88 Sentences With "intermediacy" | Random Sentence Generator

The arylation of alkylthiolates proceeds by the intermediacy of cuprous thiolates.

Such catalysis is assumed to proceed via the intermediacy of carbene complexes.

Dwarf dogwoods: Intermediacy and the morphological landscape. Systematic Botany 19: 539-556.

The conversion entails the intermediacy of gluconate and ribulose. Ribose has been detected in meteorites.

Chlorination of CS2 provides a route to carbon tetrachloride: :CS2 \+ 3 Cl2 → CCl4 \+ S2Cl2 This conversion proceeds via the intermediacy of thiophosgene, CSCl2.

Cyclooctatetraene is produced from acetylene via the intermediacy of metal alkyne complexes. Variant of this reaction are exploited for the synthesis of substituted pyridines. The Pauson–Khand reaction provides a route to cyclopentenones via the intermediacy of cobalt-alkyne complexes. With the shift away from coal-based (acetylene) to petroleum-based feedstocks (olefins), catalytic reactions with alkynes are not widely practiced industrially.

The only primitive notions in ordered geometry are points A, B, C, ... and the ternary relation of intermediacy [ABC] which can be read as "B is between A and C".

S. J. Lippard, J. M. Berg "Principles of Bioinorganic Chemistry" University Science Books: Mill Valley, CA; 1994. . Selenium- containing proteins are produced from inorganic selenium via the intermediacy of selenophosphate (PSeO33−).

VCl4 is a catalyst for the polymerization of alkenes, especially those useful in the rubber industry. The underlying technology is related to Ziegler–Natta catalysis, which involves the intermediacy of vanadium alkyls.

Many homogeneous catalysts operate via the intermediacy of metal alkyls. These reactions include hydrogenation, hydroformylation, alkene isomerization, and olefin polymerization. It is assumed that the corresponding heterogeneous reactions also involve metal- alkyl bonds.

The tetrabromide and tetrachlorides of titanium react to give a statistical mixture of the mixed tetrahalides, TiBr4−xClx (x = 0-4). The mechanism of this redistribution reaction is uncertain. One proposed pathway invokes the intermediacy of dimers.

Via Diels-Alder reactions, it is a precursor to some commercial fragrances, including lyral, norbornene-2-carboxaldehyde, and myrac aldehyde. The monomer 3,4-epoxycyclohexylmethyl-3’,4’-epoxycyclohexane carboxylate is also produced from acrolein via the intermediacy of tetrahydrobenzaldehyde.

Meyer, V.; Locher, J. "Untersuchungen über die Constitution der Nitrolsäuren (Researches on the constitution of the nitrolic acids)" Deut. Chem. Ges. Ber., 1874, volume 7, pp. 670-5. The reaction proceeds via the intermediacy of the nitronate anion.

These observations implied that the aporphine prestephanine (10) would be an obligatory intermediate in the biosynthesis, which would involve the intermediacy of the proaporphines orientalinone (8) and orientalinol (9) via the known intramolecular dienone-dienol-phenol sequence for the transformation of benzyltetrahydroisoquinolines to aporphines. A potential role for CYP80G2, a cytochrome P450 that has been demonstrated to catalyze the intramolecular C-C phenol coupling of several benzyltetrahydroisoquinolines, in this orientaline (7) to prestephanine (10) transformation has been suggested. (±)‑[aryl‑3H]‑Prestephanine was incorporated into AA-I confirming its intermediacy in the biosynthesis; and also (±)‑[aryl‑3H]‑stephanine was incorporated into AA-I.

The perrhenate ion reacts with the cyanide to give trans-[ReO2(CN)4]3−. With sulfide sources such as hydrogen sulfide, one obtains black ReS2 and Re2S7. These species form via the intermediacy of ReO3S−. Heating ammonium perrhenate gives Re2O7 and then ReO2.

Isocyanates are produced from amines by phosgenation, i.e. treating with phosgene: :RNH2 \+ COCl2 → RNCO + 2 HCl These reactions proceed via the intermediacy of a carbamoyl chloride (RNHC(O)Cl). Owing to the hazardous nature of phosgene, the production of isocyanates requires special precautions.

It is impossible to distinguish Arbutus × andrachnoides individuals from the parent species using traditional botanical methods since they display a complete spectrum of parental traits. DNA testing and statistical methods centered on characterizing the intermediacy of the individual must be used instead.

It is used as a source of the chelating agent EDTA4-. A 1% aqueous solution has a pH of approximately 11.3. When dissolved in neutral water, it converts partially to H2EDTA2-. Ethylenediaminetetraacetic acid is produced commercially via the intermediacy of tetrasodium EDTA.

Cyclononatetraenyl cation is an 8π system. Its intermediacy is implicated in the solvolysis of 1. The facile solvolysis of 1 suggests that the cation is stabilized. Computation and experimental evidence suggest that C9H9+ is a rare example of a ground state species that exhibits Möbius aromaticity.

Lipton, F.; Sorensen, M.; Sadler, C.; Shapiro, H. J. Organomet. Chem. 1980, 186, 155. Usually, vicinal difunctionalizations are carried out in one pot, without the intermediacy of a neutral protected enolate. However, in specific cases it may be necessary to protect the intermediate of β-addition.

Ordered geometry is a form of geometry featuring the concept of intermediacy (or "betweenness") but, like projective geometry, omitting the basic notion of measurement. Ordered geometry is a fundamental geometry forming a common framework for affine, Euclidean, absolute, and hyperbolic geometry (but not for projective geometry).

