Conformer

Conformer
Name	Conformer
Caption	Generic representation of a molecular conformer
Uses	Structural isomerism, stereochemistry
Related	Steric strain; Rotamer; Torsion angle; Potential energy surface

Conformer

A conformer is a stereochemical isomeric form of a molecule that differs by rotation about single bonds and can interconvert by bond rotation without breaking covalent bonds. Conformers are central to understanding molecular structure and behavior in fields that include Organic chemistry, Physical chemistry, Biochemistry, Pharmacology, and Materials science. Conformational preferences influence properties measured by techniques used in X-ray crystallography, Nuclear magnetic resonance spectroscopy, and Mass spectrometry.

Definition and overview

Conformers arise when rotation about sigma bonds produces distinguishable arrangements, illustrated historically in studies by Hermann Kolbe, Erich Hückel, Linus Pauling, Robert Robinson (chemist), and Richard R. Ernst that shaped modern stereochemistry and quantum chemistry. Classic examples include the staggered and eclipsed forms of ethane studied in work by Gilbert N. Lewis and analyzed with methods pioneered by Sir Geoffrey Wilkinson and Walter Heitler. Conformational landscapes are often described using concepts from Potential energy surface theory, with minima and transition states characterized using models by Lester R. Morss, John Pople, and Martin Karplus.

Types and nomenclature

Common nomenclature classifies conformers as staggered, eclipsed, gauche, syn, anti, axial, equatorial, boat, and chair forms used in analysis by Sir Derek Barton, Ernest L. Eliel, and Samuel H. Wilen. Ring conformations reference studies of cyclohexane conformers attributed to Hendrik Anthony Kramers and treatments in textbooks by Ira N. Levine and Donald J. Cram. Substituent effects and stereoelectronic terminology draw on concepts developed by Linus Pauling, R. B. Woodward, Roald Hoffmann, and Kenichi Fukui. IUPAC recommendations and names are discussed in guidelines influenced by committees including representatives from International Union of Pure and Applied Chemistry and academics such as Ernest W. Becker.

Conformational analysis and properties

Conformational analysis quantifies torsional barriers, steric strain, hyperconjugation, and lone-pair interactions, building on seminal contributions from A. J. Hickman, Sir John Cornforth, and Guyon F. Vallette. Energetic comparisons use enthalpy and entropy metrics applied in studies by Henry Eyring, Linus Pauling, and Max Delbrück. Conformer populations influence spectroscopic observables in Infrared spectroscopy experiments by Gerhard Herzberg and Ahmed Zewail, and affect thermochemical cycles explored by George Olah and John Warcup Cornforth. Solvent effects and dielectric screening were formalized in models from Linus Pauling and implemented in continuum models influenced by Per-Olov Löwdin.

Methods of determination

Experimental determination employs Nuclear magnetic resonance spectroscopy methods advanced by Richard R. Ernst, Kurt Wüthrich, and Edward M. Purcell, and crystallographic assignment uses techniques from William Lawrence Bragg, Dorothy Crowfoot Hodgkin, and Herbert A. Hauptman. Gas-phase conformers are probed with Rotational spectroscopy and Electron diffraction in work by Charles H. Townes and Hannes Alfvén. Computational approaches apply molecular mechanics force fields (e.g., MM2, CHARMM, AMBER) developed by groups led by Norman L. Allinger, Martin Karplus, and Peter Kollman, and quantum chemical methods at levels including HF, DFT, and post-HF pioneered by John Pople, Walter Kohn, and Richard F. W. Bader. High-throughput conformational sampling leverages algorithms from David J. Wales, Chris L. Brooks III, and software maintained by teams at Schrödinger (company), OpenEye Scientific, and Gaussian, Inc..

Role in chemical reactivity and biology

Conformational preferences dictate reaction pathways in pericyclic reactions analyzed by Robert Burns Woodward and Roald Hoffmann, and govern enzyme catalysis mechanisms studied by Daniel E. Koshland Jr., Emil Fischer, and Jennifer Doudna. Protein folding landscapes and side-chain rotamer distributions trace back to analyses from Christian Anfinsen, Anil K. Panchenko, and Jane S. Richardson. Conformers influence ligand binding, selectivity, and bioavailability in drug targets such as Human immunodeficiency virus protease, G protein-coupled receptors, and Cyclooxygenase enzymes investigated by pharmaceutical groups including Pfizer, GlaxoSmithKline, and AstraZeneca. Conformational isomerism also underlies allosteric regulation described in studies by Monod, Wyman, and Changeux and structural biology efforts at institutions like The Scripps Research Institute and European Molecular Biology Laboratory.

Applications in materials and drug design

In materials science, conformers control polymer tacticity, liquid-crystal phases, and conductive properties explored by researchers at Bell Labs, MIT, and IBM Research. Molecular conformations determine organic semiconductor packing relevant to devices developed by Sony, Samsung, and Intel Corporation. In drug design, conformational ensembles guide structure-based design workflows performed at Novartis, Roche, and academic groups at Harvard University and University of Cambridge, using docking and free-energy methods popularized by David E. Shaw, Brian K. Shoichet, and Michael Levitt. Conformer libraries and rotamer libraries underpin computational screening pipelines used in projects at Rosetta Commons and consortia such as Human Genome Project-era pharmacology initiatives.

Category:Stereochemistry