Tropone
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| Names | |||
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Preferred IUPAC name
Cyclohepta-2,4,6-trien-1-one
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| Other names
Cyclohepta-2,4,6-trienone
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| Identifiers | |||
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3D model (JSmol)
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| ChemSpider | |||
| ECHA InfoCard | 100.007.933 | ||
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PubChem CID
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| Properties | |||
| C7H6O | |||
| Molar mass | 106.12 g/mol | ||
| Density | 1.094 g/mL | ||
| Boiling point | 113 °C (235 °F; 386 K) (15 mmHg) | ||
| Hazards | |||
| Flash point | > 113 °C (235 °F; 386 K) | ||
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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 (what is   ?) |
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| Infobox references | |||
Tropone or 2,4,6-cycloheptatrien-1-one is an organic compound with some importance in organic chemistry as a non-benzenoid aromatic. The compound consists of a ring of seven carbon atoms with three conjugated alkene groups and a ketone group. The related compound tropolone (2-hydroxy-2,4,6-cycloheptatrien-1-one) has an additional alcohol (or an enol including the double bond) group next to the ketone.
The tropone moiety can be found in biomolecules such as colchicine, stipitatic acid and hinokitiol.
Tropone has been known since 1951 and is also called cycloheptatrienylium oxide. The name tropolone was coined by M. J. S. Dewar in 1945 in connection to perceived aromatic properties.
Dewar in 1945 proposed that tropones could have aromatic properties. The carbonyl group is polarized with a partial positive charge on the carbon atom (A) and a partial negative charge on oxygen. In an extreme case the carbon atom has a full positive charge (B) forming a tropylium ion ring which is an aromatic 6 electron system (C).
Tropolone is acidic (conjugate base shown, E) with a pKa of 7 which is in between that of phenol (10) and benzoic acid (4). The increased acidity compared to phenol is due to regular resonance stabilization. Tropones and to a lesser extent tropolones are also basic (D) and this is very much due to aromatic stabilization. This property can be observed in the ease of salt formation with acids. The dipole moment for tropone is 4.17 D compared to a value of only 3.04 D for cycloheptanone, which can also be taken as evidence for aromaticity.
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