Reaction scheme of the alkyne metathesis - substituents are colored Alkyne metathesis is an organic reaction that entails the redistribution of alkyne chemical bonds. The reaction requires metal catalysts. Mechanistic studies show that the conversion proceeds via the intermediacy of metal alkylidyne complexes. The reaction is related to olefin metathesis.

Metal-catalyzed oxidations with O2 proceed via the intermediacy of dioxygen complexes, although the actual oxidants are often oxo derivatives. The reversible binding of O2 to metal complexes has been used as a means to purify oxygen from air, but cryogenic distillation of liquid air remains the dominant technology.

Safranal is an organic compound isolated from saffron, the spice consisting of the stigmas of crocus flowers (Crocus sativus). It is the constituent primarily responsible for the aroma of saffron. It is believed that safranal is a degradation product of the carotenoid zeaxanthin via the intermediacy of picrocrocin.

Emma Goldman was also a radical ideologue who studied the works of people like Walt Whitman and thus disseminated the idea of "sexual intermediacy". Waisbrooker and Goldman and other women like them exeplified feminist ideology that fit into the larger anarchist canon that had developed in 20th century America.

Sulfur chloride pentafluoride (), a useful source of the SF5 group, is prepared from SF4. Hydrolysis of SF4 gives sulfur dioxide: :SF4 \+ 2 H2O → SO2 \+ 4 HF This reaction proceeds via the intermediacy of thionyl fluoride, which usually does not interfere with the use of SF4 as a reagent.

Wittig et al. invoked zwitterionic intermediate in the reaction of fluorobenzene and phenyllithium to give biphenyl. This hypothesis was later confirmed.Modern Arylation Methods. Edited by Lutz Ackermann 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim center In 1953 14C labeling experiments provided strong support for the intermediacy of benzyne.

Cobalt is found in vitamin B12 and related enzymes. These cofactors catalyze unusual reactions involving the intermediacy of Co-C bonds. In these reactions, the oxidation state of cobalt can vary from Co(III) to Co(I). In methylcobalamin the ligand is a methyl group, which is electrophilic.

The trans,trans isomer can be prepared in high yield and purity by condensation of benzaldehyde and acetone with sodium hydroxide in a water/ethanol medium followed by recrystallization. :Dibenzalacetone synthesis This reaction, which proceeds via the intermediacy of benzylideneacetone, compound is often prepared in organic chemistry classes.

In his original publication, Mukaiyama proposed that the reaction proceeded through the intermediacy of a cobalt peroxide adduct. A metal exchange reaction between a hydrosilane and the cobalt peroxide adduct leads to a silyl peroxide, which is converted to the alcohol upon reduction, presumably via action of the cobalt catalyst. mukaiyama scheme Studies investigating the mechanism of cobalt-catalyzed peroxidation of alkenes by Nojima and coworkers, support the intermediacy of a metal hydride that reacts with the alkene directly to form a transient cobalt- alkyl bond. Homolysis generates a carbon centered radical that reacts directly with oxygen and is subsequently trapped by a cobalt(II) species to form the same cobalt-peroxide adduct as suggested by Mukaiyama.

A variety of homogeneous and heterogeneous catalysts have been evaluated. Many such processes are assumed to operate via the intermediacy of metal carbon dioxide complexes. Many processes suffer from high overpotential, low current efficiency, low selectivity, slow kinetics, and/or poor catalyst stability.Halmann and Steinberg, "Greenhouse Gas Carbon Dioxide Mitigation," Lewis Publishers, 1999.

In most regions only one or two morphs occur, and females showing a level of intermediacy between these morphs are known (e.g. resembling rufous morph, but with black neck and faint vermiculations to the wings). This species has a similar voice to several other curassows, its call consisting of a "peculiar" lingering whistle.

Electropositive metals (Ti, Zr, Hf, Zn) and some other metals form hydrides with the stoichiometry MH or sometimes MH2 (M = Ti, Zr, Hf, V, Zn). The best studied are the binary hydrides of palladium, which readily forms a limiting monohydride. In fact, hydrogen gas diffuses through Pd windows via the intermediacy of PdH. K2ReH9.

This observation implies the intermediacy of the bimetallic complex [Co(NH3)5(μ-Cl)Cr(H2O)5]4+, wherein "μ-Cl" indicates that the chloride bridges between the Cr and Co atoms, serving as a ligand for both. This chloride serves as a conduit for electron flow from Cr(II) to Co(III), forming Cr(III) and Co(II).

Cyanuric chloride is prepared in two steps from hydrogen cyanide via the intermediacy of cyanogen chloride, which is trimerized at elevated temperatures over a carbon catalyst: :HCN + Cl2 → ClCN + HCl :240px In 2005, approximately 200,000 tons were produced.Klaus Huthmacher, Dieter Most "Cyanuric Acid and Cyanuric Chloride" in Ullmann's Encyclopedia of Industrial Chemistry, 2005, Wiley-VCH, Weinheim. .

Mechanism of NF-κB action. In this figure, the NF-κB heterodimer consisting of Rel and p50 proteins is used as an example. While in an inactivated state, NF- κB is located in the cytosol complexed with the inhibitory protein IκBα. Through the intermediacy of integral membrane receptors, a variety of extracellular signals can activate the enzyme IκB kinase (IKK).

The dimers are sometimes called azobenzenedioxides. The cis-trans isomerization occurs via the intermediacy of the monomer. In the case of nitrosobenzene itself, the metastable monomeric form could be prepared by sublimation onto a cold finger. The monomeric material is selectively sublimed due to its lower molecular weight and is collected on a cold finger as lustrous, dark green crystals.

