting the value of[LA-H+]eq
and [Ce(IV)]eq
from equation (1) and
(6) into equation (10),
-d[Ce(IV)]/dt=(2KrK
2[Ce(IV)]
TK
1[LA]
eq[H+]/(1+K
2[LA-H+]
eq)
+Ki[M][Ce(IV)]
T)/(1+K
2[LA - H+]
eq)
=R0+(K
i[M][Ce(IV)]
T)/(1+K
2[LA - H+]
eq)
Where R0 is the rate expression for the oxidation in the absence ofmonomer.
In any case the line weaver-Burk treatment would be still valid for the
oxidation data.
The values of the rate and equlibrium constants can be computed.These are
in Table 13.
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Table 6
[LA] = 0.2 mol.dm-3
= 1.1 mol.dm-3
[H2SO4] = 5 mol. dm-3
Temperature = 300c & 35
0c.
[M] = 0.02 mol.dm
-3
[Ce(IV)] mol. dm-310- [-d [Ce(IV)]/dt] mol. dm- . Sec-
30 C 35 C
0.00314 3.1578 4.9342
0.00418 6.1184 8.6842
0.00523 6.5131 9.0789
0.00627 9.0789 11.6447
0.00732 10.0657 12.6315
0.00784 10.6578 13.0263
Table 7
[Ce(IV)] = 0.0209 mol.dm-3 = 1.1 mol.dm-3
[H2SO4] = 5 mol. dm-3
Temperature = 300C & 35
0C.
[M] = 0.02 mol.dm-3
[LA] mol. dm-3
10
-3[-d [Ce(IV)]/dt] mol. dm
-3. Sec
-1
300C 35
0C
0.02 1.1644 1.6578
0.03 1.3223 1.6973
0.04 1.3618 1.7763
0.05 1.3815 1.8552
0.055 1.4802 1.89470.06 1.5789 1.9539
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[Ce(IV)] mol. dm-3
Fig.5 Variation of Oxidant
[LA] mol. dm-3
Fig.6 Variation of Reductant
0
2
4
6
8
10
12
14
16
0 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009
0
0.5
1
1.5
2
2.5
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07
35oC
30oC
35oC
30oC
10-4
[-d[Ce(IV)]/dt]mol.
dm
-3.
10-3
[-d[Ce(IV)]/dt]mol.
dm
-3.
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Table 8
[Ce(IV)] = 0.0209 mol.dm-3
= 1.1 mol.dm-3
[H2SO4] = 5 mol. dm-3
Temperature = 300C & 35
0C.
[LA] = 0.02 mol.dm
-3
[M] mol. dm-310- [-d [Ce(IV)]/dt] mol. dm- . Sec-
30 C 35 C
0.0004 4.9342 3.9473
0.0005 5.3289 4.3421
0.0006 6.1184 4.7368
0.0007 3.9473 5.1315
0.0008 5.9210 6.1184
0.0009 7.3026 6.9078
Table 9
[Ce(IV)] = 0.0209 mol.dm-3 = 1.1 mol.dm-3
[H2SO4] = 5 mol. dm-3
Temperature = 300C & 35
0C.
[M] = 0.02 mol.dm-3
[LA]-1(mol. dm-3)-1103[-d [Ce(IV)]/dt]-1mol. dm-3. sec-1)-1
300C 350C
50 0.8588 0.6032
30.33 0.7562 0.5892
25 0.7343 0.5629
20 0.7238 0.539018.18 0.6756 0.5278
16.66 0.6333 0.5118
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[M] mol. dm-3
Fig.7 Variation of Monomer
[LA]-1(mol. dm-3)-1
Fig.8 Variation of Reductant
0
1
2
3
4
5
6
7
8
0 0.0002 0.0004 0.0006 0.0008 0.001
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 10 20 30 40 50 60
35oC
30oC
35oC
30oC
10-4
[-d[Ce(IV)]/dt]m
ol.dm
-3.
10
3[
-d[Ce(IV)]/dt]
-1m
ol.dm
-3.
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Table 10
[Ce(IV)] = 0.0209 mol.dm-3
= 1.1 mol.dm-3
[LA] = 0.2 mol. dm-3
Temperature = 300C & 35
0C.
[M] = 0.02 mol.dm
-3
[H2SO4]-1
(mol. dm-3
)-1
10 [-d [Ce(IV)]/dt]
-(mol. dm
-. Sec
-)
-
30 C 35 C
20 0.7562 0.7238
3.333 0.7451 0.7451
1.8181 0.7343 0.7136
1.25 0.7037 0.7037
0.9523 0.6667 0.6496
0.7692 0.6414 0.6255
Table 11
[Ce(IV)] = 0.0209 mol.dm-3
= 1.1 mol.dm-3
[H2SO4] = 5 mol. dm-3
Temperature = 300C & 35
0C.
