Kinetics and mechanism of Ru(III) catalyzed periodate oxidation of methyl glycol and diacetone alcohol in perchloric acid

Article abstract of DOI:10.14233/ajchem.2014.16444

Kinetics of oxidation of methyl glycol (MG) and diacetone alcohol (DAA) by periodate in the presence of ruthenium(III) chloride as homogeneous catalyst have been studied in acidic medium. The results indicate zero order dependence of the reaction on [IO₄^-] while first order kinetics with respect to [Ru(III)] was observed. First order in both [MG] and [DAA] was observed while positive effect of [H⁺] was exhibited. Variation of ionic strength of the medium and addition of potassium chloride did not bring about any significant change in the rate of the reaction. Showing thus zero effect of ionic strength and added chloride ions. A suitable mechanism consistent with kinetic results has been proposed and rate law has been deduced for the title reactions.

Full text of DOI:10.14233/ajchem.2014.16444

Asian Journal of Chemistry; Vol. 26, No. 16 (2014), 5125-5128
ASIAN JOURNAL OF CHEMISTRY
http://dx.doi.org/10.14233/ajchem.2014.16444
Kinetics and Mechanism of Ru(III) Catalyzed Periodate Oxidation of
Methyl Glycol and Diacetone Alcohol in Perchloric Acid
*
KAMINI SINGH and R.A. SINGH
Chemical Kinetics Research Laboratory, Department of Chemistry, Tilak Dhari P.G. College, Jaunpur-222 002, India
*
Corresponding author: E-mail: rasinghtdc@rediffmail.com
Received: 28 September 2013; Accepted: 5 December 2013;
Published online: 28 July 2014;
AJC-15645
Kinetics of oxidation of methyl glycol (MG) and diacetone alcohol (DAA) by periodate in the presence of ruthenium(III) chloride as
-
4
homogeneous catalyst have been studied in acidic medium. The results indicate zero order dependence of the reaction on [IO ] while first
+
order kinetics with respect to [Ru(III)] was observed. First order in both [MG] and [DAA] was observed while positive effect of [H ] was
exhibited. Variation of ionic strength of the medium and addition of potassium chloride did not bring about any significant change in the
rate of the reaction. Showing thus zero effect of ionic strength and added chloride ions. A suitable mechanism consistent with kinetic
results has been proposed and rate law has been deduced for the title reactions.
Keywords: Kinetics, Mechanism, Methyl glycol, Diacetone alcohol, Periodate.
llization and its stock solution, prepared in doubly distilled
water was standardized iodometrically. All other chemicals
used were ofAR grade. Perchloric acid (70 % of E. Merck) was
INTRODUCTION
In recent years, the use of transition metals ions, such as
osmium, iridium, palladium and ruthenium either alone or as
binary mixtures as catalysts in the oxidation of several redox
processes is of considerable interest of these reactions.
Ruthenium(III) chloride utility as nontoxic and homogeneous
+
used as source of H ions and sodium perchlorate (E. Merck)
was used to vary the ionic strength of the medium.
Kinetic measuremental: A thermostatic water bath was
used to maintain the desired temperature within ± 0.1 ꢀC. The
appropriate volumes of methyl glycol or diacetone alcohol,
1
-7
catalyst has been known , but less attention has been paid to
7
explore the catalytic role of Ru(III) with periodate as an
-10
11
4
HClO , Ru(III) chloride and required volume of water were
oxidant. Earlier, oxidation kinetics of methyl glycol and
diacetone alcohol by osmium tetroxide in alkaline medium
have been reported. In view of less work on the periodate
oxidation with industrically important substrates, there seems
to be much exciting chemistry in further probing the oxidative
capacity of periodate in the oxidation of methyl glycol and
diacetone alcohol particularly in the presence of Ru(III) in
perchloric acid medium. In present communication, a detailed
kinetic studies based mechanistic steps in Ru(III) catalyzed
periodate oxidation of methyl glycol (MG) and diacetone
alcohol (DAA) have been reported.
taken in a black coated reaction vessel which was thermostated
at 303 K for thermal equilibrium. After about 0.5 h when the
reaction mixture had attained the temperature of the experiment,
the requisite volume of periodate solution, also thermostated
at the same temperature, was added rapidly into the reaction
vessel to make the total volume of the reaction mixture 100 mL.
Immediately 5 mL aliquot of reaction mixture was taken out
and poured into acidified potassium iodide solution.
