Ultrasound Effects on the Photopinacolization of Benzophenone

Abstract

Ultrasonic irradiation is able to modify the course of several photochemical reactions, especially bimolecular, proceeding via triplet states. These effects were illustrated in the study of benzophenone photopinacolization in ethanol. The rates and yields increase when sonication is applied simultaneously to UV irradiation. An explanation is based on a 2-fold effect: (i) light-absorbing transient species undergo sonolytic decomposition, making the photoconversion more efficient, and (ii) sonication induces the triplet state quenching, as shown by Stern-Volmer plots from experiments run in the presence of naphthalene, probably due to the easier collisional deactivation processes favored by the homogeneous distribution of the activated species.

Solution properties of sodium n-dodecyl sulfate in the presence of meso-tetrakis (N-methylpyridinium-4-yl) porphyrin

“…28 Sodium dodecyl sulfate, was purchased from chemical reagents company of Merck which was used directly without further purification. All aqueous solutions were prepared by using twice distilled water.…”

Unsymmetrical urea and thiourea derivatives: An efficient nano BF 3-SiO 2 catalyzed PEG-400 mediated sonochemical synthesis and biological evaluation

“…[14][15] Further, ultrasound is an alternative energy source to accelerate organic transformations ordinarily through heating instead of harsh conventional heating. 16 In the literature many homogeneous and heterogeneous catalyzed organic reactions 17 have established competently proceed via the formation and adiabatic collapse of transient cavitation bubbles in ultrasonication 18 by overcoming some of the demerits exposed in conventional methods. The remarkable advantages in the ultrasound irradiations are decrease the reaction time, increase the rate of the reaction, the yield enhancement of products with high purity, high efficiency and waste minimization.…”

“…Further, our attention was focused to reduce the reaction time; hence, the optimized reaction was carried out in ultrasonication at 40 o C (Table 1 entry 19) and observed remarkably high yield of the product 6b (87%) in short reaction time (25 min.). Yet again to distinguish the temperature effect on the yield of the product, the model reaction was investigated at ambient temperature and different temperatures (Table 1 entry [17][18][19][20]. As seen in the table, it was found that the reaction is proceed at 40 ºC and afforded high yield (81%) of the product in less time (25 min) and significant yield enhancement was observed upon increasing the temperature until 50 o C, and no noteworthy enhancement at 60 o C. It is well known that the amount of catalyst also play an important role in the reaction, so, the model reaction was tested in PEG-400 by loading different amounts of the catalyst, 37% nano-BF 3 -SiO 2 under conventional and ultrasonication conditions and the results are presented in Table 2, entry 1-5.…”

The Combined Use of Microwaves and Ultrasound: Methods and Practice

“…Although MWs are constituted of electromagnetic radiation, one cannot assume a reductionist view for the interaction between ''US and light.'' The coupling of US with photons of higher energy, such as ultraviolet light, also enhances photochemical transformations [10,11]. This fact has been put to good use in environmental chemistry, where sonophotocatalysis has been employed for the decontamination of water, which also allows the use of smaller amounts of the catalyst [12].…”