Theoretical study of structure of alkali metal cyanates and isocyanates and their related ion pair SN2 reactions

Leung, Simon Shun-Wang; Streitwieser, Andrew

doi:10.1002/(sici)1096-987x(199809)19:12<1325::aid-jcc1>3.0.co;2-k

Cited by 21 publications

(12 citation statements)

References 24 publications

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“…(Note that Leung and Streitwieser found that in the case of LiOCN and NaOCN all the seven conformations were real minima. 21 ) Table 2 summarizes some selected geometrical parameters of 2a, 2b, and 2c. The relative energies, the interaction energies, and the CP corrections to the interaction energy are also presented.…”

Section: Resultsmentioning

confidence: 99%

NaSCN: Striking Differences between Its Gas-Phase and Crystal-Phase Structure: A Theoretical Study

2004

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A detailed investigation of the gas-phase and crystal-phase structure of sodium thiocyanate has been presented. Using highly sophisticated ab initio calculations (MP2, QCISD, CCSD(T), CBS-Q), the existence of the four-membered ring monomer has been predicted. Three minima have been found on the PES of the NaSCN dimers using HF, B3LYP, and MP2 methods, and two of these have been identified as the main building blocks of the NaSCN crystal. The systematic enlargement of the clusters along the crystal axes at the HF level led to the convergence of the geometrical parameters and the interaction energy of the clusters. According to our results, the supermolecule model with one layer of molecules around the central molecule is not large enough to simulate the overall crystal structure of NaSCN, but the supermolecule model with a 17-member supermolecule (two layers of neighbors) has been successfully applied and found to be in excellent agreement with the experimental data, the principal findings, and point out major conclusions.

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Section: Resultsmentioning

confidence: 99%

NaSCN: Striking Differences between Its Gas-Phase and Crystal-Phase Structure: A Theoretical Study

2004

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“…Since the bent structure of the OCN group seems unusual [52] in compounds containing alkali metal atoms, we propose to view the 10 + as the complex of Na 3 O + and NaCN. This is supported by the fact that the 10 + possesses the longest O-C bond distance (1.365 Å) among all studied Na 4 OCN molecules and Na 4 OCN + cations (see Tables 1 and 2).…”

Section: Cationic Speciesmentioning

confidence: 99%

Low ionization potentials of Na₄OCN superalkali molecules

Świerszcz

Anusiewicz

2011

Molecular Physics

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“…The above order reveals that the more stable CH 3 NCO will be the main product in the view of thermodynamics and kinetics if the reactions involve the inversion mechanisms. These results are somewhat different from those of Leung and Streitwieser [9], where it was predicted that 3a-X is lower in terms of ⌬H ovr (298 K) than 3b-X (X ϭ F and Cl) at the level of RHF/6-31G(d,p).…”

Section: Ion Pair S N 2 Reactions Linco ؉ Ch 3 X (X ‫؍‬ F Cl Br Anmentioning

confidence: 99%

“…From the theoretical point of view, much less attention in the past has been paid to the ion pair S N 2 reactions that involve isocyanates. Leung and Streitwieser [9] examined the structures of alkali metal cyanates and isocyanates and their related ion pair S N 2 reactions with methyl halides Y ϩ CH 3 X [Y ϭ MNCO, MOCN, (MNCO) 2 (M ϭ Li and Na); X ϭ F and Cl]. Their results showed that methyl cyanate should form preferentially via a six-member ring transition-state structure on analysis of energetics of the transition structures if the reaction involves a monomer ion pair inversion pathway.…”

Section: Introductionmentioning

confidence: 99%

Comprehensive mechanistic study of ion pair S_N2 reactions of lithium isocyanate and methyl halides

Sun¹,

Ren²,

Wong³

et al. 2006

Int J of Quantum Chemistry

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ABSTRACT:The anionic S N 2 reactions NCO Ϫ ϩ CH 3 X and ion pair S N 2 reactions LiNCO ϩ CH 3 X (X ϭ F, Cl, Br, and I) at saturated carbon with inversion and retention mechanisms were investigated at the level of MP2/6-311ϩG(d,p). There are two possible reaction pathways in the anionic S N 2 reactions, but eight in the ion pair S N 2 reactions. Calculated results suggest that the previously reported T-shaped isomer of lithium isocyanate does not exist. All the retention pathways are not favorable based on the analysis of transition structures. Two possible competitive reaction pathways proceed via two six-member ring inversion transition structures. It is found that there are two steps in the most favorable pathway, in which less stable lithium cyanate should be formed through the isomerization of lithium isocyanate and nucleophilic site (N) subsequently attacks methyl halides from the backside. The thermodynamically and kinetically favorable methyl isocyanate is predicted as major product both in the gas phase anionic and the ion pair S N 2 reactions. In addition, good correlations between the overall barriers relative to separated reactants, ⌬H ovr , with geometrical looseness parameter %L and the heterolytic cleavage energies of the COX and LiON (or LiOO) bonds are observed for the anionic and ion pair S N 2 reactions. The trend of variation of the overall barriers predicts the leaving ability of X increase in the order: F Ͻ Cl Ͻ Br Ͻ I. The polarized continuum model (PCM) has been used to evaluate the solvent effects on the two inversion pathways with six-member transition structures for the reactions of LiNCO ϩ CH 3 X. The calculations in solution indicate that solvent effects will retard the rate of reactions and the predicted product, methyl isocyanate, is same as the one in the gas phase.

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Theoretical study of structure of alkali metal cyanates and isocyanates and their related ion pair SN2 reactions

Cited by 21 publications

References 24 publications

NaSCN: Striking Differences between Its Gas-Phase and Crystal-Phase Structure: A Theoretical Study

NaSCN: Striking Differences between Its Gas-Phase and Crystal-Phase Structure: A Theoretical Study

Low ionization potentials of Na₄OCN superalkali molecules

Comprehensive mechanistic study of ion pair S_N2 reactions of lithium isocyanate and methyl halides

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Theoretical study of structure of alkali metal cyanates and isocyanates and their related ion pair SN2 reactions

Cited by 21 publications

References 24 publications

NaSCN: Striking Differences between Its Gas-Phase and Crystal-Phase Structure: A Theoretical Study

NaSCN: Striking Differences between Its Gas-Phase and Crystal-Phase Structure: A Theoretical Study

Low ionization potentials of Na4OCN superalkali molecules

Comprehensive mechanistic study of ion pair SN2 reactions of lithium isocyanate and methyl halides

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Low ionization potentials of Na₄OCN superalkali molecules

Comprehensive mechanistic study of ion pair S_N2 reactions of lithium isocyanate and methyl halides