1625-49-6

Basic information

• Product Name: (3E)-2,3-dimethylpenta-1,3-diene
• Synonyms: (3E)-2,3-Dimethyl-1,3-pentadiene; 1,3-Pentadiene, 2,3-dimethyl-; 2,3-Dimethyl-1,3-pentadiene
• CAS NO: 1625-49-6
• Molecular Formula: C₇H₁₂
• Molecular Weight: 96.1702
• Mol File: 1625-49-6.mol
• Article Data: 6

Chemical Properties

• Boiling Point: 100.6°C at 760 mmHg
• Density: 0.726g/cm³
• Vapor Pressure: 41.9mmHg at 25°C
• Refractive Index: 1.426
• CAS DataBase Reference: (3E)-2,3-dimethylpenta-1,3-diene(CAS DataBase Reference)
• NIST Chemistry Reference: (3E)-2,3-dimethylpenta-1,3-diene(1625-49-6)
• EPA Substance Registry System: (3E)-2,3-dimethylpenta-1,3-diene(1625-49-6)

Safety Data

• Hazardous Substances Data: 1625-49-6(Hazardous Substances Data)

Upstream product

• 75-07-0 acetaldehyde 
• 565-62-8 3-methylpent-3-en-2-one 
• 74-88-4 methyl iodide 
• 1567-73-3 (E)-3-methylpent-3-en-2-one 
• 32596-24-0 1,2,3-trimethylcyclobutane 
• 19493-09-5 Methylenetriphenylphosphorane 
• 53496-45-0 4-hydroxy-3-methyl-pentan-2-one 
• 2065-66-9 methyl-triphenylphosphonium iodide 

Downstream Products

• 345930-78-1 3,4-dimethyl-1-nitro-1-(1-phenylpentyl)-3-cyclohexene 

Relevant articles and documents

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Importance of the role of secondary orbital interactions in the Diels-Alder reaction. Regioselectivity in the catalyzed and uncatalyzed reactions of juglone and aliphatic dienes

The regioselectivities in the uncatalyzed and catalyzed Diels-Alder (DA) reactions of juglone with piperylene (penta-1,3-diene) or 2,3-dimethylpenta-1,3-diene have been investigated, employing Lewis acids such as boron trifluoride (BF3) and sterically hindered aluminium catalysts in order to verify the role of the secondary orbital interactions (SOI). While the results of the uncatalyzed and catalyzed reactions using BF3 or aluminium trimethoxide agree with the prediction made by the frontier molecular orbital (FMO) theory considering SOI, steric repulsion of the aluminium catalysts causes orderly changes to the ratios of the product regioisomers, which could be interpreted by diminution of SOI. The transition states are located by AM1 calculations and their energies are estimated by CDNO/2-CI and ab initio 6-31G* calculations. The regioselectivities observed in the experiments are explained by comparison of their energies. A zwitterionic mechanism in the catalyzed reaction was strongly supported and the molecular orbital feature suggests the contribution of SOI which would stabilize the transition state to control the reaction pathway.

The Mechanism of 1,4-Addition of Dibromomethylene

Dibromomethylene produced from the Seyferth reagent (PhHgCBr3) may react as a free species or while complexed with Lewis bases.Recent reports of the long-sought 1,4-addition to dienes of dibromomethylene, produced from the Seyferth reagent, to form five-membered rings therefore could be based on reactions of either free or complexed carbenes.These modes of reaction may be distinguished by product ratio dependence on the diene concentration, on the solvent basicity, and on the basicity of additives.We have found that the addition of Seyferth-generated dibromomethylene to the exo dienes 1 and 2 gives a ratio of 1,2- and 1,4-addition that is independent of all these considerations of concentration, solvent, and additive.These observations lend strong support to the assertion that 1,4-addition occurs by a concerted, symmetry-allowed pathway.When the carbane source is 11,11-dibromo-1,6-methanoannulene, addition to 1,2-dimethylenecyclohexane (1) gives the same proportion of 1,4-addition as for the Seyferth reagent, indicating a free carbene in both cases.Addition of dibromomethylene from the annulene to the sterically congested 2, however, gives a much augmented proportion of 1,4-addition, in fact the major pathway of the first time.This observation may indicate a complexed carbene in this case.