Misplaced Pages

#818181

94-538: In terms of chemical structure, the molecule has idealized C s symmetry . It has a trigonal pyramidal molecular geometry consistent with other three-coordinate S(IV) compounds, with a nonbonded electron pair on the approximately tetrahedral sulfur atom. Dimethyl sulfoxide was first synthesized in 1866 by the Russian scientist Alexander Zaytsev , who reported his findings in 1867. Its modern use as an industrial solvent began through popularization by Thor Smedslund at

188-600: A cryoprotectant , added to cell media to reduce ice formation and thereby prevent cell death during the freezing process. Approximately 10% may be used with a slow-freeze method, and the cells may be frozen at −80 °C (−112 °F) or stored in liquid nitrogen safely. In cell culture, DMSO is used to induce differentiation of P19 embryonic carcinoma cells into cardiomyocytes and skeletal muscle cells . Use of DMSO in medicine dates from around 1963, when an Oregon Health & Science University Medical School team, headed by Stanley Jacob , discovered it could penetrate

282-866: 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 solvents are in dry cleaning (e.g. tetrachloroethylene ); as paint thinners ( toluene , turpentine ); as nail polish removers and solvents of glue ( acetone , methyl acetate , ethyl acetate ); in spot removers ( hexane , petrol ether); in detergents ( citrus terpenes ); and in perfumes ( ethanol ). Solvents find various applications in chemical, pharmaceutical , oil, and gas industries, including in chemical syntheses and purification processes When one substance

376-448: 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, such as water , solvate anions (negatively charged solutes) strongly via hydrogen bonding . Polar aprotic solvents , such as acetone or dichloromethane , tend to have large dipole moments (separation of partial positive and partial negative charges within

470-440: A large chemical library ), is readily miscible with water and cell culture media , and has a high boiling point (this improves the accuracy of test compound concentrations by reducing room temperature evaporation). One limitation with DMSO is that it can affect cell line growth and viability, with low DMSO concentrations sometimes stimulating cell growth, and high DMSO concentrations sometimes inhibiting or killing cells. DMSO

564-537: A larger scale is the use of crystal systems to describe crystallographic symmetry in bulk materials. There are many techniques for determining the symmetry of a given molecule, including X-ray crystallography and various forms of spectroscopy . Spectroscopic notation is based on symmetry considerations. The point group symmetry of a molecule is defined by the presence or absence of 5 types of symmetry element . The five symmetry elements have associated with them five types of symmetry operation , which leave

658-407: 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

752-462: A level exceeded in children exposed to DMSO during bone marrow transplant . DMSO disposed into sewers can cause odor problems in municipal effluents: waste water bacteria transform DMSO under hypoxic (anoxic) conditions into dimethyl sulfide (DMS) that has a strong disagreeable odor, similar to rotten cabbage. However, chemically pure DMSO is odorless because of the lack of C-S-C ( sulfide ) and C-S-H ( mercaptan ) linkages. Deodorization of DMSO

846-458: A manufacturer of the chemical warned that the death of an Irish woman after undergoing DMSO treatment for a sprained wrist may have been due to the treatment, although no autopsy was done, nor was a causal relationship established. Clinical research using DMSO was halted and did not begin again until the National Academy of Sciences (NAS) published findings in favor of DMSO in 1972. In 1978,

940-461: A mixture of 10% DMSO, a freezing medium, and 30% fetal bovine serum . In the cryogenic freezing of heteroploid cell lines ( MDCK , VERO , etc.) a mixture of 10% DMSO with 90%  EMEM (70% EMEM + 30% fetal bovine serum + antibiotic mixture) is used. As part of an autologous bone marrow transplant the DMSO is re-infused along with the patient's own hematopoietic stem cells . DMSO

1034-450: 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. Solvents can be broadly classified into two categories: polar and non-polar . A special case

SECTION 10

#1732845182819

1128-421: 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

1222-472: A point group is a group that summarises all symmetry operations that all molecules in that category have. The symmetry of a crystal, by contrast, is described by a space group of symmetry operations, which includes translations in space. Assigning each molecule a point group classifies molecules into categories with similar symmetry properties. For example, PCl 3 , POF 3 , XeO 3 , and NH 3 all share identical symmetry operations. They all can undergo

