A solvent (from the Latin language , "loosen, untie, solve") is a substance that dissolves a solute, resulting in a solution. A solvent is usually a liquid but can also be a solid, a gas, or a supercritical fluid. Water is a solvent for polar molecules, and the most common solvent used by living things; all the ions and proteins in a cell are dissolved in water within the cell.
Major uses of solvents are in paints, paint removers, inks, and dry cleaning. Specific uses for Organic compound solvents are in dry cleaning (e.g. tetrachloroethylene); as (toluene, turpentine); as nail polish removers and solvents of glue (acetone, methyl acetate, ethyl acetate); in spot removers (hexane, petrol ether); in detergents (D-limonene); and in (ethanol). Solvents find various applications in chemical, pharmaceutical, oil, and gas industries, including in chemical syntheses and purification processes
Some petrochemical solvents are highly toxic and emit volatile organic compounds. Biobased solvents are usually more expensive, but ideally less toxic and Biodegradation. Biogenic raw materials usable for solvent production are for example lignocellulose, starch and sucrose, but also waste and byproducts from other industries (such as Terpene, Vegetable oil and Animal fat).
In addition to mixing, the substances in a solution interact with each other at the molecular level. When something is dissolved, molecules of the solvent arrange around of the solute. Heat transfer is involved and entropy is increased making the solution more thermodynamically stable than the solute and solvent separately. This arrangement is mediated by the respective chemical properties of the solvent and solute, such as hydrogen bonding, dipole moment and polarizability.Lowery and Richardson, pp. 181–183 Solvation does not cause a chemical reaction or chemical configuration changes in the solute. However, solvation resembles a coordination complex formation reaction, often with considerable energetics (heat of solvation and entropy of solvation) and is thus far from a neutral process.
When one substance dissolves into another, a solution is formed. A solution is a homogeneous mixture consisting of a solute dissolved into a solvent. The solute is the substance that is being dissolved, while the solvent is the dissolving medium. Solutions can be formed with many different types and forms of solutes and solvents.
Generally, the dielectric constant of the solvent provides a rough measure of a solvent's polarity. The strong polarity of water is indicated by its high dielectric constant of 88 (at 0 °C). Solvents with a dielectric constant of less than 15 are generally considered to be nonpolar.Lowery and Richardson, p. 177.
The dielectric constant measures the solvent's tendency to partly cancel the field strength of the electric field of a ion immersed in it. This reduction is then compared to the field strength of the charged particle in a vacuum. Heuristically, the dielectric constant of a solvent can be thought of as its ability to reduce the solute's effective internal charge. Generally, the dielectric constant of a solvent is an acceptable predictor of the solvent's ability to dissolve common , such as salts.
The Grunwald–Winstein m Y scale measures polarity in terms of solvent influence on buildup of positive charge of a solute during a chemical reaction.
Edward Kosower's Z scale measures polarity in terms of the influence of the solvent on Ultraviolet-absorption maxima of a salt, usually pyridinium iodide or the pyridinium zwitterion.Kosower, E.M. (1969) "An introduction to Physical Organic Chemistry" Wiley: New York, p. 293
Donor number and donor acceptor scale measures polarity in terms of how a solvent interacts with specific substances, like a strong Lewis acid or a strong Lewis base.
The Hildebrand parameter is the square root of cohesive energy density. It can be used with nonpolar compounds, but cannot accommodate complex chemistry.
Reichardt's dye, a solvatochromic dye that changes color in response to polarity, gives a scale of ET(30) values. ET is the transition energy between the ground state and the lowest excited state in kcal/mol, and (30) identifies the dye. Another, roughly correlated scale ( ET(33)) can be defined with Nile red.
Gregory's solvent ϸ parameter is a quantum chemically derived charge density parameter. This parameter seems to reproduce many of the experimental solvent parameters (especially the donor and acceptor numbers) using this charge decomposition analysis approach, with an electrostatic basis. The ϸ parameter was originally developed to quantify and explain the Hofmeister series by quantifying polyatomic ions and the monatomic ions in a united manner.