The patent specifically involved the intermediacy of TiI4 and ZrI4, which were volatilized (leaving impurities as solid). At atmospheric pressure TiI4 melts at 150 °C and boils at 377 °C, while ZrI4 melts at 499 °C and boils at 600 °C. The boiling points are lower at reduced pressure. The gaseous metal tetraiodide is decomposed on a white hot tungsten filament (1400 °C).

The largest scale reaction is its esterification to give the corresponding ester ethyl cyanoacetate, which is then transformed to ethyl cyanoacrylate used as superglue, via reaction with formaldehyde. As of 2007, more than 10,000 tons of cyanoacetic acid were produced annually. Cyanoacetic acid is a versatile intermediate in the preparation of chemicals. it is a precursor to synthetic caffeine via the intermediacy of theophylline.

Such reactions proceed via the intermediacy of cis- dichlorobis(triphenylphosphine)platinum(II). Nitrogen-based ligands do not often support the formation of platinum complexes of alkenes and alkynes. Zerovalent organoplatinum complexes lacking phosphine ligands are often prepared via PtCl2(COD). :Li2C8H8 \+ PtCl2(COD) + 3 C7H10 → [Pt(C7H10)3] + 2 LiCl + C8H8 \+ C8H12 :Pt(C7H10)3 \+ 2 COD → Pt(COD)2 \+ 3 C7H10 where C7H10 is norbornene.

Na(silox) is usually prepared by deprotonation of the silanol (t-Bu)3SiOH, which is prepared by a multistep route via the intermediacy of (t-Bu)2SiF2.Edward M. Dexheimer and Leornard Spialter, Lee D. Smithson "Tri-t-butylsilane: synthesis, physical properties, derivatives, and reactivity towards ozonolysis, chlorination, fluorination, and hydrolysis" Journal of Organometallic Chemistry 102, 1975, 21-27.. It is also obtained by treatment of tBu3SiNa with nitrous oxide.

The synthesis of t-BuCP entails the reaction of pivaloyl chloride and P(SiMe3)3. The reaction proceeds via the intermediacy of a bis(trimethylsilyl)pivaloylphosphine, which undergoes a 1,3-silyl shift to form E- or Z-phosphoalkene isomers. Carrying out the phosphoalkene reaction at 120-200 °C in the presence of catalytic amounts of solid NaOH forms the final t-BuCP product.Becker, Gerd; Gresser, Gudrun; Uhl, Werner.

The reaction requires one equivalent each of the diimide, which is the dehydrating agent, and the sulfoxide, the oxidant: :(CH3)2SO + (CyN)2C + R2CHOH → (CH3)2S + (CyNH)2CO + R2C=O Typically the sulfoxide and diimide are used in excess. The reaction cogenerates dimethyl sulfide and a urea. Dicyclohexylurea ((CyNH)2CO) can be difficult to remove from the product. In terms of mechanism, the reaction is proposed to involve the intermediacy of an alkoxysulfonium ylide.

A large scale application of carbenes is the industrial production of tetrafluoroethylene, the precursor to Teflon. Tetrafluoroethylene is generated via the intermediacy of difluorocarbene: : CHClF2 → CF2 \+ HCl :2 CF2 → F2C=CF2 The insertion of carbenes into C–H bonds has been exploited widely, e.g. the functionalization of polymeric materials and electro-curing of adhesives. The applications rely on synthetic 3-aryl-3-trifluoromethyldiazirines, a carbene precursor that can be activated by heat, light, or voltage.

Most common imides are prepared by heating dicarboxylic acids or their anhydrides and ammonia or primary amines. The result is a condensation reaction: : (RCO)2O + R′NH2 → (RCO)2NR′ + H2O These reactions proceed via the intermediacy of amides. The intramolecular reaction of a carboxylic acid with an amide is far faster than the intermolecular reaction, which is rarely observed. They may also be produced via the oxidation of amides, particularly when starting from lactams.

The carbylamine reaction (also known as the Hoffmann isocyanide synthesis) is the synthesis of an isocyanide by the reaction of a primary amine, chloroform, and base. The conversion involves the intermediacy of dichlorocarbene. Illustrative is the synthesis of tert-butyl isocyanide from tert-butylamine in the presence of catalytic amount of the phase transfer catalyst benzyltriethylammonium chloride. :Me3CNH2 \+ CHCl3 \+ 3 NaOH → Me3CNC + 3 NaCl + 3 H2O Similar reactions have been reported for aniline.

The prevalent mechanism, called the Chalk-Harrod mechanism, assumes an intermediate metal complex that contains a hydride, a silyl ligand (R3Si), and the alkene substrate. Oxidative addition proceeds by the intermediacy of a sigma-complex, wherein the Si-H bond is not fully broken. Hydrosilylation of alkenes usually proceeds via anti-Markovnikov addition, i.e., silicon is placed at the terminal carbon when hydrosilylating a terminal alkene Variations of the Chalk-Harrod mechanism exist.

Juveniles of both sexes resemble the adult female. As the male plumage takes several years to complete, individuals showing a level of intermediacy between full adult male and female-like juveniles are commonly seen (in particular female-plumaged birds with red, or yellow in C. pareola regina, crowns). Manakins of the genus Chiroxiphia have an unusual mating system, based on female mate choice. In order to mate successfully, males have to form partnerships with another male.

PS–C bonds can also be formed through many comparable approaches, usually by alkylating a free phosphorous thioate anion or thioic acid. They are conceptually derived from the inorganic thiophosphates (PO4−xS). In fact, many are prepared via the intermediacy diorganodithiophosphoric acids, which are prepared by treating phosphorus pentasulfide with alcohols: :P2S5 \+ 4 ROH → 2 (RO)2PS2H + H2S Dimethyl dithiophosphoric acid and diethyl dithiophosphoric acid are obtained in this way. The former is a precursor to malathion.

