P-Toluene sulfonic acid (PTSA)-MCM-41 as a green, efficient and reusable heterogeneous catalyst for the synthesis of jasminaldehyde under solvent-free condition

Article abstract of DOI:10.1016/j.molcata.2016.04.030

This paper reports the synthesis of p-Toluene sulfonic acid (PTSA)-MCM-41 by impregnation method and its characterization XRD, FT-IR, TGA, N₂ adsorption-desorption isotherms, SEM, and TEM. The impregnated catalysts were used to catalyse cross-aldol condensation of active methylene bearing aliphatic aldehydes with aromatic aldehydes under solvent and metal-free condition particularly in the synthesis perfumery chemical-jasminaldehyde and related compounds. The as synthesized catalyst PTSA-MCM-41 has displayed high efficiency (selectivity up to 91%) in catalyzing cross-aldol condensation reaction and was reusable (5 cycles) with no apparent loss in activity. The catalytic performance of PTSA-MCM-41 was compared with other catalysts viz., ZnO, proline, proline-LDH, PTSA, PTSA-zirconia and PTSA-zeolite where PTSA-MCM-41 showed better performance particularly in synthesis of jasminaldehyde.

Full text of DOI:10.1016/j.molcata.2016.04.030

Accepted Manuscript
Title: p-Toluene sulfonic acid (PTSA)-MCM-41 as a green,
efficient and reusable heterogeneous catalyst for the synthesis
of jasminaldehyde under solvent-free condition
Author: Venkata Subba Rao Ganga Sayed H.R. Abdi
Rukhsana I. Kureshy Noor-ul H. Khan Hari C. Bajaj
PII:
S1381-1169(16)30170-4
DOI:
Reference:
http://dx.doi.org/doi:10.1016/j.molcata.2016.04.030
MOLCAA 9874
To appear in:
Journal of Molecular Catalysis A: Chemical
Received date:
Revised date:
Accepted date:
2-3-2016
25-4-2016
29-4-2016
Please cite this article as: Venkata Subba Rao Ganga, Sayed H.R.Abdi, Rukhsana
I.Kureshy, Noor-ul H.Khan, Hari C.Bajaj, p-Toluene sulfonic acid (PTSA)-MCM-
41 as a green, efficient and reusable heterogeneous catalyst for the synthesis of
jasminaldehyde under solvent-free condition, Journal of Molecular Catalysis A:
Chemical http://dx.doi.org/10.1016/j.molcata.2016.04.030
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p-Toluene sulfonic acid (PTSA)-MCM-41 as a green, efficient and
reusable heterogeneous catalyst for the synthesis of
jasminaldehyde under solvent-free condition
Venkata Subba Rao Gangaa, b, Sayed H. R. Abdia, b,* Rukhsana I. Kureshy a, b, Noor-ul
H. Khana, b, Hari C. Bajaj a, b
aInorganic Materials and Catalysis Division, CSIR-Central Salt and Marine Chemicals
Research Institute (CSIR-CSMCRI), Bhavnagar- 364 002, Gujarat, India.
bAcademy of Scientific and Innovative Research, CSIR-Central Salt and Marine Chemicals
Research Institute (CSIR-CSMCRI), G. B. Marg, Bhavnagar- 364 002, Gujarat, India.
Corresponding author: Tel.: +91 278 2567760, Fax: +91 278 2567562 / 2566970. Email
address: shrabdi@csmcri.org (S. H. R Abdi).
1

Graphical Abstract
% Conversion
% Selectivity
100
80
60
40
20
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• Metal free
• Up to 91% yield
• 15 examples
• Recyclability
• Solvent free
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Highlights:
 PTSA supported on MCM-41 (PTSA-MCM-41) was synthesized and characterized
by various analytical techniques such as XRD, FT-IR, TGA, N2 adsorption–desorption
isotherms, SEM, and TEM.
 As synthesized PTSA-MCM-41was used in cross-aldol condensation reaction for the
synthesis of jasminaldehyde and its derivatives.
 The catalytic performance of PTSA-MCM-41 was compared with other catalysts viz.,
ZnO, Proline, Proline-LDH, PTSA, PTSA-zirconia and PTSA-zeolite
 PTSA-MCM-41 showed excellent catalytic performance (Conversion & Selectivity)
in cross-aldol condensation reaction with a wide range of aromatic and aliphatic
aldehydes as substrates.
 PTSA-MCM-41 was recycled for 5 catalytic runs with no observable loss in its
performance.
2

