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Borane–dimethylsulfide
Borane dimethylsulfide (BMS) is a chemical compound with the chemical formula . It is an adduct between borane molecule () and dimethyl sulfide molecule (). It is a complexed borane reagent that is used for hydroborations and reductions. The advantages of BMS over other borane reagents, such as borane-tetrahydrofuran, are its increased stability and higher solubility. BMS is commercially available at much higher concentrations than its tetrahydrofuran counterpart (10 M) and does not require sodium borohydride as a stabilizer, which could result in undesired side reactions. In contrast, Borane–tetrahydrofuran, requires sodium borohydride to inhibit reduction of THF to tributyl borate (). BMS is soluble in most aprotic solvents. Preparation and structure Although usually purchased, BMS can be prepared by absorbing diborane into dimethyl sulfide: : It can be purified by bulb to bulb vacuum transfer. Although a structure of BMS has not been determined crystallographically, (pe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Boranes
A borane is a compound with the formula although examples include multi-boron derivatives. A large family of boron hydride clusters is also known. In addition to some applications in organic chemistry, the boranes have attracted much attention as they exhibit structures and bonding that differs strongly from the patterns seen in hydrocarbons. Hybrids of boranes and hydrocarbons, the carboranes, are also a well developed class of compounds. pp 151-195 History The development of the chemistry of boranes led to innovations in synthetic methods as well as structure and bonding. First, new synthetic techniques were required to handle diborane and many of its derivatives, which are both pyrophoric and volatile. Alfred Stock invented the glass vacuum line for this purpose. The structure of diborane was correctly predicted in 1943 many years after its discovery. Interest in boranes increased during World War II due to the potential of uranium borohydride for enrichment of the uranium ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Borane–tetrahydrofuran
Borane–tetrahydrofuran is an adduct derived from borane and tetrahydrofuran (THF). These solutions, which are colorless, are used for reductions and hydroboration, reactions that are useful in synthesis of organic compounds. A common alternative to BH3•THF is borane–dimethylsulfide, which has a longer shelf life and effects similar transformations.Marek Zaidlewicz, Herbert C. Brown, Santhosh F. Neelamkavil, "Borane–Tetrahydrofuran" Encyclopedia of Reagents for Organic Synthesis, 2008 John Wiley & Sons. Preparation and uses The complex is commercially available but can also be generated by the dissolution of diborane in THF. Alternatively, it can be prepared by the oxidation of sodium borohydride with iodine in THF. The complex can reduce carboxylic acids to alcohols and is a common route for the reduction of amino acids to amino alcohols (e.g. valinol). It adds across alkenes to give organoboron compounds that are useful intermediates. The following organoboron reage ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemical Compound
A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element is therefore not a compound. A compound can be transformed into a different substance by a chemical reaction, which may involve interactions with other substances. In this process, bonds between atoms may be broken or new bonds formed or both. There are four major types of compounds, distinguished by how the constituent atoms are bonded together. Molecular compounds are held together by covalent bonds; ionic compounds are held together by ionic bonds; intermetallic compounds are held together by metallic bonds; coordination complexes are held together by coordinate covalent bonds. Non-stoichiometric compounds form a disputed marginal case. A chemical formula specifies the number of atoms of each element in a compound molecule, usin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aprotic Solvent
A polar aprotic solvent is a solvent that lacks an acidic proton and is polar. Such solvents lack hydroxyl and amine groups. In contrast to protic solvents, these solvents do not serve as proton donors in hydrogen bonding In chemistry, a hydrogen bond (H-bond) is a specific type of molecular interaction that exhibits partial covalent character and cannot be described as a purely electrostatic force. It occurs when a hydrogen (H) atom, Covalent bond, covalently b ..., although they can be proton acceptors. Many solvents, including chlorocarbons and hydrocarbons, are classifiable as aprotic, but polar aprotic solvents are of particular interest for their ability to dissolve salts. Methods for purification of common solvents are available. References * {{Chemical solutions Solvents ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Organic Synthesis
Organic synthesis is a branch of chemical synthesis concerned with the construction of organic compounds. Organic compounds are molecules consisting of combinations of covalently-linked hydrogen, carbon, oxygen, and nitrogen atoms. Within the general subject of organic synthesis, there are many different types of synthetic routes that can be completed including total synthesis, Enantioselective synthesis, stereoselective synthesis, automated synthesis, and many more. Additionally, in understanding organic synthesis it is necessary to be familiar with the methodology, techniques, and applications of the subject. Total synthesis A total synthesis refers to the complete chemical synthesis of molecules from simple, Precursor (chemistry), natural precursors. Total synthesis is accomplished either via a linear or convergent approach. In a Linear synthesis, ''linear'' synthesis—often adequate for simple structures—several steps are performed sequentially until the molecule is com ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reaction Intermediate
In chemistry, a reaction intermediate, or intermediate, is a molecular entity arising within the sequence of a stepwise chemical reaction. It is formed as the reaction product of an elementary step, from the reactants and/or preceding intermediates, but is consumed in a later step. It does not appear in the chemical equation for the overall reaction. For example, consider this hypothetical reaction: :A + B → C + D If this overall reaction comprises two elementary steps thus: :A + B → X :X → C + D then X is a reaction intermediate. The phrase ''reaction intermediate'' is often abbreviated to the single word ''intermediate'', and this is IUPAC's preferred form of the term. But this shorter form has other uses. It often refers to reactive intermediates. It is also used more widely for chemicals such as cumene which are traded within the chemical industry but are not generally of value outside it. IUPAC definition The IUPAC Gold Book defines an ''intermediate'' as a co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Organoborane
