Propa-1 2-diene

To a solution of 1,2-bis(diisopropylamino)-3-lithiocyclopropenyliumperchlorate (0.34 g, 1.0 mmol) in THF (60 mL) was added at — 78 C with stirring under a solution of BuLi (1.0 mmol) in hexane (20 mL), which gave a brown-yellow mixture. After 1 min, a solution of l,l,3,3-tetrakis(ethoxycarbonyl)propa-1,2-diene (0.33 g, 1.0 mmol) in THF (10 mL) was added dropwise. The mixture was warmed to rt, treated... 

In the context of the ethynyl sulfones 6.30 Padwa s cycloadditions of phenylsulfonyl-substituted propa-1,2-dienes like 6.31 with diazomethane should be mentioned briefly (Padwa et al., 1993a, with many references on allenes used as dienophiles). The example in (6-22) demonstrates the regiospecificity of the cycloaddition to the more reactive electron-deficient 71 bond. The ready reactivity of cumulated double bonds is based on the relief of strain when the 1,2-propadiene... 

Fluoro-propa-1,2-diene (fluoroallene) (15) Dipole moment 332, 334,... 

I-lodo-propa-1,2-diene (iodoallene) (129) Carbon chemical shift 348,... 

Amino-A-(propa-1,2-dien-1 -yl)benzamide (2c) Off-white solid yield 99%... 

Allene (propa-1,2-diene), H2C=C=CH2, has two adjacent double bonds. What kind of hybridization must the central carbon have Sketch the bonding tt orbitals in allene. What shape do you predict for allene ... 

Figure 3,21 Example molecules belonging to D a point groups (a) propa-1,2-diene, Did, (b) ferrocene, Djd.

FIGURE 10 7 Bonding and geometry in 1 2 propa diene (allene) The green and yellow colors are meant to differentiate the orbitals and do not indicate their phases... 

The simple hydrocarbon substrates included ethene, 1,2-propa-diene, propene and cyclopropane (22). Their reactivity with Sm, Yb and Er was surveyed. In contrast to the reactions discussed above, lanthanide metal vapor reactions with these smaller hydrocarbons did not provide soluble products (with the exception of the erbium propene product, Er(C H ) ). Information on reaction pathways had to be obtained primarily by analyzing the products of hydrolysis of the metal vapor reaction product. 

The first bombs developed by the US Navy, CBU-55, were used in Vietnam, and tests to perfect an advanced version of the weapons system have continued. The CBU-55B air-to-surface free-fall cluster bombs were developed for helicopter.and siow-speed fixed-wing aircraft delivery to clear helicopter landing zones of mines booby traps. This FAE bomb was designed to disperse a mixt of vaporized fuel (ethylene oxide, propylene oxide, m e thy lacetylene/propa diene/pro pane and others) in a cloud 50 ft in dram and approx 8 ft thick. It has three 100-lb individual canisters 13.6 inches in diam by 21 inches long, each containing ca 72 lbs of fuel. The canisters separate from the dispenser after... 

FIGURE 10.6 Bonding and geometry in 1,2-propa-diene (allene). 

The double bond may also be conjugated with another, and in the series propa-diene (allene), 1,3-butadiene, 1,4-pentadieneetc. the extent of interaction decreases as the number of single bonds between the points of unsaturation increases. So, as we shall see later, in catalysed reactions propadiene and 1,3-butadiene often resemble the corresponding alkynes. There is a conjugation between double and triple bonds in ethenylethyne, and between these bonds and the aromatic ring in, for example, styrene (phenylethene) and phenylethyne. 

Overhead from the depropanizer is fed to the 03 splitter, after hydrogenation to convert the highly unsaturated methyl acetylene and propa-diene to propylene. The primary function of this tower is production of polymer grade or, in some cases, chemical grade propylene. A secondary function is propylene recovery because the bottoms from this column either is recycled to an ethane/propane cracking furnace or is used as propane fuel. 

Aryl- and alkylsulfonyl radicals have been generated from the corresponding iodides and added to, e.g., propadiene (la), enantiomerically enriched (P)-(+)-propa-2,3-diene [(P)-(lc)] and (P)-(-)-cyclonona-l,2-diene [(P)-(lk)] [47]. Diaddition of sulfo-nyl radicals may compete considerably with the monoaddition [48,49]. Also, products of diiodination have been purified from likewise obtained reaction mixtures, which points to a more complex reactivity pattern of these substrates towards cumulated Jt-bonds. An analysis of regioselectivities of arylsulfonyl radical addition to allenes is in agreement with the familiar trend that a-addition occurs in propadiene (la), whereas alkyl-substitution at the cumulated Jt-bond is associated with a marked increase in formation of /3-addition products (Scheme 11.7). 

Cycloaddition of alkenes to the benzene ring does not occur when both molecules are in their ground electronic states. The reaction can only be brought about by photoexcitation of either of the two addends. Three types of photochemical cycloaddition of alkenes to benzene and its derivatives are presently known. Ortho photocycloaddition, also referred to as 1,2-photocycloaddition or [2 + 2] photocycloaddition, leads to bicyclo[4.2.0]octa-2,4-dienes. Meta photocycloaddition, also referred to as 1,3-photocycloaddition or [2 + 3] photocycloaddition, gives triyclo[3.3.0.02 8]oct-3-enes, also named l,2,2a,2b,4a,4b-hexahydrocyclo-propa[crf]pcn(alcnes. Para photocycloaddition, also referred to as 1,4-photocy-cloaddition or [2 + 4] photocycloaddition, results in bicyclo[2.2.2]octa-2,5-... 

The heterocyclic cycloproparenes l//-4-oxacyclopropa[/]indene (15a) and l//-4-thiacyclo-propa[/]indcnc (15b) °° were synthesized from the appropriate dienes mand 1,2-dibromocy-clopropene via dehydrogenation of the cycloadducts with 2,3-dichloro-5,6-dicyanobenzo-quinonc and base-induced elimination. Both compounds decompose rapidly in the solid state and in solution. 

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