Spectrophotometric determination and kinetic studies of condensation of aromatic aldehydes with 7,9-dioxo-6,10-dioxaspiro[4.5]decane

Article abstract of DOI:10.1002/jccs.200400022

The condensation reaction rates of 7,9-dioxo-6,10-dioxaspiro[4.5]decane with aromatic aldehydes in chloroform in the presence of piperidine has been investigated spectrophotometrically at 25-50°C. The reaction follows overall second order kinetics, first

Full text of DOI:10.1002/jccs.200400022

Journal of the Chinese Chemical Society, 2004, 51, 139-145
139
Spectrophotometric Determination and Kinetic Studies of Condensation
of Aromatic Aldehydes with 7,9-Dioxo-6,10-dioxaspiro[4.5]decane
H. A. A. Mediena*, A. A. Zahrana and A. W. Erianb
aDepartment of Chemistry, Faculty of Science, Ain Shams University, Cairo, Egypt
bDepartment of Chemistry, Faculty of Science, Cairo University, Giza, Egypt
The condensation reaction rates of 7,9-dioxo-6,10-dioxaspiro[4.5]decane with aromatic aldehydes in
chloroform in the presence of piperidine has been investigated spectrophotometrically at 25-50 °C. The reac-
tion follows overall second order kinetics, first order in each of the reactants and zero order with respect to
piperidine. The rate of condensation increases with the presence of electron withdrawing groups on the aro-
matic ring of the aldehyde. From the dependence of the rate constants on temperature, activation parameters
have been calculated. Plot of DH# versus DS# for the reaction gave a good straight line with an isokinetic tem-
perature of 367.55 K. Based on this reaction, determination of ten aromatic aldehydes in a concentration range
of 2.65-69.2 mg/mL is proposed.
Keywords: Aromatic aldehydes; Kinetic; Determination and spectrophotometry.
INTRODUCTION
Reagents
All aromatic aldehydes used were of AR grade (BDH).
Chloroform (Analar) used as a solvent. The standard solution
of piperidine (E. Merck, G. R.) was directly prepared in chlo-
roform. The reagent (D) was prepared by the same procedure
of synthesis of some spiro compounds in the literature.24 To a
suspension of 52 g (0.5 mole) of malonic acid in 60 mL (0.6
mole) of acetic anhydride, 1.5 mL of concentrated sulfuric
acid and 50 mL (0.55 mole) of cyclopentanone was added
while cooling to maintain the temperature at 20-25 ºC. The
reaction mixture was allowed to stand overnight in a refriger-
ator, then filtered and washed by cold water m.p: 90 ºC
(Found: C, 56.4; H, 5.85; C8H10O4 requires C, 56.5; H, 5.9); n
Many methods are cited in the literature for kinetic re-
actions of aromatic aldehydes and comprise reactions with
chlorodipentylborane,1 5-N-benzoylamino-1,3,4-thiadiazole-
2-acetonitrile,2 1,3-dimethybarbituric acid,3 3-methyl-1-
phenylpyrazolin-5-one,4 phenylhydroxylamine,5 pyridinium
chlorochromate,6 phenylhydrazone,7 and condensation with
o-phenylenediamine in the presence of H2O28 with cysteine9
and with 2,2-dimethyl-1,3-dioxane-4,6-dione.10 Other meth-
ods are available for kinetic oxidation of aromatic alde-
hydes.11-23
This work aims to study the kinetics of the condensa-
tion reaction of some aromatic aldehydes with the active
methylene compound, 7,9-dioxo-6,10-dioxaspiro[4.5]dec-
ane (D) and to study the effect of substituents on the reactiv-
ity. This work also aims to be has a spectrophotometric method
for determination of some aromatic aldehydes.
1
cm-1 = 2950 (CH2), 1735 and 1715 (C=O); H NMR: d =
0.95-1.22 (m, 8H, 4CH2), 4.31 (s, 2H, CH2).
