Solvent

A solvent (from the Latin solvō, "loosen, untie, solve") is a substance that dissolves a solute (a chemically distinct liquid, solid or gas), resulting in a solution. A solvent is usually a liquid but can also be a solid, a gas, or a supercritical fluid. The quantity of solute that can dissolve in a specific volume of solvent varies with temperature. Common uses for organic solvents are in dry cleaning (e.g. tetrachloroethylene), as paint thinners (e.g. toluene, turpentine), as nail polish removers and glue solvents (acetone, methyl acetate, ethyl acetate), in spot removers (e.g. hexane, petrol ether), in detergents (citrus terpenes) and in perfumes (ethanol). 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 a cell. Solvents find various applications in chemical, pharmaceutical, oil, and gas industries, including in chemical syntheses and purification processes.

Acetic acid
A bottle of acetic acid, a liquid solvent

Solutions and solvation

When one substance is dissolved into another, a solution is formed.[1] This is opposed to the situation when the compounds are insoluble like sand in water. In a solution, all of the ingredients are uniformly distributed at a molecular level and no residue remains. A solvent-solute mixture consists of a single phase with all solute molecules occurring as solvates (solvent-solute complexes), as opposed to separate continuous phases as in suspensions, emulsions and other types of non-solution mixtures. The ability of one compound to be dissolved in another is known as solubility; if this occurs in all proportions, it is called miscible.

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 molecules 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.[2] 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.

Solvent classifications

Solvents can be broadly classified into two categories: polar and non-polar. A special case is mercury, whose solutions are known as amalgams; also, other metal solutions exist which are liquid at room temperature. 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).[3] Solvents with a dielectric constant of less than 15 are generally considered to be nonpolar.[4] The dielectric constant measures the solvent's tendency to partly cancel the field strength of the electric field of a charged particle immersed in it. This reduction is then compared to the field strength of the charged particle in a vacuum.[4] 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 ionic compounds, such as salts.

Other polarity scales

Dielectric constants are not the only measure of polarity. Because solvents are used by chemists to carry out chemical reactions or observe chemical and biological phenomena, more specific measures of polarity are required. Most of these measures are sensitive to chemical structure.

The Grunwald–Winstein mY scale measures polarity in terms of solvent influence on buildup of positive charge of a solute during a chemical reaction.

Kosower's Z scale measures polarity in terms of the influence of the solvent on UV-absorption maxima of a salt, usually pyridinium iodide or the pyridinium zwitterion.[5]

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.[6]

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.

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: "like dissolves like". Strongly polar compounds like sugars (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 oils or waxes 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's parameters, separate the cohesive energy density into dispersion, polar and hydrogen bonding contributions.

Polar protic and polar aprotic

Solvents with a dielectric constant (more accurately, relative static permittivity) greater than 15 (i.e. polar or polarizable) can be further divided into protic and aprotic. Protic solvents solvate anions (negatively charged solutes) strongly via hydrogen bonding. Water is a protic solvent. Aprotic solvents such as acetone or dichloromethane tend to have large dipole moments (separation of partial positive and partial negative charges within the same molecule) and solvate positively charged species via their negative dipole.[7] In chemical reactions the use of polar protic solvents favors the SN1 reaction mechanism, while polar aprotic solvents favor the SN2 reaction mechanism. These polar solvents are capable of forming hydrogen bonds with water to dissolve in water whereas non polar solvents are not capable of strong hydrogen bonds.

Multicomponent

Solvents

Name Composition
Solvent 645 toluene 50%, butyl acetate 18%, ethyl acetate 12%, butanol 10%, ethanol 10%.
Solvent 646 toluene 50%, ethanol 15%, butanol 10%, butyl- or amyl acetate 10%, ethyl cellosolve 8%, acetone 7%[8]
Solvent 647 butyl- or amyl acetate 29.8%, ethyl acetate 21.2%, butanol 7.7%, toluene or pyrobenzene 41.3%[9]
Solvent 648 butyl acetate 50%, ethanol 10%, butanol 20%, toluene 20%[10]
Solvent 649 ethyl cellosolve 30%, butanol 20%, xylene 50%
Solvent 650 ethyl cellosolve 20%, butanol 30%, xylene 50%[11]
Solvent 651 white spirit 90%, butanol 10%
Solvent KR-36 butyl acetate 20%, butanol 80%
Solvent P-4 toluene 62%, acetone 26%, butyl acetate 12%.
Solvent P-10 xylene 85%, acetone 15%.
Solvent P-12 toluene 60%, butyl acetate 30%, xylene 10%.
Solvent P-14 cyclohexanone 50%, toluene 50%.
Solvent P-24 solvent 50%, xylene 35%, acetone 15%.
Solvent P-40 toluene 50%, ethyl cellosolve 30%, acetone 20%.
Solvent P-219 toluene 34%, cyclohexanone 33%, acetone 33%.
Solvent P-3160 butanol 60%, ethanol 40%.
Solvent RCC xylene 90%, butyl acetate 10%.
Solvent RML ethanol 64%, ethylcellosolve 16%, toluene 10%, butanol 10%.
Solvent PML-315 toluene 25%, xylene 25%, butyl acetate 18%, ethyl cellosolve 17%, butanol 15%.
Solvent PC-1 toluene 60%, butyl acetate 30%, xylene 10%.
Solvent PC-2 white spirit 70%, xylene 30%.
Solvent RFG ethanol 75%, butanol 25%.
Solvent RE-1 xylene 50%, acetone 20%, butanol 15%, ethanol 15%.
Solvent RE-2 Solvent 70%, ethanol 20%, acetone 10%.
Solvent RE-3 solvent 50%, ethanol 20%, acetone 20%, ethyl cellosolve 10%.
Solvent RE-4 solvent 50%, acetone 30%, ethanol 20%.
Solvent FK-1 (?) absolute alcohol (99.8%) 95%, ethyl acetate 5%