The polarity, dipole moment, polarizability and hydrogen bonding of a solvent determines what type of compounds it is able to dissolve and with what other solvents or liquid compounds it is miscible. Generally, polar solvents dissolve polar compounds best and non-polar solvents dissolve non-polar compounds best; hence " like dissolves like". Strongly polar compounds like (e.g. sucrose) or ionic compounds, like inorganic salts (e.g. table salt) dissolve only in very polar solvents like water, while strongly non-polar compounds like or dissolve only in very non-polar organic solvents like hexane. Similarly, water and hexane (or vinegar and vegetable oil) are not miscible with each other and will quickly separate into two layers even after being shaken well.
Polarity can be separated to different contributions. For example, the Kamlet-Taft parameters are dipolarity/polarizability ( π*), hydrogen-bonding acidity ( α) and hydrogen-bonding basicity ( β). These can be calculated from the wavelength shifts of 3–6 different solvatochromic dyes in the solvent, usually including Reichardt's dye, nitroaniline and diethylnitroaniline. Another option, Hansen solubility parameters, separates the cohesive energy density into dispersion, polar, and hydrogen bonding contributions.
The boiling point is an important property because it determines the speed of evaporation. Small amounts of low-boiling-point solvents like diethyl ether, dichloromethane, or acetone will evaporate in seconds at room temperature, while high-boiling-point solvents like water or dimethyl sulfoxide need higher temperatures, an air flow, or the application of vacuum for fast evaporation.
Often, specific gravity is cited in place of density. Specific gravity is defined as the density of the solvent divided by the density of water at the same temperature. As such, specific gravity is a unitless value. It readily communicates whether a water-insoluble solvent will float (SG < 1.0) or sink (SG > 1.0) when mixed with water.
Both diethyl ether and carbon disulfide have exceptionally low autoignition temperatures which increase greatly the fire risk associated with these solvents. The autoignition temperature of carbon disulfide is below 100 °C (212 °F), so objects such as steam pipes, , , and recently extinguished are able to ignite its vapors.
In addition some solvents, such as methanol, can burn with a very hot flame which can be nearly invisible under some lighting conditions. This can delay or prevent the timely recognition of a dangerous fire, until flames spread to other materials.
The heteroatom (oxygen) stabilizes the formation of a free radical which is formed by the abstraction of a hydrogen atom by another free radical. The carbon-centered free radical thus formed is able to react with an oxygen molecule to form a peroxide compound. The process of peroxide formation is greatly accelerated by exposure to even low levels of light, but can proceed slowly even in dark conditions.
Unless a desiccant is used which can destroy the peroxides, they will concentrate during distillation, due to their higher boiling point. When sufficient peroxides have formed, they can form a crystalline, shock-sensitive solid precipitate at the mouth of a container or bottle. Minor mechanical disturbances, such as scraping the inside of a vessel, the dislodging of a deposit, or merely twisting the cap may provide sufficient energy for the peroxide to detonation or explode violently.
Peroxide formation is not a significant problem when fresh solvents are used up quickly; they are more of a problem in laboratories which may take years to finish a single bottle. Low-volume users should acquire only small amounts of peroxide-prone solvents, and dispose of old solvents on a regular periodic schedule.
To avoid explosive peroxide formation, ethers should be stored in an airtight container, away from light, because both light and air can encourage peroxide formation.
A number of tests can be used to detect the presence of a peroxide in an ether; one is to use a combination of iron(II) sulfate and potassium thiocyanate. The peroxide is able to oxidize the Fe2+ ion to an Fe3+ ion, which then forms a deep-red coordination complex with the thiocyanate.
Peroxides may be removed by washing with acidic iron(II) sulfate, filtering through alumina, or distillation from sodium/benzophenone. Alumina degrades the peroxides but some could remain intact in it, therefore it must be disposed of properly. The advantage of using sodium/benzophenone is that moisture and oxygen are removed as well.
