A theoretical study of medium effects on the structure of the glycine analogue aminomethylphosphonic acid

2008 ◽  
Vol 10 (36) ◽  
pp. 5624 ◽  
Author(s):  
Nasséra Benbrahim ◽  
Ali Rahmouni ◽  
Manuel F. Ruiz-López
Keyword(s):  
Theoretical Study ◽  
Medium Effects ◽  
Aminomethylphosphonic Acid

Microscopic medium effects on a chemical reaction. A theoretical study of decarboxylation catalyzed by cyclodextrins as an enzyme model

1993 ◽  
Vol 115 (7) ◽  
pp. 2903-2911 ◽  
Author(s):  
Takao Furuki ◽  
Fumio Hosokawa ◽  
Minoru Sakurai ◽  
Yoshio Inoue ◽  
Riichiro Chujo
Keyword(s):  
Chemical Reaction ◽  
Theoretical Study ◽  
Medium Effects ◽  
Enzyme Model

A theoretical study on the reactivity of vinyl iodonium ions

1999 ◽  
Vol 77 (5-6) ◽  
pp. 577-583 ◽  
Author(s):  
Tadashi Okuyama ◽  
Hiroshi Yamataka
Keyword(s):  
Ab Initio ◽  
Theoretical Study ◽  
Chloride Ion ◽  
Medium Effects ◽  
Double Zeta ◽  
Ab Initio Mo ◽  
Vinyl Group ◽  
Dielectric Continuum ◽  
Substituted 1 ◽  
Dielectric Continuum Model

Reactions of methyl(vinyl)iodonium ion and the β-substituted derivatives as well as divinyliodonium ion with chloride ion were examined theoretically by ab initio MO (MP2) calculations at the double-zeta (DZ) + d level. Interaction of the iodonium ion 1 with Cl- leads to chloro-λ3-iodane 2. Transition states for the SN2, ligand-coupling substitution (LC), and β-elimination (βE) are found for reactions at the vinyl group. The barrier to LC is usually the lowest in the gas phase, but relative barriers to SN2 and to βE change with the substituents. Effects of solvent were evaluated by a dielectric continuum model and found to be large on SN2 but small on LC. The experimental observations in solution that the SN2 is the most facile for the β-methyl-substituted 1 while it is retarded by the β-tert-butyl and β-chloro substitutions are reproduced by the calculations that take medium effects into account.Key words: vinyliodonium salt, polyvalent iodine, vinylic SN2 reaction, ligand coupling, ab initio MO calculation.

Gender Differences in the Mental Rotations Test (MRT) Are Not Due to Task Complexity

2008 ◽  
Vol 29 (3) ◽  
pp. 130-133 ◽  
Author(s):  
Corinna Titze ◽  
Martin Heil ◽  
Petra Jansen
Keyword(s):  
Gender Differences ◽  
Mental Rotation ◽  
Task Complexity ◽  
Time Constraints ◽  
Medium Effects ◽  
Performance Factors ◽  
Mental Rotations ◽  
Sufficient Power ◽  
Forced Choice Tasks ◽  
Choice Tasks

Gender differences are one of the main topics in mental rotation research. This paper focuses on the influence of the performance factor task complexity by using two versions of the Mental Rotations Test (MRT). Some 300 participants completed the test without time constraints, either in the regular version or with a complexity reducing template creating successive two-alternative forced-choice tasks. Results showed that the complexity manipulation did not affect the gender differences at all. These results were supported by a sufficient power to detect medium effects. Although performance factors seem to play a role in solving mental rotation problems, we conclude that the variation of task complexity as realized in the present study did not.

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