Cope rearrangements in shapeshifting molecules re-examined by means of high-level CCSDT(Q) composite ab initio methods

2020 ◽  
Vol 759 ◽  
pp. 138018
Author(s):  
Amir Karton
Keyword(s):  
Ab Initio ◽  
Ab Initio Methods ◽  
Cope Rearrangements ◽  
High Level

scholarly journals Amines are likely to enhance neutral and ion-induced sulfuric acid-water nucleation in the atmosphere more effectively than ammonia

2008 ◽  
Vol 8 (14) ◽  
pp. 4095-4103 ◽  
Author(s):  
T. Kurtén ◽  
V. Loukonen ◽  
H. Vehkamäki ◽  
M. Kulmala
Keyword(s):  
Sensitivity Analysis ◽  
Sulfuric Acid ◽  
Ab Initio ◽  
Acid Water ◽  
Ab Initio Methods ◽  
Free Energies ◽  
Ionic Clusters ◽  
The Difference ◽  
High Level ◽  
Formation Thermodynamics

Abstract. We have studied the structure and formation thermodynamics of dimer clusters containing H2SO4 or HSO4− together with ammonia and seven different amines possibly present in the atmosphere, using the high-level ab initio methods RI-MP2 and RI-CC2. As expected from e.g. proton affinity data, the binding of all studied amine-H2SO4 complexes is significantly stronger than that of NH3•H2SO4, while most amine-HSO4− complexes are only somewhat more strongly bound than NH3•HSO4−. Further calculations on larger cluster structures containing dimethylamine or ammonia together with two H2SO4 molecules or one H2SO4 molecule and one HSO4− ion demonstrate that amines, unlike ammonia, significantly assist the growth of not only neutral but also ionic clusters along the H2SO4 co-ordinate. A sensitivity analysis indicates that the difference in complexation free energies for amine- and ammonia-containing clusters is large enough to overcome the mass-balance effect caused by the fact that the concentration of amines in the atmosphere is probably 2 or 3 orders of magnitude lower than that of ammonia. This implies that amines might be more important than ammonia in enhancing neutral and especially ion-induced sulfuric acid-water nucleation in the atmosphere.

scholarly journals Amines are likely to enhance neutral and ion-induced sulfuric acid-water nucleation in the atmosphere more effectively than ammonia

2008 ◽  
Vol 8 (2) ◽  
pp. 7455-7476 ◽  
Author(s):  
T. Kurtén ◽  
V. Loukonen ◽  
H. Vehkamäki ◽  
M. Kulmala
Keyword(s):  
Sensitivity Analysis ◽  
Sulfuric Acid ◽  
Ab Initio ◽  
Acid Water ◽  
Ab Initio Methods ◽  
Free Energies ◽  
Ionic Clusters ◽  
The Difference ◽  
High Level ◽  
Formation Thermodynamics

Abstract. We have studied the structure and formation thermodynamics of dimer clusters containing H2SO4 or HSO4− together with ammonia and seven different amines possibly present in the atmosphere, using the high-level ab initio methods RI-MP2 and RI-CC2. As expected from e.g. proton affinity data, the binding of all studied amine – H2SO4 complexes is significantly stronger than that of NH3•H2SO4, while most amine – HSO4− complexes are only somewhat more strongly bound than NH3•HSO4−. Further calculations on larger cluster structures containing dimethylamine or ammonia together with two H2SO4 molecules or one H2SO4 molecule and one HSO4− ion demonstrate that amines, unlike ammonia, significantly assist the growth of not only neutral but also ionic clusters along the H2SO4 co-ordinate. A sensitivity analysis indicates that the difference in complexation free energies for amine- and ammonia-containing clusters is large enough to overcome the mass-balance effect caused by the fact that the concentration of amines in the atmosphere is probably 2 or 3 orders of magnitude lower than that of ammonia. This implies that amines might be more important than ammonia in enhancing neutral and especially ion-induced sulfuric acid-water nucleation in the atmosphere.

An ab initio Study of the Fulminate Anion-Cyanate Anion Rearrangement: Possible Intermediacy of the Oxazirinyl Anion

1997 ◽  
Vol 50 (2) ◽  
pp. 169 ◽  
Author(s):  
Yu-San Cheung ◽  
Wai-Kee Li
Keyword(s):  
Ab Initio ◽  
Basis Set ◽  
Ab Initio Methods ◽  
Ab Initio Study ◽  
High Level

The rearrangement of the fulminate anion (CNO¯) to the cyanate anion (OCN¯) has been studied with high-level ab initio methods. Geometry optimizations have been carried out at HF, MPn (n = 2-4), QCISD, QUISD(T), BD and BD(T) levels using the 6-31+G(d) basis set. The highest level of theory for the calculation of relative energies is QCISD(T)/6-311+G(3df, 2p). Results show that the rearrangement proceeds via an oxazirinyl anion intermediate, which is separated by barriers of 52·8 and 18·4 kJ mol-1 from CNO¯ and OCN¯, respectively.

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