The iodine liberated in equivalent amount was estimated
with standard solutions of sodium thiosulphate and the titre
volume at zero time was noted. Similar reading were recorded
at different intervals of time by estimating 5 mL of reaction
mixture iodometrically and thus progress of the reaction was
monitored periodate. Each kinetic run was studied for two half
EXPERIMENTAL
Standard solutions of methyl glycol and diacetone alcohol
both of E. Merck) were prepared by directly weighing their
(
samples and dissolving them in doubly distilled water. 1 g
sample of ruthenium(III) chloride (Johnson & Matthey) was
life of the reaction. The rate of the reaction (-dc/dt) was deter-
-
mined by the slope of the tangent drawn at a fixed [IO
4
] in
-3
prepared in 100 mL of 0.01 mol dm HCl solution and there
after it was diluted to 1 L in which its final strength was noted.
Sodium metaperiodate (Koch-Light) was used after recrysta-
each kinetic run. The order of the reaction in each kinetic run
was calculated by log-log plot of (-dc/dt) versus concentration
of reactants.

5
126 Singh et al.
Asian J. Chem.
Stoichiometry and product analysis: Different sets of
-
initial rate (-dc/dt) thus obtained was used to determine the
reaction mixture under the conditions [IO
4
] >> [Substrate]
order of reaction with respect to each reactant.
-
were equilibrated at 303 K for 72 h. Estimation of unconsumed
-
On varying [IO
4
] rate of reaction (-dc/dt) remains prac-
IO
4
in each set revealed that 2 and 4 moles of periodate were
tically constant in oxidation of each of MG and DAA, showing
thus zero-order kinetics in [periodate] (Table-1). At fixed
concentrations of all other reagents, increase in [MG] and
[DAA] increased the value of (-dc/dt) linearly, showing first-
order in both [MG] and [DAA]. This was further confirmed
consumed in oxidation of each mole of methyl glycol and
diacetone alcohol, respectively.Accordingly following stoichio-
metric equations can be formulated as (1) and (2).
+
Ru(III)/H
-
4
-
CH CHOH + 2 IO
3
3 3 2
CH CHOH + 2IO + H O (1)
by slopes (k
(-dc/dt) versus [MG] or [DAA], in agreement with experi-
mental k values (where k = (-dc/dt)/[Substrate]). The value
1
) of straight lines (Fig. 1) obtained on plotting
|
OH
|
COOH
CH
2
(
MG)
1
1
+
Ru(III)/H
of (-dc/dt) also increased linearly with increase in [Ru(III)] in
oxidation of both GM and DAA, indicating thus first-order in
-
4
(
CH
3
)C(OH)CH COCH
2
3
+ 4IO
CH COCH
3
3
+
-
(
DAA) CH COOH + CO
3
2
+ 4IO
3
2
+ H O
(2)
[
Ru(III)]. The graphical k
the plot between (-dc/dt) and [Ru(III)] were found in close
agreement with corresponding experimentally observed k value
Table-1), showing and confirming first-order in [Ru(III)] in
oxidation of both MG and DAA (Fig. not shown here).
1
values (obtained from the slope of
The corresponding oxidation products of MG and DAA
12
were identified by spot tests . The presence of acetone in equa-
tion (2) was also confirmed by its 2,4-dinitrophenyl hydrazone
derivative.