Organoboron chemistry or organoborane chemistry studies organoboron compounds, also called organoboranes. These chemical compounds combine boron and carbon; typically, they are organic derivatives of borane (BH3), as in the trialkyl boranes. Organoboranes and -borates enable many chemical transformations in organic chemistry — most importantly, hydroboration and carboboration. Most reactions transfer a nucleophilic boron substituent to an electrophilic center either inter- or intramolecularly. In particular, α,β-unsaturated borates and borates with an α leaving group are highly susceptible to intramolecular 1,2-migration of a group from boron to the electrophilic α position. Oxidation or protonolysis of the resulting organoboranes generates many organic products, including alcohols, carbonyl compounds, alkenes, and halides. Properties of the B-C bond The C-B bond has low polarity (electronegativity 2.55 for carbon and 2.04 for boron). Alkyl boron compounds are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Unsaturated Bond
A saturated compound is a chemical compound (or ion) that resists addition reactions, such as hydrogenation, oxidative addition, and the binding of a Lewis base. The term is used in many contexts and classes of chemical compounds. Overall, saturated compounds are less reactive than unsaturated compounds. Saturation is derived from the Latin word ''saturare'', meaning 'to fill'.An unsaturated compound is also a chemical compound (or ion) that attracts reduction reactions, such as dehydrogenation, oxidative reduction Organic chemistry Generally distinct types of unsaturated organic compounds are recognized. For hydrocarbons: *alkene (unsaturated) vs alkane (saturated) *alkyne (unsaturated) vs alkane (saturated) *arene (unsaturated) vs cycloalkane (saturated) For organic compounds containing heteroatoms (other than C and H), the list of unsaturated groups is long but some common types are: *carbonyl, e.g. ketones, aldehydes, esters, carboxylic acids (unsaturated) vs alcohol or et ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
In Situ
is a Latin phrase meaning 'in place' or 'on site', derived from ' ('in') and ' ( ablative of ''situs'', ). The term typically refers to the examination or occurrence of a process within its original context, without relocation. The term is used across many disciplines to denote methods, observations, or interventions carried out in their natural or intended environment. By contrast, ' methods involve the removal or displacement of materials, specimens, or processes for study, preservation, or modification in a controlled setting, often at the cost of contextual integrity. The earliest known use of ''in situ'' in the English language dates back to the mid-17th century. In scientific literature, its usage increased from the late 19th century onward, initially in medicine and engineering. The natural sciences typically use methods to study phenomena in their original context. In geology, field analysis of soil composition and rock formations provides direct insights into Earth' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dissociation (chemistry)
Dissociation in chemistry is a general process in which molecules (or ionic compounds such as salt (chemistry), salts, or coordination complex, complexes) separate or split into other things such as atoms, ions, or radical (chemistry), radicals, usually in a reversible manner. For instance, when an acid dissolves in water, a covalent bond between an electronegativity, electronegative atom and a hydrogen atom is broken by heterolytic fission, which gives a proton (H+) and a negative ion. Dissociation is the opposite of association or recombination. Dissociation constant For reversible dissociations in a chemical equilibrium :AB A + B the dissociation constant ''K''d is the ratio of dissociated to undissociated compound :K_d = \mathrm where the brackets denote the equilibrium concentrations of the species. Dissociation degree The dissociation degree \alpha is the fraction of original solute molecules that have dissociated. It is usually indicated by the Greek symbol α. More acc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dimethylsulfide
Dimethyl sulfide (DMS) or methylthiomethane is an organosulfur compound with the formula . It is the simplest thioether and has a characteristic disagreeable odor. It is a flammable liquid that boils at . It is a component of the smell produced from cooking of certain vegetables (notably maize, cabbage, and beetroot) and seafoods. It is also an indication of bacterial contamination in malt production and brewing. It is a breakdown product of dimethylsulfoniopropionate (DMSP), and is also produced by the bacterial metabolism of methanethiol. Occurrence and production DMS originates primarily from DMSP, a major secondary metabolite in some marine algae. DMS is the most abundant biological sulfur compound emitted to the atmosphere. Emission occurs over the oceans by phytoplankton. DMS is also produced naturally by bacterial transformation of dimethyl sulfoxide (DMSO) waste that is disposed of into sewers, where it can cause environmental odor problems. DMS is oxidized in the marine ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tetrahedral Molecular Geometry
In a tetrahedral molecular geometry, a central atom is located at the center with four substituents that are located at the corners of a tetrahedron. The bond angles are arccos(−) = 109.4712206...° ≈ 109.5° when all four substituents are the same, as in methane () as well as its heavier analogues. Methane and other perfectly symmetrical tetrahedral molecules belong to point group ''Td'', but most tetrahedral molecules have lower symmetry. Tetrahedral molecules can be chiral. Tetrahedral bond angle The bond angle for a symmetric tetrahedral molecule such as CH4 may be calculated using the dot product of two vectors. As shown in the diagram at left, the molecule can be inscribed in a cube with the tetravalent atom (e.g. carbon) at the cube centre which is the origin of coordinates, O. The four monovalent atoms (e.g. hydrogens) are at four corners of the cube (A, B, C, D) chosen so that no two atoms are at adjacent corners linked by only one cube edge. If the edge len ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
