Grignard reagents crotyl, isomerization

The only olefinic acid isolated from the carbonation of the Grignard reagent prepared from the isomeric mixture of crotyl and methylvinylcar-binyl bromides is 2-methyl-3-butenoic acid (70%). Separation of the halides is unnecessary because of this fortunate allylic isomerization. 

The major product (19) from addition of the crotyl Grignard to ethylene was found to be in equilibrium with a small concentration of isomeric secondary Grignard 20. From the equilibrium constant [19]/[20] = 290 at 70°C, and thermodynamic data for the corresponding alkenes, a value of 3.3 kcal/mole was derived as the difference in free energy between primary and secondary Grignard reagents (46). 

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