A heterocumulene is a molecule or ion containing a chain of at least three double bonds between consecutive atoms, in which one or more atoms in the doubly bonded chain is a heteroatom. Such species are analogous to a cumulene in which the chain of doubly bonded atoms contains only carbon, except that at least one carbon is replaced by a heteroatom. [1] Some authors relax the definition to include species with chains of only two double bonds between consecutive atoms, [2] also known as heteroallenes .
Because of the double bond rule, heterocumulenes are rarely isolated. Instead they tend to polymerize. Many are however common in the interstellar medium, where they exist as a dilute gas. Most of the longer ones are very unstable and reactive, and thus have a transient existence, or can only survive when dilute or in an inert matrix. Molecular clouds in space are very dilute and allow heterocumulenes to exist long enough to be detected. Some simple heterocumulenes are common chemicals or ions. These include carbon dioxide, carbon disulfide, carbon diselenide, cyanate, and thiocyanate. Some definitions of heterocumulenes include compounds that contain concatenated double bonds with more than one element, but may have other parts to them. This class includes ketene, sulfur diimide, sulfine, and dicyclohexylcarbodiimide. Some heterocumulenes can act as ligands with various metals.
Some energised heterocumulenes can cyclise by bending into a circle and bonding the two ends of the chain. Molecules that can do this are CCCB, CCCAl, CCCSi, CCCN, and CCCP. [3]
Other four-atom heterocumulenes include CCBO, tricarbon monoxide (CCCO), and CCCS.
Four-atom heterocumulenes when cyclised can have two forms. In the kite (or rhombic) form, a triangle of carbon has two of its atoms bonded to the heteroatom. In the fan form the hetero atom links to three carbon atoms arranged in a fan shape. CCCSi has linear, rhombic or fan isomers. The rhombic form is known in space near the carbon star IRC+10216.
CCCCO cyclises to a three-member ring. [3] CCCCN undergoes an isonitrile conversion. [3]
Other known five-atom heterocumulenes include CCBCC, CCCCB, CCOCC, CCCCSi, CNCCO, HCCCO, HCCCS, and NCCCN. CCCCSi is known as a linear molecule in space.
CCCCBO turns into a six-member ring. Other six atom heterocumulenes include OCCCCN and HCNCNH.
Seven atom heterocumulenes include NCCCCCN, HCCBCCH.
A known nine atom heterocumulene is HCCCCCCCH.
Thiocumulenes have a sulfur atom. They include dicarbon monosulfide CCS and tricarbon monosulfide CCCS, both known from molecular clouds. [4] SCnS chains can be made by laser ablation with n up to 27. [5]
This table lists heterocumulene molecules. Heterocumulenes are supposed to be straight, but some combinations of elements result in bent or cyclic molecules.
one kind of heteroatom | |||||||||
heteroatom | 1 carbon | 2 carbon | 3 carbon | 4 carbon | 5 carbon | 6 carbon | 7 carbon | 8 carbon | 9 carbon |
---|---|---|---|---|---|---|---|---|---|
B | CCB | CCBCC, CCCCB | |||||||
N | CCN NCCN | CCCN [6] NCCCN | CCCCN NCCCCN | NCCCCCN C5N [6] | |||||
O | OCO | CCO [7] | CCCO OCCCO >CCCO | C4O [7] C4O2 | OC5O | C6O [7] | C8O [7] | ||
Si | CCSi bent | CCCSi ring | CCCCSi [6] | C6Si [6] | |||||
P | CCP | ||||||||
S | SCS | CCS SCCS | CCCS SCCCS | C4S [8] SCCCCS [8] | C5S [8] SC5S [8] [9] | C6S [10] | SC7S [10] | SC9S [10] | |
Cl | CCCl | CCCCl is bent | |||||||
Se | CSe2 | SeCCCSe [11] | |||||||
Ir | IrC3– [12] | ||||||||
Pt | PtC3 [12] | ||||||||
Au | AuC3+ [12] |
Two different hetero atoms
atom 1 | H | N | O | S |
---|---|---|---|---|
N | HCN HCCCN HCnN n=5,7,9,11 HCNCC [6] HCCNC [6] | -OCN -NCO | -SNC -NCS | |
S | HC2-8S (HCS bent) [13] | NCS (NCCS bent) NC3-7S [13] | OCS | |
Se | -SeCN | |||
In chemistry, a heteroatom is, strictly, any atom that is not carbon or hydrogen.
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In chemistry, catenation is the bonding of atoms of the same element into a series, called a chain. A chain or a ring may be open if its ends are not bonded to each other, or closed if they are bonded in a ring. The words to catenate and catenation reflect the Latin root catena, "chain".
The skeletal formula, line-angle formula, bond-line formula or shorthand formula of an organic compound is a type of molecular structural formula that serves as a shorthand representation of a molecule's bonding and some details of its molecular geometry. A skeletal formula shows the skeletal structure or skeleton of a molecule, which is composed of the skeletal atoms that make up the molecule. It is represented in two dimensions, as on a piece of paper. It employs certain conventions to represent carbon and hydrogen atoms, which are the most common in organic chemistry.
In organic chemistry, free-radical addition is an addition reaction which involves free radicals. These reactions can happen due to the free radicals having an unpaired electron in their valence shell, making them highly reactive. Radical additions are known for a variety of unsaturated substrates, both olefinic or aromatic and with or without heteroatoms.
Organosulfur chemistry is the study of the properties and synthesis of organosulfur compounds, which are organic compounds that contain sulfur. They are often associated with foul odors, but many of the sweetest compounds known are organosulfur derivatives, e.g., saccharin. Nature is abound with organosulfur compounds—sulfur is vital for life. Of the 20 common amino acids, two are organosulfur compounds, and the antibiotics penicillin and sulfa drugs both contain sulfur. While sulfur-containing antibiotics save many lives, sulfur mustard is a deadly chemical warfare agent. Fossil fuels, coal, petroleum, and natural gas, which are derived from ancient organisms, necessarily contain organosulfur compounds, the removal of which is a major focus of oil refineries.
A polyyne is any organic compound with alternating single and triple bonds; that is, a series of consecutive alkynes, (−C≡C−)n with n greater than 1. These compounds are also called polyacetylenes, especially in the natural products and chemical ecology literature, even though this nomenclature more properly refers to acetylene polymers composed of alternating single and double bonds (−CR=CR′−)n with n greater than 1. They are also sometimes referred to as oligoynes, or carbinoids after "carbyne" (−C≡C−)∞, the hypothetical allotrope of carbon that would be the ultimate member of the series. The synthesis of this substance has been claimed several times since the 1960s, but those reports have been disputed. Indeed, the substances identified as short chains of "carbyne" in many early organic synthesis attempts would be called polyynes today.
Tricarbon is an inorganic compound with the chemical formula C
2(μ-C). It is a colourless gas that only persists in dilution or solution as an adduct. It is one of the simplest unsaturated carbenes. Tricarbon can be found in interstellar space and can be produced in the laboratory by a process called laser ablation.
In organic chemistry, umpolung or polarity inversion is the chemical modification of a functional group with the aim of the reversal of polarity of that group. This modification allows secondary reactions of this functional group that would otherwise not be possible. The concept was introduced by D. Seebach and E.J. Corey. Polarity analysis during retrosynthetic analysis tells a chemist when umpolung tactics are required to synthesize a target molecule.
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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.
Hydrogen chalcogenides are binary compounds of hydrogen with chalcogen atoms. Water, the first chemical compound in this series, contains one oxygen atom and two hydrogen atoms, and is the most common compound on the Earth's surface.
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