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Stephen Aldehyde Synthesis
Stephen aldehyde synthesis, a named reaction in chemistry, was invented by Henry Stephen ( OBE/MBE). This reaction involves the preparation of aldehydes (R-CHO) from nitriles (R-CN) using tin(II) chloride (SnCl2), hydrochloric acid (HCl) and quenching the resulting iminium salt ( -CH=NH2sup>+Cl−) with water (H2O). During the synthesis, ammonium chloride is also produced. Mechanism The following scheme shows the reaction mechanism: By addition of hydrogen chloride the used nitrile (1) reacts to its corresponding salt (2). It is believed that this salt is reduced by a single electron transfer by the tin(II) chloride (3a and 3b). The resulting salt (4) precipitates after some time as aldimine tin chloride (5). Hydrolysis of 5 produces a hemiaminal (6) from which an aldehyde (7) is formed. Substitutes that increase the electron density promote the formation of the aldimine-tin chloride adduct. With electron withdrawing substituents, the formation of an amide chloride is faci ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Henry Stephen (chemist)
Henry Stephen Order of the British Empire, OBE, DSc. (10 July 1889 – 6 July 1965) was an England, English chemist known for inventing the Stephen reaction, Stephen Reaction, a method of deriving aldehydes (R-CHO) from nitriles (R-CN). Career Leonard Henry Nelson Stephen, later known as Henry Stephen, was born at 11 Dalton Terrace, Manchester, son of John Stephen, printer, and Mary Eliza (née Owen). He studied chemistry under Dr Chaim Weizmann at Victoria University of Manchester. Along with Dr. J. E. Myers, Stephen contributed to the British World War I effort by developing a process to make mustard gas that was more rapid than the process being used by the Germans. In 1920, both received the OBE award for their work. He received his DSc degree from Victoria University of Manchester in 1920 and continued on as a senior lecturer. In 1925 he published ''A New Synthesis of Aldehydes'', known as the Stephen aldehyde synthesis, Stephen Reaction. From 1926 to 1954, Stephen was p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nitrile
In organic chemistry, a nitrile is any organic compound that has a functional group. The prefix ''cyano-'' is used interchangeably with the term ''nitrile'' in industrial literature. Nitriles are found in many useful compounds, including methyl cyanoacrylate, used in super glue, and nitrile rubber, a nitrile-containing polymer used in latex-free laboratory and medical gloves. Nitrile rubber is also widely used as automotive and other seals since it is resistant to fuels and oils. Organic compounds containing multiple nitrile groups are known as cyanocarbons. Inorganic compounds containing the group are not called nitriles, but cyanides instead. Though both nitriles and cyanides can be derived from cyanide salts, most nitriles are not nearly as toxic. Structure and basic properties The N−C−C geometry is linear in nitriles, reflecting the sp hybridization of the triply bonded carbon. The C−N distance is short at 1.16 Å, consistent with a triple bond. Nitriles a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orthoester
In organic chemistry, an ortho ester is a functional group containing three alkoxy groups attached to one carbon atom, i.e. with the general formula . Orthoesters may be considered as products of exhaustive alkylation of unstable orthocarboxylic acids and it is from these that the name 'ortho ester' is derived. An example is ethyl orthoacetate, , more correctly known as 1,1,1-triethoxyethane. Synthesis Ortho esters can be prepared by the Pinner reaction, in which nitriles react with alcohols in the presence of one equivalent of hydrogen chloride. The reaction proceeds by formation of imido ester hydrochloride: :RCN + R′OH + HCl → C(OR′)=NH2sup>+Cl− Upon standing in the presence of excess alcohol, this intermediate converts to the ortho ester: : C(OR′)=NH2sup>+Cl− + 2R′OH → RC(OR′)3 + NH4Cl The reaction requires anhydrous conditions. Although a less common method, ortho esters were first produced by reaction of 1,1,1-trichloroalkanes with sodium alkoxide ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carboximidate