Some metal hydrides form when a metal complex is treated with hydrogen in the presence of a base. The reaction involves no changes in the oxidation state of the metal and can be viewed as splitting H2 into hydride (which binds to the metal) and proton (which binds to the base). :MLnx+ \+ Base + H2 ⇌ HMLn(x-1)+ \+ HBase+ Such reaction are assumed to involve the intermediacy of dihydrogen complexes. Bifunctional catalysts activate H2 in this way.

The Frilly Gecko, the smallest of them, travel from trees uniquely on the lowest part of the same tree to avoid predators. Geckos are cryptic species that are hidden during the day and active during the night, unlike the many arboreal agamids. In addition, their color patterns normally match the substrate where they stay allowing them to go ignored. The flat-tailed gecko (Cosymbotus platyuurus), a species strongly related to the frilly gecko, is another example of intermediacy.

Bromopentafluorobenzene is an organofluorine compound with the formula C6F5Br. It is a colorless liquid that is used to prepare pentafluophenyl compounds. These syntheses typically proceed via the intermediacy of C6F5Li or the Grignard reagent. Illustrative is preparation of tris(pentafluorophenyl)borane:Piers, W. E.; Chivers, T. “Pentafluorophenylboranes: from Obscurity to Applications”, Chemical Society Reviews, 1997, 26, 345-354. :3 C6F5MgBr + BCl3 → (C6F5)3B + 3 MgBrCl Other derivatives include LiB(C6F5)4, [CuC6F5]4, and Ni(C6F5)2(dioxane)2.

YCl3 is often prepared by the "ammonium chloride route," starting from either Y2O3 or hydrated chloride or oxychloride. or YCl3·6H2O. These methods produce (NH4)2[YCl5]: ::10 NH4Cl + Y2O3 → 2 (NH4)2[YCl5] + 6 NH3 \+ 3 H2O ::YCl3·6H2O + 2 NH4Cl → (NH4)2[YCl5] + 6 H2O The pentachloride decomposes thermally according to the following equation: :: (NH4)2[YCl5] → 2 NH4Cl + YCl3 The thermolysis reaction proceeds via the intermediacy of (NH4)[Y2Cl7]. Treating Y2O3 with aqueous HCl produces the hydrated chloride (YCl3·6H2O).

That exchange occurs at all illustrates the ability of some compounds to be labile (fast reactions) but also stable (high formation constants). The reaction rate is described as follows: ::rate = k2[M(CN)42−][CN−], where k2 120 M−1−s−1 The bimolecular kinetics implicate a so-called associative pathway. The associative mechanism of exchange entails rate-limiting attack of cyanide on [Pd(CN)4]2−, possibly with the intermediacy of a highly reactive pentacoordinate species [Pd(CN)5]3−.

HCN is the precursor to sodium cyanide and potassium cyanide, which are used mainly in gold and silver mining and for the electroplating of those metals. Via the intermediacy of cyanohydrins, a variety of useful organic compounds are prepared from HCN including the monomer methyl methacrylate, from acetone, the amino acid methionine, via the Strecker synthesis, and the chelating agents EDTA and NTA. Via the hydrocyanation process, HCN is added to butadiene to give adiponitrile, a precursor to Nylon-6,6.

Triflic acid reacts with acyl halides to give mixed triflate anhydrides, which are strong acylating agents, e.g. in Friedel–Crafts reactions. :CH3C(O)Cl + CF3SO3H → CH3C(O)OSO2CF3 \+ HCl :CH3C(O)OSO2CF3 \+ C6H6 → CH3C(O)C6H5 \+ CF3SO3H Triflic acid catalyzes the reaction of aromatic compounds with sulfonyl chlorides, probably also through the intermediacy of a mixed anhydride of the sulfonic acid. Triflic acid promotes other Friedel–Crafts-like reactions including the cracking of alkanes and alkylation of alkenes, which are very important to the petroleum industry.

In general, on the typical laboratory scale, the direct reaction of a haloalkane with sodium hydrosulfide is inefficient owing to the competing formation of sulfides. Instead, alkyl halides are converted to thiols via an S-alkylation of thiourea. This multistep, one-pot process proceeds via the intermediacy of the isothiouronium salt, which is hydrolyzed in a separate step:. : CH3CH2Br + SC(NH2)2 → [CH3CH2SC(NH2)2]Br : [CH3CH2SC(NH2)2]Br + NaOH → CH3CH2SH + OC(NH2)2 \+ NaBr The thiourea route works well with primary halides, especially activated ones.

In practice, terminal and disubstituted alkenes are good substrates, but more hindered alkenes are slower to hydrogenate. The hydrogenation of alkynes is troublesome to control since alkynes tend to be reduced to alkanes, via intermediacy of the cis-alkene.Kevin Burgess, Wilfred A. van der Donk, Chul-Ho Jun, Young Jun Park, "Chlorotris(triphenylphosphine)-rhodium(I)" Encyclopedia of Reagents for Organic Synthesis 2005 John Wiley & Sons. Ethylene reacts with Wilkinson's catalyst to give RhCl(C2H4)(PPh3)2, but it is not a substrate for hydrogenation.

