Dimethylketene dimer

The preparation of ketenes has been discussed by Hanford and Sauer in Organic Reactions Dimethylketene has been prepared by the treatment of a-bromoisobutyryl bromide with zinc,3 and by the pyrolysis of isobutyrylphthalimide,4 dimethylmalonic anhydride,6 or a-carbomethoxy-a,j3-dimethyl- -butyrolactone. Dimethylketene dimer has been prepared by heating isobutyryl chloride with a tertiary amine. Pyrolysis of the dimer yields dimethylketene.7... 

The dry powdered condensation product of sodium acz-nitromethanide (2 mol) with dimethylketene dimer exploded violently when added to crushed ice. 

Although these reactions can be duplicated in most cases with the normal dimer of dimethylketene,11 the more reactive lactone dimer is the preferred reagent. The liquid form of this dimer is convenient to handle. A distinct difference in behavior of the dimethylketene dimers is noted when they are pyrolyzed. The normal dimer is dissociated at 600° to dimethylketene,12 but the lactone dimer is decarboxylated almost quantitatively at 450° to tetramethylallene.13... 

Tetramethyl-l,3-cyclobutanedione, dimethylketene dimer (12), was hydrogenated to the corresponding glycol in excellent yields with Ru-C as catalyst in methanol at 125°C and 6.9-10.3 MPaH2 (eq. 5.41).131 Hydrogenation over Raney Ni in methanol was often accompanied by formation of a high-boiling byproduct that was shown to consist of 1-hydroxy-2,2,4-trimethyl-3-pentanone (13) and methyl 2,2,4-trimethyl-3-oxovalerate (14). 

Examples for the treatment of other ketenes are few. The ordinary ketene lamp has been modified for the depolymerization of dimethylketene dimer (86%). Ethylcarbethoxyketene can be obtained from its dimer in 80-90% yields by heating at 180-200° under a pressure of 15 mm. ... 

The symmetrical trimers of disubstituted ketenes are obtained by heating the corresponding dimers with a catalytic amount of base. For example, heating of the symmetrical dimer of dimethylketene 77 with sodium methoxide at 100 °C affords a 97 % yield of the trimer 78 . In a similar manner, 78 is obtained from the unsymmetrical dimethylketene dimer 79 in high yield. The symmetrical trimer of diphenylketene was similarly obtained... 

In 1946, Lipscomb gained a PhD. degree in chemistry from Caltech with a dissertation in four parts. The first two were entitled Electron Diffraction Investigations of Vanadium Tetrachloride, Dimethylketene Dimer, Tetrachloroethylene, and Trichloroethylene, and The Crystal Structure of Methylammonium Chloride. Parts... 

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