Laser flash photolysis of nanocrystalline α-azido-p-methoxy-acetophenone

Abstract

Irradiation of nanocrystals of azide 1 results in a solid-to-solid reaction that forms imine 2 in high chemical yield. In contrast, solution photolysis of azide 1 yields a mixture of products, with 7 as the major one. Laser flash photolysis (LFP) of a nanocrystalline suspension of azide 1 in water shows selective formation of benzoyl radical 4 (λ ∼ 400 nm), which is short-lived (τ = 833 ns) as it intersystem crosses to form imine 2. In comparison, LFP of azide 1 in methanol reveals the formation of triplet alkylnitrene 10 (λ ∼ 340 nm). The selectivity observed in the solid-state is related to stabilization of the triplet ketone with (n,π*) configuration by the crystal lattice, which results in α-cleavage being favored over triplet energy transfer to the azido chromophore. Both the solid-state and solution reaction mechanisms are further supported by density functional theory calculations. Thus, laser flash photolysis has been used to effectively elucidate the medium dependent reaction mechanisms of azide 1.

Efficient and Economic Heparin Recovery from Porcine Intestinal Mucosa Using Quaternary Ammonium-Functionalized Silica Gel

“…Quaternary salts contain additional asymmetric and symmetric C-H stretching peaks over amine-functionalized silica, which are located between 2926–2742 cm −1 . N-H stretching peaks, for example, at 3509 cm −1 in DASi, are absent in QDASi due to the methyl quaternization of amine [ 29 , 30 , 31 , 32 ].…”

“…Additionally, HEP adsorption on the QDASi surface was confirmed by FTIR analysis ( Figure 2 ). FTIR spectra of store-bought sodium heparin salt and QDASi were compared, and the C=O stretching band at 1712 cm −1 in QDASi-Heparin conjugate confirms the adsorption of the HEP on the QDASi surface [ 31 , 32 , 34 ].…”

Modified Diatomaceous Earth in Heparin Recovery from Porcine Intestinal Mucosa

“…Additional vibrational frequencies of both asymmetric and symmetric C-H stretching can be observed in the quaternary salts situated between 3014 and 2690 cm −1 . The N-H stretching frequencies, present in various DE amides (such as at 3473 cm −1 in MADE), disappeared in quaternized salts [46][47][48][49].…”

α-Cleavage of 2,2-Diazido-2,3-dihydroinden-1-one in Solution and Cryogenic Matrices

“…6 We demonstrated the use of this method in crystals to form radical pairs that yield photoproducts rather than re-form the starting material (Scheme 1). 7 Specifically, irradiating α-azido-acetophenone derivatives in the solid state yields N-methylenebenzamide derivatives. Laser flash photolysis of nanocrystals showed that the photoreaction occurs through α-cleavage to form a benzoyl and methyl azido radical pair.…”