1316-415: A single equilibrium geometry. Longuet-Higgins introduced a more general type of symmetry group suitable not only for classifying the vibrational and electronic states of rigid molecules but also for classifying their rotational and nuclear spin states. Further, such groups can be used to classify the states of non-rigid (or fluxional ) molecules that tunnel between equivalent geometries and to allow for

1410-424: 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 . 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

1504-401: 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. The boiling point is an important property because it determines

1598-476: A table whose rows and columns correspond to elements of the group and whose entries correspond to their products. The successive application (or composition ) of one or more symmetry operations of a molecule has an effect equivalent to that of some single symmetry operation of the molecule. For example, a C 2 rotation followed by a σ v reflection is seen to be a σ v ' symmetry operation: σ v * C 2 = σ v '. ("Operation A followed by B to form C "

1692-449: A tool for the selection of solvents based on a principal component analysis of solvent properties. The Hansen solubility parameter (HSP) values 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

1786-901: 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 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,

1880-406: A way that mimics the multiplication table of the elements of a group is called a representation of the group. For example, for the C 2v point group, the following three matrices are part of a representation of the group: Although an infinite number of such representations exist, the irreducible representations (or "irreps") of the group are all that are needed as all other representations of

1974-551: Is dissolved into another, a solution is formed. 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

SECTION 20

#1732845182819

2068-444: Is a polar aprotic solvent and is less toxic than other members of this class, such as dimethylformamide , dimethylacetamide , N -methyl-2-pyrrolidone , and hexamethylphosphoramide (HMPA). DMSO is frequently used as a solvent for chemical reactions involving salts, most notably Finkelstein reactions and other nucleophilic substitutions . It is also extensively used as an extractant in biochemistry and cell biology. Because DMSO

2162-555: 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

2256-458: 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

2350-533: Is a solid, which can limit its utility in some chemical processes (e.g. crystallization with cooling). In its deuterated form ( DMSO- d 6 ), it is a useful solvent for NMR spectroscopy, again due to its ability to dissolve a wide range of analytes, the simplicity of its own spectrum, and its suitability for high-temperature NMR spectroscopic studies. Disadvantages to the use of DMSO- d 6 are its high viscosity, which broadens signals, and its hygroscopicity , which leads to an overwhelming H 2 O resonance in

2444-415: Is a symmetry operation. The symmetry operations of a molecule (or other object) form a group . In mathematics, a group is a set with a binary operation that satisfies the four properties listed below. In a symmetry group , the group elements are the symmetry operations (not the symmetry elements), and the binary combination consists of applying first one symmetry operation and then the other. An example

2538-731: Is achieved by removing the odorous impurities it contains. Dimethyl sulfoxide can produce an explosive reaction when exposed to acyl chlorides ; at a low temperature, this reaction produces the oxidant for Swern oxidation . DMSO can decompose at the boiling temperature of 189 °C at normal pressure, possibly leading to an explosion. The decomposition is catalyzed by acids and bases and therefore can be relevant at even lower temperatures. A strong to explosive reaction also takes place in combination with halogen compounds, metal nitrides, metal perchlorates, sodium hydride, periodic acid and fluorinating agents. Molecular symmetry#Common point groups In chemistry , molecular symmetry describes

2632-510: Is an acceptable predictor of the solvent's ability to dissolve common ionic compounds , such as salts. 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 m Y scale measures polarity in terms of solvent influence on buildup of positive charge of

2726-538: Is an effective paint stripper , being safer than many of the others such as nitromethane and dichloromethane . DMSO is used in polymerase chain reaction (PCR) to inhibit secondary structures in the DNA template or the DNA primers . It is added to the PCR mix before reacting, where it interferes with the self-complementarity of the DNA, minimizing interfering reactions. DMSO in a PCR

2820-536: Is an ingredient in some products listed by the U.S. FDA as fake cancer cures and the FDA has had a running battle with distributors. One such distributor is Mildred Miller, who promoted DMSO for a variety of disorders and was consequently convicted of Medicare fraud . The use of DMSO as an alternative treatment for cancer is of particular concern, as it has been shown to interfere with a variety of chemotherapy drugs, including cisplatin , carboplatin , and oxaliplatin . There

2914-451: Is applicable for supercoiled plasmids (to relax before amplification) or DNA templates with high GC-content (to decrease thermostability ). For example, 10% final concentration of DMSO in the PCR mixture with Phusion decreases primer annealing temperature (i.e. primer melting temperature) by 5.5–6.0 °C (9.9–10.8 °F). It is well known as a reversible cell cycle arrester at phase G1 of human lymphoid cells. DMSO may also be used as