Thinners

Name Composition
Thinner RKB-1 butanol 50%, xylene 50%
Thinner RKB-2 butanol 95%, xylene 5%
Thinner RKB-3 xylene 90%, butanol 10%
Thinner M ethanol 65%, butyl acetate 30%, ethyl acetate 5%.
Thinner P-7 cyclohexanone 50%, ethanol 50%.
Thinner R-197 xylene 60%, butyl acetate 20%, ethyl cellosolve 20%.
Thinner of WFD toluene 50%, butyl acetate (or amyl acetate) 18%, butanol 10%, ethanol 10%, ethyl acetate 9%, acetone 3%.

Physical properties

Properties table of common solvents

The solvents are grouped into nonpolar, polar aprotic, and polar protic solvents, with each group ordered by increasing polarity. The properties of solvents which exceed those of water are bolded.

Solvent Chemical formula Boiling point[12]
(°C)
Dielectric constant[13] Density
(g/mL)
Dipole moment
(D)

Nonpolar solvents

Pentane CH3CH2CH2CH2CH3 36 1.84 0.626 0.00
Cyclopentane Cyclopentane 200
C5H10
40 1.97 0.751 0.00
Hexane CH3CH2CH2CH2CH2CH3 69 1.88 0.655 0.00
Cyclohexane Cyclohexane-2D-skeletal
C6H12
81 2.02 0.779 0.00
Benzene Benzene 200
C6H6
80 2.3 0.879 0.00
Toluene C6H5-CH3 111 2.38 0.867 0.36
1,4-Dioxane 1-4-Dioxane
C4H8O2
101 2.3 1.033 0.45
Chloroform CHCl3 61 4.81 1.498 1.04
Diethyl ether CH3CH2-O-CH2CH3 35 4.3 0.713 1.15
Dichloromethane (DCM) CH2Cl2 40 9.1 1.3266 1.60

Polar aprotic solvents

Tetrahydrofuran (THF) Tetrahydrofuran
C4H8O
66 7.5 0.886 1.75
Ethyl acetate Essigsäureethylester
CH3-C(=O)-O-CH2-CH3
77 6.02 0.894 1.78
Acetone Acetone-2D-skeletal
CH3-C(=O)-CH3
56 21 0.786 2.88
Dimethylformamide (DMF) Dimethylformamide
H-C(=O)N(CH3)2
153 38 0.944 3.82
Acetonitrile (MeCN) CH3-C≡N 82 37.5 0.786 3.92
Dimethyl sulfoxide (DMSO) Dimethylsulfoxid
CH3-S(=O)-CH3
189 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

Polar protic solvents

Formic acid Formic acid
H-C(=O)OH
101 58 1.21 1.41
n-Butanol CH3CH2CH2CH2OH 118 18 0.810 1.63
Isopropyl alcohol (IPA) 2-Propanol2
CH3-CH(-OH)-CH3
82 18 0.785 1.66
n-Propanol CH3CH2CH2OH 97 20 0.803 1.68
Ethanol CH3CH2OH 79 24.55 0.789 1.69
Methanol CH3OH 65 33 0.791 1.70
Acetic acid Essigsäure - Acetic acid
CH3-C(=O)OH
118 6.2 1.049 1.74
Water Wasser Strukturformel V1
H-O-H
100 80 1.000 1.85

Hansen solubility parameter values

The Hansen solubility parameter values[14][15] are based on dispersion bonds (δD), polar bonds (δP) and hydrogen bonds (δH). These contain information about the inter-molecular interactions with other solvents and also with polymers, pigments, nanoparticles, etc. This allows for rational formulations knowing, for example, that there is a good HSP match between a solvent and a polymer. Rational substitutions can also be made for "good" solvents (effective at dissolving the solute) that are "bad" (expensive or hazardous to health or the environment). The following table shows that the intuitions from "non-polar", "polar aprotic" and "polar protic" are put numerically – the "polar" molecules have higher levels of δP and the protic solvents have higher levels of δH. Because numerical values are used, comparisons can be made rationally by comparing numbers. For example, acetonitrile is much more polar than acetone but exhibits slightly less hydrogen bonding.