Abstract
This paper reports the synthesis of p-Toluene sulfonic acid (PTSA)-MCM-41 by impregnation
method and its characterization XRD, FT-IR, TGA, N2 adsorption–desorption isotherms, SEM,
and TEM. The impregnated catalysts were used to catalyze cross-aldol condensation of active
methylene bearing aliphatic aldehydes with aromatic aldehydes under solvent and metal-free
condition particularly in the synthesis perfumery chemical-jasminaldehyde and related
compounds. The as synthesized catalyst PTSA-MCM-41 has displayed high efficiency
(selectivity up to 91%) in catalyzing cross-aldol condensation reaction and was reusable (5
cycles) with no apparent loss in activity. The catalytic performance of PTSA-MCM-41 was
compared with other catalysts viz., ZnO, proline, proline-LDH, PTSA, PTSA-zirconia and
PTSA-zeolite where PTSA-MCM-41 showed better performance particularly in synthesis of
jasminaldehyde.
Keywords. Jasminaldehyde • Heterogeneous catalysis • Cross-aldol condensation • Solvent
free • 1-Heptanal.
1. Introduction
Jasminaldehyde, (-amyl cinnamaldehyde), is a traditional perfumery product with a violet
scent which can be obtained by the cross aldol condensation of 1-heptanal with benzaldehyde
(Scheme 1) [1-5]. Its synthesis is traditionally carried out by using sodium or potassium
hydroxide as base catalysts, where 1-heptanal is added slowly to the reaction mixture at
moderate temperatures and is usually marred by the co-production of unwanted self-condensed
products of 1-heptanal to form 2-n-pentyl- 2-n-nonenal [6]. The formation of self-condensation
products can be inhibited, to some extent, by maintaining a very low concentration of 1-
heptanal relative to benzaldehyde in the reaction mixture. This can be achieved by using a high
benzaldehyde/1-heptanal molar ratio or/ and by adding slowly 1-heptanal into the reaction
mixture [7]. Different solid base catalysts have also been reported [8-9] for the synthesis of
jasminaldehyde. It is known in the literature that the condensation of 1-heptanal and
benzaldehyde can also be carried out in the presence of solid acid catalysts [10-11] and acid-
base catalysts [1, 2, 7, 12]. Moreover, for the aldol condensation mostly transition metal salts
or their complexes have been used as catalyst under homogeneous reaction condition [13-14].
The use of strong acid or base catalyst at process level poses operational problems of corrosion
3

