Conformational study of some 4'-substituted 2-(phenylselanyl)-2-(ethylsulfanyl)-acetophenones
Carlos R Cerqueira1, Paulo R Olivato2, Maurizio Dal Colle3
1Escola Superior de Engenharia e Gestão, ESEG, 04101-000 São Paulo, SP, Brazil.
Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
|January 11, 2015
Summary
Conformational analysis of substituted acetophenones reveals that electrostatic repulsions, not orbital interactions, dictate stability. This finding impacts understanding molecular structure and reactivity in organic chemistry.
Area of Science:
- Organic Chemistry
- Computational Chemistry
- Spectroscopy
Background:
- Understanding molecular conformation is crucial for predicting chemical properties.
- Acetophenone derivatives with selenium and sulfur moieties present complex conformational landscapes.
- Previous studies have explored substituent effects on molecular geometry, but the interplay of electrostatic and orbital interactions requires further investigation.
Purpose of the Study:
- To investigate the conformational preferences of 4'-substituted 2-(phenylselanyl)-2-(ethylsulfanyl)-acetophenones.
- To elucidate the dominant factors governing the stability of different conformers.
- To correlate computational findings with experimental spectroscopic data.
Main Methods:
- Conformational analysis using B3LYP/6-31+G(d,p) density functional theory calculations.
- Infrared (IR) spectroscopy for experimental validation of vibrational frequencies (ν(CO)).
- Natural Bond Orbital (NBO) analysis to assess orbital interactions and charge distributions.
- Polarizable Continuum Model (PCM) for solvent effect calculations.
Main Results:
- Three stable conformations (c1, c2, c3) were identified for all analyzed acetophenone derivatives.
- Conformer stability is primarily governed by electrostatic repulsions between charged atoms, particularly involving sulfur and oxygen.
- A decrease in the molar fraction of more stable conformers (c2 and c3) was observed with increasing electron-donating substituents.
- Experimental IR data aligns with computational predictions regarding the distribution of conformers.
Conclusions:
- Electrostatic repulsions, rather than orbital delocalization energies, are the key determinants of conformer stability in these systems.
- The geometrical arrangement and substituent effects significantly influence the balance of electrostatic and orbital interactions.
- The study provides insights into the structure-property relationships of selenium- and sulfur-containing organic molecules.
![Cercosporin-Photocatalyzed [4+1]- and [4+2]-Annulations of Azoalkenes Under Mild Conditions](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F60786.jpg&w=3840&q=50)
Related Concept Videos
02:26Preparation and Reactions of Sulfides
6.1K
Sulfides are the sulfur analog of ethers, just as thiols are the sulfur analog of alcohol. Like ethers, sulfides also consist of two hydrocarbon groups bonded to the central sulfur atom. Depending upon the type of groups present, sulfides can be symmetrical or asymmetrical. Symmetrical sulfides can be prepared via an SN2 reaction between 2 equivalents of an alkyl halide and one equivalent of sodium sulfide.
6.1K
02:30Chirality at Nitrogen, Phosphorus, and Sulfur
7.5K
Chirality is most prevalent in carbon-based tetrahedral compounds, but this important facet of molecular symmetry extends to sp3-hybridized nitrogen, phosphorus and sulfur centers, including trivalent molecules with lone pairs. Here, the lone pair behaves as a functional group in addition to the other three substituents to form an analogous tetrahedral center that can be chiral.
A consequence of chirality is the need for enantiomeric resolution. While this is theoretically possible for all...
A consequence of chirality is the need for enantiomeric resolution. While this is theoretically possible for all...
7.5K
02:05Prochirality
5.4K
The concept of prochirality leads to the nomenclature of the individual faces of a molecule and plays a crucial role in the enantioselective reaction. It is a concept where two or more achiral molecules react to produce chiral products. A typical process is the reaction of an achiral ketone to generate a chiral alcohol. Here, the achiral reactant reacts with an achiral reducing agent, sodium borohydride, to generate an equimolar mixture of the chiral enantiomers of the product. For example, an...
5.4K
01:22Electrophilic Aromatic Substitution: Sulfonation of Benzene
9.5K
Sulfonation of benzene is a reaction wherein benzene is treated with fuming sulfuric acid at room temperature to produce benzenesulfonic acid. Fuming sulfuric acid is a mixture of sulfur trioxide and concentrated sulfuric acid.
9.5K
02:23SN2 Reaction: Stereochemistry
13.3K
In an SN2 reaction, the nucleophilic attack on the substrate and departure of the leaving group occurs simultaneously through a transition state. As the nucleophile approaches the substrate from the back-side, the configuration of the substrate carbon changes from tetrahedral to trigonal bipyramidal and then back to tetrahedral, leading to an inversion in the configuration of the product.
If the substrate is an achiral molecule at the α-carbon, the inversion of configuration is not...
If the substrate is an achiral molecule at the α-carbon, the inversion of configuration is not...
13.3K
01:30Nucleophilic Aromatic Substitution: Addition–Elimination (SNAr)
5.4K
Nucleophilic substitution in aromatic compounds is feasible in substrates bearing strong electron-withdrawing substituents positioned ortho or para to the leaving group. The reaction proceeds via two steps: the addition of the nucleophile and the elimination of the leaving group.
The reaction begins with an attack of the nucleophile on the carbon that holds the leaving group. This results in the delocalization of the π electrons over the ring carbons. The resonance interaction between...
The reaction begins with an attack of the nucleophile on the carbon that holds the leaving group. This results in the delocalization of the π electrons over the ring carbons. The resonance interaction between...
5.4K