Solvent Chemical formula δD Dispersion δP Polar δH Hydrogen bonding

Non-polar solvents

n-Hexane CH3CH2CH2CH2CH2CH3 14.9 0.0 0.0
Benzene C6H6 18.4 0.0 2.0
Toluene C6H5-CH3 18.0 1.4 2.0
Diethyl ether CH3CH2-O-CH2CH3 14.5 2.9 4.6
Chloroform CHCl3 17.8 3.1 5.7
1,4-Dioxane /-CH2-CH2-O-CH2-CH2-O-\ 17.5 1.8 9.0

Polar aprotic solvents

Ethyl acetate CH3-C(=O)-O-CH2-CH3 15.8 5.3 7.2
Tetrahydrofuran (THF) /-CH2-CH2-O-CH2-CH2-\ 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 (MeCN) CH3-C≡N 15.3 18.0 6.1
Dimethylformamide (DMF) H-C(=O)N(CH3)2 17.4 13.7 11.3
Dimethyl sulfoxide (DMSO) CH3-S(=O)-CH3 18.4 16.4 10.2

Polar protic solvents

Acetic acid CH3-C(=O)OH 14.5 8.0 13.5
n-Butanol CH3CH2CH2CH2OH 16.0 5.7 15.8
Isopropanol CH3-CH(-OH)-CH3 15.8 6.1 16.4
n-Propanol CH3CH2CH2OH 16.0 6.8 17.4
Ethanol CH3CH2OH 15.8 8.8 19.4
Methanol CH3OH 14.7 12.3 22.3
Formic acid H-C(=O)OH 14.6 10.0 14.0
Water H-O-H 15.5 16.0 42.3

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 weighted averages of the values for the neat solvents. This can be calculated by trial-and-error, a spreadsheet of values, or HSP software.[14][15] 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.

Boiling point

Solvent Boiling point (°C)[12]
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

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.

  • Low boilers: boiling point below 100 °C (boiling point of water)
  • Medium boilers: between 100 °C and 150 °C
  • High boilers: above 150 °C

Density

Most organic solvents have a lower density than water, which means they are lighter than and will form a layer on top of water. Important exceptions are most of the halogenated solvents like dichloromethane or chloroform will sink to the bottom of a container, leaving water as the top layer. This is crucial to remember when partitioning compounds between solvents and water in a separatory funnel during chemical syntheses.

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.

Safety

Fire

Most organic solvents are flammable or highly flammable, depending on their volatility. Exceptions are some chlorinated solvents like dichloromethane and chloroform. Mixtures of solvent vapors and air can explode. Solvent vapors are heavier than air; they will sink to the bottom and can travel large distances nearly undiluted. Solvent vapors can also be found in supposedly empty drums and cans, posing a flash fire hazard; hence empty containers of volatile solvents should be stored open and upside down.

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, light bulbs, hotplates, and recently extinguished bunsen burners are able to ignite its vapours.

In addition some solvents, such as methanol, can burn with a very hot flame which can be nearly invisible under some lighting conditions.[17][18] This can delay or prevent the timely recognition of a dangerous fire, until flames spread to other materials.

Explosive peroxide formation

Ethers like diethyl ether and tetrahydrofuran (THF) can form highly explosive organic peroxides upon exposure to oxygen and light. THF is normally more likely to form such peroxides than diethyl ether. One of the most susceptible solvents is diisopropyl ether, but all ethers are considered to be potential peroxide sources.

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-centred 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 or the dislodging of a deposit, merely twisting the cap may provide sufficient energy for the peroxide to explode or detonate. 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 aritight container, away from light, because both light and air can encourage peroxide formation.[19]

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 distilling from sodium/benzophenone. Alumina does not destroy the peroxides but merely traps them, and must be disposed of properly. The advantage of using sodium/benzophenone is that moisture and oxygen are removed as well.

Health effects

General health hazards associated with solvent exposure include toxicity to the nervous system, reproductive damage, liver and kidney damage, respiratory impairment, cancer, and dermatitis.[20]

Acute exposure

Many solvents can lead to a sudden loss of consciousness if inhaled in large amounts. Solvents like diethyl ether and chloroform have been used in medicine as anesthetics, sedatives, and hypnotics for a long time. Ethanol (grain alcohol) is a widely used and abused psychoactive drug. Diethyl ether, chloroform, and many other solvents e.g. from gasoline or glues are abused recreationally in glue sniffing, often with harmful long term health effects like neurotoxicity or cancer. Fraudulent substitution of 1,5-pentanediol by the psychoactive 1,4-butanediol by a subcontractor caused the Bindeez product recall.[21] If ingested, the so-called toxic alcohols (other than ethanol) such as methanol, propanol, and ethylene glycol metabolize into toxic aldehydes and acids, which cause potentially fatal metabolic acidosis.[22] The commonly available alcohol solvent methanol can cause permanent blindness or death if ingested. The solvent 2-butoxyethanol, used in fracking fluids, can cause hypotension and metabolic acidosis.[23]

Chronic exposure

Some solvents including chloroform and benzene a common ingredient in gasoline are known to be carcinogenic, while many others are considered by the World Health Organization to be likely carcinogens. Solvents can damage internal organs like the liver, the kidneys, the nervous system, or the brain. The cumulative effects of long-term or repeated exposure to solvents are 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.[24] Ethanol has a synergistic 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.

