Reactive hydrogen atoms

The weight in grams to provide one reactive hydrogen atom for every epoxide group in lOOg of liquid epoxide resin of epoxide equivalent 190. 

For the acetoxy radical, the for decarboxylation is about 6.5 kcal/mol and the rate is about 10 s at 60°C and 10 s at —80°C. Thus, only very rapid reactions can compete with decarboxylation. As would be expected because of the lower stability of aryl radicals, the rates of decarboxylation of aroyloxy radicals are slower. The rate for p-methoxybenzoyloxy radical has been determined to be 3 x 10 s near room temperature. Hydrogen donation by very reactive hydrogen-atom donors such as triethylsilane can compete with decarboxylation at moderate temperatures. 

In the single-stage production of polyurethanes, di-, tri-, or polyisocyanates are mixed directly with molecules containing two or more reactive hydrogen atoms, such as diols, diamines, and dicarboxylic acids. We typically increase the reaction rate by adding amine or organotin based catalysts. The reaction normally occurs rapidly, evolving much heat. In order to ensure... 

The hydrogen set free can add to unsaturated compounds these reactions occur in the lower reaches of the Titanian atmosphere. Hydrogen cannot escape from the upper atmosphere before it reacts. The authors suggest a catalytic scheme in which reactive hydrogen atoms are converted into molecular hydrogen (H2) without a net loss of unsaturated compound (here C4H2) ... 

Mannich reaction org chem Condensation of a primary or secondary amine or ammonia (usually as the hydrochloride) with formaldehyde and a compound containing at least one reactive hydrogen atom, for example, acetophenone. Also known as Mannich condensation reaction. man-ik re,ak-shon mannite See mannitol. ma,nlt ... 

In contrast to the sulfinylimines, the sulfonylimines are used only at a low temperature. Nagai et have studied the reaction of a sulfonylimine with enamines that do not have any reactive hydrogen atoms in the molecule ( Type C enamine). The cyclic product may be produced via a two-step mechanism in which a zwitterionic intermediate (168) occurs (Eq. 34). The Me... 

With the formation of free radicals having been initiated, these radicals react with oxygen (Reaction 3) to begin the propagation of the radical chains in forming a peroxy radical. The peroxy radical then attacks the 10-carbon-hydrogen bond to form the hydroperoxide radical (Reaction 4). [The possibility of such an intramolecular attack has been demonstrated in an aliphatic system where two reactive hydrogen atoms are located in the favorable 1,4-positions (9)]. 

In many cases, rate constants for the fragmentation reactions are not available, but the reactions can be deduced to be quite fast because intermediate radicals are not trapped efficiently by reactive hydrogen atom donors. 

Results of the polymerization of propylene oxide by these four kinds of organometallic compounds showed that the zinc compounds are superior to the aluminum compounds with respect to their stereoregulating power. It is noteworthy that the zinc catalyst is generally superior to the aluminum catalyst as the stereospedfic polymerization catalyst. Among the two organozinc compounds, EtZnNBu ZnEt was thought to be more suitable than EtZnNHBu for detailed studies, because the former was monomeric and had no reactive hydrogen atom. 

Comparison of the oxidation rates of carbon monoxide and hydrogen on transition metal carbides indicates that there is parallelism between both (Figure 16.1). It was found that the reactivity of hydrogen was higher than that of CO. This could be due to the formation mobile, reactive hydrogen atoms from hydrogen activation. 

This peroxyl radical can then abstract reactive hydrogen atoms from the substance undergoing autoxidation. 

From these examples one could infer that diazomethane would react with those nitro compounds which contain a reactive hydrogen atom. With that respect particularly important is recent work of de Boer [160],... 

The availability of a reactive hydrogen atom for chain transfer... 

Replacement of functional groups in the substrate other than the reactive hydrogen atom... 

A much higher stereoselectivity has been observed in the analogous reactions on the more rigid cyclic ketones, the reactive hydrogen atom to be replaced being in this case the Hax or Heq of cyclohexanone or analogous heterocyclic system 94, or the Hondo or Hexo of polycyclic ketones 95 of the norbomanonc series. 

Reaction (2) corresponds to the successive reactions (3) to (8). Because H is dissociatively adsorbed on Ni, numerous highly reactive hydrogen atoms are available on the surface and consequently, hydrogenation reactions (3), (5) and (7) are catalysed on nickel. Reactions (9b and 10) describe the decomposition of the ligand C Hj. Incorporation of aliphatic carbon is represented by reaction (lOa) that of interstitial or graphitic carbon is represented by reaction (10b). Incorporation of condensed species is represented by reactions (9c) and (9d). The methanation of carbon on nickel, reaction (12), has been extensively studied and references therein), generally from decomposition of CO, because it plays a key... 

If, however, the monomer has no such reactive hydrogen atom, some protogenic (e.g. HjO or HCl) or catiogenic (e.g. RCl) co-initiator is required to provide a source of protons or carbonium ions respectively, e.g. 

These processes can continue as on account of its three highly reactive hydrogen atoms, the phenol can form not only phenol monofurfurylol but also phenol difurfurylol, and phenol trifurfurylol, the latter being shown below, thus permitting the formation of arbitrarily... 

The highly reactive hydrogen atom is adsorbed on the cathodic metal and it chemically combines with a neighbor-bound hydrogen atom to form a hydrogen molecule that leaves the cathode as a gas after the bubble surpasses the surface tension of the electrode. 

---