[M] = 0.02 mol.dm-3
[LA]-1
(mol. dm-3
)-1
10
7[-d [M]/dt]
-1(mol. dm
-3. Sec
-1)-1
300C 35
0C
50 9.2311 0.8541
33.33 4.6153 0.7224
25 3.7509 0.670720 0.8889 0.5522
18.18 0.6956 0.5217
16.66 0.6476 0.4580
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[H2SO4]-1
(mol. dm-3
)-1
Fig.9 Variation of H2SO4
[LA]-1
(mol. dm-3
)-1
Fig.10 Variation of Reductant
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
0 5 10 15 20 25
-2
0
2
4
6
8
10
0 1 2 3 4 5 6 7
35oC
30oC
35oC
30oC
10
3[
-d[Ce(IV)]/dt]-1
(mo
l.dm
-3.
10
7[
-d[M]/dt]-1
(mol.d
m-3
.sec
-
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Table 12
[Ce(IV)] = 0.0209 mol.dm-3
= 1.1 mol.dm-3
[LA] = 0.2 mol. dm-3
Temperature = 300C & 35
0C.
[M] = 0.02 mol.dm
-3
[H2SO4]-1(mol. dm-3)-1
10 [-d [M]/dt]- (mol. dm- . sec- )-
30 C 35 C
20 0.7224 0.9884
3.333 0.4472 0.8163
1.8181 0.3683 0.7224
1.25 0.3354 0.6956
1.9523 0.3183 0.6956
0.7692 0.2981 0.6030
[H2SO4]-1(mol. dm-3)-1
Fig.11 Variation of H2SO4
0
0.2
0.4
0.6
0.8
1
1.2
0 5 10 15 20 25
35oC
30oC
10
7[
-d[M]/dt]-1
(mo
l.dm
-3.sec
-
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Rate and thermodynamic parameters for the oxidation of lactic acid in the
presence of monomer
Temperature Kr K1
K2
Ka H S
K S-1 dm3.mol-1 dm3.mol-1 KJ.mol-1 KJ.mol-1 J.mol-1k-1
303
308
Kinetics of polymerization
The polymerization of methyl methacrylate using redox couple Ce
(IV) - lactic acid was carried out at the temperature 300C and 350C under nitrogen
atmosphere. The polymerization was found to takes place without an induction
period, and the steady state rate was attained with in a short time. The rates of
polymerization and also varied with [LA] (Table16, Fig14),but tend to become
independent of substrate at high subtrate concentration. The rate of polymerization
were proportional to [M] being linear passing through the origin (Table14, Fig12)
furnishing strong, evidence, for the mutual termination of the growing chain. The
rates were decreased by [H+]showing 0.5 order in [H+](Table15, Fig13).
The initial rate was increased with increase in monomer concentration at
fixed [Ce(IV)], [LA]and [H2SO
4]. It was found that the greater the monomer the
greater the possibility of initiation by primary radicals.
All the above data of polymerization can be accounted for by the following
scheme.
scheme-III
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K
Ce (IV) + LA ----- complex C ................(i)
KrC -------- R
+ Ce(III) + H+ ..............(ii)
Ko
R.+ Ce(IV) ------- products ..............(iii)
Ki
R
+ M -------- R - M
............(iv)
Kp
R - M
+ M ------- R - M2
etc
Kt
2R Mn
-------- polymer
The mutual termination assumed here does not distinguished betweenthe combination and disproportionation modes.
The steady state concentration of radical intermediates will be given by the
following equation
d[R
]/dt=Kr[C]-K
o[R
][Ce(IV)]eq
-Ki[R
][M]=0
[R
]=K1[C] / K0[Ce (IV)]eq+Ki[M]) .............................(ii)
substituting the value of [C] from the equation (5),
[R.]=(K
rK
2[LA- H+]
eq[Ce(IV)]
eq) / K
0[Ce(IV)]
eq+K
i[M]) .........(12)
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then,
d[R Mn
] / dt = Ki[R
][M] - Kt[R Mn
]2=0
Ki[R
.][M] = K
t[R-M
.n]2
[R- Mn.] = (K
i/K
t)[R
.][M]1/2 ..........................(13)
By appling the value of [R.]from equation (12)
(KrK
2[LA - H+]
eq[Ce[(IV)
]eq) 1/2
[R- Mn
] = ((Ki/K
t)[M]1/2 .(14)
K0[Ce(IV)
eq+K
i[M]
The rate of polymerization can be writen as
-d[M] / dt =Kp[M][R-Mn
] .............................(15)
Combining equation(14) and (15) the following expression can be derived
(KiK
rK
2[LA - H+]
eq[Ce(IV)]
eq1/2
--d[M]/dt = Kp/Kt1/2[M]3/2 .......(16)(K
0[Ce(IV)]
eq+ K
i[M]
Introducing the equation (3) and (6) in to (16)
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Kp/Kt1/2[M]3/2 (K
iK
rK
2(Ce(IV)
T/ 1+K
2[LA - H+]
eqK
i[H] + [LA]
-d[M]/dt =
1+K1
[H+] / K0Ce(IV)]
T/ (1+K2[LA -H
+]eq
) + Ki[M
.])1/2
Rearranging the above equation
-d[M]/dt = [M]3/2[Ce(IV)]t1/2[LA]1/2
T[H+]1/2.Kp/K
t1/2][K
iK
rK
1K
2/K
0]1/2 x
(a constant) ....................................(17)
The data of polymerization statisfy the requirments of the above equation.