Many solvents are known or suspected to be cataractogenic, greatly increasing the risk of developing cataracts in the lens of the eye.[25] Solvent exposure has also been associated with neurotoxic damage causing hearing loss[26][27] and color vision losses.[28]

Environmental contamination

A major pathway to induce health effects arises from spills or leaks of solvents that reach the underlying soil. Since solvents readily migrate substantial distances, the creation of widespread soil contamination is not uncommon; this is particularly a health risk if aquifers are affected. Vapor intrusion can occur from sites with extensive subsurface solvent contamination.[29]

See also

References

  1. ^ Tinoco I, Sauer K, Wang JC (2002). Physical Chemistry. Prentice Hall. p. 134. ISBN 978-0-13-026607-1.
  2. ^ Lowery and Richardson, pp. 181–183
  3. ^ Malmberg CG, Maryott AA (January 1956). "Dielectric Constant of Water from 0° to 100°C". Journal of Research of the National Bureau of Standards. 56 (1): 1. doi:10.6028/jres.056.001.
  4. ^ a b Lowery and Richardson, p. 177.
  5. ^ Kosower, E.M. (1969) "An introduction to Physical Organic Chemistry" Wiley: New York, p. 293
  6. ^ Gutmann V (1976). "Solvent effects on the reactivities of organometallic compounds". Coord. Chem. Rev. 18 (2): 225. doi:10.1016/S0010-8545(00)82045-7.
  7. ^ Lowery and Richardson, p. 183.
  8. ^ dcpt.ru Solvent 646 Characteristics (ru)
  9. ^ dcpt.ru Solvent 647 Characteristics (ru)
  10. ^ dcpt.ru Solvent 648 Characteristics (ru)
  11. ^ dcpt.ru Solvent 650 Characteristics (ru)
  12. ^ a b Solvent Properties – Boiling Point Archived 14 June 2011 at the Wayback Machine. Xydatasource.com. Retrieved on 2013-01-26.
  13. ^ Dielectric Constant Archived 4 July 2010 at the Wayback Machine. Macro.lsu.edu. Retrieved on 2013-01-26.
  14. ^ a b Abbott S, Hansen CM (2008). Hansen solubility parameters in practice. Hansen-Solubility. ISBN 978-0-9551220-2-6.
  15. ^ a b Hansen CM (January 2002). Hansen solubility parameters: a user's handbook. CRC press. ISBN 978-0-8493-7248-3.
  16. ^ Selected solvent properties – Specific Gravity Archived 14 June 2011 at the Wayback Machine. Xydatasource.com. Retrieved on 2013-01-26.
  17. ^ Fanick ER, Smith LR, Baines TM (1 October 1984). "Safety Related Additives for Methanol Fuel". SAE Technical Paper Series. 1. Warrendale, PA. doi:10.4271/841378. Archived from the original on 12 August 2017.
  18. ^ Anderson JE, Magyarl MW, Siegl WO (1985-07-01). "Concerning the Luminosity of Methanol-Hydrocarbon Diffusion Flames". Combustion Science and Technology. 43 (3–4): 115–125. doi:10.1080/00102208508947000. ISSN 0010-2202.
  19. ^ "Peroxides and Ethers | Environmental Health, Safety and Risk Management". www.uaf.edu. Retrieved 2018-01-25.
  20. ^ U.S. Department of Labor > Occupational Safety & Health Administration > Solvents Archived 15 March 2016 at the Wayback Machine. osha.gov
  21. ^ "Recall ordered for toy that turns into drug - National - theage.com.au". www.theage.com.au. 7 November 2007. Retrieved 2018-07-01.
  22. ^ Kraut JA, Mullins ME (January 2018). "Toxic Alcohols". The New England Journal of Medicine. 378 (3): 270–280. doi:10.1056/NEJMra1615295. PMID 29342392.
  23. ^ Hung T, Dewitt CR, Martz W, Schreiber W, Holmes DT (July 2010). "Fomepizole fails to prevent progression of acidosis in 2-butoxyethanol and ethanol coingestion". Clinical Toxicology. 48 (6): 569–71. doi:10.3109/15563650.2010.492350. PMID 20560787.
  24. ^ Lundberg I, Gustavsson A, Högberg M, Nise G (June 1992). "Diagnoses of alcohol abuse and other neuropsychiatric disorders among house painters compared with house carpenters". British Journal of Industrial Medicine. 49 (6): 409–15. doi:10.1136/oem.49.6.409. PMC 1012122. PMID 1606027.
  25. ^ Raitta C, Husman K, Tossavainen A (August 1976). "Lens changes in car painters exposed to a mixture of organic solvents". Albrecht von Graefes Archiv Fur Klinische und Experimentelle Ophthalmologie. Albrecht von Graefe's Archive for Clinical and Experimental Ophthalmology. 200 (2): 149–56. doi:10.1007/bf00414364. PMID 1086605.
  26. ^ Campo P, Morata TC, Hong O (April 2013). "Chemical exposure and hearing loss". Disease-A-Month. 59 (4): 119–38. doi:10.1016/j.disamonth.2013.01.003. PMC 4693596. PMID 23507352.
  27. ^ Johnson AC, Morata TC (2010). "Occupational exposure to chemicals and hearing impairment. The Nordic Expert Group for Criteria Documentation of Health Risks from Chemicals" (PDF). Arbete och Hälsa. 44: 177. Archived (PDF) from the original on 4 June 2016.
  28. ^ Mergler D, Blain L, Lagacé JP (1987). "Solvent related colour vision loss: an indicator of neural damage?". International Archives of Occupational and Environmental Health. 59 (4): 313–21. doi:10.1007/bf00405275. PMID 3497110.
  29. ^ Forand SP, Lewis-Michl EL, Gomez MI (April 2012). "Adverse birth outcomes and maternal exposure to trichloroethylene and tetrachloroethylene through soil vapor intrusion in New York State". Environmental Health Perspectives. 120 (4): 616–21. doi:10.1289/ehp.1103884. PMC 3339451. PMID 22142966.