and recycling/post-reaction handling of the spent catalyst. To this effect development of
heterogeneous catalyst is relevant [15]. p-Toluene sulfonic acid (PTSA), has been found to be
remarkably active to catalyse diverse organic transformations including aldol and other carbon-
carbon bond forming reactions [16-23]. Heterogenization of PTSA in such a way that it retains
its catalytic prowess of homogeneous condition while making its separation and reuse in post-
catalytic run easy, is of great interest from practical point of view. To this effect MCM-41
presents significant advantage as a catalyst support due to its high specific surface area, large
pore size and high thermal stability [24-25]. The PTSA-MCM-41 has also received great
attraction as an acid catalyst for several organic transformations [26-28].
Therefore, for the present study we have synthesized PTSA-MCM-41 and used it as a solid
acid catalyst in the cross-aldol condensation reaction to synthesize jasminaldehyde and related
compounds under solvent-free condition. The catalytic performance of PTSA-MCM-41 was
compared with other solid acid and base catalysts viz., ZnO, proline-LDH, PTSA-zirconia and
PTSA-zeolite. PTSA-MCM-41 was found to be efficient recyclable catalyst (5 cycles) in the
synthesis of cross-aldol products particularly jasminaldehyde.
2. Experimental
2.1. Materials
The different aldehydes and reagents were used as received. Benzaldehyde, 1-heptanal and L-
proline were procured from Sigma-Aldrich and used as received. All the solvents were purified
before use. For the product purification flash chromatography was performed using silica gel
100-200 mesh.
2.2. Synthesis of MCM-41
Synthesis of MCM-41 silica was carried out at 35 °C by adding silicate solution to the
surfactant solution as per the reported method [29]. In a typical synthesis, a solution of sodium
silicate (SiO2/Na2O mole ratio 3.24) having 1 M SiO2 concentration was added at a controlled
rate with a peristaltic pump in 10 min to the 0.2 M solution of CTAB, followed by aging at
room temperature for 20 min. This aged reaction mixture was partially neutralized under a
controlled rate in 50 min with HCl to adjust the SiO2/Na2O mole ratio to 21 and subsequently
aged for 1 h. The final composition of the gel was SiO2/Na2O/CTAB/H2O was 1:0.048:0.1:109.
The final pH of the gel after completion of the reaction was 8.5 (0.1. The gel was collected by
filtration, washed thoroughly with deionized water until Cl¯ free, dried at 100 °C, and calcined
in air at 600 °C for 6 h. CHNS data: C% (0.08), H% (0.777), S% (0.13).
2.3. Synthesis of PTSA-MCM-41
4

To a solution of PTSA (15 mL; 0.5 M in water) MCM-41 (1.0 g) was added and the resulting
suspension was stirred for 24 h. Subsequently, water was evaporated at 80 °C under reduced
pressure on a rotary evaporator and finally dried at 110 °C for 12 h to get PTSA-MCM-41.
CHNS data: C% (21.18), H% (3.378), S% (7.92).
2.4. Characterization techniques
Powder X-ray diffraction patterns of the catalyst samples were recorded with Phillips X’Pert
MPD system equipped with XRK 900 reaction chamber, using Ni-filtered Cu-Kα radiation (λ
=1.54050 Å) over a 2θ range of 1-10°C at a step time of 0.05°s-1. The 1H-NMR and 13C (δ in
ppm) spectra were recorded on Bruker 500 MHz spectrometer at operating frequencies of 500
MHz and 125 MHz, respectively, in CDCl3 (δ = 77.33) using tetramethylsilane as an internal
standard. The FT-IR spectra of the samples were recorded from 400 to 4000 cm-1 with a Perkin–
Elmer Spectrum GX FT-IR system using KBr pellets. Thermo gravimetric analysis (TGA) was
carried out on a Mettler TGA/DTA 851e, under nitrogen atmosphere with the flow rate of 50
ml/min. Surface morphology of samples were measured in a SEM instrument (Leo Series
VP1430) equipped with EDX facility (Oxford instruments). SEM analysis was carried out at
an accelerating voltage of 20 kV and probe current of 102 pA. The surface area analysis and
pore size distribution of the samples were measured by nitrogen adsorption-desorption
isotherm at -196 °C using a volumetric adsorption measurement system (Model: ASAP-2020,
Micromeritics, Inc., USA). All the samples were degassed at 80 °C for 4 h prior to the
measurements. The product was carried out using Gas Chromatography (GC) (Shimadzu 17A,
Japan) using 5% diphenyl and 95% dimethyl siloxane universal capillary column and flame
ionization detector (FID). The column temperature was programmed for 50 °C to 210 °C at a
heating rate of 10 °C /min. N2 gas was used as a carrier gas. The temperature of injection port
and FID were kept constant at 250 °C during product analysis. The retention time for different
compounds was determined by injecting pure compounds under identical conditions (GC-
parameters).
2.5. Synthesis of Jasminaldehyde
In a three necked round bottom flask, benzaldehyde (39.5 mmol), n-decane (0.01g) as an
internal standard and PTSA-MCM-41 (100 mg) were taken under inter gas atmosphere to
which 1-heptanal (7.9 mmol) was added at a rate of 1130 µL/h by using syringe pump, while
keeping the reaction temperature at 125 °C. The controlled addition of 1-heptanal is important
in order to minimize its self-condensation and maximize the yield of main product
5

