7-bromo-1,3,5-cycloheptatriene

One compound, either 7-bromo-1,3,5-cycloheptatriene or 5-bromo-1,3-cyclopentadiene, dissociates into ions when dissolved in water. Which molecule do you think displays this behavior How do you think the other molecule behaves when mixed with water ... 

Dicyanoheptafulvene 2,4,6-Cycloheptatriene-A1 -malononitrile (8) Propanedinitrile, 2,4,6-cycloheptatrien-1-ylidene- (9) (2860-54-0) Cycloheptatrienylium tetrafluoroborate Aldrich Tropylium tetrafluoroborate Cycloheptatrienylium, tetrafluoroborate (1-) (8,9) (27081-10-3) Bromomalononitrile, Malononitrile, bromo- (8) Propanedinitrile, bromo- (8) (1885-22-9)... 

The cycloheptatrienyl carbocation, also known as the tropylium cation, has six pi electrons. It is also aromatic and is quite stable. In fact, 7-bromo-l,3,5-cycloheptatriene actually exists as an ionic compound. 

The reaction with simple, nonbenzenoid furans was less successful. Thus, reaction of tita-nium(III) chloride and lithium aluminum hydride with the adduct 8 (R = Me) of l-bromo-2-chlorocyclopropene and 2,5-dimethylfuran gave only 30% of the cycloheptatriene 10 (R = Me) and no cycloproparene. With the 2-methylfuran adduct 8 (R = H), an additional 30% of 2-methyl-l/f-cyclopropabenzene (9, R = H) was obtained. 

With cycloheptatriene it is possible to saturate mainly just one of the C=C bonds by using 40% hydrobromic-acetic acid in the cold one obtains, besides the dibromide, 65% of 6-bromo-l,3-cycloheptadiene which acts as intermediate in the first tropine synthesis.195... 

When 7-bromo-l,3,5-cycloheptatriene is mixed with KCN in aqueous THF, one observes an 8n1 reaction. Draw the intermediate for this reaction and the final product. Comment on the stability of the intermediate. 

Cycloheptatriene.—Synthesis. Details have been published on the preparation of specifically substituted cycloheptatrienes by the cycloadditon of cyclopropenes to thiophene-1,1-dioxides followed by expulsion of S02. Substituted tropones have been obtained from the furan adducts of bromo-oxyallyl cations e.g. treatment of l,l,3,3-tetrabromo-4-methylpentan-2-one with di-iron nonacarbonyl in the presence of furan gave adduct (141) which was converted into a-thujaplicin (142). Acid hydrolysis of the norbornyl ketal (143) followed by warming to 70 "C gave 7,7-dimethyl-cycloheptatriene. ... 

Scheme 94 Preparation of dihalogeno-cycloheptatrienes frran cycloaddition of l-bromo-2-chlorocyclopropene to thiophene 1,1-dioxide [117]...

The bicyclo[2.2.0]but-l(3)-enes belong to the latter class. As systematic investigations by Gunter Szeimies have disclosed, tricyclo[4.1.0.0 ]hept-l(7)-ene acts as a turntable in the reactions of alkyl- and aryllithiums with 1-chlorotricyclo[4.1.0.0 ]heptanes (Scheme 1-219). Lithium aziridine is basic enough to sustain such a sequence of metaiation, elimination, and nucleophilic addition. The A-tricycloheptylaziridine thus formed thermolyses at 150 °C to cyclohex-2-ene-l-carbonitrile. The weekly basic lithium benzenethiolate requires the assistence of LITMP to accomplish the deprotonation step before it can add smoothly to give the intermediate 276 (Scheme 1-219). Dienes rather than nucleophiles may be also used to trap strained bicyclo[2.2.0]but-l(3)-enes like 276. Such species may also be generated from l-bromo-7-(trimethylsilyl)tricyclo[4.1.0.0 ]heptanes and cesium fluoride in DMSO at +25 °C. At elevated temperatures (about +100 °C), the bicyclobutene 276 isomerizes rapidly to 1,3,5-cycloheptatriene by [2+2]-cycloelimination. ... 

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