Carboximidates (or more general imidates) are organic compounds, which can be thought of as esters formed between a carboximidic acid (R-C(=NR')OH) and an alcohol, with the general formula R-C(=NR')OR". They are also known as imino ethers, since they resemble imines (>C=N-) with an oxygen atom connected to the carbon atom of the C=N double bond. Synthesis Imidates may be generated by a number of synthetic routes, but are in general formed by the Pinner reaction. This proceeds via the acid catalyzed attack of nitriles by alcohols. Imidates produced in this manner are formed as their hydrochloride salts, which are sometimes referred to as Pinner salts. Carboximidates are also formed as intermediates in the Mumm rearrangement and the Overman rearrangement. Imidate/amidate anions An amidate/imidate anion is formed upon deprotonation of an amide or imidic acid. Since amides and imidic acids are tautomers, they form the same anion upon deprotonation. The two names are thus sy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Organic Redox Reaction
Organic reductions or organic oxidations or organic redox reactions are redox reactions that take place with organic compounds. In organic chemistry oxidations and reductions are different from ordinary redox reactions, because many reactions carry the name but do not actually involve electron transfer.March Jerry; (1985). Advanced Organic Chemistry reactions, mechanisms and structure (3rd ed.). New York: John Wiley & Sons, inc. Instead the relevant criterion for organic oxidation is gain of oxygen and/or loss of hydrogen, respectively.''Organic Redox Systems: Synthesis, Properties, and Applications'', Tohru Nishinaga 2016 Simple functional groups can be arranged in order of increasing oxidation state. The oxidation numbers are only an approximation: When methane is oxidized to carbon dioxide its oxidation number changes from −4 to +4. Classical reductions include alkene reduction to alkanes and classical oxidations include oxidation of alcohols to aldehydes. In oxidations ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pinner Reaction
The Pinner reaction refers to the acid catalysed reaction of a nitrile with an alcohol to form an imino ester salt (alkyl imidate salt); this is sometimes referred to as a Pinner salt. The reaction is named after Adolf Pinner, who first described it in 1877. Pinner salts are themselves reactive and undergo additional nucleophilic additions to give various useful products: * With an excess of alcohol to form an orthoester * With ammonia or an amine to form an amidine (di-nitriles may form imidines, for instance succinimidine from succinonitrile) * With water to form an ester * With hydrogen sulfide to form a thionoester Commonly the Pinner salt itself is not isolated, with the reaction being continued to give the desired functional group (orthoester etc.) in one go. It should be appreciated that the Pinner reaction refers specifically to an acid catalyzed process, but that similar results can often be achieved using base catalysis. The two approaches can be complementary, with ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nitrile Reduction
In nitrile reduction a nitrile is reduced to either an amine or an aldehyde with a suitable chemical reagent. Catalytic hydrogenation The catalytic hydrogenation of nitriles is often the most economical route available for the production of primary amines. Catalysts for the reaction often include group 10 metals such as Raney nickel, palladium black, or platinum dioxide. However, other catalysts, such as cobalt boride, also can be regioselective for primary amine production: : R-C≡N + 2 H2 → R-CH2NH2 A commercial application of this technology includes the production of hexamethylenediamine from adiponitrile, a precursor to Nylon 66. Depending on reaction conditions, reactive intermediate imines can also undergo attack by amine products to afford secondary and tertiary amines: : 2 R-C≡N + 4 H2 → (R-CH2)2NH + NH3 : 3 R-C≡N + 6 H2 → (R-CH2)3N + 2 NH3 Such reactions proceed via enamine intermediates. The most important reaction condition for selective primary am ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amide Reduction
Amide reduction is a reaction in organic synthesis where an amide is reduced to either an amine or an aldehyde functional group. Catalytic hydrogenation Catalytic hydrogenation can be used to reduce amides to amines; however, the process often requires high hydrogenation pressures and reaction temperatures to be effective (i.e. often requiring pressures above 197 atm and temperatures exceeding 200 °C). Selective catalysts for the reaction include copper chromite, rhenium trioxide and rhenium(VII) oxide or bimetallic catalyst. Non-catalytic routes to amines Reducing agents able to effect this reaction include metal hydrides such as lithium aluminium hydride, or lithium borohydride in mixed solvents of tetrahydrofuran and methanol. : Noncatalytic routes to aldehydes N,N-disubstituted amides can be reduced to aldehydes by using an excess of the amide: :R(CO)NRR' + LiAlH4 → RCHO + HNRR' With further reduction the alcohol is obtained. Some amides can be reduced to aldehy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phosphorus Pentachloride
