©　2018　The　Combustion　Institute　H-atom　abstraction　and　addition　are　the　two　most　important　reactions　in　alkene　oxidation.　As　a　complement　of　our　synchronization　work　of　3-hexene　chemistry　(Feiyu　Yang　et　al.,　Kinetics　of　Hydrogen　Abstraction　and　Addition　Reactions　of　3-Hexene　by　ȮH　Radicals,　J.　Phys.　Chem.　A　2017,　121,　1877–1889),　high-accuracy　electronic　structure　calculations　(DLPNO–CCSD(T)/CBS)　and　canonical　variational　transition　state　theory　are　used　to　predict　the　rate　coefficients　of　the　H-atom　abstraction　and　addition　reactions　of　3-hexene　+　ĊH3/Ḣ/Ö　system.　Although　ĊH3/Ḣ/Ö　are　all　nonpolar　radicals,　Ḣ　+　3-hexene　system　shows　some　unique　features.　Unlike　the　3-hexene　+　ĊH3/Ö　systems,　the　potential　energy　surface　of　3-hexene　+　Ḣ　system　exhibits　a　unique　“negative　well”　characteristic,　suggesting　the　energy　of　the　well　is　higher　than　its　corresponding　reactant　or　product.　Analysis　shows　that　the　“negative　well”　characteristic　is　caused　by　the　relative　larger　zero-point　energies　of　Van　der　Waals　complex　of　H　+　3-hexene　system.　Moreover,　the　evolution　of　adiabatic　ground-state　energy　shows　wells/well-like　curves　at　both　reactant　and　product　sides　for　3-hexene　+　ĊH3　and　Ö　systems,　but　only　at　reactant　end　for　3-hexene　+　Ḣ　system.　Vibrational　analysis　reveals　that　for　3-hexene　+　ĊH3　and　Ö　systems,　the　wells/well-like　curves　are　generated　by　the　C　=　C　double　bond　stretch　motion,　while　it　is　generated　by　the　forming　H–H　single　bond　stretch　motion　for　3-hexene　+　Ḣ　system.　Branching　ratio　shows　that　addition　and　abstraction　dominate　at　low　and　high　temperatures　and　the　critical　temperatures　are　478　K,　794　K　and　735　K　for　3-hexene　+　ĊH3,　Ḣ　and　Ö　systems,　respectively.　Rate　coefficients　with　a　conservative　uncertainty　of　a　factor　of　5　are　estimated　based　on　similar　algorithm　of　Sun　and　Law.　In　addition,　analyses　on　the　potential　energy　surface,　minimum　energy　path,　adiabatic　ground-state　energy　and　activation　free　Gibbs　energy　change　are　also　performed　in　this　work.