jasminaldehyde. The reaction was monitored on GC. All the reactions were done in triplicate
to ensure the reproducibility of the reaction.
Following formula was used to report conversions and selectivity
Molesof jasminaldehyde
%Selectivityof jasminaldehyde=
100
Molesof jasminaldehyde+2-n-pentyl-2-nonenal
Molesof 1-heptanalreacted
%Conversion =
×100
Molesof 1-heptanalfed
3. Results and discussion
3.1. Catalyst characterizations
3.1.1. Powder X-ray diffraction (P-XRD)
The PXRD patterns of MCM-41 and PTSA-MCM-41 are shown in Fig. 1. The XRD
pattern of MCM-41 showed a very broad peak, which does not change much on loading the
PTSA indicating the loaded PTSA was highly dispersed on the surface of MCM-41.
3.1.2. FT-IR spectroscopy
The FT-IR spectra of PTSA, MCM-41, and PTSA-MCM-41 are given in Fig 2. FT-IR
spectrum of MCM-41 the band at 1080-1090 cm-1 due to Si-O stretching of Si-O-Si structure.
The PTSA impregnation on MCM-41 in PTSA-MCM-41 sample was confirmed by the
presence of characteristic bands due to symmetric and asymmetric O=S=O stretching
vibrations of the -SO3H in PTSA (1189 and 1124 cm−1).
3.1.3. Thermo gravimetric analysis
The TGA of PTSA, MCM-41, and PTSA-MCM-41 under nitrogen atmosphere are shown in
Fig.3. All the samples were dried under vacuum at 110 °C for 4-6 h before the TGA
measurements. In the case of PTSA-MCM-41 first weight loss before 120 °C corresponds to
the removal of water. The second stage of weight loss of 33.75 % at around 340 °C is associated
to the decomposition of impregnated PTSA in the silica matrix.
6

3.1.4. Surface area measurements
Textural characteristics of MCM-41 and PTSA-MCM-41:
The Nitrogen adsorption-desorption isotherms (at 77 K) of PTSA-MCM-41 is shown in Fig.
4. The N2 adsorption-desorption isotherms (at 77 K) of MCM-41 and PTSA-MCM-41 falls in
type-IV among the six types according to IUPAC nomenclature indicating the presence
mesopores. Further the capillary condensation (hysteresis) was also observed, which further
confirms the presence of mesopores. The nature of isotherms and hysteresis loop remained
unchanged even after PTSA loadings, except that there was some reduction in N2 adsorption
capacity. The BET surface area and total pore of virgin/pure MCM-41 and PTSA-MCM-41
are 734 m2/g & 0.91 cm3/g and 431 m2/g and 0.69 cm3/g respectively, the reduction in surface
area and total pore volume confirms the effective loading of PTSA on MCM-41. The catalytic
activity of pure and PTSA loaded MCM-41 are discussed with the help of textural properties
in section.
3.1.5. Scanning electron micrograph (SEM)
The SEM images of fresh (5a) and reused (5b) PTSA-MCM-41(Fig.5) show no change
in its elliptical morphology. The TEM image of PTSA-MCM-41(5c) shows typical channel
type structure of MCM-41. The EDX mapping image of PTSA-MCM-41 in Fig. (5d) exhibited
the presence of C, O and S elements, which proved that C,O and S particles were deposited on
silica.
3.2. Catalytic activity for the synthesis of jasminaldehyde
3.2.1. Effect of catalysts
To begin with we have used the conventionally used reaction condition for the condensation
of benzaldehyde (5 equivalents) with slow addition of 1-heptanal (1 equivalent) over a period
of 120 min at 125 °C under nitrogen in the presence of 50 mg ZnO catalyst. Under this
condition we got 39 % conversion (with respect to 1-heptanal) with jasminaldehyde selectivity
of 59 % (Table 1; entry 1). At this juncture we thought of switching over to L-proline as catalyst
7