Kinetic procedure
The rate of reaction of the aldehydes tested (p-dimeth-
ylaminobenzaldehyde, p-nitrobenzaldehyde, p-hydroxy-
benzaldehyde, p-methoxybenzaldehyde, p-chlorobenzalde-
hyde, and benzaldehyde) with (D) in the presence of piperidine
was followed by monitoring the increase in the absorbance of
the product at its wavelength of maximum absorption with
time.
Freshly prepared samples of aldehydes (5 ´ 10-3M),
piperidine (0.1 M) and 0.1 M (D) in chloroform were allowed
to equilibrate to 25 °C for 10 min in a thermostat. Mixing was
carried out by withdrawing 0.5-2.0 mL aliquots of the alde-
hyde solution to 10 mL flasks containing 1.0 mL of 0.1 M
MATERIALS AND METHODS
Apparatus
Visible absorption spectra were recorded on a Unicam
SP 1800 recording spectrometer. An SP 6-200 Pye-Unicam
spectrophotometer was used for the kinetic spectrophto-
metry. IR spectra were recorded (KBr) on a Pye Unicam SP
1000 spectrophotometer. 1H NMR spectra were taken at 270
MHz using CDCl3 as a solvent.

140 J. Chin. Chem. Soc., Vol. 51, No. 1, 2004
Medien et al.
piperidine, 1.0 mL of 0.1 M (D) solution, and the appropriate
volume of chloroform. A portion of the reaction mixture was
transferred to a quartz cuvette placed in a thermostated (25
ºC) cell compartment. A blank solution was similarly pre-
pared without aldehyde and the absorbance readings were
also recorded and followed as a function of time. Another set
stants k2 = kobs / [D].
Analytical procedure
A calibration graph for 2.5 ´ 10-3 M each of the alde-
hydes p-nitrobenzaldehyde, p-hydroxybenzaldehyde, p-di-
methylaminobenzaldehyde, p-methoxybenzaldehyde, vanil-
lin, syringaldehyde, 2,4-dihydroxybenzaldehyde, m-nitro-
benzaldehyde, benzaldehyde, p-cyanobenzaldehyde and p-
chlorobenzaldehyde was obtained by transferring (0.1-1.0
mL) aliquots in chloroform to test tubes followed by the addi-
tion of 1.0 mL of the (0.1 M) solution of 7,9-dioxo-6,10-
dioxaspiro[4.5]decane (D) in chloroform and 1.0 mL of the
(0.1 M) piperidine solution in chloroform. The mixtures are
thermostated at 50 °C in a water bath for 15 min and then di-
luted to 10 mL with chloroform and the absorbance of the re-
sulting yellow color is measured at the maximum wavelength
of each aldehyde derivative. The points on standard calibration
curves each represent the outcome of three determinations.
of runs was carried out in a similar manner using 5 ´ 10-3
(D) solution and 5 ´ 10-2 M aldehyde solution.
M
Initial rates were determined by the method of initial
rates,25,26 whereby the absorbance (A) was plotted against
time for each run. The initial slopes (dA/dt) for each run were
determined and used in the following equation for calculating
the rate of the reaction.25,26
dA C¥ -Ci
´
dt A¥ - A
Rate =
i
Ci and C are the initial and final concentrations of the col-
4
ored reaction products, respectively, calculated by using the
molar extinction coefficients e; Ai and A are the absorben-
4
cies of the colored species at the initial and the end of the re-
action. Since both Ci and Ai are nearly equal to zero at the be-
ginning of the reaction, then the above equation reduced to:
Preparation and analysis of reaction products
To a 5 mL solution of (D) (0.004 mol) in chloroform 5
mL. Solution of the aromatic aldehyde (0.004 mol) was
added. To the reaction mixture 5 mL of 0.1 M piperidine was
added. The reaction mixture was warmed at 50 ºC for 5 min
and left at room temperature overnight. The crystals obtained
were filtered off, dried and crystallized from chloroform. The
physical properties, spectra, and elemental analyses are given
in Table 1.