Phosphorus pentachloride is the chemical compound with the formula PCl5. It is one of the most important phosphorus chlorides, others being PCl3 and POCl3. PCl5 finds use as a chlorinating reagent. It is a colourless, water-sensitive and moisture-sensitive solid, although commercial samples can be yellowish and contaminated with hydrogen chloride. Structure The structures for the phosphorus chlorides are invariably consistent with VSEPR theory. The structure of PCl5 depends on its environment. Gaseous and molten PCl5 is a neutral molecule with trigonal bipyramidal geometry and (''D''3h) symmetry. The hypervalent nature of this species (as well as of , see below) can be explained with the inclusion of non-bonding molecular orbitals (molecular orbital theory) or resonance (valence bond theory). This trigonal bipyramidal structure persists in nonpolar solvents, such as CS2 and CCl4. In the solid state PCl5 is an ionic compound, formulated . In solutions of polar solvents, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amide
In organic chemistry, an amide, also known as an organic amide or a carboxamide, is a compound with the general formula , where R, R', and R″ represent organic groups or hydrogen atoms. The amide group is called a peptide bond when it is part of the main chain of a protein, and an isopeptide bond when it occurs in a side chain, such as in the amino acids asparagine and glutamine. It can be viewed as a derivative of a carboxylic acid () with the hydroxyl group () replaced by an amine group (); or, equivalently, an acyl (alkanoyl) group () joined to an amine group. Common examples of amides are acetamide (), benzamide (), and dimethylformamide (). Amides are qualified as primary, secondary, and tertiary according to whether the amine subgroup has the form , , or , where R and R' are groups other than hydrogen. The core of amides is called the amide group (specifically, carboxamide group). Amides are pervasive in nature and technology. Proteins and important plastics l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reactive Intermediate
In chemistry, a reactive intermediate or an intermediate is a short-lived, high-energy, highly reactive molecule. When generated in a chemical reaction, it will quickly convert into a more stable molecule. Only in exceptional cases can these compounds be isolated and stored, e.g. low temperatures, matrix isolation. When their existence is indicated, reactive intermediates can help explain how a chemical reaction takes place. Most chemical reactions take more than one elementary step to complete, and a reactive intermediate is a high-energy, yet stable, product that exists only in one of the intermediate steps. The series of steps together make a reaction mechanism. A reactive intermediate differs from a reactant or product or a simple reaction intermediate only in that it cannot usually be isolated but is sometimes observable only through fast spectroscopic methods. It is stable in the sense that an elementary reaction forms the reactive intermediate and the elementary reaction ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electron Density
In quantum chemistry, electron density or electronic density is the measure of the probability of an electron being present at an infinitesimal element of space surrounding any given point. It is a scalar quantity depending upon three spatial variables and is typically denoted as either \rho(\textbf r) or n(\textbf r). The density is determined, through definition, by the normalised N-electron wavefunction which itself depends upon 4N variables (3N spatial and N spin coordinates). Conversely, the density determines the wave function modulo up to a phase factor, providing the formal foundation of density functional theory. According to quantum mechanics, due to the uncertainty principle on an atomic scale the exact location of an electron cannot be predicted, only the probability of its being at a given position; therefore electrons in atoms and molecules act as if they are "smeared out" in space. For one-electron systems, the electron density at any point is proportional to th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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