instead of thus far used base catalysts. Although L-proline turned out to be excellent catalyst
(Table 1; conversion, 99%; selectivity, 83%) but it required 40 mol% catalyst loading and faced
catalyst recovery issues in post catalytic run. Supporting L-proline on LDH (PR-LDH) was not
so helpful (Table 1; entry 3; conversion, 56%; selectivity, 83%). subsequently, we considered
the use of an acid catalyst. Accordingly, we used PTSA as catalyst under homogeneous
condition (Table 1; entry 4; conversion, 99%; selectivity, 85%) that provided excellent
conversion and jasminaldehyde selectivity at relatively low catalyst loading (5 mol%). Excited
by this result, we considered several inorganic supports for PTSA to prepare supported
catalysts viz., PTSA-MCM-41(Table 1; entry 5), PTSA-zirconia (Table 1; entry 6) and PTSA-
zeolite-A (Table 1; entry 7) so as to make the catalyst easily recyclable. Among these supported
catalysts, PTSA-MCM-41(Table 1; entry 5; conversion 62 %; selectivity 86 %) was found to
be the best, hence it was used as preferred catalyst for this reaction for further work on process
optimization. Here it is to be noted that all the supports used here (without loading PTSA) were
individually screened as catalyst for this reaction but they failed to show the formation of
product jasminaldehyde under the reaction conditions used, although we noticed the formation
of some unidentified side-products (data not included).
3.2.2. Effect of catalyst loading
The Effect of catalyst amount on the selectivity to jasminaldehyde was studied over a range of
25-300 mg with respect to 1-heptanal (7.9 mmol) and the data are given in Table 2 (Table 2;
entries 1-5). It is evident from the results that 100 mg catalyst per 7.9 mmol of 1-heptanal is
optimum for getting higher conversion and selectivity towards the formation of jasminaldehyde
(Table 2; entry 3).
3.2.3. Effect of temperature
Temperature has great influence in the selectivity as well as the conversion of jasminaldehyde.
So, the effect of reaction temperature on selectivity of jasminaldehyde was studied in the
temperature range of 40-170 °C at constant 1-heptanal: benzaldehyde molar ratio 1:5 and 100
mg of PTSA-MCM-41 as catalyst and the data are given in Table 3. It is evident from the data
that as we increase the temperature of reaction from 40 °C, the conversion as well as the
selectivity of the jasminaldehyde increase till 125 °C (Table 3; entries 1-5), thereafter a further
increase in the temperature loss in jasminaldehyde selectivity was observed particularly above
8

140 °C (Table 3; entry 7). Therefore, 125 °C was taken as optimum temperature for this
reaction.
In order to highlight the utility of our methodology, the reaction was also performed on a
relatively larger scale (50g of 1-heptanal, Table 3; entry 8) under the optimized reaction as per
Table 3; entry 5 of this Table, and found no change in the outcome of the reaction. This shows
that the present protocol for the preparation of jasminaldehyde is scalable and may find
application in industry.
Having established the utility of PTSA-MCM-41 as catalyst in cross aldol-condensation of
benzaldehyde with 1-heptanal to form jasminaldehyde, we next explored its capability to
accommodate various aromatic aldehydes as well as aliphatic aldehydes using the above
optimized reaction conditions.
3.2.4. Expansion of substrate scope (aromatic aldehyde)
To expand the substrate scope, we first varied aromatic aldehydes by keeping 1-heptanal as
common aliphatic substrate as constant and the results are given in Table 4 (Table 4; entries 1-
11). In majority of the cases aromatic aldehydes produces the desired cross-condensation
products with selectivity at par with benzaldehyde. However, for 3-methoxy benzaldehyde
(Table 4 , entry 11) both conversion (85 %) and selectivity (60 %) were remarkably less,
possibly due to the strong electron donating nature of methoxy group causing carboxy carbon
poorer electrophile; consequently formation of self-condensation product of heptanal was
more (40 %) in this case.
3.2.5. Effect of substrate variation (aliphatic aldehyde)
Next, we kept benzaldehyde as common aromatic aldehyde and varied aliphatic aldehyde with
variable alkyl chain and results are given in Table 5 (entries 1-5). It is evident from the results
that on increasing chain length (as compared to heptanal, Table 5, entry 1) conversions (99 %)
and cross-aldol product selectivity (89 %) remained good (Table 5, entries 2 and 3). Whereas,
shorter chain length aldehydes like butanal (Table 5, entry 4) though the conversion remained
99 %, gave relatively more self-condensation product (12 %) and the self-condensation product
was even more (entry 5; 14 %) with branched aldehyde viz. 3-methyl butanal.
9

