Effect of Alkyl Chain-Length on Dissociative Attachment: 1-Bromoalkanes on Si(100)-c(4×2)
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Bibliographic record
Abstract
Chemical reactivity as a function of chain-length was investigated for three 1-bromoalkanes on silicon. The physisorption and subsequent thermal dissociative attachment of bromoethane (EtBr), 1-bromopropane (PrBr), and 1-bromobutane (BuBr) on Si(100)-c(4×2) were examined by scanning tunneling microscopy in ultrahigh vacuum from 50 to 180 K, and interpreted by ab initio theory. These 1-bromoalkanes were found to physisorb and react exclusively over the inter-row sites of Si(100)-c(4×2), with activation barriers, E a, increasing with alkyl chain-length: E a = 343 ± 5 meV for EtBr, E a = 410 ± 6 meV for PrBr, and E a = 536 ± 2 meV for BuBr. Extensive ab initio calculations gave increasing barriers along the series: E c = 317 meV for EtBr, E c = 406 meV for PrBr, and E c = 430 meV for BuBr. On the basis of our calculated geometries, we interpret this dependence of thermal barrier on chain-length as due to the additional energy required with increasing chain-length in order to lift the alkyl chain away from the surface, in going from the initial physisorbed state to the reactive transition state. For BuBr, the measured E a significantly exceeded the calculated value. This increase in effective barrier-height could be due to a “dynamical delay” in optimizing the configuration of the alkyl chain.
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Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
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