3.4 Applications of Ultrasound and Neoteric Solvents
49
et al. (2016) reach the same conclusions with the synthesis of isoxazoline derivatives
using different ratio of a mixture of benzalkonium chloride and urea. These papers
suggest that the increase in mass transfer combined with the chemical effects of
cavitation bubbles causes an increase in reaction yields and a reduction in synthesis
time.
The synthesis of metal–organic framework (MOF) was also investigated by using
the combination US/ChCl: dimethylurea (Kim et al. 2011). The examination of
results shows that Cu-benzotricarboxylate derivatives exhibit identical uptake capacities than materials obtained by conventional method in DMF but with a drastic
reduction in reaction time (36 h for conv. vs. 30–120 min. for US, respectively).
Recently, a mixture of ChCl: urea was also used to perform the heterogeneous
synthesis of nitroaromatic derivatives catalysed by silica-based magnetic composite
by working at frequency of 40 kHz and at an output power of 250 W (Maleki and
Agahie 2017). The authors concluded on the positive synergistic effects of ChCl:
urea/US to promote selective ultrasonoxidations. All these examples, although yet
very few, emphasize that reactions usually done in ILs in the presence of ultrasound
might be also done in DES. The substation of ILs by DES may be even more beneficial
considering that DES are made of cheap and natural products, thereby eliminating
possible problems of environmental concern and drastically decreasing production
and operating costs.
3.4.2 Ultrasound-Assisted-NES-Extraction (UA-NS-E)
Such as in the field of synthetic organic chemistry, the combined use of neoteric
solvents and ultrasound in microextraction and extraction applications, particularly
in the food industry, began in the same pivotal period of early 2000s. High-intensity
and low-frequency ultrasonic cavitation allows obviously to enhance mass transfer
processes and proves to be an effective tool in extraction processes. The solvation
properties, high chemical and thermal stabilities, and tunability of ILs have been
leveraged for increasing extraction yields in reduced times compared to conventional conditions. Extractions processes can be carried out on water, biological and
food matrices in order to extract the active compounds (organic or inorganic), oil
from seeds or to pre-concentrate organic pollutants for analytical purpose (Han and
Row 2010; Passos et al. 2014). While the supercritical fluid extraction (SFE) is relatively implemented in agro-industry, the use at laboratory scale is reversely much
lower than that of ionic liquids. Indeed, accessing to SFC technology is costlier than
synthesizing organic molecules such as ILs or DES and to use them on classical
or easily accessible conditions of temperature and pressure. Most of the ILs applications combined with ultrasound are generally implemented with cleaning bathes
probably because of a higher commercial availability, lower price and easiness to use
the latter as compared to probes equipment although greater mechanical effects are
expected. Owing to their youngness, DES are not yet as highly investigated as ILs but
as emphasized earlier their striking potential will certainly ensure a bright future for
49
et al. (2016) reach the same conclusions with the synthesis of isoxazoline derivatives
using different ratio of a mixture of benzalkonium chloride and urea. These papers
suggest that the increase in mass transfer combined with the chemical effects of
cavitation bubbles causes an increase in reaction yields and a reduction in synthesis
time.
The synthesis of metal–organic framework (MOF) was also investigated by using
the combination US/ChCl: dimethylurea (Kim et al. 2011). The examination of
results shows that Cu-benzotricarboxylate derivatives exhibit identical uptake capacities than materials obtained by conventional method in DMF but with a drastic
reduction in reaction time (36 h for conv. vs. 30–120 min. for US, respectively).
Recently, a mixture of ChCl: urea was also used to perform the heterogeneous
synthesis of nitroaromatic derivatives catalysed by silica-based magnetic composite
by working at frequency of 40 kHz and at an output power of 250 W (Maleki and
Agahie 2017). The authors concluded on the positive synergistic effects of ChCl:
urea/US to promote selective ultrasonoxidations. All these examples, although yet
very few, emphasize that reactions usually done in ILs in the presence of ultrasound
might be also done in DES. The substation of ILs by DES may be even more beneficial
considering that DES are made of cheap and natural products, thereby eliminating
possible problems of environmental concern and drastically decreasing production
and operating costs.
3.4.2 Ultrasound-Assisted-NES-Extraction (UA-NS-E)
Such as in the field of synthetic organic chemistry, the combined use of neoteric
solvents and ultrasound in microextraction and extraction applications, particularly
in the food industry, began in the same pivotal period of early 2000s. High-intensity
and low-frequency ultrasonic cavitation allows obviously to enhance mass transfer
processes and proves to be an effective tool in extraction processes. The solvation
properties, high chemical and thermal stabilities, and tunability of ILs have been
leveraged for increasing extraction yields in reduced times compared to conventional conditions. Extractions processes can be carried out on water, biological and
food matrices in order to extract the active compounds (organic or inorganic), oil
from seeds or to pre-concentrate organic pollutants for analytical purpose (Han and
Row 2010; Passos et al. 2014). While the supercritical fluid extraction (SFE) is relatively implemented in agro-industry, the use at laboratory scale is reversely much
lower than that of ionic liquids. Indeed, accessing to SFC technology is costlier than
synthesizing organic molecules such as ILs or DES and to use them on classical
or easily accessible conditions of temperature and pressure. Most of the ILs applications combined with ultrasound are generally implemented with cleaning bathes
probably because of a higher commercial availability, lower price and easiness to use
the latter as compared to probes equipment although greater mechanical effects are
expected. Owing to their youngness, DES are not yet as highly investigated as ILs but
as emphasized earlier their striking potential will certainly ensure a bright future for