3.2.6. Recycling of the catalysts PTSA-MCM-41 in the cross-aldol condensation reaction
The study on the reusability (5 times at 125 °C) of the catalyst PTSA-MCM-41 in the
cross-aldol condensation reaction was performed and corresponding results are depicted in Fig
6. The catalyst was reused under identical conditions of the cross-aldol condensation reaction.
The catalyst showed high stability under reaction environment and showed no significant
change in its ability in imparting selectivity and conversion. The catalyst recyclability was
checked by retrieving the catalyst by centrifugation of reaction mass in the post-catalysis unit
operation. The recovered catalyst was washed sequentially with DCM, acetone and dried at 60
°C. The recovered catalyst showed characteristics peaks in IR (see Fig 2) as observed in fresh
catalyst. The recovered catalyst was used as fresh catalyst in subsequent catalytic runs that
showed no sign of deactivation over 5 cycles used.
4. Conclusions
In conclusion, we have developed a simple and green method for the synthesis of fine chemical
jasminaldehyde catalysed by PTSA-MCM-41 under solvent-free condition at 125 °C. The
major advantages of the method lies in its easy catalyst preparation using inexpensive raw
materials, thereby making the catalytic protocol attractive for commercial exploitation. This
cross-aldol protocol was found to be equally competent in accommodating other substrates as
well.
Acknowledgements
CSIR-CSMCRI registration no is 66/2015. The authors acknowledge CSIR and DST
(SR/S1/OC-56/2009), New Delhi for the financial support through the Network Project on
Catalysis. G. V. S. Rao is thankful to the Academy of Scientific and Innovative Research
(AcSIR) for Ph.D. enrolment. G. V. S. Rao acknowledges CSIR, New Delhi, for the award of
Senior Research Fellowship and Analytical Discipline and Centralized Instruments Facility
(AD&CIF) of CSMCRI.
10

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2500
2000
1500
1000
500
(a)
PTSA-MCM-41
0
2
3
4
5
6
7
8
2
(b)
1200
1000
800
600
400
200
0
MCM-41
PTSA-MCM-41
Reused PTSA-MCM-41
20
30
40
50
60
70
80
2
Fig. 1. Small angle PXRD of PTSA-MCM-41 (a) and Wide angle PXRD of MCM-41, PTSA-
MCM-41(b).
13

PTSA
MCM-41
PTSA-MCM-41
Reused PTSA-MCM-41
65
60
55
50
45
40
35
30
25
20
1124
1131
1189
1183
4000
3500
3000
2500
2000
1500
1000
500
cm-1
Fig. 2. FT-IR of PTSA, MCM-41, PTSA-MCM-41.
14

PTSA
MCM-41
PTSA-MCM-41
100
80
60
40
20
0
100
200
300
400
500
600
700
800
TemperatureC
Fig. 3. TGA of PTSA, MCM-41, PTSA-MCM-41.
15

600
500
400
300
200
100
0
PTSA-MCM-41
0.0
0.2
0.4
0.6
0.8
1.0
Relative pressure p/p0
Fig. 4. Nitrogen adsorption-desorption isotherms (at 77 K) of PTSA-MCM-41.
16

