In organic chemistry, hydrocarbons are divided into two classes: aromatic compounds and aliphatic compounds. Aliphatic compounds can be saturated like hexane, or unsaturated, like hexene and hexyne. Open-chain compounds, whether straight or branched, and which contain no rings of any type, are always aliphatic. Cyclic compounds can be aliphatic if they are not aromatic.
In organic chemistry, allenes are organic compounds in which one carbon atom has double bonds with each of its two adjacent carbon atoms. Allenes are classified as cumulated dienes. The parent compound of this class is propadiene, which is itself also called allene. A group of the structure R2C=C=CR− is called allenyl, while a substituent attached to an allene is referred to as an allenic substituent. In analogy to allylic and propargylic, a substituent attached to a saturated carbon α to an allene is referred to as an allenylic substituent. While allenes have two consecutive ('cumulated') double bonds, compounds with three or more cumulated double bonds are called cumulenes.
In chemistry, a pentose is a monosaccharide with five carbon atoms. The chemical formula of many pentoses is C
5H
10O
5, and their molecular weight is 150.13 g/mol.
In organic chemistry, aromaticity is a chemical property describing the way in which a conjugated ring of unsaturated bonds, lone pairs, or empty orbitals exhibits a stabilization stronger than would be expected by the stabilization of conjugation alone. The earliest use of the term was in an article by August Wilhelm Hofmann in 1855. There is no general relationship between aromaticity as a chemical property and the olfactory properties of such compounds.
3-Methylenecyclopropene, also called methylenecyclopropene or triafulvene, is a hydrocarbon with chemical formula C4H4. It is a colourless gas that polymerizes readily as a liquid or in solution but is stable as a gas. This highly strained and reactive molecule was synthesized and characterized for the first time in 1984, and has been the subject of considerable experimental and theoretical interest. It is an example of a cross-conjugated alkene, being composed of cyclopropene with an exocyclic double bond attached.
A silabenzene is a heteroaromatic compound containing one or more silicon atoms instead of carbon atoms in benzene. A single substitution gives silabenzene proper; additional substitutions give a disilabenzene, trisilabenzene, etc.
In organic chemistry, transannular strain is the unfavorable interactions of ring substituents on non-adjacent carbons. These interactions, called transannular interactions, arise from a lack of space in the interior of the ring, which forces substituents into conflict with one another. In medium-sized cycloalkanes, which have between 8 and 11 carbons constituting the ring, transannular strain can be a major source of the overall strain, especially in some conformations, to which there is also contribution from large-angle strain and Pitzer strain. In larger rings, transannular strain drops off until the ring is sufficiently large that it can adopt conformations devoid of any negative interactions.
In organic chemistry, a cyclophane is a hydrocarbon consisting of an aromatic unit and a chain that forms a bridge between two non-adjacent positions of the aromatic ring. More complex derivatives with multiple aromatic units and bridges forming cagelike structures are also known. Cyclophanes are well-studied examples of strained organic compounds.
The root alk- is used in organic chemistry to form classification names for classes of organic compounds which contain a carbon skeleton but no aromatic rings. It was extracted from the word alcohol by removing the -ol suffix. See e.g. alkyl, alkane.
A cyclic compound is a term for a compound in the field of chemistry in which one or more series of atoms in the compound is connected to form a ring. Rings may vary in size from three to many atoms, and include examples where all the atoms are carbon, none of the atoms are carbon, or where both carbon and non-carbon atoms are present. Depending on the ring size, the bond order of the individual links between ring atoms, and their arrangements within the rings, carbocyclic and heterocyclic compounds may be aromatic or non-aromatic; in the latter case, they may vary from being fully saturated to having varying numbers of multiple bonds between the ring atoms. Because of the tremendous diversity allowed, in combination, by the valences of common atoms and their ability to form rings, the number of possible cyclic structures, even of small size numbers in the many billions.
Homoaromaticity, in organic chemistry, refers to a special case of aromaticity in which conjugation is interrupted by a single sp3 hybridized carbon atom. Although this sp3 center disrupts the continuous overlap of p-orbitals, traditionally thought to be a requirement for aromaticity, considerable thermodynamic stability and many of the spectroscopic, magnetic, and chemical properties associated with aromatic compounds are still observed for such compounds. This formal discontinuity is apparently bridged by p-orbital overlap, maintaining a contiguous cycle of π electrons that is responsible for this preserved chemical stability.
A geodesic polyarene in organic chemistry is a polycyclic aromatic hydrocarbon with curved convex or concave surfaces. Examples include fullerenes, nanotubes, corannulenes, helicenes and sumanene. The molecular orbitals of the carbon atoms in these systems are to some extent pyramidalized resulting a different pi electron density on either side of the molecule with consequences for reactivity.
Boroxine is a 6-membered heterocyclic compound composed of alternating oxygen and singly-hydrogenated boron atoms. Boroxine derivatives such as trimethylboroxine and triphenylboroxine also make up a broader class of compounds called boroxines. These compounds are solids that are usually in equilibrium with their respective boronic acids at room temperature. Beside being used in theoretical studies, boroxine is primarily used in the production of optics.
Linear acetylenic carbon (LAC), also known as carbyne or Linear Carbon Chain (LCC), is an allotrope of carbon that has the chemical structure (−C≡C−)n as a repeat unit, with alternating single and triple bonds. It would thus be the ultimate member of the polyyne family.
SMILES arbitrary target specification (SMARTS) is a language for specifying substructural patterns in molecules. The SMARTS line notation is expressive and allows extremely precise and transparent substructural specification and atom typing.
In chemistry, an oxocarbon or oxide of carbon is a chemical compound consisting only of carbon and oxygen. The simplest and most common oxocarbons are carbon monoxide (CO) and carbon dioxide. Many other stable or metastable oxides of carbon are known, but they are rarely encountered, such as carbon suboxide and mellitic anhydride.
In organic chemistry, a cyclo[n]carbon is a chemical compound consisting solely of a number n of carbon atoms covalently linked in a ring. Since the compounds are composed only of carbon atoms, they are allotropes of carbon. Possible bonding patterns include all double bonds or alternating single bonds and triple bonds.
Tricarbon monoxide C3O is a reactive radical oxocarbon molecule found in space, and which can be made as a transient substance in the laboratory. It can be trapped in an inert gas matrix or made as a short lived gas. C3O can be classified as a ketene or an oxocumulene a kind of heterocumulene.
Cyclooctadeca-1,3,5,7,9,11,13,15,17-nonayne or cyclo[18]carbon is an allotrope of carbon with molecular formula C
18. The molecule is a ring of eighteen carbon atoms, connected by alternating triple and single bonds; thus, it is a polyyne and a cyclocarbon.
Boraacenes are polycyclic aromatic hydrocarbons containing at least one boron atom. Structurally, they are related to acenes, linearly fused benzene rings. However, the boron atom is electron deficient and may act as a Lewis Acid when compared to carbon. This results in slightly less negative charge within the ring, smaller HOMO-LUMO gaps, as well as differences in redox chemistry when compared to their acene analogues. When incorporated into acenes, Boron maintains the planarity and aromaticity of carbon acenes, while adding an empty p-orbital, which can be utilized for the fine tuning of organic semiconductor band gaps. Due to this empty p orbital, however, it is also highly reactive when exposed to nucleophiles like water or normal atmosphere, as it will readily be attacked by oxygen, which must be addressed to maintain its stability.
