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Polar solvents refer to solvents containing polar groups such as hydroxyl or carbonyl groups, that is, solvents in which the solvent molecules are polar molecules, and the molecules are polarized due to the fact that the center of gravity of the positive and negative charges in the molecules do not overlap.
The physical quantity used to characterize the polarity of a molecule is the dipole moment or dielectric constant.
A large dielectric constant indicates a large polarity.
Chemical covalent bonds are divided into polar bonds and non-polar bonds.
The non-polar bond means that the shared electron pair has no offset, and appears in elemental substances such as O2; the polar bond is the shared electron pair has an offset such as HCl.
And when the offset is very severe, it seems that one side completely loses electrons and the other side gets electrons, and it becomes an ionic bond, such as NaCl.
The polarity of a compound is determined by the functional groups and molecular structure contained in the molecule.
The polarity of various compounds increases in the following order: —CH3, —CH2—, —CH=, —C3, —O—R, —S—R, —NO2, —N(R)2, —OCOR, — CHO, —COR, —NH2, —OH, —COOH, —SO3H1, strong polar solvent methanol>ethanol>isopropanol2, medium polar solvent acetonitrile>ethyl acetate>chloroform>dichloromethane>diethyl ether>toluene 3.
Non-polar solvent cyclohexane>petroleum ether>hexane>pentane 4.
The order of polarity of single solvent petroleum ether (small) ＜cyclohexane＜carbon tetrachloride＜trichloroethylene＜benzene＜toluene＜ Dichloromethane＜chloroform＜diethyl ether＜ethyl acetate＜methyl acetate＜acetone＜n-propanol＜methanol＜pyridine＜acetic acid (large) 5.
The order of polarity of mixed solvents Benzene: chloroform(1+1)＜cyclohexane ：Ethyl acetate (8+2)<chloroform: acetone (95+5)<benzene: acetone (9+1)<benzene: ethyl acetate (8+2)<chloroform: ether (9+1)<benzene: Methanol (95+5)<benzene:diethyl ether (6+4)<cyclohexane:ethyl acetate (1+1)<chloroform:diethyl ether (8+2)<chloroform:methanol (99+1)<benzene:methanol (9+1)<chloroform:acetone (85+15)<benzene:ether (4+6)<benzene:ethyl acetate (1+1)<chloroform:methanol (95+5)<chloroform:acetone (7+ 3) <benzene: ethyl acetate (3+7) <benzene: ether (1+9) <ether: methanol (99+1) <ethyl acetate: methanol (99+1) <benzene: acetone (1+1 )<Chloroform: Methanol (9+1) Explain: Benzene: Methanol (95+5) means 95 volumes of benzene mixed with 5 volumes of methanol to make a mixed solvent 6.
Commonly used mixed solvent ethyl acetate/hexane: commonly used The concentration is 0~30%.
But sometimes it is difficult to completely remove the solvent on the rotary evaporator.
Ether/Pentane system: The concentration of 0-40% is more commonly used.
It is very easy to remove on a rotary evaporator.
Ethanol/hexane or pentane: 5~30% is more suitable for strong polar compounds.
Dichloromethane/hexane or pentane: 5~30%, can be considered when other mixed solvents fail.
7.
Comparison of the polarity of functional groups.
Alkanes (—CH3, —CH2—)<Alkenes (—CH=CH —)<Ethers (—O—CH3, —O—CH2—)<Nitro compounds (—NO2) <2 Methylamine (CH3—N—CH3) <lipids (—COOR) <ketones (—CO—) <aldehydes (—CHO) <mercaptans (— SH) <amines (— NH2) <amides (— NHCO —CH3)＜Alcohols (-OH)＜Phenols (＜Ar-OH)＜Carboxylic acids (-COOH) 8.
Commonly used mobile phase polar petroleum ether＜gasoline＜heptane＜hexane＜carbon disulfide＜xylene＜ Toluene <chloropropane <benzene <bromoethane <brominated benzene <dichloroethane (DCM) <chloroform <isopropyl ether <nitromethane <butyl acetate <diethyl ether <ethyl acetate <n-pentane <normal Butanol＜phenol＜methyl alcohol＜tert-butanol＜tetrahydrofuran＜dioxane＜acetone＜ethanol＜acetonitrile＜methanol＜DMF (DMF) ＜water represents the polarity of organic solvents and is related to its physics Chemical properties, such as dielectric constant, dipole moment, or refractive index.