Ethanol (grain alcohol) is a widely used and abused psychoactive drug. If ingested, the so-called "toxic alcohols" (other than ethanol) such as methanol, 1-propanol, and ethylene glycol metabolize into toxic aldehydes and acids, which cause potentially fatal metabolic acidosis. The commonly available alcohol solvent methanol can cause permanent blindness or death if ingested. The solvent 2-butoxyethanol, used in , can cause hypotension and metabolic acidosis.
Some solvents can damage internal organs like the liver, the , the nervous system, or the Human brain. The cumulative brain effects of long-term or repeated exposure to some solvents is called chronic solvent-induced encephalopathy (CSE).
Chronic exposure to organic solvents in the work environment can produce a range of adverse neuropsychiatric effects. For example, occupational exposure to organic solvents has been associated with higher numbers of painters suffering from alcoholism. Ethanol has a synergy effect when taken in combination with many solvents; for instance, a combination of toluene/benzene and ethanol causes greater nausea/vomiting than either substance alone.
Some organic solvents are known or suspected to be cataractogenic. A mixture of aromatic hydrocarbons, aliphatic hydrocarbons, alcohols, Ester, Ketone, and Terpene were found to greatly increase the risk of developing in the lens of the eye.
Other polarity scales
Polar protic and polar aprotic
Physical properties
Properties table of common solvents
The ACS Green Chemistry Institute maintains a tool for the selection of solvents based on a principal component analysis of solvent properties.
Pentane CH3CH2CH2CH2CH3 36.1
1.84 0.626 0.00 Hexane CH3CH2CH2CH2CH2CH3 69
1.88 0.655 0.00 Benzene
C6H680.1 2.3 0.879 0.00 Heptane H3C(CH2)5CH3 98.38 1.92 0.680 0.0 Toluene C6H5-CH3 111 2.38 0.867 0.36 1,4-Dioxane
C4H8O2101.1 2.3 1.033 0.45 Diethyl ether CH3CH2-O-CH2CH3 34.6
4.3 0.713 1.15 Tetrahydrofuran (THF)
C4H8O66 7.5 0.886 1.75 Chloroform CHCl3 61.2
4.81 1.498 1.04 Dichloromethane (DCM) CH2Cl2 39.6
9.1 1.3266 1.60 Ethyl acetate
CH3-C(=O)-O-CH2-CH377.1 6.02 0.894 1.78 Acetone
CH3-C(=O)-CH356.1 21 0.786 2.88 Dimethylformamide (DMF)
H-C(=O)N(CH3)2153 38 0.944 3.82 Acetonitrile (MeCN) CH3-C≡N 82
37.5 0.786 3.92 Dimethyl sulfoxide (DMSO)
CH3-S(=O)-CH3189 46.7 1.092 3.96 Nitromethane CH3-NO2 100–103
35.87 1.1371 3.56 Propylene carbonate C4H6O3 240
64.0 1.205 4.9
Ammonia NH3 -33.3
17 0.674
(at -33.3 °C) 1.42 Formic acid
H-C(=O)OH100.8 58 1.21 1.41 n-Butanol CH3CH2CH2CH2OH 117.7
18 0.810 1.63 Isopropyl alcohol (IPA)
CH3-CH(-OH)-CH382.6 18 0.785 1.66 n-Propanol CH3CH2CH2OH 97
20 0.803 1.68 Ethanol CH3CH2OH 78.2
24.55 0.789 1.69 Methanol CH3OH 64.7
33 0.791 1.70 Acetic acid
CH3-C(=O)OH118 6.2 1.049 1.74 Water
H-O-H100 80 1.000 1.85
Hansen solubility parameter values
If, for environmental or other reasons, a solvent or solvent blend is required to replace another of equivalent solvency, the substitution can be made on the basis of the Hansen solubility parameters of each. The values for mixtures are taken as the of the values for the neat solvents. This can be calculated by trial-and-error, a spreadsheet of values, or HSP software. A 1:1 mixture of toluene and 1,4 dioxane has δD, δP and δH values of 17.8, 1.6 and 5.5, comparable to those of chloroform at 17.8, 3.1 and 5.7 respectively. Because of the health hazards associated with toluene itself, other mixtures of solvents may be found using a full HSP dataset.
