title: G2(+)M study on N-alkylamino cation affinities of neutral main-group element hydrides: trends across the periodic table.
abstract: We have made an extensive theoretical exploration of gas-phase N-alkylamino cation affinities (NAAMCA), including amino cation affinities (AMCA) and N-dimethylamino cation affinities (NDMAMCA), of neutral main-group element hydrides of groups 15-17 and periods 2-4 in the periodic table by using the G2(+)M method. Some similarities and differences are found between NAAMCA and the corresponding alkyl cation affinities (ACA) of H(n)X. Our calculations show that the AMCA and NDMAMCA are systematically lower than the corresponding proton affinities (PA) for H(n)X. In general, there is no linear correlation between NAAMCA and PA of H(n)X. Instead, the correlations exist only within the central elements X in period 2, or periods 3-4, which is significantly different from the reasonable correlations between ACA and PA for all H(n)X. NAAMCA (H(n)X) are weaker than NAAMCA (H(n-1)X(-)) by more than 700 kJ/mol and generally stronger than ACA (H(n)X), with three exceptions: H2ONR2(+)(R = H, Me) and HFNH2(+). These new findings can be rationalized by the negative hyperconjugation and Pauli repulsion.
authors.affiliation: College of Chemistry and Key State Laboratory of Biotherapy, Sichuan University , Chengdu 610064, Sichuan, China.
authors.forename: Song
authors.initials: S
authors.lastname: Geng
authors.forename: Ding-Lu
authors.initials: DL
authors.lastname: Wu
authors.forename: Jing
authors.initials: J
authors.lastname: Yang
authors.forename: Xi-Guang
authors.initials: XG
authors.lastname: Wei
authors.forename: Jun
authors.initials: J
authors.lastname: Zhu
authors.forename: Hai-Bo
authors.initials: HB
authors.lastname: Zhang
authors.forename: Yi
authors.initials: Y
authors.lastname: Ren
authors.forename: Kai-Chung
authors.initials: KC
authors.lastname: Lau
mesh_terms: D000588:Amines / Q000737:chemistry*; D002412:Cations / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D000588:Amines; D002412:Cations