Bond dissociation energy 1-butene

Fig. 32. Schematic potential energy diagram for the reaction of ground state Y(a2 D) with cis-2-butene. Energies of stationary points estimated from calculations on Y f C2H4.22 Energies of product asymptotes calculated from known thermodynamic values and calculated bond dissociation energies.22 31 34 156 157...

Compare the carbon-carbon bonds that distinguish these compounds. cw-2-Butene is an alkene which has a carbon-carbon double bond. 1-Butyne is an alkyne and has a carbon-carbon triple bond and butane has carbon-carbon single bonds. The triple bonded carbon-carbon bonds have the highest bond dissociation energy. Bottle B contains 1-propyne. 

A fundamentally similar situation is obtained with the initiation of styrene by alkylaluminum halides or trialkylaluminum compounds. In the case of this monomer the demarcation between poor and good coinitiators is perhaps even more evident than with isobutylene. Fig. 2 shows the essential data obtained in a series of experiments in which various alkyl chlorides were added to styrene/Al(C2H5)2Cl charges in methyl chloride 24). Alkyl halides with high R—Cl heterolytic bond dissociation energies are very poor coinitiators compared with those with lower dissociation energies. Thus 3-chloro-l-butene, crotyl chloride, fert-butyl chloride, 1-chloroethylbenzene and diphenyl chloromethane are efficient because the carbocations which arise from these chlorides... 

Remarkably, however, the logarithm of the rate constant varies linearly with the dissociation energy of the allylic C—H bond, which indicates that the rupture of the C—H bond is included in the rate-determining reaction step. Mixed olefin feeds (propene and butene) were also used. It appears that co-dimerization can occur yielding C2 -dimers. 

However the dissociation energies of the C3—H bond in propene-i and the C4—C3 bond in butene-1 are also particularly low (Table i8b Schmidt s rule). 

The differences between the heat of dissociation and the bond energy for the C—H bond in propylene and toluene and for the C—C bond in butene-1 and diphenylethane are interesting. The cause lies here not so much in the bonds of the molecules in question, as can be seen from the total binding energy deduced from the heat of combustion (or heat of hydrogenation), but in the peculiar stability of the ally] and toluyl radicals formed (p. 237). 

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