Dimethyl sulfoxide - Misplaced Pages Continue

3008-629: Is associated with three vector components . The symmetry group C 3v for NH 3 has the three symmetry species A 1 , A 2 and E. The modes of vibration include the vibrational, rotational and translational modes. Total modes = 3A 1 + A 2 + 4E. This is a total of 12 modes because each E corresponds to 2 degenerate modes (at the same energy). Rotational modes = A 2 + E (3 modes) Translational modes = A 1 + E Vibrational modes = Total modes - Rotational modes - Translational modes = 3A 1 + A 2 + 4E - A 2 - E - A 1 - E = 2A 1 + 2E (6 modes). Each molecular orbital also has

3102-403: Is associated with two Ĉ 4 rotations in opposite directions (90° and 270°), a Ĉ 2 rotation (180°) and Ĉ 1 (0° or 360°). Because Ĉ 1 is equivalent to Ê , Ŝ 1 to σ and Ŝ 2 to î , all symmetry operations can be classified as either proper or improper rotations. For linear molecules, either clockwise or counterclockwise rotation about the molecular axis by any angle Φ

3196-568: 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 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. Ethers like diethyl ether and tetrahydrofuran (THF) can form highly explosive organic peroxides upon exposure to oxygen and light. THF

3290-517: Is bonded through oxygen. In general, the oxygen-bonded mode is more common. In carbon tetrachloride solutions DMSO functions as a Lewis base with a variety of Lewis acids such as I 2 , phenols , trimethyltin chloride , metalloporphyrins, and the dimer Rh 2 Cl 2 (CO) 4 . The donor properties are discussed in the ECW model . The relative donor strength of DMSO toward a series of acids, versus other Lewis bases, can be illustrated by C-B plots . DMSO

3384-823: 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. Multicomponent solvents appeared after World War II in the USSR , and continue to be used and produced in the post-Soviet states. These solvents may have one or more applications, but they are not universal preparations. 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

3478-468: Is elemental 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). Solvents with a dielectric constant of less than 15 are generally considered to be nonpolar. The dielectric constant measures

3572-415: Is insufficient evidence to support the hypothesis that DMSO has any effect, and most sources agree that its history of side effects when tested warrants caution when using it as a dietary supplement, for which it is marketed heavily with the usual disclaimer . DMSO is commonly used in veterinary medicine as a liniment for horses , alone or in combination with other ingredients. In the latter case, often,

3666-446: 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

3760-463: Is listed as a Schedule 4 (S4) Drug, and a company has been prosecuted for adding it to products as a preservative. Early clinical trials with DMSO were stopped because of questions about its safety, especially its ability to harm the eye. The most commonly reported side effects include headaches and burning and itching on contact with the skin. Strong allergic reactions have been reported. On September 9, 1965, The Wall Street Journal reported that

3854-412: Is mediated by the respective chemical properties of the solvent and solute, such as hydrogen bonding , dipole moment and polarizability . 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

Dimethyl sulfoxide - Misplaced Pages Continue

3948-451: Is metabolized by disproportionation to dimethyl sulfide and dimethyl sulfone . It is subject to renal and pulmonary excretion. A possible side effect of DMSO is therefore elevated blood dimethyl sulfide, which may cause a blood borne halitosis symptom. DMSO is marketed as an alternative medicine . Its popularity as an alternative cure is stated to stem from a 60 Minutes documentary in 1980 featuring an early proponent. However, DMSO

4042-479: Is much more polar than acetone but exhibits slightly less hydrogen bonding. 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 ,

4136-440: 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-centered free radical thus formed is able to react with an oxygen molecule to form

4230-479: Is only weakly acidic, it tolerates relatively strong bases and as such has been extensively used in the study of carbanions . A set of non-aqueous pKa values (C-H, O-H, S-H and N-H acidities) for thousands of organic compounds have been determined in DMSO solution. Because of its high boiling point, 189 °C (372 °F), DMSO evaporates slowly at normal atmospheric pressure. Samples dissolved in DMSO cannot as easily be recovered compared to other solvents, as it

4324-399: Is referred to as dimsyl sodium . It is a base, e.g., for the deprotonation of ketones to form sodium enolates , phosphonium salts to form Wittig reagents , and formamidinium salts to form diaminocarbenes . It is also a potent nucleophile. In organic synthesis , DMSO is used as a mild oxidant. It forms the basis of several selective sulfonium-based oxidation reactions including