By applying the value of [Ce(IV)]eq in the equation (16) the equation
becomes,
-d[M]/dt = (Kp
/Kt1/2) [M] 3/2[Ce(IV)]
T1/2/ (1+K
2[LA-H+]
eq)
[LA - H+]eq
1/2 + Kt1/21+K
2[LA-H+]
eqK
iK
rK
2(K
0[Ce(IV)]
eq+K
i[M]))1/2............(18)
Under conditions such that
K0[Ce(IV)]
eq
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presence of monomer. The value of Kp and Ktwhich refer to the reactivity of the
growing radicals (R - M.) towards the monomer and towards themselves
respectively depend not on nature of the monomer but on the medium and
temperature.
Effect of organic substrate
On increasing the concentration of lactic acid the rate of polymerization
was increased the plots of versus [LA] were linear and passed through the origin.
Effect of [H]+
The increase in concentration of acid leads to a decrease in the rate Rp (obs) at
constant ionic strength. But Rp (obs) was independent of [H+]. This may be
attributed to formation of less active Ce(IV) species given by the following
eqilibrium.
Ce(IV) + H2SO
4 ---> CeSO
4 (III) + H+
At constant [H2SO
4], the increase in [H+] will lead to a decrease in the ratio
Ce[SO4] (III) / Ce(IV). Hence with lower [H+] the reactivity of CeSO
4(III)
predominates where as at higher [H+] the effect was reveserd.
Effect of Ce(IV)
It was observed that Rp (obs) increase with increasing Ce(IV) concentration. This
can be explained by an increase number of Ce(IV) in the stern layer of SDS
micelles due to electrostatic attraction.The plot of Rp (obs) Vs Ce(IV) shows a
straight line passing through the origin.
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Table 14
[Ce(IV)] = 0.0209 mol.dm-3
= 1.1 mol.dm-3
[LA] = 0.2 mol. dm
-3
Temperature = 30
0
C & 35
0
C.[H2SO4] = 5 mol.dm
-3
[M] mol. dm-3Rpx 10
-7
30 C 35 C
0.0004 1.8655 1.5112
0.0005 2.3488 2.0239
0.0006 2.8537 2.6232
0.0007 3.3288 3.1013
0.0008 3.8259 3.6859
0.0009 4.4411 4.2285
Table 15
[LA] = 0.2 mol.dm-3
= 1.1 mol.dm-3
[H2SO4] = 5 mol. dm-3 Temperature = 300C & 350C.
[M] = 0.02 mol.dm-3
[Ce(IV)] mol. dm-3
Rpx 10
-7
300C 350C
0.00314 2.9076 2.6588
0.00418 2.9243 2.8360
0.00523 2.9423 2.9068
0.00627 3.0297 2.9423
0.00732 3.0658 2.9778
0.00784 3.1017 3.0133
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[M] mol. dm-3
Fig.12 Variation of Monomer
[Ce(IV)] mol. dm-3
Fig.13 Variation of Oxidant
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
0 0.0002 0.0004 0.0006 0.0008 0.001
2.6
2.65
2.7
2.75
2.8
2.85
2.9
2.95
3
3.05
3.1
3.15
0 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009
35oC
30oC
35oC
30oC
Rp
x10-7
Rp
x10-7
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Table 14
[Ce(IV)] = 0.0209 mol.dm-3 = 1.1 mol.dm-3
[H2SO4] = 5 mol. dm
-3
Temperature = 30
0
C & 35
0
C.[M] = 0.02 mol.dm
-3
[LA] mol. dm-3
Rpx 10
-
30 C 35 C
0.02 0.3607 3.8981
0.03 0.7214 4.6083
0.04 0.8878 4.9634
0.05 3.7455 6.0288
0.055 4.7859 6.3806
0.06 5.1327 7.2663
[LA] mol. dm-3
Fig.14 Variation of Reductant
-1
0
1
2
3
4
5
6
7
8
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07
35
o
C
30oC
Rp
x10-8