Related Experiment Video
Updated: Aug 14, 2026
08:43
Protocol for the Synthesis of Ortho-trifluoromethoxylated Aniline Derivatives
Published on: January 19, 2016
Conformational preferences and orbital interactions for methyl haloacetates
Cláudio F Tormena1, Fabiana Yoshinaga, Telma R Doi
1Chemistry Department, FFCLRP, São Paulo University, Av. Bandeirantes 3900, 14040-901 Ribeirão Preto, SP, Brazil. tormena@ffclrp.usp.br
Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
|December 20, 2005
Summary
Methyl haloacetates exhibit distinct conformational preferences, with gauche forms often favored due to orbital interactions. Solvent polarity influences the equilibrium between cis and gauche rotamers for methyl chloroacetate.
Area of Science:
- Organic Chemistry
- Computational Chemistry
- Spectroscopy
Background:
- Understanding molecular conformation is crucial for predicting chemical reactivity and physical properties.
- Haloacetate esters are important functional groups in organic synthesis.
Purpose of the Study:
- To investigate the conformational preferences of methyl chloroacetate, methyl bromoacetate, and methyl iodoacetate.
- To elucidate the role of orbital interactions in determining these conformational preferences.
Main Methods:
- Experimental infra-red spectroscopy.
- Theoretical calculations.
- Natural Bond Orbital (NBO) analyses.
Main Results:
- Conformational equilibria involve cis and gauche rotamers for methyl haloacetates.
- Methyl chloroacetate shows solvent-dependent preferences (gauche in non-polar, cis in polar).
- Methyl bromoacetate and methyl iodoacetate predominantly exist in the gauche form across phases.
Conclusions:
- Orbital interactions, specifically pi(C=O)(*)-->sigma(C-X)(*), dictate the observed conformational preferences.
- High electron density on pi(C=O)(*), influenced by the ether oxygen lone pair, facilitates this interaction.
Related Concept Videos
01:28Multiple Halogenation of Methyl Ketones: Haloform Reaction
A method involving the transformation of methyl ketones to carboxylic acids using excess base and halogen is called the haloform reaction. It begins with the deprotonation of α hydrogen to form an enolate ion which reacts with the electrophilic halogen to give an α-halo ketone. The step continues until all the α protons are substituted to form a trihalomethyl ketone. The resulting molecule is unstable, and in the presence of a hydroxide base, it readily undergoes nucleophilic acyl substitution.
02:30Stability of Substituted Cyclohexanes
This lesson discusses the stability of substituted cyclohexanes with a focus on energies of various conformers and the effect of 1,3-diaxial interactions.
The two chair conformations of cyclohexanes undergo rapid interconversion at room temperature. Both forms have identical energies and stabilities, each comprising equal amounts of the equilibrium mixture. Replacing a hydrogen atom with a functional group makes the two conformations energetically non-equivalent.
For example, in...
The two chair conformations of cyclohexanes undergo rapid interconversion at room temperature. Both forms have identical energies and stabilities, each comprising equal amounts of the equilibrium mixture. Replacing a hydrogen atom with a functional group makes the two conformations energetically non-equivalent.
For example, in...
01:28Structures of Carboxylic Acid Derivatives
Structure of Carboxylic Acid Derivatives
Carboxylic acid derivatives contain an acyl group attached to a heteroatom such as chlorine, oxygen, or nitrogen. The carbonyl carbon and oxygen are both sp2-hybridized with an unhybridized p orbital.
The three sp2 orbitals of the carbonyl carbon form three σ bonds, one each with the carbonyl oxygen, the α carbon, and the heteroatom, whereas the other two sp2 orbitals of the carbonyl oxygen are occupied by the lone pairs. Further, the unhybridized p...
Carboxylic acid derivatives contain an acyl group attached to a heteroatom such as chlorine, oxygen, or nitrogen. The carbonyl carbon and oxygen are both sp2-hybridized with an unhybridized p orbital.
The three sp2 orbitals of the carbonyl carbon form three σ bonds, one each with the carbonyl oxygen, the α carbon, and the heteroatom, whereas the other two sp2 orbitals of the carbonyl oxygen are occupied by the lone pairs. Further, the unhybridized p...
02:17Regioselectivity of Electrophilic Additions to Alkenes: Markovnikov's Rule
If a set of reactants can yield multiple constitutional isomers, but one of the isomers is obtained as the major product, the reaction is said to be regioselective. In such reactions, bond formation or breaking is favored at one reaction site over others.
The hydrohalogenation of an unsymmetrical alkene can yield two haloalkane products, depending on which vinylic carbon takes up the halogen. However, one product usually predominates, where hydrogen adds to the vinylic carbon bearing the...
The hydrohalogenation of an unsymmetrical alkene can yield two haloalkane products, depending on which vinylic carbon takes up the halogen. However, one product usually predominates, where hydrogen adds to the vinylic carbon bearing the...
02:18Conformations of Ethane and Propane
In an organic molecule, free rotation about the carbon-carbon single bond results in energetically different conformers of the molecule. Due to this rotation, called the internal rotation, ethane has two major conformations — staggered and eclipsed.
Staggered conformation is a low energy and more stable conformation with the C-H bonds on the front carbon placed at 60°dihedral angles relative to the C-H bonds on the back carbon, leading to a reduced torsional strain. In staggered ethane, the...
Staggered conformation is a low energy and more stable conformation with the C-H bonds on the front carbon placed at 60°dihedral angles relative to the C-H bonds on the back carbon, leading to a reduced torsional strain. In staggered ethane, the...
02:36Regioselectivity and Stereochemistry of Hydroboration
A significant aspect of hydroboration–oxidation is the regio- and stereochemical outcome of the reaction.
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn stereochemistry.
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn stereochemistry.