4418-411: Is the sequence of a C 4 rotation about the z-axis and a reflection in the xy-plane, denoted σ(xy) C 4 . By convention the order of operations is from right to left. A symmetry group obeys the defining properties of any group. The order of a group is the number of elements in the group. For groups of small orders, the group properties can be easily verified by considering its composition table,

4512-497: 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 E T (30) values. E T 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 ( E T (33)) can be defined with Nile red . Gregory's solvent ϸ parameter

4606-447: Is used as a vehicle in in vivo studies of test compounds. It has, for example, been employed as a co-solvent to assist absorption of the flavonol glycoside Icariin in the nematode worm Caenorhabditis elegans . As with its use in in vitro studies, DMSO has some limitations in animal models . Pleiotropic effects can occur and, if DMSO control groups are not carefully planned, then solvent effects can falsely be attributed to

4700-478: Is used in embolization , the therapeutic occlusion of blood vessels. In cryobiology DMSO has been used as a cryoprotectant and is still an important constituent of cryoprotectant vitrification mixtures used to preserve organs, tissues, and cell suspensions. Without it, up to 90% of frozen cells will become inactive. It is particularly important in the freezing and long-term storage of embryonic stem cells and hematopoietic stem cells , which are often frozen in

4794-497: Is very difficult to remove all traces of DMSO by conventional rotary evaporation . One technique to fully recover samples is removal of the organic solvent by evaporation followed by addition of water (to dissolve DMSO) and cryodesiccation to remove both DMSO and water. Reactions conducted in DMSO are often diluted with water to precipitate or phase-separate products. The relatively high freezing point of DMSO, 18.5 °C (65.3 °F), means that at, or just below, room temperature it

SECTION 50

#1732845182819

4888-549: Is written BA = C ). Moreover, the set of all symmetry operations (including this composition operation) obeys all the properties of a group, given above. So ( S , * ) is a group, where S is the set of all symmetry operations of some molecule, and * denotes the composition (repeated application) of symmetry operations. This group is called the point group of that molecule, because the set of symmetry operations leave at least one point fixed (though for some symmetries an entire axis or an entire plane remains fixed). In other words,

4982-532: 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. Solvents with

5076-641: The Pfitzner–Moffatt oxidation , Corey–Kim oxidation and the Swern oxidation . The Kornblum oxidation is conceptually similar. These all involve formation of an intermediate sulfonium species (R 2 SX where X is a heteroatom) Related to its ability to dissolve many salts, DMSO is a common ligand in coordination chemistry . Illustrative is the complex dichlorotetrakis(dimethyl sulfoxide)ruthenium(II) (RuCl 2 (dmso) 4 ). In this complex, three DMSO ligands are bonded to ruthenium through sulfur. The fourth DMSO

5170-467: The methane (CH 4 ) and H 3 molecules have highly symmetric equilibrium structures with T d and D 3h point group symmetries respectively; they lack permanent electric dipole moments but they do have very weak pure rotation spectra because of rotational centrifugal distortion. Sometimes it is necessary to consider together electronic states having different point group symmetries at equilibrium. For example, in its ground (N) electronic state

5264-534: The point groups applicable to molecules, labelled using the Schoenflies notation , which is common in chemistry and molecular spectroscopy. The descriptions include common shapes of molecules, which can be explained by the VSEPR model . In each row, the descriptions and examples have no higher symmetries, meaning that the named point group captures all of the point symmetries. A set of matrices that multiply together in

5358-429: The skin , substances dissolved in DMSO may quickly be absorbed. Glove selection is important when working with DMSO. Butyl rubber , fluoroelastomer , neoprene , or thick (15   mil / 0.4   mm ) latex gloves are recommended. Nitrile gloves, which are very commonly used in chemical laboratories, may protect from brief contact but have been found to degrade rapidly with exposure to DMSO. In Australia, it

5452-480: The sulfur ylide : The methyl groups of DMSO are only weakly acidic, with a p K a = 35 . For this reason, the basicities of many weakly basic organic compounds have been examined in this solvent. Deprotonation of DMSO requires strong bases like lithium diisopropylamide and sodium hydride . Stabilization of the resultant carbanion is provided by the S(O)R group. The sodium derivative of DMSO formed in this way