n-Pentane CH3-(CH2)3-CH3 14.5 0.0 0.0 n-Hexane CH3-(CH2)4-CH3 14.9 0.0 0.0 n-Heptane CH3-(CH2)5-CH3 15.3 0.0 0.0 Cyclohexane /-(CH2)6-\ 16.8 0.0 0.2 Benzene C6H6 18.4 0.0 2.0 Toluene C6H5-CH3 18.0 1.4 2.0 Diethyl ether C2H5-O-C2H5 14.5 2.9 4.6 Chloroform CHCl3 17.8 3.1 5.7 1,4-Dioxane /-(CH2)2O(CH2)2O-\ 17.5 1.8 9.0 Ethyl acetate CH3-C(=O)-O-C2H5 15.8 5.3 7.2 Tetrahydrofuran /-(CH2)4-O-\ 16.8 5.7 8.0 Dichloromethane CH2Cl2 17.0 7.3 7.1 Acetone CH3-C(=O)-CH3 15.5 10.4 7.0 Acetonitrile CH3-C≡N 15.3 18.0 6.1 Dimethylformamide H-C(=O)-N(CH3)2 17.4 13.7 11.3 Dimethylacetamide CH3-C(=O)-N(CH3)2 16.8 11.5 10.2 Dimethylimidazolidinone C5H10N2O 18.0 10.5 9.7 DMPU C6H12N2O 17.8 9.5 9.3 N-Methylpyrrolidone /-(CH2)3-N(CH3)-C(=O)-\ 18.0 12.3 7.2 Propylene carbonate C4H6O3 20.0 18.0 4.1 Pyridine C5H5N 19.0 8.8 5.9 Sulfolane /-(CH2)4-S(=O)2-\ 19.2 16.2 9.4 Dimethyl sulfoxide CH3-S(=O)-CH3 18.4 16.4 10.2 Acetic acid CH3-C(=O)-OH 14.5 8.0 13.5 n-Butanol CH3-(CH2)3-OH 16.0 5.7 15.8 Isopropanol (CH3)2-CH-OH 15.8 6.1 16.4 n-Propanol CH3-(CH2)2-OH 16.0 6.8 17.4 Ethanol C2H5-OH 15.8 8.8 19.4 Methanol CH3-OH 14.7 12.3 22.3 Ethylene glycol HO-(CH2)2-OH 17.0 11.0 26.0 Glycerol HO-CH2-CH(OH)-CH2-OH 17.4 12.1 29.3 Formic acid H-C(=O)-OH 14.6 10.0 14.0 Water H-O-H 15.5 16.0 42.3
Boiling point
ethylene dichloride 83.48 pyridine 115.25 methyl isobutyl ketone 116.5 methylene chloride 39.75 isooctane 99.24 carbon disulfide 46.3 carbon tetrachloride 76.75 o-xylene 144.42
Density
Pentane 0.626 Petroleum ether 0.656 Hexane 0.659 Heptane 0.684 Diethyl amine 0.707 Diethyl ether 0.713 Triethyl amine 0.728 tert-Butyl methyl ether 0.741 Cyclohexane 0.779 tert-Butyl alcohol 0.781 Isopropanol 0.785 Acetonitrile 0.786 Ethanol 0.789 Acetone 0.790 Methanol 0.791 Methyl isobutyl ketone 0.798 Isobutyl alcohol 0.802 1-Propanol 0.803 Methyl ethyl ketone 0.805 2-Butanol 0.808 Isoamyl alcohol 0.809 1-Butanol 0.810 Diethyl ketone 0.814 1-Octanol 0.826 p-Xylene 0.861 m-Xylene 0.864 Toluene 0.867 Dimethoxyethane 0.868 Benzene 0.879 Butyl acetate 0.882 1-Chlorobutane 0.886 Tetrahydrofuran 0.889 Ethyl acetate 0.895 o-Xylene 0.897 Hexamethylphosphorus triamide 0.898 2-Ethoxyethyl ether 0.909 N, N-Dimethylacetamide 0.937 Diglyme 0.943 N, N-Dimethylformamide 0.944 2-Methoxyethanol 0.965 Pyridine 0.982 Propanoic acid 0.993 Water 1.000 2-Methoxyethyl acetate 1.009 Benzonitrile 1.01 1-Methyl-2-pyrrolidinone 1.028 