WO2Cl2 is prepared by ligand redistribution reaction from tungsten trioxide and tungsten hexachloride: : 2 WO3 \+ WCl6 -> 3 WO2Cl2 Using a two-zone tube furnace, a vacuum-sealed tube containing these solids is heated to 350 °C. The yellow product sublimes to the cooler end of the reaction tube. No redox occurs in this process. An alternative route highlights the oxophilicity of tungsten: :WCl6 \+ 2 O(Si(CH3)3)2 -> 3 WO2Cl2 \+ 4 ClSi(CH3)3 This reaction, like the preceding one, proceeds via the intermediacy of WOCl4.

Insight into the biosynthesis of the isopropoxy-2-naphthonate appendage was similarly gained by comparative analysis of the ked cluster to those of neocarzinostatin and maduropeptin, enediynes with naphthonate or benzoate substructures, respectively. Five genes, KedN1–N5, bear high sequence homology with the enzymes responsible for naphthonate synthesis in neocarzinostatin—consequently, the intermediacy of 3,6,8-trihydroxy-2-naphthoic acid is proposed in kedarcidin biosynthesis. This compound is believed to be oxygenated to the 3,6,7,8-tetrahydroxy derivative, then triply O-methylated by KedN1, an O-methyltransferase.

One queen of A. silvestrii from a Winkler sample has a shred of membranous wing, as though it were irregularly torn or chewed off. Intercaste individuals show variable intermediacy between workers and queens, with variable presence of a single median ocellus, compound eyes of intermediate size, and an enlarged promesonotum. In spite of the relative commonness of these putative reproductives, males and winged queens are rare in Central America. None have appeared in hundreds of Winkler samples, and none have appeared in Malaise samples from the same sites where Adelomyrmex are abundant in the litter.

Prior to the Wacker process and the availability of cheap ethylene, acetaldehyde was produced by the hydration of acetylene. This reaction is catalyzed by mercury(II) salts: :C2H2 \+ Hg2+ \+ H2O → CH3CHO + Hg The mechanism involves the intermediacy of vinyl alcohol, which tautomerizes to acetaldehyde. The reaction is conducted at 90–95 °C, and the acetaldehyde formed is separated from water and mercury and cooled to 25–30 °C. In the wet oxidation process, iron(III) sulfate is used to reoxidize the mercury back to the mercury(II) salt.

In 1957, Ronald Breslow proposed that a relatively stable nucleophilic carbene, a thiazol-2-ylidene derivative, was involved in the catalytic cycle of vitamin B1 (thiamine) that yields furoin from furfural. In this cycle, the vitamin's thiazolium ring exchanges a hydrogen atom (attached to carbon 2 of the ring) for a furfural residue. In deuterated water, the C2-proton was found to rapidly exchange for a deuteron in a statistical equilibrium. Deuterium exchange of the C2-proton of thiazolium salt This exchange was proposed to proceed via intermediacy of a thiazol-2-ylidene.

The Nef isocyanide reaction is an addition reaction that takes place between isocyanides and acyl chlorides to form imidoyl chloride products, a process first discovered by John Ulrich Nef. 400x400px The product imidoyl chloride can be hydrolyzed to give the amide, trapped with other nucleophiles, or undergo halide abstraction with silver salts to form an acyl nitrilium intermediate. The reaction is of some theoretical interest, as kinetic measurements and DFT studies have indicated that the addition occurs in one step, without the intermediacy of a tetrahedral intermediate that is commonly proposed for carbonyl addition reactions.

In native chemical ligation, the thiol group of an N-terminal cysteine residue of an unprotected peptide 2 attacks the C-terminal thioester of a second unprotected peptide 1 in an aqueous buffer at pH 7.0, 20 °C The reaction proceeded through the intermediacy of a thioester containing the sulfur of the cysteine residue. Wieland's work led to the 'active ester' method for making protected peptide segments in conventional solution synthesis in organic solvents. In the 1990s, Stephen Kent and coworkers at The Scripps Research Institute independently developed "Native Chemical Ligation", the first practical method to ligate large unprotected peptide fragments.

Cyclohexanone is produced by the oxidation of cyclohexane in air, typically using cobalt catalysts: :C6H12 \+ O2 → (CH2)5CO + H2O This process co-forms cyclohexanol, and this mixture, called "KA Oil" for ketone-alcohol oil, is the main feedstock for the production of adipic acid. The oxidation involves radicals and the intermediacy of the hydroperoxide C6H11O2H. In some cases, purified cyclohexanol, obtained by hydration of cyclohexene, is the precursor. Alternatively, cyclohexanone can be produced by the partial hydrogenation of phenol: :C6H5OH + 2 H2 → (CH2)5CO This process can also be adjusted to favor the formation of cyclohexanol.

Guanidine can be obtained from natural sources, being first isolated by Adolph Strecker via the degradation of guanine. It was first synthesized in 1861 by the oxidative degradation of an aromatic natural product, guanine, isolated from Peruvian guano. A laboratory method of producing guanidine is gentle (180-190 °C) thermal decomposition of dry ammonium thiocyanate in anhydrous conditions: :3 NH4SCN = 2 CH5N3 + H2S + CS2 The commercial route involves a two step process starting with the reaction of dicyandiamide with ammonium salts. Via the intermediacy of biguanidine, this ammonolysis step affords salts of the guanidinium cation (see below).

Some metal alkyls feature agostic interactions between a C-H bond on the alkyl group and the metal. Such interactions are especially common for complexes of early transition metals in their highest oxidation states. One determinant of the kinetic stability of metal-alkyl complexes is the presence of hydrogen at the position beta to the metal. If such hydrogens are present and if the metal center is coordinatively unsaturated, then the complex can undergo beta-hydride elimination to form a metal-alkene complex: center These conversions are assumed to proceed via the intermediacy of agostic interactions.