dA C¥
´
dt A¥
Rate =
The observed rate constants kobs using excess (D) are
calculated from the initial rate Ri values by dividing it by the
concentrations of the aldehydes. The second order rate con-
Table 1. Properties, Wave Length, IR and 1H NMR Spectral Data and Elemental Analyses of Products from Reaction of Some
Aromatic Aldehyde Substituents with (D)
Substituent M.P
l
n (cm-1)
1H NMR [d (ppm)] in CDCl3
Molecular
formula
Cal. (%) (Found)
(°C) (nm.)
C
H
N
Cl
-
H
110 360 2950 (CH2), 1730, 1715 (C=O), 0.95-1.22 (m, 8H, 4CH2), 6.75- C15H14O4
1590 (C=C) 7.23 (m, 6 H, aromatic protons)
p-N(CH3)2 142 445 3100, 3050, 2950 (CH), 1735, 0.95-1.22 (m, 8H, 4CH2), 2.12 C17H19NO4 67.8
69.8
(69.6) (5.49)
6.4
5.5
-
4.6
1715 (C=O), 1660, 1620 (C=C) (6H, CH3), 6.73-7.14 (5H,
aromatic protons)
125 365 3050, 2950 (CH2), 1735, 1710 0.92-1.22 (m, 8H, CH2), 3.52 (s, C16H16O5
(67.6) (6.38) (4.59)
-
-
p-OCH3
66.7
5.6
(C=O), 1660 (C=C)
3H, CH3), 6.72-7.31 (m, 5,
aromatic protons)
(66.6) (5.58)
-
-
p-Cl
160 325 2950 (CH2), 1730, 1715
1780 (C=O), 1675 (C=C)
136 370 3450-3390 (OH), 3050, 2950
(CH2), 1630 (C=O)
0.95-1.22 (m, 8H, 4CH2), 6.75- C15H13O4Cl 61.5
4.5
(61.4) (4.46)
65.7 5.1
(65.68) (5.0)
12.1
(12.0)
7.12 (5H, aromatic protons)
0.95-1.22 (m, 8H, 4CH2), 3.5 (s, C15H14O5
OH), 6.72-7.35 (5H, aromatic
protons)
p-OH
-
-
-
p-NO2
135 340 2950 (CH2), 1735, 1715 (C=O), 0.95-1.22 (m, 8H, 4CH2), 6.75- C15H13NO6 59.4
1670 (N=O), 1600 (C=C) 7.12 (5H, aromatic protons)
4.3
4.6
(59.38) (4.29) (4.59)

A Condensation Study of Aldehydes with R-[4.5]decane
J. Chin. Chem. Soc., Vol. 51, No. 1, 2004 141
Table 2. Rate Constants of the Reaction of p-Methoxybenzalde-
hyde with 7,9-Dioxo-6,10-dioxaspiro[4.5]decane (D) at
298 K
RESULTS AND DISCUSSION
The compound 7,9-dioxo-6,10-dioxaspiro[4.5]decane
(D) undergoes condensation with aromatic and heteroaro-
matic aldehydes furnishing the corresponding arylidene de-
rivatives, which are versatile substrates for different kinds of
reactions.27 They are useful intermediates for cycloaddition
reaction and for the synthesis of heterocyclic compounds
with potential pharmacological activity.28 The 1,4-addition
of nucleophiles has been widely used synthetically and dis-
play some advantages over the acyclic malonate analogous,
and the conjugated reduction is the way most often used to
prepare 5-monoalkyl Meldrum’s acids derivatives or analog
and are also applied to obtain deuterated carboxylic acids.29
The different reactivity of variously substituted alde-
hydes could be rationalized taking into account that the reac-
tion occurs in two steps, i.e. the nucleophilic attack and the
dehydration (Scheme I). Electron-withdrawing substituents
facilitate the first step, meanwhile electron-donor substitu-
ents facilitate the loss of water giving a conjugated stabilized
olefin.
