Hydrogenation of ethane

To give an idea of the wide rai e of catalytic systems that have been investigated where chemisorption data were essential to interpret the results, some of the author s papers will be discussed. Measurements were reported on the surface areas of a very wide range of metals that catalyze the hydrogenation of ethane. In the earliest paper, on nickel, the specific catalytic activity of a supported metal was accurately measured for the first time it was shown also that the reaction rate was direcdy proportional to the nickel surface area. Studies on the same reaction... 

An argument from heats of hydrogenation concludes that resonance is responsible for about two-thirds of the difference in stability between the central bond of hexaphenylethane and normal carbon-carbon bonds. It can be calculated from other thermochemical data that the heat of hydrogenation of ethane to two moles of methane is —13 kcal. In contrast the heat of hydrogenation of hexaphenylethane has been shown to be —35 kcal. per mole. 

The first report of rhodium catalysts for aldehyde reduction came from Marko who reported the use of RhCl3 3H20 under hydroformylation conditions [9]. It was suggested that the active species were rhodium carbonyls, and the catalyst system was successfully utilized in the hydrogenation of ethanal, propanal, and benzalde-... 

By replacing a hydrogen of ethane by methyl group, we obtain propane and the picture is like the same as in ethane and the eclipsed and staggered forms are as follows ... 

Hydrogenation reactions typify processes in which the total number of bonds and total number of lone pairs are conserved, but the numbers of each kind of formal bond are not conserved. For example, hydrogenation of ethane leads to the destruction of one CC bond and one HH bond, but to the creation of two new CH bonds. 

Dehydrogenation, hydrogenolysis, and hydrogenation of ethane Anodic AI2O3 with Pt layer 473 132... 

As the hydrogens of ethane are replaced by other atoms or groups of atoms, other factors affecting the relative stability of conformations appear van der Waals forces, dipole-dipole interactions, hydrogen bonding. But the tendency for the bond orbitals on adjacent carbons to be staggered remains, and any rotation away from the staggered conformation is accompanied by torsional strain. 

For example, if equimolar amounts of methane and ethane are allowed to react with a small amount of chlorine, about 400 times as much ethyl chloride as methyl chloride is obtained, showing that ethane is 400 times as reactive as methane. When allowance is made for the relative numbers of hydrogens in the two kinds of molecules, we see that each hydrogen of ethane i Aboill/5MF tmes as reactive as each hydrogen of methane. 

This section presents detailed procedures for determining which hydrogens in a molecule have identical chemical shifts due to chemical equivalence. The simplest examples of this are the four hydrogens of methane or the six hydrogens of ethane. There are some minor complications that might require a review of the material toward the end of Chapter 5, but on the whole these procedures are not difficult. 

Consider the hydrogens of ethane as an example. Replacing any one of the six hydrogens of ethane by a different atom, say, by chlorine, gives the same compound chloroethane. 

The six hydrogens of ethane are homotopic and are, therefore, chemical shifl equivalent. Ethane, consequently, gives only one signal in its NMR spectrum. [Remember, the barrier to rotation of the carbon—carbon bond of ethane is so low (Section 4.8), the various conformations of chloroethane interconvert rapidly.]... 

Table 16. Calculated Energies (kJ/mol) for the Hydrogenation of Ethane (ZPE = Zero point energy)...

Gufo, M., Prieto, J. and Cortes, C. (2006) Determination of kinetic parameters of the oxide-hydrogenation of ethane with CO2 on nanosized calcium-doped ceria under fast deactivation processes, Catal. Today, 112, pp. 148-152. 

The reaction between hydrogen and chlorine is probably also of this type and many organic free radical reactions (e.g. the decomposition of ethanal) proceed via chain mechanisms. 

CCls CHO. A colourless oily liquid with a pungent odour b.p. 98°C. Manut actured by the action of chlorine on ethanol it is also made by the chlorination of ethanal. When allowed to stand, it changes slowly to a white solid. Addition compounds are formed with water see chloral hydrate), ammonia, sodium hydrogen sulphite, alcohols, and some amines and amides. Oxidized by nitric acid to tri-chloroethanoic acid. Decomposed by alkalis to chloroform and a methanoate a convenient method of obtaining pure CHCI3. It is used for the manufacture of DDT. It is also used as a hypnotic. 

CH2 CH CH0. a colourless, volatile liquid, with characteristic odour. The vapour is poisonous, and intensely irritating to eyes and nose b.p. 53"C. It is prepared by the distillation of a mixture of glycerin, potassium sulphate and potassium hydrogen sulphate. It is manufactured by direct oxidation of propene or cross-condensation of ethanal with meth-anal. 

Figure 2-16. a) The redundant incidence matrix of ethanal can be compressed by b) omitting the zero values and c) omitting the hydrogen atoms, in the non-square matrix, the atoms are listed in columns and the bonds in rows. 

Figure 2-17. a) The redundanl bond malrix of ethanal with ihe zero values omitted, b) It can be compressed by reduction to the top right triangle, c) Omitting the hydrogen atoms provides the simplest non-redundant matrix representation. 

Figure 2-22. Non-redundant connection table of ethanal. Only non-hydrogen atoms are considered bonds with the lowest indices are counted once (see Figure 2-21).

The origin of a torsional barrier can be studied best in simple cases like ethane. Here, rotation about the central carbon-carbon bond results in three staggered and three eclipsed stationary points on the potential energy surface, at least when symmetry considerations are not taken into account. Quantum mechanically, the barrier of rotation is explained by anti-bonding interactions between the hydrogens attached to different carbon atoms. These interactions are small when the conformation of ethane is staggered, and reach a maximum value when the molecule approaches an eclipsed geometry. 

Methane ethane and cyclobutane share the common feature that each one can give only a single monochloro derivative All the hydrogens of cyclobutane for example are equivalent and substitution of any one gives the same product as substitution of any other Chlorination of alkanes m which the hydrogens are not all equivalent is more com plicated m that a mixture of every possible monochloro derivative is formed as the chlo rmation of butane illustrates... 

The relationship between reactants and products m addition reactions can be illustrated by the hydrogenation of alkenes to yield alkanes Hydrogenation is the addition of H2 to a multiple bond An example is the reaction of hydrogen with ethylene to form ethane... 

The relative rates of reaction of ethane toluene and ethylbenzene with bromine atoms have been measured The most reactive hydrocarbon undergoes hydrogen atom abstraction a million times faster than does the least reactive one Arrange these hydrocarbons in order of decreasing reactivity... 

Hydrogenation. Acetylene can be hydrogenated to ethylene and ethane. The reduction of acetylene occurs in an ammoniacal solution of chromous chloride (20) or in a solution of chromous salts in H2SO4 (20). The selective catalytic hydrogenation of acetylene to ethylene, which proceeds... 

Petroleum Gases and Naphtha. Methane is the main hydrocarbon component of petroleum gases. Lesser amounts of ethane, propane, butane, isobutane, and some 0 + light hydrocarbons also exist. Other gases such as hydrogen, carbon dioxide, hydrogen sulfide, and carbonyl sulfide are also present. 

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