1
(
+
Table-2 contains the results of variation of [H ] and tempe-
+
rature as well as effect due to addition of KCl. Increase in [H ]
+
increased the rate non-linearly, showing positive effect of [H ]
RESULTS AND DISCUSSION
The kinetics of oxidation of methyl glycol (MG) and
diacetone alcohol (DAA) by periodic in the presence of little
on the rate of oxidation of both MG and DAA. Addition of
KCl to the reaction mixture was found to have no significant
[
Ru(III)] in aqueous acidic solution were investigated at several
initial concentrations of all the reactants at 303 K. The value
of initial rate (-dc/dt) in each kinetic run was calculated from
the slope of the tangent of the straight line obtained on plotting
-
effect, indicating zero effect of [Cl ] on rate oxidations.Variation
-2
-2
of ionic strength from 1.20 × 10 M to 6 × 10 M (in case of
-2
-2
MG) and from 2.33 × 10 M to 7.33 × 10 M (in case of DAA)
did not bring about significant change in oxidation of their
rates, showing negligible effect of ionic strength on rate of
-
-
-
unconsumed [IO
4 4 4
] versus time at, fixed [IO ] except in [IO ]
variation when tangent has been drawn at a fixed time. The
TABLE-1
EFFECT OF VARIATION OF [REACTANTS] ON RATE OF REACTION AT 30 ꢀC
-
2
-3
-2
-3
-3
HClO ] = 1.00 × 10 mol dm [MG] AND 2 × 10 mol dm [DAA], [KCl] = 1.00 ×10 mol dm
-3
[
4
3
2
6
7
-3 -1
[–dc/dt] × 10 (mol dm s )
a
1
6
-1
k × 10 (s )
[
NaIO ] × 10
4
[Substrate] × 10
-3
(mol dm )
[Ru(III)] × 10
-3
(mol dm )
-3
(mol dm )
MG
0.65
0.64
0.67
0.63
0.68
0.64
0.17
0.33
0.49
0.66
0.84
1.02
–
DAA
1.72
1.68
1.70
1.74
1.64
1.72
0.42
0.86
1.29
1.74
2.12
2.60
0.22
MG
–
DAA
–
0.80
1.00
1.25
1.67
2.50
4.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
2.00
2.00
2.00
2.00
2.00
2.00
0.50
1.00
1.50
2.00
2.50
3.00
2.00
9.60
9.60
9.60
9.60
9.60
9.60
9.60
9.60
9.60
9.60
9.60
–
–
–
–
–
–
–
–
–
–
3.40
3.30
3.26
3.30
3.36
3.40
–
8.40
8.60
8.60
8.70
8.48
8.66
9.60
b
c
1
1
1
2
3
3
4
6
6
8
9
.20
.60
.80
.40
.20
.60
.80
.00
.40
.00
.60
18.33
–
b
b
b
b
b
b
b
b
b
b
1
1
1
1
1
1
1
1
1
1
.00
.00
.00
.00
.00
.00
.00
.00
.00
.00
6
2.00
2.00
2.00
2.00
2.00
2.00
2.00
2.00
2.00
2.00
0.11
–
–
0.32
0.44
–
6.87
–
c
17.78
c
–
–
18.33
–
0.21
–
6.56
–
c
c
c
0.63
0.85
1.08
–
17.50
17.71
0.31
–
6.46
–
18.00
–
0.42
0.53
0.64
6.40
6.62
6.67
–2
–
–
–
–
(−dc / dt)
6
–1
,
3
(
−dc / dt)
3
–1
(−dc / dt)
–3
a ꢀ k ×10 =
= k ×10 s b ꢀ k × 10 =
= k ×10 s and c ꢀ [HClO ] =
= 1.00×10 mol dm
1
1
1
1
4
[
Substrate]
[Ru(III)]
[Ru(III)]

Vol. 26, No. 16 (2014)
Kinetics and Mechanism of Ru(III) Catalyzed Periodate Oxidation of Methyl Glycol and DiacetoneAlcohol 5127
-
-2
+
oxidation. Rate measurements at 298, 303, 308 and 313 K in
oxidation of MG and DAA led to calculate energy of activation
H
4
IO
6
H
3
IO
6
+ H
(c)
(d)
2
-
-3
H IO6
3
2
H IO6 + H+
#
), entropy of activation (DS ), free energy of activation (∆G )
#
-
(E
a
4 6
The mono anion H IO is largly dehydrated to tetrahedral
-
4
whose values are given in Table-3.
IO . The activity of periodate ion as an oxidizing agent varies
greatly as the function of pH and this is expected because of
accompanying change in the degree of ionization of perio-
–2
–3
[DAA] × 10 mol dm
.00 3.50 3.00 2.50 2.00 1.50 1.00 0.50
1
3,14
-
-
-2
4
2.00
date . Thus in acidic solution H IO
5
6 4 6 4 3 6
, H IO , IO , H IO and
1
0.00
-3
6
H
2
IO
can act as oxidizing species. Of these species, possi-
-
2-
3-
6
10.50
4.00
bility of H IO , H IO and H IO as oxidizing species is ruled
4
6
3
6
2
+
out as these will require negative effect of [H ] contrary to the
9.00
7.50
6.00
4.50
3.00
1.50
8.00
+
observed positive effect of [H ] on the rate. H
5
IO
6
will also
+
require decreasing effect of [H ] and hence it is also ruled out
–6 –1
12.00
16.00
20.00
24.00
k1 = 3.32 × 10
s (MG)
-
4
as oxidizing species. Now the only choice left is IO which
when taken as oxidizing species explains all the observed
kinetic results. Since order in [periodate] is zero which requires
its involvement in fast reaction after slow and rate determining
step, hence it matters little which one of the aforesaid species
is involved in fast step.