[Aldehyde], M
[D], M
[Pip.], M 108 R, mol. l-1.sec-1
2.5 ´ 10-4
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.015
0.02
0.03
4.70
9.78
14.5
19.58
2.45
4.90
7.35
9.80
9.76
9.72
9.75
5.0 ´ 10-4
-4
7.5 10
10.0 ´ 10-4
0.005
´
0.01
2.5 ´ 10-4
5.0 ´ 10-4
7.5
0.005
0.005
0.005
´ 10-4
10.0 ´ 10-4
0.01
5.0 ´ 10-4
5.0 ´ 10-4
5.0 ´ 10-4
0.01
0.01
of (D) on the aldehyde or the dehydration of compound (I),
both steps being consistent with a second order equation. The
study of the stoichiometry of the reaction indicates that the
products have a maximum absorption at a molar ratio of 1:1
(aldehyde:D).
The kinetic results in Table 3 show that the rate of the
reaction between different substituted benzaldehydes and (D)
decreases in the following order:
Scheme I
second step
first step
p-NO2 > p-Cl > H > p-OCH3 > p-OH > p-N(CH3)2
CH2
+
Ald
I
Product
addition
dehydration
It can be noted that electron-attracting groups increase
the rate of reaction, whereas electron-repelling groups sup-
press it. In fact, the addition of (D) to substituted benzalde-
hydes (first step) is favored by electron withdrawing groups,
and the dehydration step (second step) is favored by electron
donating ones. The results for the reaction obtained can then
be rationalized considering the first step is the rate-limiting
one and the second step is the fast step.
From the data compiled in Table 2, it was shown that for
all aldehydes studied the kinetics is second order overall, first
order with respect to each of the reactants, and zero order
with respect to piperidine, according to the simple rate law:
d[product]/dt = kobs [aldehyde][D]
From this equation it can not be distinguished if the
Therefore, the reaction process can be represented by
the following equations, where (ald), (D) and (I) refer to the
rate-limiting step is the nucleophilic attack of the carbanion
Table 3. Rate Constants and the Activation Parameters of the Reaction of Substituted
Benzaldehydes with (D) Using 0.1 M Piperidine in Chloroform
Substituent
102 k2, l.mol-1s-1
DE#
DH#
DG#
DS#
298 K 308 K 313 K 323 K
KJ.mol-1
J mol-1 K-1
p-NO2
p-Cl
H
p-OCH3
p-OH
p-N(CH3)2
4.8
3.1
3.1
1.96
1.21
0.90
10.9
7.6
6.1
4.61
2.60
3.40
19.8
16.5
7.8
7.33
7.60
6.10
33.0
25.0
22.0
21.0
13.4
10.9
63.4
67.7
75.05
77.36
80.40
93.75
60.94
65.18
73.12
74.89
77.70
80.51
80.64
81.61
82.74
82.74
84.00
84.80
-65.69
-55.10
-32.09
-26.33
-20.20
-13.89

142 J. Chin. Chem. Soc., Vol. 51, No. 1, 2004
Medien et al.
aldehyde, 7,9-dioxo-6,10-dioxaspiro[4.5]decane and the in-
termediate (I) in equation (i) respectively:
DS# is substituent dependent. Since all the substituents are lo-
cated in para position, direct steric interaction is unlikely, so
that resonance and/or inductive effects are the operating fac-
tors. Within the series, electron-withdrawing substituents in
the aromatic aldehyde, through their resonance and/or induc-
tive effects, localize the formal charge on the T.S. This fa-
vours the formation of more ordered transition states reflect-
ing high and negative entropies of activation. On the other
hand, the presence of electron donating substituents in the al-
dehyde alters their nature, leading to much more delocaliza-
tion of the charge in T.S., and hence reflecting low and nega-
tive entropies of activation.