The species was originally described by Carl Christensen in 1924 as Pellaea connectens. Genera in the cheilanthoid ferns have proven difficult to circumscribe due to homoplasy, and Christensen bestowed its epithet because he considered it to connect, by morphological intermediacy, the genera Adiantopsis, Cheilanthes, Notholaena and Pellaea. Progress in fern taxonomy has resulted in the subdivision of several of these genera: in particular, a group of ferns, frequently bearing farina on the leaf underside and previously placed either in Notholaena or Pellaea as sect. Argyrochosma, were elevated to become the genus Argyrochosma by Michael D. Windham in 1987.

These reactions proceed via the intermediacy of metal acyl hydrides. An example of this is the Tsuji–Wilkinson decarbonylation reaction using Wilkinson's catalyst. (Strictly speaking, the noncatalytic version of this reaction results in the formation of a rhodium carbonyl complex rather than free carbon monoxide.) This reaction is generally carried out on small scale in the course of a complex natural product total synthesis, because although this reaction is very efficient at slightly elevated temperatures (e.g., 80 °C) when stoichiometric rhodium is used, catalyst turnover via extrusion of CO requires dissociation of a very stable rhodium carbonyl complex and temperatures exceeding 200 °C are required.

Mo6Cl12 is prepared by the reaction of molybdenum(V) chloride with molybdenum metal: :12 MoCl5 \+ 18 Mo -> 5 Mo6Cl12 This reaction proceeds via the intermediacy of MoCl3 and MoCl4, which also are reduced by the presence of excess Mo metal. The reaction is conducted in a tube furnace at 600–650 °C. Once isolated, Mo6Cl12 undergoes many reactions with retention of the Mo612+ core. Heating in concentrated HCl gives (H3O)2[Mo6Cl14]. The terminal chloride ligands, labeled "ausser" are readily exchanged: :(H3O)2[Mo6Cl14] + 6 HI -> (H3O)2[Mo6Cl8I6] + 6 HCl Under more forcing conditions, all 14 ligands can be exchanged, to giving salts of [Mo6Br14]2− and [Mo6I14]2−.

Copper(II) acetate has found some use as an oxidizing agent in organic syntheses. In the Eglinton reaction Cu2(OAc)4 is used to couple terminal alkynes to give a 1,3-diyne: :Cu2(OAc)4 \+ 2 RC≡CH → 2 CuOAc + RC≡C−C≡CR + 2 HOAc The reaction proceeds via the intermediacy of copper(I) acetylides, which are then oxidized by the copper(II) acetate, releasing the acetylide radical. A related reaction involving copper acetylides is the synthesis of ynamines, terminal alkynes with amine groups using Cu2(OAc)4.. It has been used for hydroamination of acrylonitrile. It is also an oxidising agent in Barfoed's test.

DyCl3 is often prepared by the "ammonium chloride route", starting from either Dy2O3 or the hydrated chloride DyCl3·6H2O. These methods produce (NH4)2[DyCl5]: :10 NH4Cl + Dy2O3 → 2 (NH4)2[DyCl5] + 6 NH3 \+ 3 H2O :DyCl3·6H2O + 2 NH4Cl → (NH4)2[DyCl5] + 6 H2O The pentachloride decomposes thermally according to the following equation: :(NH4)2[DyCl5] → 2 NH4Cl + DyCl3 The thermolysis reaction proceeds via the intermediacy of (NH4)[Dy2Cl7]. Treating Dy2O3 with aqueous HCl produces the hydrated chloride DyCl3·6H2O, which cannot be rendered anhydrous by heating. Instead one obtains an oxychloride: :DyCl3 \+ H2O → DyOCl + 2 HCl Dysprosium(III) chloride is a moderately strong Lewis acid, which ranks as "hard" according to the HSAB concept.

The film, which co-starred and was co-written by sexologist Magnus Hirschfeld, refers to Hirschfeld's theory of "sexual intermediacy". The theory places homosexuality within a broad spectrum comprising heterosexuality, bisexuality, transgenderism, and transvestism (a word invented by Hirschfeld). The film's protagonist first meets his blackmailer at a costume party, and the blackmailer also frequents a drag club; these scenes are the earliest film footage of gay men and lesbians dancing. The film was initially shipped in 40 copies throughout Germany and the Netherlands by Oswald, and it was shown for nearly a year before the authorities stepped in and banned public screenings, allowing it to be shown only to doctors and lawyers.

Monothioacetals are less common, have the functional group RC(OR')(SR")H. Dithioacetals have the formula RC(SR')2H (symmetric dithioacetals) and RC(SR')(SR")H (asymmetric dithioacetals). The symmetric dithioacetals are relatively common. They are prepared by condensation of thiols or dithiols with aldehydes. These reactions proceed via the intermediacy of hemithioacetals: #Thiol addition to give hemithioacetal: RSH + R'CH(O) → R'CH(SR)(OH) #Thiol addition with loss of water to give dithioacetal: RSH + R'CH(OH)SR → R'CH(SR)2 \+ H2O Such reactions typically employ either a Lewis acid or Brønsted acid as catalyst. Dithioacetals generated from aldehydes and either 1,2-ethanedithiol or 1,3-propanedithiol are especially common among this class of molecules for use in organic synthesis.