This method of expression treats all solvents as continuous media, rather than as a discontinuous unit composed of individual molecules, and does not take into account the special interaction between the solvent and the solute.
The physical quantity used to characterize the polarity of a molecule is the dipole moment or dielectric constant.
A large dielectric constant indicates a large polarity.
Chemical covalent bonds are divided into polar bonds and non-polar bonds.
The non-polar bond means that the shared electron pair has no offset, and appears in elemental substances such as O2; the polar bond is the shared electron pair has an offset such as HCl.
And when the offset is very severe, it seems that one side completely loses electrons and the other side gets electrons, and it becomes an ionic bond, such as NaCl.
The polarity of a compound is determined by the functional groups and molecular structure contained in the molecule.
The polarity of various compounds increases in the following order: —CH3, —CH2—, —CH=, —C3, —O—R, —S—R, —NO2, —N(R)2, —OCOR, — CHO, —COR, —NH2, —OH, —COOH, —SO3H1, strong polar solvent methanol>ethanol>isopropanol2, medium polar solvent acetonitrile>ethyl acetate>chloroform>dichloromethane>diethyl ether>toluene 3.
Non-polar solvent cyclohexane>petroleum ether>hexane>pentane 4.
The order of polarity of single solvent petroleum ether (small) ＜cyclohexane＜carbon tetrachloride＜trichloroethylene＜benzene＜toluene＜ Dichloromethane＜chloroform＜diethyl ether＜ethyl acetate＜methyl acetate＜acetone＜n-propanol＜methanol＜pyridine＜acetic acid (large) 5.
The order of polarity of mixed solvents Benzene: chloroform(1+1)＜cyclohexane ：Ethyl acetate (8+2)<chloroform: acetone (95+5)<benzene: acetone (9+1)<benzene: ethyl acetate (8+2)<chloroform: ether (9+1)<benzene: Methanol (95+5)<benzene:diethyl ether (6+4)<cyclohexane:ethyl acetate (1+1)<chloroform:diethyl ether (8+2)<chloroform:methanol (99+1)<benzene:methanol (9+1)<chloroform:acetone (85+15)<benzene:ether (4+6)<benzene:ethyl acetate (1+1)<chloroform:methanol (95+5)<chloroform:acetone (7+ 3) <benzene: ethyl acetate (3+7) <benzene: ether (1+9) <ether: methanol (99+1) <ethyl acetate: methanol (99+1) <benzene: acetone (1+1 )<Chloroform: Methanol (9+1) Explain: Benzene: Methanol (95+5) means 95 volumes of benzene mixed with 5 volumes of methanol to make a mixed solvent 6.
Commonly used mixed solvent ethyl acetate/hexane: commonly used The concentration is 0~30%.
But sometimes it is difficult to completely remove the solvent on the rotary evaporator.
Ether/Pentane system: The concentration of 0-40% is more commonly used.
It is very easy to remove on a rotary evaporator.
Ethanol/hexane or pentane: 5~30% is more suitable for strong polar compounds.
Dichloromethane/hexane or pentane: 5~30%, can be considered when other mixed solvents fail.
7.
Comparison of the polarity of functional groups.
Alkanes (—CH3, —CH2—)<Alkenes (—CH=CH —)<Ethers (—O—CH3, —O—CH2—)<Nitro compounds (—NO2) <2 Methylamine (CH3—N—CH3) <lipids (—COOR) <ketones (—CO—) <aldehydes (—CHO) <mercaptans (— SH) <amines (— NH2) <amides (— NHCO —CH3)＜Alcohols (-OH)＜Phenols (＜Ar-OH)＜Carboxylic acids (-COOH) 8.
Commonly used mobile phase polar petroleum ether＜gasoline＜heptane＜hexane＜carbon disulfide＜xylene＜ Toluene <chloropropane <benzene <bromoethane <brominated benzene <dichloroethane (DCM) <chloroform <isopropyl ether <nitromethane <butyl acetate <diethyl ether <ethyl acetate <n-pentane <normal Butanol＜phenol＜methyl alcohol＜tert-butanol＜tetrahydrofuran＜dioxane＜acetone＜ethanol＜acetonitrile＜methanol＜DMF (DMF) ＜water represents the polarity of organic solvents and is related to its physics Chemical properties, such as dielectric constant, dipole moment, or refractive index.
This method of expression treats all solvents as continuous media, rather than as a discontinuous unit composed of individual molecules, and does not take into account the special interaction between the solvent and the solute.