5546-428: The symmetry present in molecules and the classification of these molecules according to their symmetry. Molecular symmetry is a fundamental concept in chemistry, as it can be used to predict or explain many of a molecule's chemical properties , such as whether or not it has a dipole moment , as well as its allowed spectroscopic transitions . To do this it is necessary to use group theory . This involves classifying

5640-434: The 2 p z orbital is seen to have the symmetry of the A 1 irreducible representation ( i.e .: none of the symmetry operations change it), 2 p y B 2 , and the 3 d xy orbital A 2 . These assignments and others are noted in the rightmost two columns of the table. Hans Bethe used characters of point group operations in his study of ligand field theory in 1929, and Eugene Wigner used group theory to explain

5734-493: The H-NMR spectrum. It is often mixed with CDCl 3 or CD 2 Cl 2 for lower viscosity and melting points. DMSO is used to dissolve test compounds in in vitro drug discovery and drug design screening programs, including high-throughput screening programs. This is because it is able to dissolve both polar and nonpolar compounds, can be used to maintain stock solutions of test compounds (important when working with

SECTION 60

#1732845182819

5828-528: The N-H bonds, either in the direction of the nitrogen atom or away from it. This mode is known as symmetric stretch (v₁) and reflects the symmetry in the N-H bond stretching. Of the three vibrational modes, this one has the highest frequency . In the Bending (ν₂) vibration, the nitrogen atom stays on the axis of symmetry, while the three hydrogen atoms move in different directions from one another, leading to changes in

5922-575: The Stepan Chemical Company. Dimethyl sulfoxide is produced industrially from dimethyl sulfide , a by-product of the Kraft process , by oxidation with oxygen or nitrogen dioxide . The sulfur center in DMSO is nucleophilic toward soft electrophiles and the oxygen is nucleophilic toward hard electrophiles. With methyl iodide it forms trimethylsulfoxonium iodide , [(CH 3 ) 3 SO]I: This salt can be deprotonated with sodium hydride to form

6016-590: The US FDA approved DMSO for treating interstitial cystitis . In 1980, the US Congress held hearings on claims that the FDA was slow in approving DMSO for other medical uses. In 2007, the US FDA granted "fast track" designation on clinical studies of DMSO's use in reducing brain tissue swelling following traumatic brain injury . DMSO exposure to developing mouse brains can produce brain degeneration. This neurotoxicity could be detected at doses as low as 0.3   mL/kg,

6110-446: The addition of EDTA . It is frequently compounded with antifungal medications, enabling them to penetrate not just skin but also toenails and fingernails. DMSO has been examined for the treatment of numerous conditions and ailments, but the U.S. Food and Drug Administration (FDA) has approved its use only for the symptomatic relief of patients with interstitial cystitis . A 1978 study concluded that DMSO brought significant relief to

6204-422: The bond angles. The hydrogen atoms move like an umbrella, so this mode is often referred to as the "umbrella mode". There is also an Asymmetric Stretch mode (ν₃) in which one hydrogen atom approaches the nitrogen atom while the other two hydrogens move away. The total number of degrees of freedom for each symmetry species (or irreducible representation ) can be determined. Ammonia has four atoms, and each atom

6298-456: 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

6392-433: The conformations occurs at ordinary temperatures by internal rotation of one methyl group relative to the other. This is not a rotation of the entire molecule about the C 3 axis, although each conformation has D 3d symmetry, as in the table above. Similarly, ammonia (NH 3 ) has two equivalent pyramidal ( C 3v ) conformations which are interconverted by the process known as nitrogen inversion . Additionally,

6486-456: The distorting effects of molecular rotation. These groups are known as permutation-inversion groups, because the symmetry operations in them are energetically feasible permutations of identical nuclei, or inversion with respect to the center of mass (the parity operation), or a combination of the two. Examples of molecular nonrigidity abound. For example, ethane (C 2 H 6 ) has three equivalent staggered conformations . Tunneling between

6580-465: The ethylene molecule C 2 H 4 has D 2h point group symmetry whereas in the excited (V) state it has D 2d symmetry. To treat these two states together it is necessary to allow torsion and to use the double group of the permutation-inversion group G 16 . Solvent A solvent (from the Latin solvō , "loosen, untie, solve") is a substance that dissolves a solute, resulting in