Ureas in the more general sense can be accessed in the laboratory by reaction of phosgene with primary or secondary amines, proceeding through an isocyanate intermediate. Non-symmetric ureas can be accessed by the reaction of primary or secondary amines with an isocyanate. Also, urea is produced when phosgene reacts with ammonia: : COCl2 \+ 4 NH3 → (NH2)2CO + 2 NH4Cl Urea is byproduct of converting alkyl halides to thiols via a S-alkylation of thiourea. Such reactions proceed via the intermediacy of isothiouronium salts: : RX + CS(NH2)2 → RSCX(NH2)2X : RSCX(NH2)2X + MOH → RSH + (NH2)2CO + MX In this reaction R is alkyl group, X is halogen and M is an alkali metal.

The first general method for preparation of sulfene as an intermediate, reported simultaneously in 1962 by Gilbert Stork and by Günther Optiz, involved removal of hydrogen chloride from methanesulfonyl chloride using triethylamine in the presence of an enamine as trapping agent. The formation of a thietane 1,1-dioxide derivative was taken as evidence for the intermediacy of sulfene. Because of the highly electrophilic character of sulfene, the use of amines presents difficulties, since they can intercept the sulfene to form adducts. A simple alternative which avoids the use of amines involves desilylation of trimethylsilylmethanesulfonyl chloride with cesium fluoride in the presence of trapping agents. : (CH3)3SiCH2SO2Cl + CsF → [CH2=SO2] + (CH3)3SiF + CsCl Alternatively, sulfenes can be stabilized by installing amido substituents on the alkylidene substituent.

Epona (the horse-goddess) as seen at the Historical Museum of Bern, the most important Celtic cult attested to in Roman Dacia, 2nd century AD The Dacian priestly class may have influenced the druids of the Celts with the important Christian author Hippolytus of Rome (170-236 AD), claiming that the druids adopted the teachings of Pythagoras through the intermediacy of Zalmoxis. Roman Dacia's pantheon includes Celtic divinities brought to the province by both military and civilian elements. The most important Celtic cult attested in the new province is that of the horse- goddess Epona. Specific epithets in her honor as Augusta, Regina and Sancta are found on inscriptions from Alba Iulia, on the site of ancient settlement Apulon (Latin Apulum).

Under normal conditions, vinyl alcohol converts (tautomerizes) to acetaldehyde: :250px At room temperature, acetaldehyde (H3CC(O)H) is more stable than vinyl alcohol (H2C=CHOH) by 42.7 kJ/mol: :H2C=CHOH → H3CC(O)H ΔH298,g = −42.7 kJ/mol The industrial synthesis of acetaldehyde (Wacker process) proceeds via the intermediacy of a vinyl alcohol complex. The uncatalyzed keto–enol tautomerism by a 1,3-hydrogen migration is forbidden by the Woodward–Hoffmann rules and therefore has a high activation barrier and is not a significant pathway at or near room temperature. However, even trace amounts of acids or bases (including water) can catalyze the reaction. Even with rigorous precautions to minimize adventitious moisture or proton sources, vinyl alcohol can only be stored for minutes to hours before it isomerizes to acetaldehyde.

Ring size determines the stability of simple cycloalkynes Due to the significant geometric constraints imposed by the R–C≡C–R functionality, cycloalkynes smaller than cyclodecyne (C10H16) result in highly strained structures. While the cyclononyne (C9H14) and cyclooctyne (C8H12) are isolable (though strongly reactive) compounds, cycloheptyne (C7H10), cyclohexyne (C6H8) and cyclopentyne (C5H6) only exist as transient reaction intermediates or as ligands coordinating to a metal center. There is little experimental evidence supporting the existence of cyclobutyne (C4H4) or cyclopropyne (C3H2), aside from studies reporting the isolation of an osmium complex with cyclobutyne ligands. Initial studies which demonstrated the transient intermediacy of the seven-, six- and five-membered cycloalkynes relied on trapping of the high-energy alkyne with a suitable reaction partner, such as a cyclic dienes or diazo compounds to generate the Diels–Alder or diazoalkane 1,3-dipolar cycloaddition products, respectively.

Contamination from handling and intrusion from microbes create obstacles to the recovery of Ancient DNA. Consequently, most DNA studies have been carried out on modern Egyptian populations with the intent of learning about the influences of historical migrations on the population of Egypt. In general, various DNA studies have found that the gene frequencies of North African populations are intermediate between those of the Near East, the Horn of Africa, southern Europe and Sub Saharan Africa,Cavalli-Sforza, History and Geography of Human Genes, The intermediacy of North Africa and to a lesser extent Europe is apparent though Egypt's NRY frequency distributions appear to be much more similar to those of the Middle East than to any sub-Saharan African population, suggesting a much larger Eurasian genetic component.Cavalli-Sforza, L.L., P. Menozzi, and A. Piazza. 1994.

GdCl3 is usually prepared by the "ammonium chloride" route, which involves the initial synthesis of (NH4)2[GdCl5]. This material can be prepared from the common starting materials at reaction temperatures of 230 °C from gadolinium oxide: ::10 NH4Cl + Gd2O3 → 2 (NH4)2[GdCl5] + 6 NH3 \+ 3 H2O from hydrated gadolinium chloride: ::4 NH4Cl + 2 GdCl3∙6H2O → 2 (NH4)2[GdCl5] + 12 H2O from gadolinium metal: ::10 NH4Cl + 2 Gd → 2 (NH4)2[GdCl5] + 6 NH3 \+ 3 H2 In the second step the pentachloride is decomposed at 300 °C: :: (NH4)2[GdCl5] → GdCl3 \+ 2 NH4Cl This pyrolysis reaction proceeds via the intermediacy of NH4[Gd2Cl7]. The ammonium chloride route is more popular and less expensive than other methods. GdCl3 can, however, also be synthesized by the reaction of solid Gd at 600 °C in a flowing stream of HCl.

