Hydrogen addition reactions with

The aromatic primary and secondary stibines are readily oxidized by air, but they are considerably more stable than their aHphatic counterparts. Diphenylstibine is a powerful reducing agent, reacting with many acids to Hberate hydrogen (79). It has also been used for the selective reduction of aldehydes and ketones to the corresponding alcohols (80). At low temperatures, diphenylstibine undergoes an addition reaction with ketene (81) ... 

Butadiene also undergoes a 1,4-addition reaction with SO2 to give sulfolene [77-79-2]. This reaction followed by hydrogenation is commercially used to manufacture sulfolane [126-33-0] (56). 

Other special additions are used to deoxidize copper. Such alloys may be preferred in appHcations where embrittlement by hydrogen through reaction with internally dispersed copper oxide particles is a concern, such as in CllO. The most common deoxidized copper is C122, in which phosphoms reacts with copper oxide to form phosphoms pentoxide that can be slagged from the copper while molten. 

RhCl(PPh3)3 is a very active homogenous hydrogenation catalyst, because of its readiness to engage in oxidative addition reactions with molecules like H2, forming Rh—H bonds of moderate strength that can subsequently be broken to allow hydride transfer to the alkene substrate. A further factor is the lability of the bulky triphenylphosphines that creates coordinative unsaturation necessary to bind the substrate molecules [44]. 

Ene and Carbonyl-Ene Reactions. Certain double bonds undergo electrophilic addition reactions with alkenes in which an allylic hydrogen is transferred to the reactant. This process is called the ene reaction and the electrophile is known as an enophile A When a carbonyl group serves as the enophile, the reaction is called a carbonyl-ene reaction and leads to [3,-y-unsalurated alcohols. The reaction is also called the Prins reaction. 

Ketones and aromatic aldehydes undergo facile addition reactions with CDI (A) or better with A -sulfmyldiimidazole (B) to give diimidazolylmethanes and N-alkylene-imidazoles, depending on the presence of hydrogen atoms a to the carbonyl group ... 

Addition reactions with bromine, chlorine, hydrogen bromide or hydrogen chloride are very vigorous and may be explosive if uncontrolled. 

In the two previous sections, evidence has been presented concerning the chemisorbed states formed when benzene interacts with metal surfaces. It is not the intention in this Section to discuss benzene hydrogenation in detail, but rather to enquire whether studies of this hydrogen-addition reaction provide information about the chemisorbed state of benzene. 

However, selenium and tellurium do not react with hydrogen, so the hydrogen compounds are prepared by reacting the elements with a metal, then treating it with an acid. Selenium and tellurium undergo addition reactions with cyanides to yield selenocyanates and tellurocyanates ... 

Similar waves in the cathodic polarogram were observed by Donnet and Henrich 58) using oxidized carbon black. The wave disappeared after treatment with isobutyronitrile. It was assumed that isobutyro-nitrile gives an addition reaction with quinones. No reaction with this reagent was observed after reduction with hydrogen iodide, after treatment with aniline, or after treatment with diazomethane. The latter finding confirms the assumption by Studebaker et al. 38) that diazomethane is added to the quinones in the carbon black surface. 

Alkenes undergo addition reactions with hydrogen to form alkanes, with halogens to form dihaloalkanes, with hydrogen halides to form monohaloalkanes and with water to form alcohols. For example ... 

Certain electrophilic carbon-carbon and carbon-oxygen double bonds can undergo an addition reaction with alkenes in which an allylic hydrogen is transferred to the... 

Hydrogen chloride undergoes addition reactions with carbon-carbon double and triple bonds. Many addition products of olefins and acetylenes are important industrial raw materials. It adds to ethylene forming ethyl chloride ... 

Thieno[3,4-c]pyridines undergo an addition reaction with acrylonitrile followed by elimination of hydrogen sulfide to afford a mercaptoisoquinoline product (Equation 2) <2002CHE1342>. 

Discrete dimers of the head-to-head type have been found in the structures of the Ag+ complex of (145)570 and the Na+ complex of (145)571 respectively. The complexes were recrystallized from carbon tetrachloride. In both complexes each metal is five-coordinated in the cavity provided by one anion, and there is an additional reaction with the second anion [through an Ag+-phenyl interaction or an Na+-carboxylate oxygen atom (Figure 32a)]. When the Na+ complex was crystallized from a solvent of medium polarity, acetone, the head-to-head dimer was recovered.571 In contrast, recrystallization from a polar medium, methanol, gave a monomeric complex in which one methanol of solvation was also present.572 In all of these complexes an intramolecular head-to-tail hydrogen bond was present to hold the ligand in its pseudo-macrocyclic conformation. 

Most of the reported DSC studies involving base-catalysed cure are concerned with dicyanodiamide (DICY) which is a crystalline material, melting at 208 °C. At ambient temperature the solubility in epoxy resins is very low but above about 100 °C it is sufficiently soluble to initiate cure. DICY has free amino-hydrogen groups which can partake in addition reactions with epoxides ... 

Further chemistry of alkenes and alkynes is described in this chapter, with emphasis on addition reactions that lead to reduction and oxidation of carbon-carbon multiple bonds. First we explain what is meant by the terms reduction and oxidation as applied to carbon compounds. Then we emphasize hydrogenation, which is reduction through addition of hydrogen, and oxidative addition reactions with reagents such as ozone, peroxides, permanganate, and osmium tetroxide. We conclude with a section on the special nature of 1-alkynes— their acidic behavior and how the conjugate bases of alkynes can be used in synthesis to form carbon-carbon bonds. 

The use of hydrogen gas in hydrogenation reactions is often considered inconvenient, because of the necessity to carry out the reactions in closed vessels in an oxygen-free atmosphere. Additionally, reactions with hydrogen gas often require high pressure and the use of autoclaves. 

By this technique these authors have determined the rate constants and collision yields for a number of simple olefins, substituted olefins, and some aromatic hydrocarbons. For a number of years these determinations represented the only extensive set of rate constants of hydrogen atom reactions with olefins. The technique did not differentiate between addition and abstraction by hydrogen atoms from the olefins and the rates were the sum of the two. 

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