The linear correlation between DH# and DS# for the re-
action of different substituents of benzaldehyde with (D)
shows that all the compounds react by the same mechanism.31
The value of the slope was 367.55 K (r = 0.997), which is the
value of the isokinetic temperature b (the temperature at
which the substituent effects is supposed to be reversed). This
value is not the real temperature used in the kinetic runs.
The constancy of DG# may be explained on the basis of
an isokinetic relationship that exists for a series of com-
pounds of slightly different structures but undergoing reac-
tion essentially by the same mechanism. The DG# may be
more or less constant with relative changes in DH# and DS# as
pointed out by Leffler.31
The above equations lead to rate expression (iv),
Rate = k [D-] [AldH+]
(iv)
(v)
Then,
Rate = kK1K2 [D] [Ald]
From equation (v), one can conclude that
kobs = kK1K2 [D]
(vi)
Equation (v) shows that the reaction follows second or-
der kinetics, first order each in aldehyde and (D). The ob-
served pseudo-first order rate constant kobs is therefore a
product of the equilibrium constants of the two steps, the rate
constant k of the third step and (D). The rate constant k could
not be evaluated since no data are available for the equilib-
rium constants K1 and K2. The second order rate constants
were calculated using the equation, k2 = kobs / [D].
The mechanism for the title reaction is common for all
members in the series as indicated by (a) the good straight-
line plot of DH# versus DS#, and (b) the linear plots of log k2 at
50 ºC against log k2 at 25 ºC (gradient, 0.658, r = 0.95).
At studied temperatures, an electron-withdrawing sub-
The rate constants of the reaction of different substi-
tuted aldehydes correlate well with Hammett’s s (Hammett’s
polar substituent constants) values for the aldehydes as
shown in Fig. 1. The positive r value (0.465) (r = 0.962)
means that electron-attracting groups enhance the rate of the
reaction.
Activation Parameters
The rates of the reaction of six different benzaldehydes
were determined at three different temperatures, viz., 298,
308, 313 and 323 K. The activation energies DE# were deter-
mined from the slopes of the Arrhenius plots of log k2 versus
T-1, as shown in Fig. 2. The other thermodynamic parameters
DH#, DS# and DG# were calculated30 at 298 K and are given in
Table 3.
The activation parameters show that the entropy of acti-
vation values is negative as expected for bimolecular or ter-
molecular reactions. In this study the entropy of activation
Fig. 1. Hammett plot for the reaction of substituted
benzaldehydes with (D).

A Condensation Study of Aldehydes with R-[4.5]decane
J. Chin. Chem. Soc., Vol. 51, No. 1, 2004 143
Table 4. Effect of Time on the Absorption of the Product of
Reaction of the Aldehydes Tested with Excess 7,9-
Dioxo-6,10-dioxaspiro[4.5]decane (D)
stituent in the para position of the aldehyde increases the re-
action rates, while a similarly positioned electron releasing or
donating substituent decreases it. This behavior could be ex-
Substituent
Absorption at different times (min)
10 15 30 60 90
plained by the observation that the ratio kp- NO / kp- N (CH
)
2
3
2
was 5.33, 4.54, 3.25 and 3.03 at 25, 35, 40 and 50 ºC, respec-
tively (Table 3). Consequently, the variation of the rate con-
stant depends on the nature of the substituent in the aldehyde.
The order of decreasing reactivity of substituted aldehyde in
chloroform is p-NO2 > p-Cl > H > p-OCH3 > p-OH >
p-N(CH3)2. This order of decrease in magnitude of the
substituent effect is expected on the basis of both inductive
and resonance effects.
