Hydrogen probability

Agnello and Laubach suggested that the dehydrogenation of A" -3-ketones to A -3-ketones by chloranil proceeds through the A -enol, which suffers hydride loss from C-7. The failure of 7a-methyl-A -3-ketones to undergo dehydrogenation while the 7/5-isomers do so readily indicates that specific removal of the 7a (axial) hydrogen probably occurs in unsubstituted compounds. ... 

Reduction of cyclic hydroxamic acids generally leads to lactams or the corresponding amines. Chemical methods have frequently been preferred to catalytic hydrogenation, probably because the choice of... 

Reports of reductive elimination from early transition metals are uncommon. However, Bullock and co-workers have reported the elimination of IMes from [WCp(IMes)(CO)2][B(C Fj) J to form the 2-H-imidazolium salt, during ketone hydrogenation probably via a form of reductive elimination process [38]. 

Dissolution of a zinc-ruthenium alloy in hydrochloric acid leaves an explosive residue of finely divided ruthenium [1], More probably this is the hydride, which may decompose on slight stimulus, the evolved hydrogen probably igniting because of the catalytic activity of the metal. Ruthenium prepared from its compounds by borohydride reduction is especially dangerous in this respect [2],... 

The mechanism for the hydrogenation probably involves Rh-jt interaction with the unsaturated systems. The selectivity of competitive hydrogenation experiments has established the relative order of the interaction forces [3] ... 

Not only the case of vinyl chloride but also styrene shows that the observed chain transfer to monomer is not the simple reaction described by Eq. 3-112. Considerable evidence [Olaj et al., 1977a,b] indicates that the experimentally observed Cm may be due in large part to the Diels-Alder dimer XII transferring a hydrogen (probably the same hydrogen transferred in the thermal initiation process) to monomer. 

A substantial difference was observed in the reactivities of the cis- and /ra j-isomers of 3,5-disubstituted quaternary isoxazolinium iodides on alkaline treatment. The attack by the base at the A -methyl hydrogens probably led to a hydroxyiminium intermediate, which, for the zA-isomers, gave tetrahydro-l,3-oxazine derivatives 551 as the main products by recyclization, besides small amounts of the 0 ,/3-enones 552, formed by a Hofmann-like elimination (Scheme 104). For the /ra j-counterparts, the 0 ,/3-enones 552 were obtained as the exclusive products <1995T2979>. 

This result prooves that the C=0 of a saturated molecule and the C=0 of an unsaturated aldehyde behave differently, and a sequence of hydrogenation probabilities can be defined unsaturated C=0 bond > alcohol C=C bond > saturated C=0 bond. 

Aromatic compounds with alkyl groups having a chain of at least three carbon atoms can undergo a shift of a y-hydrogen probably via a type of McLafferty rearrangement, giving rise to a prominent peak at m/z 92. 

The differences in deuterium and carbon isotope effects indicate the asymmetric transition state with more advanced carbon-carbon bond formation to the terminal Cl atom. The difference between deuterium isotope effects for HCI-S and Htmns hydrogens probably originates from experimental uncertainty. Theoretical calculations (B3LYP/6-31G, B3LYP/6-311+G ) for carbene addition to 1-butene were carried out for two modes with carbene approaching carbon atom Cl or C2. The best agreement for experimental isotope effects is for carbene attack on terminal carbon atom and the carbene-alkene separation in the transition state of 2.5 A. 

Ammonia is regenerated in the secondary reactions and atomic hydrogen probably takes a part in the regeneration process. 

The adsorption of each of the reactants and products on cobalt molybdate was studied under conditions as close as possible to reaction conditions. Butene and thiophene both showed strong temperature dependence, adsorption of the latter in particular being slow at the lower reaction temperatures. The temperature coefficients were 8.5 and 9.5 kcal. per mole, respectively. H2S adsorbed quickly and desorbed at a rate proportional to coverage, and hydrogen apparently behaved in the same way. Only relatively weakly bound or free hydrogen appeared to be reactive, but adsorbed hydrogen probably modified the adsorption of thiophene and of butene. 

The conduction is by a transient form of the occluded hydrogen, probably monatomic, and consists in a transport of electrical charges between points of different potential within the metal. 

Relatively little work has been done on the pyrolyses of cyclopentane and the higher cyclic paraffins, and the nature of the reactions has not been established. Cyclopentane decomposes by two processes, giving (a) cyclopentadiene and hydrogen probably by way of cyclopentene and (b) propene and ethylene (ring cleavage), viz. 

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