–
6
–1
s (DAA)
k1 = 8.65 × 10
2
8.00
2.00
1
5
It has been reported that in dilute HCl solution ruthe-
3-
] , which is involved in the
3
nium(III) chloride exists as [RuCl
6
0.0
0.5 1.00 1.520 2.00 –32.50 3.00 3.50 4.00
MG] × 10 mol dm
following equilibrium.
[
3-
2-
O)] + Cl
-
[
RuCl ] + H
6
2
O
[RuCl (H
5
2
(e)
Fig. 1. Plot of (-dc/dt) vs. [MG] or [DAA] under the condition of Table-1
3
-
2-
O)] may be effective
Thus either of [RuCl
6
] or [RuCl (H
5
2
catalytic species. It has also been reported that in acidic medium
In aqueous solution (pH = 0 to 7) of acid periodic acid
16
periodate ion rapidly converts Ru(III) to Ru(VIII) according
to the reaction given below which is faster than periodate
oxidations.
exists as equilibrium between free acid (H
5
IO ) and its various
6
ions.
-
6
+
H
5
IO
6
6
H
4
IO
-
+ H
(a)
(b)
-
+
-
-
2 Ru(III) + 5 IO + 10 H
→
3 2
2 Ru(VIII) + 5IO + 5H O (f)
4
H
4
IO
IO
4
+ 2H
2
O
TABLE-2
EFFECT OF VARIATION OF [HClO ], TEMPERATURE AND ADDITION OF KCl ON THE RATE OF OXIDATION OF MG AND DAA AT
4
–3
–3
0 ꢀC (UNLESS OTHERWISE STATED) [NaIO ] = 1 × 10 mol dm , [Substrate] = 2 × 10 mol dm , & [Ru(III)] = 9.60 × 10 mol dm
–2
–3
–6
–3
3
4
7 -3 -1
[–dc/dt] × 10 (mol dm s )
2
[HClO ] × 10 (mol dm )
-3
3
[KCl] × 10 (mol dm )
-3
Temperature (ꢀC )
4
MG
0.40
DAA
a
25
30
35
40
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.02
1.70
2.36
3.96
a
a
a
0.64
1.08
1.38
3
3
3
3
3
3
3
0
0
0
0
0
0
0
0.50
1.00
1.50
2.00
2.50
3.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
0.50
0.48
0.64
0.84
1.04
1.26
1.48
0.64
0.76
1.08
1.36
1.70
1.84
2.16
a
a
a
a
a
a
1.72
1.66
1.70
1.68
1.72
1.74
30
30
30
30
30
1.00
1.00
1.00
1.00
1.00
1.00
1.50
2.00
2.50
3.00
0.67
0.62
0.68
0.65
0.66
-
2
-3
a ꢀ [HClO ] = 2 × 10 mol dm
4
TABLE-3
ACTIVATION PARAMETERS IN Ru(III) CATALYSED OXIDATION OF METHYL GLYCOL (MG) AND
DIACETONE ALCOHOL (DAA) BY ACIDIC SOLUTION OF SODIUM METAPERIODATE AT 30 ꢀC
#
∆H (kcal/mol)
#
∆S eu
#
-
2
2
-1
k (mol L s )
Substrate
log A
Ea (kcal/mol)
∆G (kcal/mol)
16.67
r
MG
6.03
12.78
12.59
16.65
15.74
16.04
15.13
–2.07
–2.94
DAA
19.95
16.02

5
128 Singh et al.
Asian J. Chem.
1
7
Ru(VIII) is reported to be present in the form of H
2
RuO
5
k [S][H RuO ]
1
2
5
or RuO (OH) in the acidic medium. Hence, here H RuO
3
2
2
5
is
[
C
2
] =
On substituting the value of [C
[S][H RuO ][H]
2 5
+
(3)
k + k [H]
–
1
2
assumed to be effective catalytic species in the present investi-
gation. Thus catalytic action of Ru(III) occurs through Ru(VIII)
centre.
1
] from eqn (3) in eqn (2)
+
-
4
k
1
K
2
On the basis of IO
and H RuO
2
5
as oxidizing and catalytic
[C
2
] =
+
(4)
k–1 + k [H]
species, respectively and considering other kinetic results and
stoichiometric data, the following reaction mechanism is
suggested for oxidation of MG and DAA as both exhibit
common kinetic results. Here, S stands for substrates (MG
and/or DAA).