5
24 h
p-OCH3
p-OH
p-NO2
0.7
0.9
0.88 0.87 0.87 0.86 0.86 0.86
1.00 1.10 1.11 1.12 1.12 1.11
0.21 0.30 0.35 0.36 0.35 0.35 0.35
1.15 1.22 1.24 1.25 1.25 1.26
p-N(CH3)2 1.0
Table 5. Effect of Temperature on the Absorption of the Product
of Reaction of Aldehydes Tested with Excess 7,9-
Dioxo-6,10-dioxaspiro[4.5]decane (D) in Chloroform
Determination of the aldehydes tested
Substituent
Absorption at different temperatueres (°C)
Effect of time and temperature
25
30
40
50
The absorbance of the color due to reaction of the
aldehydes tested with excess (D) in the presence of 0.1 M
piperidine in ethanol reached a maximum intensity after 15
min at 50 °C, as shown in Tables 4 & 5.
p-OCH3
p-OH
p-NO2
0.34
0.45
0.12
0.64
0.63
0.75
0.19
0.78
0.75
0.90
0.25
0.95
0.87
1.10
0.35
1.22
p-N(CH3)2
Linearity and interferences
Table 6 shows linear regression analysis of the data ob-
tained from calibration graphs of the aldehydes tested from
the relation A = a + bc, where A is the absorbance at the rele-
vant peak in a 1.0 cm quartz cell, a and b are the intercept and
the slope of the calibration graphs, respectively, and c is the
Fig. 2. Arrhenius plots for the reaction of (D) with different substituents of benzadehyde in the presence of 0.1 M piperidine
in chloroform: (1) p-NO2, (2) p-Cl, (3) H, (4) p-OCH3, (5) p-OH and (6) p-N(CH3)2.

144 J. Chin. Chem. Soc., Vol. 51, No. 1, 2004
Medien et al.
Table 6. Statistical Analysis of the Calibration Graphs for the Determination of Some Aromatic
Aldehydes by Reaction with 7,9-Dioxo-6,10-dioxaspiro[4.5]decane (D) in Chloroform at 50
°C in the Presence of Piperidine
Aldehydes
lmax/nm Concentration e (l mol-1 cm-1) Slope (b) Intercept (a)
range (mg/mL)
p-Dimethylamino-
benzaldehyde
445
3.73-37.25
4890
0.0333
0.012
Syringaldehyde
365
365
370
340
340
325
340
370
360
4.55-45.50
3.40-34.00
3.05-30.5
3.78-37.75
3.78-37.75
3.76-37.62
6.90-69.2
3.80-38.0
2.65-26.5
2580
3510
4430
700
710
600
850
3440
950
0.0141
0.026
0.004
-0.005
0.005
0.000
0.001
0.000
0.002
0.004
0.00
p-Methoxybenzaldehyde
p-Hydroxybenzaldehyde
p-Nitrobenzaldehyde
m-Nitrobenzaldehyde
p-Chlorobenzaldehyde
p-Cyanobenzaldehyde
Vanillin
0.0361
0.0093
0.0046
0.0043
0.0071
0.141
Benzaldehyde
0.0093
concentration of the aldehyde in µg/mL in the final solution.
The points on standard calibration curves each represent the
outcome of three determinations. The relative standard devi-
ations (R.S.D%) vary between 0.7 and 1.0% for 10 mg mL-1 of
each aldehyde used (n = 3), and the reproducibility varies be-
tween 95.8 and 101% for each aldehyde.
A piperidine molecule removes a proton from the (D)
molecule to yield the carbanion (1), which adds in a slow step
to the benzaldehyde molecule (2) to give intermediate (3),
which is transformed to product (4) via a fast dehydration
step. The observed negative entropy of the activation sup-
ports the above mechanism also.
No interference is caused by the presence of 10 mM
formaldehyde, 5.17 mM acetone, 2.46 mM benzoic acid, 6.82
mM acetaldehyde and 3.2 mM aniline. In summary, thirteen
aromatic aldehydes have been shown to be assessable with a
new simple analytical method.
Received March 24, 2003.
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