6674-445: The fourth row of the character table above, with x in the sixth column). It is oriented perpendicular to the plane of the molecule and switches sign with a C 2 and a σ v '(yz) operation, but remains unchanged with the other two operations (obviously, the character for the identity operation is always +1). This orbital's character set is thus {1, −1, 1, −1}, corresponding to the B 1 irreducible representation. Likewise,

6768-427: The geometry of the molecule indistinguishable from the starting geometry. They are sometimes distinguished from symmetry elements by a caret or circumflex . Thus, Ĉ n is the rotation of a molecule around an axis and Ê is the identity operation. A symmetry element can have more than one symmetry operation associated with it. For example, the C 4 axis of the square xenon tetrafluoride (XeF 4 ) molecule

6862-418: The group can be described as a direct sum of the irreducible representations. Also, the irreducibile representations are those matrix representations in which the matrices are in their most diagonal form possible. For any group, its character table gives a tabulation (for the classes of the group) of the characters (the sum of the diagonal elements) of the matrices of all the irreducible representations of

6956-476: The group. As the number of irreducible representations equals the number of classes, the character table is square. The representations are labeled according to a set of conventions: The tables also capture information about how the Cartesian basis vectors, rotations about them, and quadratic functions of them transform by the symmetry operations of the group, by noting which irreducible representation transforms in

7050-442: The groups had been applied by other researchers to the external morphology of crystals much earlier in the 19th century. The complete set of 32 crystallographic point groups was published in 1936 by Rosenthal and Murphy One can determine the symmetry operations of the point group for a particular molecule by considering the geometrical symmetry of its molecular model. However, when one uses a point group to classify molecular states,

7144-636: The identity operation E , two different C 3 rotation operations, and three different σ v plane reflections without altering their identities, so they are placed in one point group, C 3v , with order 6. Similarly, water (H 2 O) and hydrogen sulfide (H 2 S) also share identical symmetry operations. They both undergo the identity operation E , one C 2 rotation, and two σ v reflections without altering their identities, so they are both placed in one point group, C 2v , with order 4. This classification system helps scientists to study molecules more efficiently, since chemically related molecules in

7238-623: The intended function of the DMSO is as a solvent, to carry the other ingredients across the skin. Also in horses, DMSO is used intravenously, again alone or in combination with other drugs. It is used alone for the treatment of increased intracranial pressure and/or cerebral edema in horses. The perceived garlic taste upon skin contact with DMSO may be due to nonolfactory activation of TRPA1 receptors in trigeminal ganglia . Unlike dimethyl and diallyl disulfides (which have odors resembling garlic), mono- and tri- sulfides (which typically have foul odors), and similar odiferous sulfur compounds,

7332-465: The majority of the 213 patients with inflammatory genitourinary disorders that were studied. The authors recommended DMSO for genitourinary inflammatory conditions not caused by infection or tumor in which symptoms were severe or patients failed to respond to conventional therapy. In interventional radiology , DMSO is used as a solvent for ethylene vinyl alcohol in the Onyx liquid embolic agent, which

7426-412: 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 detonate 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

7520-428: The operations in it are not to be interpreted in the same way. Instead the operations are interpreted as rotating and/or reflecting the vibronic (vibration-electronic) coordinates and these operations commute with the vibronic Hamiltonian. They are "symmetry operations" for that vibronic Hamiltonian. The point group is used to classify by symmetry the vibronic eigenstates of a rigid molecule. The symmetry classification of

7614-480: The prospective drug. For example, even a very low dose of DMSO has a powerful protective effect against paracetamol (acetaminophen)-induced liver injury in mice. DMSO is finding increased use in manufacturing processes to produce microelectronic devices. It is widely used to strip photoresist in TFT-LCD 'flat panel' displays and advanced packaging applications (such as wafer-level packaging / solder bump patterning). DMSO

7708-528: The pure chemical DMSO is odorless. DMSO is a non-toxic solvent with a median lethal dose higher than ethanol (DMSO: LD 50 , oral, rat, 14,500 mg/kg; ethanol: LD 50 , oral, rat, 7,060 mg/kg). DMSO can cause contaminants, toxins, and medicines to be absorbed through the skin, which may cause unexpected effects. DMSO is thought to increase the effects of blood thinners, steroids, heart medicines, sedatives, and other drugs. In some cases this could be harmful or dangerous. Because DMSO easily penetrates