(5a)
(5b)
(5c)
1 µm
20 nm
1 µm
(5d)
Fig. 5. SEM (5a), TEM (5c) and EDX (5d) image of PTSA-MCM-41.
17

% Conversion
% Selectivity
100
80
60
40
20
0
1
2
3
4
5
Recyling times
Reaction conditions: heptanal = 7.9 mmol, benzaldehyde = 39.5 mmol, Time 13 h, 100 mg of
catalyst. Selectivity and conversion is determined by GC analysis.
Fig. 6. Reusability of the catalyst (PTSA-MCM-41).
18

Scheme 1. Condensation of benzaldehyde with 1-heptanal.
19

Table 1 Screening of catalysta
Selectivity (%)c
jasminaldehyde
Catalyst
Conversion
(%)b
Entry
Time
2-pentyl
enal
41
non-2-
(loading)
(h)
5
1
2
3
4
ZnO
39
99
56
99
59
83
83
85
*L-proline
PR-LDH
#PTSA
1
17
5
17
1
15
PTSA-MCM-
41
5
5
62
86
14
6
7
PTSA-zirconia
5
5
60
49
81
64
19
36
PTSA-Zeolite
aReaction conditions: heptanal = 7.9 mmol, benzaldehyde = 39.5 mmol, temperature = 125 °C,
50 mg of catalyst. b, cDetermined by GC analysis. *Catalyst loading 40 mol%, #Catalyst
loading 5%.
20

Table 2 Variation of Catalyst amounta
Catalyst Loading
Selectivity (%)c
Entry
Conversion (%)b
Jasminaldehyde
2-pentyl non-2-enal
(mg)
25
1
2
3
4
5
39
76
99
99
99
55
79
91
90
88
45
21
09
10
12
50
100
200
300
aReaction conditions: heptanal = 7.9 mmol, benzaldehyde = 39.5 mmol, temperature =125°C,
Time 13 h. b, c Determined by GC analysis.
21

Table 3 Effect of reaction temperaturea
Selectivity (%)c
Jasminaldehyde
Entry
1
Temperature (°C)
40
Conversion (%)b
52
2-pentyl
enal
non-2-
53
47
2
60
67
71
89
99
99
99
98
59
67
73
91
91
88
90
41
33
27
09
09
12
10
3
80
4
100
125
140
170
125
5
6
7
8*
aReaction conditions: heptanal = 7.9 mmol, benzaldehyde = 39.5 mmol, Time 13 h, 100 mg of
catalyst. b, c Determined by GC analysis.*Bulk scale.
22

Table 4 Cross-aldol condensation between heptanal and various aromatic aldehydes PTSA-
MCM-41 as a catalysta
Selectivity (%)c
Entry
Ar-CHO
Conversion (%)b
CA
SA
1
2
3
4
99
99
99
99
91
09
91
89
91
09
11
09
5
6
7
99
99
99
91
91
90
09
09
10
8
9
99
99
91
89
09
11
10
99
91
09
11
85
61
39
aReaction conditions: heptanal = 7.9 mmol, aromatic aldehyde = 39.5 mmol, temperature = 125
°C, Time 13 h, 100 mg of catalyst. b,cDetermined by GC analysis. CA= cross-aldol condensed
product of aromatic aldehyde and 1-aliphatic aldehyde. SA= self aldol condensed product of
1-aliphatic aldehyde.
23

Table 5 Cross aldol condensation between benzaldehyde and various aliphatic aldehydes
PTSA-MCM-41 as a catalysta
Selectivity (%)c
Entry
1
R-CHO
Conversion (%)b
99
CA
SA
09
91
2
3
99
99
89
89
11
11
4
5
99
99
88
86
12
14
aReaction conditions: Aliphatic aldehyde = 7.9 mmol, benzaldehyde = 39.5 mmol, temperature
= 125°C, Time 13 h, 100 mg of catalyst. b, cDetermined by GC analysis. CA= cross-aldol
condensed product of aromatic aldehyde and 1-aliphatic aldehyde. SA= self aldol condensed
product of 1-aliphatic aldehyde.
24