Single neopentane reactions

Fig. 8.18. Schematic, two-dimensional description of the replacement process corresponding to reaction (8.105). (a) Four methane molecules are brought from infinite separation to the positions of the four peripheral methyl groups of neopentane. The four hydrogens pointing toward the center are indicated by the dark areas. The distance of closest approach between any two of the methane molecules is 2.51 A (compared to 1.53 A in the case of ethane), (b) The four methane molecules are replaced by a single neopentane molecule in roughly the same configuration as in (a). There is a new carbon nucleus added which partially compensates for the loss of the four inner hydrogens.

The hydrogenolysis of neopentane occurs primarily by breaking of a single C—C bond to produce methane and isobutane as the major reaction products Small amounts of ethane and propane were also produced. The reaction kinetics were similar on the two surfaces, indicating a similar mechanism for both surfaces. 

Davis et al. (23) also studied the isomerization and hydrogenolysis of isobutane, n-butane, and neopentane over flat, stepped, and kinked Pt single-crystal surfaces. The rates and selectivities of butane isomerization and consecutive rearrangements were maximized on (100) portions of the surfaces. Competing hydrogenolysis reactions were most rapid on surfaces containing the greatest step- and kink-site densities. 

Engstrom et al. (75-78) have compared the reactions of several small hydrocarbons with H2 over different single-crystal surfaces of iridium. For ethane, propane, n-butane, and neopentane, the dominant reaction pathway on both Ir(lll) and Ir(l 10)—(1 x 2) was cleavage of a single C—C bond, except for the case of n-butane or Ir(lll) (77). The major reaction channels involved demethylization of the parent hydrocarbon, except for butane on Ir(l 10)-(1 x 2), which made mostly ethane (75). This... 

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