Related Experiment Video
Updated: Jul 5, 2026
09:23
Fabrication, Densification, and Replica Molding of 3D Carbon Nanotube Microstructures
Published on: July 2, 2012
Clar-Kekule structuring in armchair carbon nanotubes.
Francisco J Martín-Martínez1, Santiago Melchor, José A Dobado
1Grupo de Modelización y Diseño Molecular, Departamento de Química Orgánica, Facultad de Ciencias, Universidad de Granada, 18071, Granada, Spain.
Organic Letters
|April 24, 2008
Summary
Finite armchair nanotubes exhibit non-uniform bonding, unifying structural classifications into alternating Clar and Kekule domains as length increases. This finding impacts their mechanical and electronic properties.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Nanotechnology
Background:
- Armchair nanotubes are a class of carbon nanotubes with unique structural properties.
- Previous models, like periodic boundary condition (PBC) models, suggested uniform bond structures in nanotubes.
- Understanding the precise geometrical patterns is crucial for predicting nanotube behavior.
Purpose of the Study:
- To investigate the geometrical patterns of finite armchair nanotubes.
- To determine how these patterns change with nanotube length, up to 10 nm.
- To re-evaluate existing structural classifications of armchair nanotubes.
Main Methods:
- Utilized first-principles computational methods.
- Simulated armchair nanotubes of varying lengths (up to 10 nm).
- Analyzed the resulting geometrical and electronic structures.
Main Results:
- Finite armchair nanotubes do not possess a uniform bond structure.
- Structural classifications (Clar, Kekule, incomplete-Clar) unify into an alternated sequence of Clar and Kekule domains as length increases.
- This unification occurs in all cases, contrary to uniform structures predicted by PBC models.
Conclusions:
- The study reveals a novel, length-dependent, non-uniform bonding pattern in armchair nanotubes.
- Existing classifications are unified into a more complex, yet consistent, domain structure.
- These findings have potential implications for the mechanical and electronic properties of nanotubes.
Related Concept Videos
01:07Structure of Benzene: Kekulé Model
In 1865, August Kekule suggested the structure of benzene according to the structural theory of organic chemistry based on the three assertions—formula of benzene is C6H6, all the hydrogens of benzene are equivalent, and each carbon must have four bonds due to its tetravalency.
He proposed that benzene has a cyclic structure of six carbon atoms attached to one hydrogen atom each, with three alternating pi bonds.
He proposed that benzene has a cyclic structure of six carbon atoms attached to one hydrogen atom each, with three alternating pi bonds.
01:16Structure of Conjugated Dienes
Introduction
Conjugated dienes are compounds characterized by the presence of alternating double and single bonds. In a conjugated system like 1,3-butadiene, the unhybridized 2p orbital on each carbon overlaps continuously, allowing the π electrons to be delocalized across the entire molecule. In contrast, this type of overlap does not occur in cumulated and isolated dienes, such as 2,3-pentadiene and 1,4-pentadiene, respectively. Instead, the π electrons remain localized between the double...
Conjugated dienes are compounds characterized by the presence of alternating double and single bonds. In a conjugated system like 1,3-butadiene, the unhybridized 2p orbital on each carbon overlaps continuously, allowing the π electrons to be delocalized across the entire molecule. In contrast, this type of overlap does not occur in cumulated and isolated dienes, such as 2,3-pentadiene and 1,4-pentadiene, respectively. Instead, the π electrons remain localized between the double...
01:32Assembly of Complex Microtubule Structures
Complex microtubule structures are present in resting cells and in dividing cells. In resting cells, they are responsible for maintaining the cellular architecture, tracks for intracellular transport, positioning of organelles, assembly of cilia and flagella. They mediate the bipolar spindle assembly for chromosomal segregation and positioning of the cell division plate in dividing cells. The formation of microtubule complex structures depends on the cell type, cell stage, and cell function.
01:18Structure of Benzene: Molecular Orbital Model
According to the molecular orbital (MO) model, benzene has a planar structure with a regular hexagon of six sp2 hybridized carbons. As shown in Figure 1, each carbon is bonded to three other atoms with C–C–C and H–C–C bond angles of 120°. The C–H bond length is 109 pm, and the C–C bond length is 139 pm which is midway between the single bond length of sp3 hybridized carbons (154 pm) and sp2 hybridized carbons (133 pm).
02:47Structure and Bonding of Alkenes
Olefins, which are unsaturated hydrocarbons containing one or more carbon–carbon double bonds, are broadly divided into alkenes and cycloalkenes. The general chemical formula of an alkene is CnH2n.
Doubly bonded carbons are sp2 hybridized and have a trigonal planar geometry. The double bond is composed of a σ bond formed by the overlap of hybrid orbitals and a π bond produced by the lateral overlap of unhybridized 2p orbitals on both the carbons. Each carbon atom is bonded to two hydrogen atoms...
Doubly bonded carbons are sp2 hybridized and have a trigonal planar geometry. The double bond is composed of a σ bond formed by the overlap of hybrid orbitals and a π bond produced by the lateral overlap of unhybridized 2p orbitals on both the carbons. Each carbon atom is bonded to two hydrogen atoms...
01:12Carbon Skeletons
Life on Earth is carbon-based, as all macromolecules that make up living organisms contain carbon atoms. All organic compounds have a carbon backbone. Each carbon atom is tetravalent and can bond with four other atoms, making it an extraordinarily flexible component of biological molecules. Because carbon’s valence electrons are stable, it rarely becomes an ion. As the carbon chain increases in length, structural modifications such as ring structures, double bonds, and branching side chains...