Hydrocarbon hydrogenation, molecular

Iodine reacts with hydrocarbons to form iodine compounds, but compared to the other halogens, the equiUbria are unfavorable because the displacement step with the iodine atom is endothermic, requiring 4066.3 J (971.9 cal) for methane and 799.9 J (191.2 cal) for toluene. Hydrogen iodide can be used to reduce an alkah iodide to hydrocarbon plus molecular iodine. 

Let s assume that we want to find the structure of an unknown hydrocarbon. A molecular weight determination on the unknown yields a value of 82, which corresponds to a molecular formula of CfcHjo Since the saturated Q alkane (hexane) has the formula C61-114, the unknown compound has two fewer pairs of hydrogens (H]4 - H l() = H4 = 2 H2), and its degree of unsaturation is two. The unknown therefore contains two double bonds, one ring and one double bond, two rings, or one triple bond. There s still a long way to go to establish structure, but the simple calculation has told us a lot about the molecule. 

Another example of a solvent-dependent atom-transfer reaction is hydrogen abstraction by chlorine atoms during the photochemical chlorination of hydrocarbons with molecular chlorine for an excellent review, see reference [571]. Russel reported that in the photochlorination of 2,3-dimethylbutane, according to reaction scheme (5-68), certain solvents do not have any effect on the selectivity of the reaction as measured by the rate ratio whereas other solvents increase this ratio significantly (c/. 

The reverse reaction of protolytic ionization of hydrocarbons to carbenium ions is the reaction of carbenium ions with molecular hydrogen giving their parent hydrocarbons [Eq. (6.6)]. It can be considered as alkylation of H2 by the electrophilic carbenium ion through a pentacordinate carbonium ion. Indeed, Hogeveen and Bickel have experimentally reduced stable alkyl cations in superacids to hydrocarbons with molecular hydrogen. 

The direct reduction of SbFs in the absence of hydrocarbon by molecular hydrogen necessitates, however, more forcing conditions (50 atm, high temperature), which suggests that the protolytic ionization of alkanes proceeds probably via solvation of the pentacoordinate carbocation by SbFs and concurrent ionization-reduction [Eq. (6.13)]. 

Pan, J.-W. Rogers, D. W. Me Lafferty, F. J. (1999). Density functional calculations of enthalpies of hydrogenation, isomerization, and formation of small cyclic hydrocarbons, J. Molecular Structure (Theochem.), 468, pp. 59-66. 

Compounds A and B are both hydrocarbons of molecular weight 98. They re both optically active but have different specific rotations. Ozonolysis of A gives formaldehyde (CH20) and a ketone ozonolysis of B produces formaldehyde and another aldehyde. Treating either A or B with hydrogen/catalyst yields C, whose molecular weight is 100. C is an optically active compound. Give structures for A, B, and C. 

The very considerable research work of Bone and his associates led to his support of the hydroxylation mechanism for homogeneous oxidation of hydrocarbons with molecular oxygen. According to this mechanism, reaction between methane and oxygen takes place in steps methanol, formaldehyde, formic acid, and carbon dioxide, in the order named. That methanol has not been found among the products of methane oxidation under conditions where its presence could logically be expected does not necessarily preclude the possibility that it was the initial product. This is due to the thermal instability of methanol under the conditions and its tendency to decompose to hydrogen, carbon monoxide, and formaldehyde. 

The oxidation of hydrocarbons by molecular oxygen in the absence of metal complexes has been discussed in Chapter II. The oxidation of hydrocarbons with molecular oxygen, as well as with donors of an oxygen atom (hydrogen peroxide, alkyl hydroperoxides and some other compounds), is a very important field since many industrial processes are based on these reactions [1], In many cases, chain radical non-catalyzed autoxidation of samrated hydrocarbons is not very selective and the yields of valuable products are often low. The use of salts and complexes of transition metals creates great possibilities for solving problems of selective oxidation, as has been demonstrated for a number of important processes. 

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