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Polymers Containing Pendent Pesticide Substituents
Published in Agis F. Kydonieus, Controlled Release Technologies: Methods, Theory, and Applications, 2019
As stated earlier, pendent pesticidal moieties are released from polymer backbones by chemically or biologically induced cleavages of the pesticide-polymer chemical bonds. The most common cleavage reaction employed is hydrolysis induced by water in the surrounding environment. The kinetic expressions that describe the rate of release of pesticide vary depending on whether the hydrolysis reaction is purely homogeneous, purely heterogeneous, or some combination of the two. The observed release rate is determined by both the reaction kinetics and by the diffusion rate of the liberated pesticide through the polymer.15 Boundary layer effects can also play a role in determining the actual rate of release.16
Alkyl Halides and Substitution Reactions
Published in Michael B. Smith, A Q&A Approach to Organic Chemistry, 2020
Certain molecules are characterized by breaking a bond in a homolytic manner (homolytic cleavage, where each atom of the covalent bond receives one electron) and the resulting products have a single electron. These intermediates are called free radicals and are capable of reacting with alkanes (and other molecules) to remove a hydrogen, generating a carbon radical. What is the normal reactivity of a radical once formed?
The impact of radicals in cold atmospheric plasma on the structural modification of gap junction: a reactive molecular dynamics study
Published in International Journal of Smart and Nano Materials, 2019
Rong-Guang Xu, Zhitong Chen, Michael Keidar, Yongsheng Leng
The newly found C-N bond breaking mechanism is shown in Figures 4 and 5. As one radical approaches the OH group in Ser (see in Figure 4(a)), This OH group abstracts the H atom from the radicals, forming a water molecule and an oxygen molecule (see in Figure 4(b)), which is similar to the previous observation that the OH residue of the disaccharide in peptidoglycan can be abstracted upon impact of radicals [39]. After abstraction of OH group of Ser, a primary alkyl radical is produced in Ser, which is not stable. This finally leads to cleavage of C-N bond and subsequently creation of the double C-C bond and formation of a resonance-stabilized amide radical (see in Figures 4(c) and Figure 5). The driving force for the C-N bond breaking reaction is that the resonance-stabilized amide radical is more stable than the primary alkyl radical. Such bond breaking reaction is termed as the homolytic cleavage. This process is very similar to the interaction of an radical with Ala residue, during which radical abstracts H atom in the Ala residue and results in cleavage of C-N bond and creation of the double C-C bond and formation of a resonance-stabilized amide radical in the same way [39].
The correlation between structure, multifunctional properties and application of PVD MAX phase coatings. Part I. Texture and room temperature properties
Published in Surface Engineering, 2020
The cleavage is a process of bond breaking between ions, groups of ions or atoms which constitute those bonds. The cleavage process results in two fracture surfaces consisting of matching pairs of ions or atoms across the newly created surfaces. The bond density concept of Schultz proposes that a minimum in the number of bonds per unit area determines the cleavage planes [284]. Lower bond densities are associated with weaker bonding crystal planes which can in turn be more readily cleaved. However, this analytical bond density approach cannot easily include the varying bond strengths and their anisotropy due to the rather imprecise nature of bonds in ceramics [284].