7802-456: The rotational levels, the eigenstates of the full (rotation-vibration-electronic) Hamiltonian, can be achieved through the use of the appropriate permutation-inversion group, as introduced by Longuet-Higgins . Each normal mode of molecular vibration has a symmetry which forms a basis for one irreducible representation of the molecular symmetry group. For example, the water molecule has three normal modes of vibration: symmetric stretch in which

7896-1043: The same molecule) and solvate positively charged species via their negative dipole. In chemical reactions the use of polar protic solvents favors the S N 1 reaction mechanism , while polar aprotic solvents favor the S N 2 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. 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. CH 3 CH 2 CH 2 CH 2 CH 3 CH 3 CH 2 CH 2 CH 2 CH 2 CH 3 H 3 C(CH 2 ) 5 CH 3 C 6 H 5 -CH 3 CH 3 CH 2 -O-CH 2 CH 3 CHCl 3 CH 2 Cl 2 CH 3 -C≡N CH 3 -NO 2 C 4 H 6 O 3 NH 3 (at -33.3 °C) CH 3 CH 2 CH 2 CH 2 OH CH 3 CH 2 CH 2 OH CH 3 CH 2 OH CH 3 OH The ACS Green Chemistry Institute maintains

7990-450: The same point group tend to exhibit similar bonding schemes, molecular bonding diagrams, and spectroscopic properties. Point group symmetry describes the symmetry of a molecule when fixed at its equilibrium configuration in a particular electronic state. It does not allow for tunneling between minima nor for the change in shape that can come about from the centrifugal distortion effects of molecular rotation. The following table lists many of

8084-466: The same way. These indications are conventionally on the righthand side of the tables. This information is useful because chemically important orbitals (in particular p and d orbitals) have the same symmetries as these entities. The character table for the C 2v symmetry point group is given below: Consider the example of water (H 2 O), which has the C 2v symmetry described above. The 2 p x orbital of oxygen has B 1 symmetry as in

8178-541: The selection rules of atomic spectroscopy . The first character tables were compiled by László Tisza (1933), in connection to vibrational spectra. Robert Mulliken was the first to publish character tables in English (1933), and E. Bright Wilson used them in 1934 to predict the symmetry of vibrational normal modes . All of the group operations described above and the symbols for crystallographic point groups themselves were first published by Arthur Schoenflies in 1891 but

8272-480: The skin and other membranes without damaging them and could carry other compounds into a biological system. In medicine, DMSO is predominantly used as a topical analgesic , a vehicle for topical application of pharmaceuticals, as an anti-inflammatory , and an antioxidant . Because DMSO increases the rate of absorption of some compounds through biological tissues , including skin , it is used in some transdermal drug delivery systems. Its effect may be enhanced with

8366-399: 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. 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

8460-436: 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. Most organic solvents have a lower density than water, which means they are lighter than and will form

8554-566: The states of the molecule using the irreducible representations from the character table of the symmetry group of the molecule. Symmetry is useful in the study of molecular orbitals , with applications to the Hückel method , to ligand field theory , and to the Woodward-Hoffmann rules . Many university level textbooks on physical chemistry , quantum chemistry , spectroscopy and inorganic chemistry discuss symmetry. Another framework on

8648-521: The symmetry of one irreducible representation. For example, ethylene (C 2 H 4 ) has symmetry group D 2h , and its highest occupied molecular orbital ( HOMO ) is the bonding pi orbital which forms a basis for its irreducible representation B 1u . As discussed above in the section Some applications of molecular symmetry, point groups are useful for classifying the vibrational and electronic states of rigid molecules (sometimes called semi-rigid molecules) which undergo only small oscillations about

8742-404: The three vibrational modes is therefore Γ vib = 2A 1 + B 2 . The molecular symmetry of ammonia (NH 3 ) is C 3v , with symmetry operations E, C 3 and σ v . For N = 4 atoms, the number of vibrational modes for a non-linear molecule is 3N-6 = 6, due to the relative motion of the nitrogen atom and the three hydrogen atoms. All three hydrogen atoms travel symmetrically along

8836-407: The two O-H bond lengths vary in phase with each other, asymmetric stretch in which they vary out of phase, and bending in which the bond angle varies. The molecular symmetry of water is C 2v with four irreducible representations A 1 , A 2 , B 1 and B 2 . The symmetric stretching and the bending modes have symmetry A 1 , while the asymmetric mode has symmetry B 2 . The overall symmetry of

#818181