Hexamethylphosphoramide 1.03 1,4-Dioxane 1.033 Acetic acid 1.049 Acetic anhydride 1.08 Dimethyl sulfoxide 1.092 Chlorobenzene 1.1066 Deuterium oxide 1.107 Ethylene glycol 1.115 Diethylene glycol 1.118 Propylene carbonate 1.21 Formic acid 1.22 1,2-Dichloroethane 1.245 Glycerin 1.261 Carbon disulfide 1.263 1,2-Dichlorobenzene 1.306 Methylene chloride 1.325 Nitromethane 1.382 2,2,2-Trifluoroethanol 1.393 Chloroform 1.498 1,1,2-Trichlorotrifluoroethane 1.575 Carbon tetrachloride 1.594 Tetrachloroethylene 1.623
Multicomponent solvents
Solvents
toluene 50%, butyl acetate 18%, ethyl acetate 12%, butanol 10%, ethanol 10%. toluene 50%, ethanol 15%, butanol 10%, butyl- or amyl acetate 10%, ethyl cellosolve 8%, acetone 7% butyl- or amyl acetate 29.8%, ethyl acetate 21.2%, butanol 7.7%, toluene or benzopyrene 41.3% butyl acetate 50%, ethanol 10%, butanol 20%, toluene 20% ethyl cellosolve 30%, butanol 20%, xylene 50% ethyl cellosolve 20%, butanol 30%, xylene 50% white spirit 90%, butanol 10% butyl acetate 20%, butanol 80% toluene 62%, acetone 26%, butyl acetate 12%. xylene 85%, acetone 15%. toluene 60%, butyl acetate 30%, xylene 10%. cyclohexanone 50%, toluene 50%. solvent 50%, xylene 35%, acetone 15%. toluene 50%, ethyl cellosolve 30%, acetone 20%. toluene 34%, cyclohexanone 33%, acetone 33%. butanol 60%, ethanol 40%. xylene 90%, butyl acetate 10%. ethanol 64%, ethylcellosolve 16%, toluene 10%, butanol 10%. toluene 25%, xylene 25%, butyl acetate 18%, ethyl cellosolve 17%, butanol 15%. toluene 60%, butyl acetate 30%, xylene 10%. white spirit 70%, xylene 30%. ethanol 75%, butanol 25%. xylene 50%, acetone 20%, butanol 15%, ethanol 15%. petroleum spirits 70%, ethanol 20%, acetone 10%. petroleum spirits 50%, ethanol 20%, acetone 20%, ethyl cellosolve 10%. petroleum spirits 50%, acetone 30%, ethanol 20%. absolute alcohol (99.8%) 95%, ethyl acetate 5%
Thinners
butanol 50%, xylene 50% butanol 95%, xylene 5% xylene 90%, butanol 10% ethanol 65%, butyl acetate 30%, ethyl acetate 5%. cyclohexanone 50%, ethanol 50%. xylene 60%, butyl acetate 20%, ethyl cellosolve 20%. toluene 50%, butyl acetate (or amyl acetate) 18%, butanol 10%, ethanol 10%, ethyl acetate 9%, acetone 3%.
Safety
Fire
Explosive peroxide formation
Health effects
Acute exposure
Chronic exposure
Environmental contamination
See also
Bibliography
External links
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