歷來，反應箭頭圖（arrow-pushing diagrams）是一種描繪化學反應中電子移動的視覺工具，對理解反應機構具重要意義。隨著理論化學方法的進展，特別是內稟鍵軌域（Intrinsic Bond Orbital, IBO）分析的發展，使得這些圖示能夠從量子力學計算中嚴謹地建立。然而，現階段此類方法的應用多侷限於反應機構中的單一步驟或局部過程。
丙烷氧化脫氫（ODH）反應轉化為丙烯是一項具高度催化重要性的轉化過程，對其反應機構進行軌域層次的理解將有助於深化機理認識。在本研究中，我們結合密度泛函理論（DFT）與IBO分析，針對V₄O₁₀簇模型構建一套涵蓋整個丙烷ODH催化循環的、以量子力學為基礎的箭頭推進機構圖。
本研究結果顯示，電子結構變化集中於催化劑中的局部區域，主要涉及一個V=O雙鍵與其相鄰的一個橋氧原子。在反應過程中，該區域的V–O鍵在σ鍵與配位鍵（dative bond）性質之間交替轉換，以促進電子流動。此外，每個丙烷分子會經歷兩次氫移除步驟：首次為氫原子轉移（HAT），其次則為質子轉移（PT）。
我們鑑別出兩類機理上不同的異丙基自由基捕捉路徑，分別為同步發生的碳離子耦合電子轉移（carbocation-coupled electron transfer）與碳自由基轉移（carbon radical transfer）。本研究凸顯了量子化學方法計算的反應箭頭圖在解構複雜催化機制、提供軌域層次見解方面的價值與潛力。

Arrow-pushing diagrams are foundational tools for visualizing electron flow in chemical reactions. With recent advances, particularly intrinsic bond orbital (IBO) analysis, these diagrams can now be rigorously derived from quantum mechanical (QM) calculations. However, most applications remain limited to individual steps.
Here, we employ density functional theory and IBO analysis to construct a complete QM-based arrow-pushing diagram for propane oxidative dehydrogenation (ODH) to propene on a V₄O₁₀ cluster, representing vanadium oxide catalysis.
Our results show that electronic changes are highly localized, involving a single terminal V=O group and an adjacent bridging oxygen. Electron flow is mediated by V–O bonds that alternate between σ and dative character. The ODH cycle features two distinct hydrogen removal steps—hydrogen atom transfer (HAT) and proton transfer (PT)—and two mechanistically different isopropyl radical trapping events: one via carbocation-coupled electron transfer, the other via carbon radical transfer.
This study demonstrates the power of QM-derived arrow-pushing diagrams in revealing orbital-level insights into complex catalytic mechanisms.

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