3.4.5.6.6- Pentamethyl-3- -hepten

Pentamethyl-3-hepten-2-one [81786-73-4], also contains other double... 

Pentamethyl-3-hepten-2-one [81786-73-4], also contains other double bond isomers [81786-74-5], [81786-75-6], [81786-76-7], [81786-77-8]... 

Two of the substances detected, pentamethyl heptene and tetramethyloctene were considered as substances known to contribute to the odour of extrusion film coatings. The fact that these substances could transfer from the film to the gas phase supported the potential for these substances to give rise to odour problems in foodstuffs. They also impregnated a filter paper with octanal and placed it in the test cell in contact with paperboard laminated to various films including PE, PP, poly(ethylene terephthalate) (PET) and aluminium/PE (Al/PE) (with PE on the outer surface). They monitored transfer of octanal across the material held at 30 °C for 8-10 hours. Transfer was most rapid through uncoated paperboard. Octanal was shown to transfer across PE film laminated to the paperboard within ten minutes. There was no transfer of octanal through PP, Al/PE and PET over ten hours. 

A small amount of this mixture can also be obtained when the isomeric 3-oxatetracy-clo[3.1.1.02,4.06,7]heptene is heated to 145°C. The major product, however, is 2-oxabi-cyclo[3.2.0]hepta-3,6-diene.113 2,3,5,6,9-Pentamethyl-4-oxa-9-azatetracyclo[5.3.0.02,6.03 5]dec-l(7)-ene-8,10-dione readily isomerizes to the corresponding oxepino[4,5-c]pyrrole. 14... 

While there was apparently no olefin corresponding to the carbonium ion XXXII present in the dimer formed in the presence of 80% sulfuric acid, it has been reported that such a compound, namely, 2,2,3,6,6-pentamethyl-3-heptene, is the principal product when 84% acid is used (Whitmore, 18). 

Trimers may be formed through the addition of a tert-butyl carbocation to 2 or via addition of carbocation 1 to isobutylene. The trimer fraction mainly consists of 4-methylene-2,2,6,6-tetramethylheptane and 2,2,4,6,6-pentamethyl-3-heptene. 

The reaction scheme also considered the olefin distribution arising via proton elimination of the C 2 ion A) l,l -dineopentylethylene and B) 2,2, 4,6,6 -pentamethyl-3-heptene. 

The byproduct, 2,2,3,6,6-pentamethyl-3-hepten-5-one, was difficult to separate from the enamine by distillation. When the conditions optimized for enamine synthesis from methyl isobutyl ketone were applied to the synthesis from pinacolone, ca. 30 % of the byproduct was formed. A response surface study was undertaken to overcome the problem and to determine how the experimental conditions should be adjusted to achieve a maximum yield of the enamine, with a concomitant suppression of the formation of the byproduct. 

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