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The Anthrosphere
Published in Stanley E. Manahan, Environmental Chemistry, 2022
Media is a term used to refer to the matrix in which or on which chemical processes occur. The type and strength of interaction between the media and reactants in a chemical process play a very important role in determining the type, degree, and rate of the process. Although media may include solids on the surface of which reactions take place, by far the most common type of media consists of liquid solvents in which reagents are dissolved. Solvents interact to various extents and in various ways with the solutes dissolved in them, particularly through solvation, in which the solvent molecules cluster around and may bond with solute molecules. Solvation of dissolved cations and anions by polar water molecules makes water an extraordinarily good solvent for ionic substances—acids, bases, and salts—that are commonly used in chemical reactions. The ability of water to form hydrogen bonds is particularly important in its ability to dissolve a wide range of biological materials capable of forming hydrogen bonds.
Water
Published in P.K. Tewari, Advanced Water Technologies, 2020
Latent heat of vaporization is another unique property of water useful for several purposes. It is the heat required to convert water into steam at constant temperature. Water molecules form hydrogen bonds with one another. The partial negative charge on the oxygen (O) of one molecule can form a hydrogen bond with the partial positive charge on the hydrogen of other molecules. Water molecules are drawn to other polar ions. Because the bonding electrons are shared unequally by the hydrogen and oxygen atoms, a partial negative charge (ð−) forms at the oxygen end of the water molecule, and a partial positive charge (ð+) forms at the hydrogen ends (Figure 1.1).
Ionizing Radiation
Published in Ivan G. Draganić, Zorica D. Draganić, Jean-Pierre Adloff, Radiation and Radioactivity on Earth and Beyond, 2020
Ivan G. Draganić, Zorica D. Draganić, Jean-Pierre Adloff
Proteins constitute the principal nitrogeneous organic compounds in living matter and contain about 15 percent nitrogen and 50 percent carbon. They are polymers with molecular masses ranging from 5000 to 6 million atomic mass units. They consist of hundreds or thousands of amino acids joined together by a peptide link (-CO-NH-) to form a chain structure. A protein may contain more than one peptide chain. The three-dimensional arrangement of peptides is largely maintained by hydrogen bonds and is very important in determining properties of the protein. The constituents of a protein comprise about 20 different amino acids and each protein polymer may contain all of these arranged in a variety of sequences. A particular sequence in an individual protein confers specific properties.
Recent advance in enhanced adsorption of ionic dyes from aqueous solution: A review
Published in Critical Reviews in Environmental Science and Technology, 2023
The essence of hydrogen bond is an electrostatic force, which is a dipole-dipole interaction formed between hydrogen atoms and other atoms with high electronegativity. But the hydrogen bonding force is unlikely to be the main adsorption driving force. It is because the hydrogen bond between the anionic dye and the water molecule is greater than that between the adsorbent and dye. Non-aromatic hydroxyl groups or functional groups containing heteroatoms and lone pairs of electrons in the adsorbent may combine with the dye in the form of hydrogen bond (Li, Nu, et al., 2019).
Evaluating direct and indirect effects of low-energy electrons using Geant4-DNA
Published in Radiation Effects and Defects in Solids, 2020
Eunae Choi, Kwon Su Chon, Myong Geun Yoon
The biological effect of ionizing radiation is fundamentally determined by nuclear DNA (1–3). DNA consists of two strands forming a double helix and bases bound to each other by hydrogen bonds. Ionizing radiation results in physical and chemical changes in the cell followed by biological changes causing DNA damage. Major DNA damage includes single and double strand breaks (SSB and DSB) and base damages.(4–6) Such DNA damage leads to cell death, mutation, and carcinogenesis if misrepaired or unrepaired. DSB is the most detrimental of all types of DNA damage (7,8).
Some characterizations of a new metal–organic framework (n-C14H29NH3)2CdCl4 and the role of hydrogen bonding
Published in Phase Transitions, 2018
The role of hydrogen bond and how it triggers and initiates the disorder process is closely related to the recent picture of the room temperature crystal structure of G1 of this series where monomeric (metal halide) moieties bind or link with the organic chains (CnH2n+1NH3)+1 through hydrogen bonding system of the type N–H … Cl of different lengths (i.e. different strengths) but all belong to the range of weak type [43,73]. Obviously, this picture strongly clarifies how such a bond plays a major role in stabilization of structure. Simply, a hydrogen bond is a special type of dipole–dipole attraction and occurs when a hydrogen atom bonded to a strongly electronegative atom with a lone pair of electrons. However, another point of interest is that the hydrogen bonds are directional but much weaker than the covalent bonds binding atoms into molecules and is stronger than van der Waals interaction [74,75], thus the hydrogen-bonded aggregates can go easily phase transformations by weakening or breaking and formation of alternative hydrogen bonds, proton transfer and /or proton-disorder. Going back to the mechanism of phase transitions in the herein hybrid which may be summarize as follow: with the increase of temperature, the length N–H … Cl increases and the weakening of hydrogen bond is achieved which is also reflected on the constraints between the two entities (organic and inorganic) of the hybrid since they are linked by hydrogen bonds and hence they are also weakened. This case of say relaxation, triggers and initiates the order–disorder process which continue over a short range of temperature until a new structural phase(partially disordered) is formed at Tminor ≅ 344 K which is clearly belongs to order–disorder transition type. Furthermore, the present hybrid is characterized by the existence of intermediate transitions temperature at ≈ 346.8 K resulting in two intermediate phases IMI (phase III) and IMII or phase II which are exist only over a short range of temperature similar to other Cd hybrids of this series, i.e.C10Cd [25] and C12Cd [16,23,51] and C16Cd [17,53]. It is believed that these intermediate phases are related more or less with the gauche defects which have been confirmed almost near the end of the room temperature phase.From spectroscopic technique, since with heating up inside the room temperature phase, the molecular is weaken, suggesting an increase of the chain mobility and hence few defects of the kink form appear. It is to be noted that these defects have been lost in the transition IMI–IMII.