One is bond strength. The easier the bond is to break, the more stable the free radical is.
One is a group connected to the central atom of the radical. The more electron-pushing groups, the more stable the free radicals are.
Monoatomic radicals such as CL- and BR- I- depend on electronegativity and nonmetal, and the bigger they are, the more unstable they are. The stability of free radicals in organic molecules is determined by substituents and molecular space configuration, such as phenyl "CH3-"C2H5-"NH2-"NO2-,and the more symmetrical the space configuration, the more stable it is. For example: tetraphenylcarbocation, methyl carbocation. The ratio with electron delocalization effect is unstable, such as propenyl C2H5-
Free radicals, also called "free radicals" in chemistry, refer to molecules of compounds under external conditions such as light and heat. * * * valence bond occurs? Atoms or groups with unpaired electrons formed by homogenization. (When the valence bond of * * * is unevenly cracked, the * * between two atoms is completely transferred to one of them by electron pairs, forming positively charged and negatively charged ions, which is called bond hetero-cracking. ) When writing, do you usually use atomic symbols or? Adding a ""next to the atomic group symbol means that there are no paired electrons. For example, hydrogen radicals (H, that is? Hydrogen atom), chlorine group (Cl, namely chlorine atom) and methyl group (CH3). Free radical reaction is used in combustion, gas chemistry, polymerization and so on. It plays an important role in plasma chemistry, biochemistry and other chemical disciplines. The first free radical in history was discovered and confirmed by Moses Gomberg in 1900? Triphenylmethyl radical discovered by University of Michigan. China organic chemist? Academician Liu Youcheng has also made outstanding contributions in the field of free radical chemistry.
In chemical reactions, or under the influence of the outside world (light, heat, radiation, etc.). ), the valence bond of * * * in the molecule is broken, so that the electron pair of * * * becomes one side exclusive, and then ions are formed; If * * * and electrons belong to two atoms (or groups) as a result of splitting, a free radical is formed.
The chemical reaction of organic compounds is always accompanied by the breaking of some covalent bonds and the formation of new covalent bonds. When the valence bond of * * * is homogeneous, two bonding electrons are separated, and the fragments formed have an unpaired electron, such as H, ch, Cl, etc. If it is composed of more than one atom, it is called a free radical. Due to unpaired electrons, free radicals and free atoms are very active and usually cannot be separated. But in many reactions, free radicals and free atoms exist in the form of intermediates, although the concentration is very low and the residence time is very short.
Solar radiation, air pollution, smoking, pesticides, etc. in the external environment will make the human body produce more reactive oxygen radicals and mutate nucleic acids, which is the root of human aging and illness. Active oxygen free radicals in the body have certain functions, such as immunity and signal transduction. However, too much reactive oxygen species will have destructive effects, leading to the damage of normal cells and tissues of human body, thus causing many diseases. Such as heart disease, Alzheimer's disease, Parkinson's disease and tumor.