The　catalytic　oxidations　of　α-C-H　bond　in　o-nitro-substituted　arenes　and　p-nitro-substituted　arenes　(toluene,　ethylbenzene　and　cumene)　by　iron　porphyrin　were　studied　using　density　functional　theory.　The　calculation　results　were　compared　with　those　of　α-C-H　bond　oxidation　in　arenes　without　nitro　substituent.　The　reactivity　difference　of　α-C-H　bond　oxidation　between　o-nitro-substituted　arenes　and　p-nitro-substituted　arenes　catalyzed　by　iron　porphyrin　were　focused　on　and　the　essential　factors　affecting　the　reactivity　were　explored.　By　calculating　the　bond　dissociation　energy　of　α-C-H　bond　and　the　activation　energy　of　α-C-H　bond　oxidation　in　arenes　by　iron　porphyrin,　it　is　found　that　the　conjugation　effect　between　nitro　and　benzene　ring　in　p-nitro-substituted　arenes　reduce　the　bond　dissociation　energy　of　α-C-H　bond　and　the　activation　energy　of　α-C-H　bond　oxidation　by　high-valent　iron-oxo　porphyrin.　In　o-nitro-substituted　arenes,　there　are　not　only　conjugation　effect,　but　also　steric　hindrance　effect.　The　steric　hindrance　effect　is　dominant　in　o-nitro-substituted　arenes.　The　bond　dissociation　energy　of　α-C-H　bond　and　the　activation　energy　of　α-C-H　bond　oxidation　by　high-valent　iron-oxo　porphyrin　increase　due　to　the　steric　hindrance　effect.　Further　decomposition　of　the　activation　energy　of　α-C-H　bond　oxidation　reveals　that　the　interaction　energy　between　the　arene　and　high-valent　iron-oxo　porphyrin　in　the　transition　structure　is　relatively　weak　and　the　distortion　energy　is　the　main　factor　affecting　the　activation　energy.　The　distortion　energy　mainly　comes　from　the　distortion　of　the　arene　molecule.　©　2023　Cailiao　Daobaoshe/　Materials　Review.　All　rights　reserved.