Bibliography

External links

Aqueous solution

An aqueous solution is a solution in which the solvent is water. It is mostly shown in chemical equations by appending (aq) to the relevant chemical formula. For example, a solution of table salt, or sodium chloride (NaCl), in water would be represented as Na+(aq) + Cl−(aq). The word aqueous (comes from aqua) means pertaining to, related to, similar to, or dissolved in, water. As water is an excellent solvent and is also naturally abundant, it is a ubiquitous solvent in chemistry. Aqueous solution is water with a pH of 7.0 where the hydrogen ions (H+) and hydroxide ions (OH-) are in Arrhenius balance (10-7).

A non-aqueous solution is a solution in which the solvent is a liquid, but is not water.Substances that are hydrophobic ('water-fearing') often do not dissolve well in water, whereas those that are hydrophilic ('water-friendly') do. An example of a hydrophilic substance is sodium chloride. Acids and bases are aqueous solutions, as part of their Arrhenius definitions.

The ability of a substance to dissolve in water is determined by whether the substance can match or exceed the strong attractive forces that water molecules generate between themselves. If the substance lacks the ability to dissolve in water the molecules form a precipitate.

Reactions in aqueous solutions are usually metathesis reactions. Metathesis reactions are another term for double-displacement; that is, when a cation displaces to form an ionic bond with the other anion. The cation bonded with the latter anion will dissociate and bond with the other anion.

Aqueous solutions that conduct electric current efficiently contain strong electrolytes, while ones that conduct poorly are considered to have weak electrolytes. Those strong electrolytes are substances that are completely ionized in water, whereas the weak electrolytes exhibit only a small degree of ionization in water.

Nonelectrolytes are substances that dissolve in water yet maintain their molecular integrity (do not dissociate into ions). Examples include sugar, urea, glycerol, and methylsulfonylmethane (MSM).

When writing the equations of aqueous reactions, it is essential to determine the precipitate. To determine the precipitate, one must consult a chart of solubility. Soluble compounds are aqueous, while insoluble compounds are the precipitate. There may not always be a precipitate.

When performing calculations regarding the reacting of one or more aqueous solutions, in general one must know the concentration, or molarity, of the aqueous solutions. Solution concentration is given in terms of the form of the solute prior to it dissolving.

Aqueous solutions may contain, especially in alcaline zone or subjected to radiolysis, hydrated atomic hydrogen an hydrated electron.

Diethyl ether

Diethyl ether, or simply ether, is an organic compound in the ether class with the formula (C2H5)2O, sometimes abbreviated as Et2O (see Pseudoelement symbols). It is a colorless, highly volatile flammable liquid. It is commonly used as a solvent in laboratories and as a starting fluid for some engines. It was formerly used as a general anesthetic, until non-flammable drugs were developed, such as halothane. It has been used as a recreational drug to cause intoxication.

Dry cleaning

Dry cleaning is any cleaning process for clothing and textiles using a chemical solvent other than water. The modern dry cleaning process was developed and patented by Thomas L. Jennings. Despite its name, dry cleaning is not a "dry" process; clothes are soaked in a liquid solvent. Tetrachloroethylene (perchloroethylene), which the industry calls "perc", is the most widely used solvent. Alternative solvents are trichloroethane and petroleum spirits.

Liquid–liquid extraction

Liquid–liquid extraction (LLE), also known as solvent extraction and partitioning, is a method to separate compounds or metal complexes, based on their relative solubilities in two different immiscible liquids, usually water (polar) and an organic solvent (non-polar). There is a net transfer of one or more species from one liquid into another liquid phase, generally from aqueous to organic. The transfer is driven by chemical potential, i.e. once the transfer is complete, the overall system of protons and electrons that make up the solutes and the solvents are in a more stable configuration (lower free energy). The solvent that is enriched in solute(s) is called extract. The feed solution that is depleted in solute(s) is called the raffinate. LLE is a basic technique in chemical laboratories, where it is performed using a variety of apparatus, from separatory funnels to countercurrent distribution equipment called as mixer settlers. This type of process is commonly performed after a chemical reaction as part of the work-up, often including an acidic work-up.

The term partitioning is commonly used to refer to the underlying chemical and physical processes involved in liquid–liquid extraction, but on another reading may be fully synonymous with it. The term solvent extraction can also refer to the separation of a substance from a mixture by preferentially dissolving that substance in a suitable solvent. In that case, a soluble compound is separated from an insoluble compound or a complex matrix.From a hydrometallurgical perspective, solvent extraction is exclusively used in separation and purification of uranium and plutonium, zirconium and hafnium, separation of cobalt and nickel, separation and purification of rare earth elements etc., its greatest advantage being its ability to selectively separate out even very similar metals. One obtains high-purity single metal streams on 'stripping' out the metal value from the 'loaded' organic wherein one can precipitate or deposit the metal value. Stripping is the opposite of extraction: Transfer of mass from organic to aqueous phase.