2
where K = k /k
2
2
-2
By considering eqn (1) and (4) together
−
d[IO4 ]
+
nk k K [S][H] [H RuO ]
d
1
2
2
5
–
=
(5)
+
dt
k−1 + k [H]
OH
|
2
k
1
The rate law (5) satisfies and explains all the observed
+
kinetic results. It explains positive effect of [H] and zero effect
-
of [Cl ] on the rate of the reaction.
S + H RuO
2
5
[S- -> RuO
3
]
(i)
k-
1
(C )
1
k
2
+
+
C
1
+ H
2
[C ]
(ii)
k-
2
REFERENCES
+
k
d
+
(H)] + S + H
[
C
2
]
[OH-RuO
-
3
2
O
(iii)
1
.
C.V. Hiremath, T.S. Kiran and S.T. Nandibewoor, J. Mol. Catal. Chem.,
248, 163 (2006).
slow
-
3
[OH-RuO
S + IO
3
(H)] + IO
4
H
2
RuO
5
+ IO
(iv)
(v)
(v)
+
-
-
+
2. B. Singh, A. Ratan, V. Prakash and D.M. Kesarwani, Oxid. Commun.,
9, 552 (1996).
D.L. Kamble and S.T. Nandibewoor, J. Phys. Org. Chem., 11, 171 (1998).
4. M.M. Taqui Khan and R.S. Shukla, J. Mol. Catal., 34, 19 (1986).
4
RCOOH + IO
3
+ H
1
where R is CH CHOH - group in MG and in step
3
3
.
+
S stands for CH
3
CHOH carbonium ion from MG.
5
6
7
.
.
.
A.K. Singh, A. Singh, R. Gupta, M. Saxena and B. Singh, Transition
Met. Chem., 17, 413 (1992).
|
CHOH
AK. Singh, R. Negi, B. Jain, Y. Katre, S.P. Singh and V.K. Sharma,
Catal. Lett., 132, 285 (2009).
In case of DAA,
G.A. Hiremath, P.L. Timmanagoudar, R.B. Chougale and S.T.
Nandibewoor, J. Indian Chem. Soc., 75, 363 (1988).
O
C
+
S stands for CH
3
-C(OH)-CH
2
-
–CH
3
which is oxidizing
(vi)
8. Ashish, S.P. Singh, A.K. Singh and B. Singh, J. Mol. Catal. Chem.,
66, 226 (2007).
2
|
CH
⊕
2
9. C.A. Bunton, in ed.: K.B. Wiberg, Oxidation in Organic Chemistry,
Part A, Academic Press, New York, p. 368 (1965).
in step
+
S + 3IO
-
4
10. S.P. Srivastava, G. Bhattacharjee and P. Malik, Indian J. Chem., 25A,
CH COCH
3
3
+ CH
3
COOH +
(vi)
48 (1986).
-
3
+
+ H + CO
3
IO
2
1
1
1
1. A.K. Singh and A.K. Sisodia, S. Saxena and M. Saxena, Indian J.
Chem., 26A, 600 (1987).
2. F. Feigl, Spot Tests in Organic Analysis, Elsevier, New York, edn 7
-
Thus in oxidation of MG and DAA, n moles of IO
4
are
consumed where n = 2 in MG and 4 in DAA oxidation.
Considering aforesaid reaction steps and stoichiometry
(
1975).
3. C.E. Crouthamel, H.V. Meek, D.S. Martin and C.V. Banks, J. Am. Chem.
Soc., 71, 3031 (1949).
of the reactions, rate of reactions can be written in term of rate
-
of loss of [IO
4
] as eqn (1) -
14. C.E. Grouthamel, A.M. Hayes and D.S. Martin, J. Am. Chem. Soc., 73,
2 (1951).
15. C. Waquar, J.P. Sharma and B. Singh, Oxid. Commun., 12, 115 1989).
8
−
d[IO4 ]
+
−
= nk [C ]
d
(1)
2
1
6. T.D. Avtokratova, Analytical Chemistry of Ruthenium, Humphrey Sci-
ence Publication, London (1969).
7. F.S. Martin, J. Chem. Soc., 2564 (1954).
dt
By applying the law of equilibrium in step (II) -
1
+
[C
2
] = K
On applying steady state to [C
and (ii),
2
[C
1
] [H]
(2)
] and considering steps (i)
1