Related Experiment Video
Updated: Jun 13, 2026
08:15
Temperature-programmed Deoxygenation of Acetic Acid on Molybdenum Carbide Catalysts
Published on: February 7, 2017
Reactivity of CO2 towards Mo[N(R)Ph]3
Nigel J Brookes1, Alireza Ariafard, Robert Stranger
1School of Chemistry, University of Tasmania, Private Bag 75, Hobart, Tas 7001, Australia.
Dalton Transactions (Cambridge, England : 2003)
|May 8, 2010
Summary
The Laplaza/Cummins L(3)Mo complex activates small molecules but not CO(2). This study explains CO(2)
Area of Science:
- Organometallic chemistry
- Computational chemistry
Background:
- The Laplaza/Cummins L(3)Mo system activates small molecules like N(2).
- CS(2) binds to L(3)Mo forming an Mo-CS-Mo intermediate.
- CO(2) is unreactive with the L(3)Mo system.
Purpose of the Study:
- To elucidate the contrasting reactivity of CS(2) and CO(2) with the L(3)Mo system.
- To explain the lack of CO(2) activation by L(3)Mo.
Main Methods:
- Density functional theory (DFT) calculations.
- Molecular orbital analysis.
- Consideration of steric and entropic effects.
Main Results:
- Initial coordination of CO(2) to L(3)Mo is unfavorable due to CO(2) bending, spin state energy barriers, and weaker metal-CO(2) binding.
- Formation of the L(3)Mo-CO-MoL(3) intermediate is hindered by steric and entropic factors.
- DFT calculations accurately predict reactivity differences when steric factors are included.
Conclusions:
- The unreactivity of CO(2) with L(3)Mo is attributed to multiple energetic and steric barriers.
- Accurate computational modeling requires incorporating steric considerations for organometallic systems.
Related Concept Videos
01:12Cycloaddition Reactions: MO Requirements for Photochemical Activation
Some cycloaddition reactions are activated by heat, while others are initiated by light. For example, a [2 + 2] cycloaddition between two ethylene molecules occurs only in the presence of light. It is photochemically allowed but thermally forbidden.
01:16Cycloaddition Reactions: MO Requirements for Thermal Activation
Thermal cycloadditions are reactions where the source of activation energy needed to initiate the reaction is provided in the form of heat. A typical example of a thermally-allowed cycloaddition is the Diels–Alder reaction, which is a [4 + 2] cycloaddition. In contrast, a [2 + 2] cycloaddition is thermally forbidden.
01:11ortho–para-Directing Activators: –CH3, –OH, –NH2, –OCH3
All ortho–para directors, excluding halogens, are activating groups. These groups donate electrons to the ring, making the ring carbons electron-rich. Consequently, the reactivity of the aromatic ring towards electrophilic substitution increases. For instance, the nitration of anisole is about 10,000 times faster than the nitration of benzene. The electron-donating effect of the methoxy group in anisole activates the ortho and para positions on the ring and stabilizes the corresponding...
01:13Relative Reactivity of Carboxylic Acid Derivatives
Carboxylic acid derivatives such as acid halides, anhydrides, esters, and amides undergo nucleophilic acyl substitution reactions with varying degrees of reactivity.
A key factor in assessing the reactivity of the acid derivatives is the basicity of the substituent or the leaving group. The lower the basicity of the leaving group, the higher the reactivity of the derivative. The basicity of the leaving group follows this order:
Halide ions < Acyloxy ions < Alkoxy ions < Amine ions
A key factor in assessing the reactivity of the acid derivatives is the basicity of the substituent or the leaving group. The lower the basicity of the leaving group, the higher the reactivity of the derivative. The basicity of the leaving group follows this order:
Halide ions < Acyloxy ions < Alkoxy ions < Amine ions
02:34Nucleophilic Substitution Reactions
Historical perspective
In 1896, the German chemist Paul Walden discovered that he could interconvert pure enantiomeric (+) and (-) malic acids through a series of reactions. This conversion suggested the involvement of optical inversion during the substitution reaction. Further, in 1930, Sir Christopher Ingold described for the first time two different forms of nucleophilic substitution reactions, which are known as SN1 (nucleophilic substitution unimolecular) and SN2 (nucleophilic substitution...
In 1896, the German chemist Paul Walden discovered that he could interconvert pure enantiomeric (+) and (-) malic acids through a series of reactions. This conversion suggested the involvement of optical inversion during the substitution reaction. Further, in 1930, Sir Christopher Ingold described for the first time two different forms of nucleophilic substitution reactions, which are known as SN1 (nucleophilic substitution unimolecular) and SN2 (nucleophilic substitution...
02:10Carbocations
Carbocations are one of the reaction intermediates formed during several nucleophilic substitutions or elimination reactions. A carbocation is an electron-deficient species with the central carbon atom having six electrons and three bonded atoms. The central carbon in a carbocation is sp2 hybridized with trigonal planar geometry. It has an empty p orbital perpendicular to the plane of the structure that can accept electrons. Thus, carbocations act as strong electrophiles and may react with any...