LLE is also widely used in the production of fine organic compounds, the processing of perfumes, the production of vegetable oils and biodiesel, and other industries. It is among the most common initial separation techniques, though some difficulties result in extracting out closely related functional groups.

Liquid–liquid extraction is possible in non-aqueous systems: In a system consisting of a molten metal in contact with molten salts, metals can be extracted from one phase to the other. This is related to a mercury electrode where a metal can be reduced, the metal will often then dissolve in the mercury to form an amalgam that modifies its electrochemistry greatly. For example, it is possible for sodium cations to be reduced at a mercury cathode to form sodium amalgam, while at an inert electrode (such as platinum) the sodium cations are not reduced. Instead, water is reduced to hydrogen. A detergent or fine solid can be used to stabilize an emulsion, or third phase.

Organochloride

An organochloride, organochlorine compound, chlorocarbon, or chlorinated hydrocarbon is an organic compound containing at least one covalently bonded atom of chlorine that has an effect on the chemical behavior of the molecule. The chloroalkane class (alkanes with one or more hydrogens substituted by chlorine) provides common examples. The wide structural variety and divergent chemical properties of organochlorides lead to a broad range of names and applications. Organochlorides are very useful compounds in many applications, but some are of profound environmental concern.

Osmosis

Osmosis () is the spontaneous net movement of solvent molecules through a selectively permeable membrane into a region of higher solute concentration, in the direction that tends to equalize the solute concentrations on the two sides. It may also be used to describe a physical process in which any solvent moves across a selectively permeable membrane (permeable to the solvent, but not the solute) separating two solutions of different concentrations. Osmosis can be made to do work. Osmotic pressure is defined as the external pressure required to be applied so that there is no net movement of solvent across the membrane. Osmotic pressure is a colligative property, meaning that the osmotic pressure depends on the molar concentration of the solute but not on its identity.

Osmosis is a vital process in biological systems, as biological membranes are semipermeable. In general, these membranes are impermeable to large and polar molecules, such as ions, proteins, and polysaccharides, while being permeable to non-polar or hydrophobic molecules like lipids as well as to small molecules like oxygen, carbon dioxide, nitrogen, and nitric oxide. Permeability depends on solubility, charge, or chemistry, as well as solute size. Water molecules travel through the plasma membrane, tonoplast membrane (vacuole) or protoplast by diffusing across the phospholipid bilayer via aquaporins (small transmembrane proteins similar to those responsible for facilitated diffusion and ion channels). Osmosis provides the primary means by which water is transported into and out of cells. The turgor pressure of a cell is largely maintained by osmosis across the cell membrane between the cell interior and its relatively hypotonic environment.

Osmotic pressure

Osmotic pressure is the minimum pressure which needs to be applied to a solution to prevent the inward flow of its pure solvent across a semipermeable membrane.

It is also defined as the measure of the tendency of a solution to take in pure solvent by osmosis. Potential osmotic pressure is the maximum osmotic pressure that could develop in a solution if it were separated from its pure solvent by a semipermeable membrane.

Osmosis occurs when two solutions, containing different concentration of solute, are separated by a selectively permeable membrane. Solvent molecules pass preferentially through the membrane from the low-concentration solution to the solution with higher solute concentration. The transfer of solvent molecules will continue until equilibrium is attained.

Paint

Paint is any pigmented liquid, liquefiable, or mastic composition that, after application to a substrate in a thin layer, converts to a solid film. It is most commonly used to protect, color, or provide texture to objects. Paint can be made or purchased in many colors—and in many different types, such as watercolor, synthetic, etc. Paint is typically stored, sold, and applied as a liquid, but most types dry into a solid.

Paper chromatography

Paper chromatography is an analytical method used to separate colored chemicals or substances. It is primarily used as a teaching tool, having been replaced by other chromatography methods, such as thin-layer chromatography. A paper chromatography variant, two-dimensional chromatography involves using two solvents and rotating the paper 90° in between. This is useful for separating complex mixtures of compounds having similar polarity, for example, amino acids. The setup has three components. The mobile phase is a solution that travels up the stationary phase, due to capillary action. The mobile phase is generally mixture of polar organic solvent with water, while the stationary phase is water. Paper is used to support stationary phase (water). Difference between TLC and paper chromatography is that stationary phase in TLC is a layer of adsorbent (usually silica gel, or aluminium oxide), and stationary phase in paper chromatography is water.

Protic solvent

In chemistry, a protic solvent is a solvent that has a hydrogen atom bound to an oxygen (as in a hydroxyl group), a nitrogen (as in an amine group) or a fluorine (as in hydrogen fluoride). In general terms, any solvent that contains a labile H+ is called a protic solvent. The molecules of such solvents readily donate protons (H+) to reagents. Conversely, aprotic solvents cannot donate hydrogen.