The mechanistic details of this reaction have been extensively explored by Crich’s laboratories.Crich, D.; Sun, S. J. Am. Chem. Soc. 1997, 119, 11217.Crich, D.; Chandrasekera, N. S. Angew. Chem. Int. Ed. 2004, 43, 5386. Low-temperature 1H, 13C, and 19F NMR spectroscopic investigations revealed that anomeric triflate 3 derived from 1 is the intermediate glycosyl donor. Moreover, the mechanism of glycosidic bond forming reaction (3→2) was examined thoroughly by the determination of kinetic isotopic effects (KIEs) and NMR spectroscopy. Consequently, the magnitude of KIEs indicated that the displacement of the triflate from 3 proceeded with the development of significant oxacarbenium ion character at the anomeric position. This might be rationalized either by (1) a dissociative mechanism involving the intermediacy of either a transient contact ion pair (CIP) 4 or a solvent-separated ion pair (SSIP) 5, or (2) a mechanistically variant transition state 7 (Scheme 2).

For instance, the synthesis of tetrakis(t-butyl)cyclopentadienone from the tris(t-butyl)bromocyclopentadienone (itself synthesized with much difficulty) required over 50 attempts before working conditions could be found. The synthesis was described as requiring "astonishing persistence and experimental skill" in one retrospective of the work. In a classic reference work on stereochemistry, the authors remark that "the relatively straightforward scheme shown [...] conceals both the limited availability of the starting material and the enormous amount of work required in establishing the proper conditions for each step." :Tetra-tert-butyl-tetrahedrane synthesis 1978 Eventually, a more scalable synthesis was conceived, in which the last step was the photolysis of a cyclopropenyl-substituted diazomethane, which affords the desired product through the intermediacy of tetra(tert- butyl)cyclobutadiene: This approach took advantage of the observation that the tetrahedrane and the cyclobutadiene could be interconverted (uv irradiation in the forward direction, heat in the reverse direction).

The one-million-year-old Homo sample BOU-VP-2/66 from the Dakanihylo Member, referred to as “Daka” calvaria, was discovered in Bouri, Ethiopia, found in the Middle Awash region of the Afar Rift. This area has, not surprisingly, been the source of many human ancestor fossils, with ages ranging from half a million years old to more than 6 million years old. The resemblance of the Daka Skull to Asian counterparts indicates that the early Eurasian and African fossil hominids represent demes of a widespread palaeospecies. The anatomical intermediacy of Daka between earlier and later African fossils provides evolutionary change evidence. There is a consensus that there is a “lack of calvarial evidence for a deep phylo-genetic division between the African and Asian fossils.” According to researchers, a phenetic approach, quantifying overall similarity of single specimens, found that the Daka calvaria shares affinities with two fossils from the Koobi Fora region of Africa, KNM-ER 3733 and KNM-ER 3883.

The general idea is that a charged species, RY+, can give rise to dissociation fragments via a transient complex, [R+ Y], in which the electrically charged partner, R+, can undergo molecular rearrangements at the same time as it rotates relative to the neutral partner, Y. Similarly, the neutral partner, Y, can also rotate relative to the charged partner, as well as having the ability to exchange Hydrogens and internal energy with it. More recently several research groups have provided evidence that revives Maccoll's original hypothesis, but with the variation that the fragments that sojourn in the presence of one another are both electrically uncharged.Suits, A.G., Roaming Atoms and Radicals: A New Mechanism in Molecular Dissociation Accounts of Chemical Research 2008, 41, 873–881 In other words, dissociations of a neutral molecule RX can take place in the gas phase via the intermediacy of radical pairs [R· X·], where X· can be as small as a hydrogen atom. In the gas phase such intermediates are often called roaming radicals.

Proposed catalytic cycle based on work by Nojima It is important to note that the mechanism laid out above is in marked contrast to previous mechanistic proposals, which suggest that a cobalt-peroxy complex inserts directly into alkenes. The aforementioned study by Nojima and coworkers disagrees with this proposal due to three observations: 1) the intermediacy of a cobalt-hydride observed via 1H NMR 2) the propensity of alkenes to undergo autooxidation to the α, β-unsaturated ketones or allylic alcohols when the same reaction is run in the absence of a hydrosilane 3) the predominant mode of decomposition of alkylperoxo-cobalt(III) species to an alkoxy or alkylperoxy radical via the Haber-Weiss mechanism. A recent review by Shenvi and coworkers, proposed that the Mukaiyama hydration operates via the same principles as metal hydride hydrogen atom transfer (MH HAT), elucidated by Jack Halpern and Jack R. Norton in their studies on hydrogenation of anthracenes by syngas and Co2(CO)8 and the chemistry of vitamin B12 mimics, respectively.

In a New Republic article, Coyne wrote that "we have many examples of transitional fossils between what anyone would consider different kinds: fish and amphibians (like Tiktaalik, which Nye mentioned), between amphibians and reptiles, between reptiles and mammals, between reptiles and birds, between land animals and whales, and of course, between early and modern humans, with early fossils showing intermediacy between the features of apelike ancestors and modern humans." Coyne believes that both sides of such debates between evolutionists and young earth creationists could benefit from a better understanding of the fossil record and for modern tools such as Isochron dating. He considers that the inability of creationists to address these subjects fully suggests that "religion can poison one's mind so deeply that it becomes immunized to the real truth about the cosmos." Coyne is also a critic of the Neurodiversity movement, claiming that in its extreme, neurodiversity wishes to deny medical treatment for any person with a mental condition, particularly autism, even if the person wants a medical treatment.