Recrystallization (chemistry)

In chemistry, recrystallization is a technique used to purify chemicals. By dissolving both impurities and a compound in an appropriate solvent, either the desired compound or impurities can be removed from the solution, leaving the other behind. It is named for the crystals often formed when the compound precipitates out. Alternatively, recrystallization can refer to the natural growth of larger ice crystals at the expense of smaller ones.

Reverse osmosis

Reverse osmosis (RO) is a water purification technology that uses a partially permeable membrane to remove ions, molecules and larger particles from drinking water. In reverse osmosis, an applied pressure is used to overcome osmotic pressure, a colligative property, that is driven by chemical potential differences of the solvent, a thermodynamic parameter. Reverse osmosis can remove many types of dissolved and suspended chemical species as well as biological ones (principally bacteria) from water, and is used in both industrial processes and the production of potable water. The result is that the solute is retained on the pressurized side of the membrane and the pure solvent is allowed to pass to the other side. To be "selective", this membrane should not allow large molecules or ions through the pores (holes), but should allow smaller components of the solution (such as solvent molecules, i.e., water, H2O) to pass freely.In the normal osmosis process, the solvent naturally moves from an area of low solute concentration (high water potential), through a membrane, to an area of high solute concentration (low water potential). The driving force for the movement of the solvent is the reduction in the free energy of the system when the difference in solvent concentration on either side of a membrane is reduced, generating osmotic pressure due to the solvent moving into the more concentrated solution. Applying an external pressure to reverse the natural flow of pure solvent, thus, is reverse osmosis. The process is similar to other membrane technology applications.

Reverse osmosis differs from filtration in that the mechanism of fluid flow is by osmosis across a membrane. The predominant removal mechanism in membrane filtration is straining, or size exclusion, where the pores are 0.01 micrometers or larger, so the process can theoretically achieve perfect efficiency regardless of parameters such as the solution's pressure and concentration. Reverse osmosis instead involves solvent diffusion across a membrane that is either nonporous or uses nanofiltration with pores 0.001 micrometers in size. The predominant removal mechanism is from differences in solubility or diffusivity, and the process is dependent on pressure, solute concentration, and other conditions. Reverse osmosis is most commonly known for its use in drinking water purification from seawater, removing the salt and other effluent materials from the water molecules.

Solubility

Solubility is the property of a solid, liquid or gaseous chemical substance called solute to dissolve in a solid, liquid or gaseous solvent. The solubility of a substance fundamentally depends on the physical and chemical properties of the solute and solvent as well as on temperature, pressure and presence of other chemicals (including changes to the pH) of the solution. The extent of the solubility of a substance in a specific solvent is measured as the saturation concentration, where adding more solute does not increase the concentration of the solution and begins to precipitate the excess amount of solute.

Insolubility is the inability to dissolve in a solid, liquid or gaseous solvent.

Most often, the solvent is a liquid, which can be a pure substance or a mixture. One may also speak of solid solution, but rarely of solution in a gas (see vapor–liquid equilibrium instead).

Under certain conditions, the equilibrium solubility can be exceeded to give a so-called supersaturated solution, which is metastable. Metastability of crystals can also lead to apparent differences in the amount of a chemical that dissolves depending on its crystalline form or particle size. A supersaturated solution generally crystallises when 'seed' crystals are introduced and rapid equilibration occurs. Phenylsalicylate is one such simple observable substance when fully melted and then cooled below its fusion point.

Solubility is not to be confused with the ability to 'dissolve' a substance, because the solution might also occur because of a chemical reaction. For example, zinc 'dissolves' (with effervescence) in hydrochloric acid as a result of a chemical reaction releasing hydrogen gas in a displacement reaction. The zinc ions are soluble in the acid.

The solubility of a substance is an entirely different property from the rate of solution, which is how fast it dissolves. The smaller a particle is, the faster it dissolves although there are many factors to add to this generalization.

Crucially solubility applies to all areas of chemistry, geochemistry, inorganic, physical, organic and biochemistry. In all cases it will depend on the physical conditions (temperature, pressure and concentration) and the enthalpy and entropy directly relating to the solvents and solutes concerned.

By far the most common solvent in chemistry is water which is a solvent for most ionic compounds as well as a wide range of organic substances. This is a crucial factor in acidity/alkalinity and much environmental and geochemical work.

Solution

In chemistry, a solution is a special type of homogeneous mixture composed of two or more substances. In such a mixture, a solute is a substance dissolved in another substance, known as a solvent. The mixing process of a solution happens at a scale where the effects of chemical polarity are involved, resulting in interactions that are specific to solvation. The solution assumes the phase of the solvent when the solvent is the larger fraction of the mixture, as is commonly the case. The concentration of a solute in a solution is the mass of that solute expressed as a percentage of the mass of the whole solution. The term aqueous solution is when one of the solvents is water.

Solvation

Solvation describes the interaction of solvent with dissolved molecules. Ionized and uncharged molecules interact strongly with solvent, and the strength and nature of this interaction influence many properties of the solute, including solubility, reactivity, and color, as well as influencing the properties of the solvent such as the viscosity and density. In the process of solvation, ions are surrounded by a concentric shell of solvent. Solvation is the process of reorganizing solvent and solute molecules into solvation complexes. Solvation involves bond formation, hydrogen bonding, and van der Waals forces. Solvation of a solute by water is called hydration.Solubility of solid compounds depends on a competition between lattice energy and solvation, including entropy effects related to changes in the solvent structure.

Tetrahydrofuran

Tetrahydrofuran (THF) is an organic compound with the formula (CH2)4O. The compound is classified as heterocyclic compound, specifically a cyclic ether. It is a colorless, water-miscible organic liquid with low viscosity. It is mainly used as a precursor to polymers. Being polar and having a wide liquid range, THF is a versatile solvent.

Thin-layer chromatography

Thin-layer chromatography (TLC) is a chromatography technique used to separate non-volatile mixtures. Thin-layer chromatography is performed on a sheet of glass, plastic, or aluminium foil, which is coated with a thin layer of adsorbent material, usually silica gel, aluminium oxide (alumina), or cellulose. This layer of adsorbent is known as the stationary phase.

After the sample has been applied on the plate, a solvent or solvent mixture (known as the mobile phase) is drawn up the plate via capillary action. Because different analytes ascend the TLC plate at different rates, separation is achieved. The mobile phase has different properties from the stationary phase. For example, with silica gel, a very polar substance, non-polar mobile phases such as heptane are used. The mobile phase may be a mixture, allowing chemists to fine-tune the bulk properties of the mobile phase.

After the experiment, the spots are visualized. Often this can be done simply by projecting ultraviolet light onto the sheet; the sheets are treated with a phosphor, and dark spots appear on the sheet where compounds absorb the light impinging on a certain area. Chemical processes can also be used to visualize spots; anisaldehyde, for example, forms colored adducts with many compounds, and sulfuric acid will char most organic compounds, leaving a dark spot on the sheet.

To quantify the results, the distance traveled by the substance being considered is divided by the total distance traveled by the mobile phase. (The mobile phase must not be allowed to reach the end of the stationary phase.) This ratio is called the retardation factor (Rf). In general, a substance whose structure resembles the stationary phase will have low Rf, while one that has a similar structure to the mobile phase will have high retardation factor. Retardation factors are characteristic, but will change depending on the exact condition of the mobile and stationary phase. For this reason, chemists usually apply a sample of a known compound to the sheet before running the experiment.

Thin-layer chromatography can be used to monitor the progress of a reaction, identify compounds present in a given mixture, and determine the purity of a substance. Specific examples of these applications include: analyzing ceramides and fatty acids, detection of pesticides or insecticides in food and water, analyzing the dye composition of fibers in forensics, assaying the radiochemical purity of radiopharmaceuticals, or identification of medicinal plants and their constituents A number of enhancements can be made to the original method to automate the different steps, to increase the resolution achieved with TLC and to allow more accurate quantitative analysis. This method is referred to as HPTLC, or "high-performance TLC". HPTLC typically uses thinner layers of stationary phase and smaller sample volumes, thus reducing the loss of resolution due to diffusion.

Tincture

A tincture is typically an extract of plant or animal material dissolved in ethyl alcohol (ethanol). Solvent concentrations of 25–60% are common, but may run as high as 90%. In chemistry, a tincture is a solution that has ethanol as its solvent. In herbal medicine, alcoholic tinctures are made with various ethanol concentrations, 20% being the most common.Other solvents for producing tinctures include vinegar, glycerol (also called glycerine), diethyl ether and propylene glycol, not all of which can be used for internal consumption. Ethanol has the advantage of being an excellent solvent for both acidic and basic (alkaline) constituents. A tincture using glycerine is called a glycerite. Glycerine is generally a poorer solvent than ethanol. Vinegar, being acidic, is a better solvent for obtaining alkaloids but a poorer solvent for acidic components. For individuals who choose not to ingest alcohol, non-alcoholic extracts offer an alternative for preparations meant to be taken internally.

Low volatility substances such as iodine and mercurochrome can also be turned into tinctures.

White spirit

White spirit (UK) or mineral spirits (US, Canada), also known as mineral turpentine (AU/NZ), turpentine substitute, petroleum spirits, solvent naphtha (petroleum), Varsol, Stoddard solvent, or, generically, "paint thinner", is a petroleum-derived clear liquid used as a common organic solvent in painting.A mixture of aliphatic, open-chain or alicyclic C7 to C12 hydrocarbons, white spirit is insoluble in water and is used as an extraction solvent, as a cleaning solvent, as a degreasing solvent and as a solvent in aerosols, paints, wood preservatives, lacquers, varnishes, and asphalt products. In western Europe about 60% of the total white spirit consumption is used in paints, lacquers and varnishes. White spirit is the most widely used solvent in the paint industry. In households, white spirit is commonly used to clean paint brushes after use, to clean auto parts and tools, as a starter fluid for charcoal grills, to remove adhesive residue from non-porous surfaces, and many other common tasks.

The word "mineral" in "mineral spirits" or "mineral turpentine" is meant to distinguish it from distilled spirits (distilled directly from fermented grains and fruit) or from true turpentine (distilled tree resin).

Solvent Specific gravity[16]
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
Diethylene glycol dimethyl ether 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
Nucleophilic substitutions
Elimination reactions
Addition reactions
Related topics
Chemical kinetics
Solution
Concentration
and related quantities
Solubility
Solvent

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