Levulin aldehyde

The levulinic aldehyde and acid obtained by Harries on hydrolyzing the ozonide of rubber demonstrated recurrence of the structure... 

Ozonolysis of polyisoprene formed by free radical polymerization yields much levulinic aldehyde and acid and only very small amounts... 

Oxidation of S.S-dimethyl-zP-pyrroline (109) with hydrogen peroxide, or irradiation of the A-oxide (110), gave the bicyclic oxazirane m.332 333 Thermal rearrangement of the oxazirane followed by hydrolysis yielded levulinic aldehyde. 

The ethanol-insoluble mixture of phenylhydrazones was extracted several times with hot chloroform and the solvent removed. The reddish residue was then recrystallized from pyridine yield of levulinic aldehyde, 2,4-dinitrophenylhydrazone, 90.5% melting point, 232° C. Literature melting point, 235-6° C. (5). 

The acid fission of the bicyclic oxazirane 14 to levulinic aldehyde [Eq. (17)]18 is a further example of a dealkylation involving a methyl shift. 

The same authors82 suggested a mechanism for the reaction of 1,4-dicarbonyl compounds with monosubstituted hydrazines, which affords, depending on reaction conditions and structural factors, the mono- and bishydrazones, N-aminopyrroles, and 1,4-dihydropyridazines. Some relatively simple 1,4-dihydropyridazines (31) were prepared by condensation of monosubstituted hydrazines with succinic or levulinic aldehyde.83... 

Smlth (Wyeth) utilized an aldol cyclization of a substituted levulinic aldehyde to form the cyclopentenone i+1 to which the elements of water... 

The ozonolysis of natural rubber gives levulinic aldehyde, CH3CCH2CH2CH=0. Explain how this result is... 

The stereochemistry of the substituents was not defined. The patent elaborates a series of reactions, starting with acyclic chemicals, to arrive at substituted levulinic aldehyde 2. This was then cyclized and transformed as shown to a substituted eyelopentanone having the correct substituents of 13,14-dihydro PGEj. 

The history of polymer science (169,170), takes the reader back to before the macromolecular hypothesis. Natural rubber, civ-polyisoprene, was investigated around the turn of the twentieth century. Morawetz (169) writes of the destructive distillation of rubber to isoprene, and of the ozonolysis of rubber to levulinic aldehyde. These studies led to the dimer ring structure of dimethyl-cyclooctadiene for ds-polyisoprene ... 

In practice, acids are also formed through oxidation of aldehyde by hydrogen peroxide. When Harries subjected rubber to ozonolysis, he obtained high yields of levulinic aldehyde (II) and levulinic acid (III). These results are readily explained if it is assumed that rubber hydrocarbon consists of isoprene units joined head-to-tail by 1,4-links (see also Sections 1.4.2.2 and 1.6.3) ... 

If the isoprene units were joined in some other way, ozonolysis would not yield levulinic aldehyde (and acid). It may be noted that Harries took his results to indicate that rubber hydrocarbon molecules were cyclic structures of low molecular weight which formed aggregates by means of ill-defined forces. This view was in accordance with the then current ideas concerning the nature of polymers. It was not until after 1920, when the concept of the macromolecule was introduced, that rubber hydrocarbon was accepted as consisting of linear polymers composed of isoprene units linked together by normal carbon-carbon bonds in a 1,4-, head-to-tail manner. (See also Section 1.3.) Modern techniques of infrared spectroscopy have since verified the essential correctness of these conclusions it has been shown that in rubber hydrocarbon about 98% of the links between isoprene units are 1,4-bonds, the remainder probably being 3,4-bonds. 

Evidence for this scheme is that levulinic aldehyde has been isolated from aged rubber. Further, it is known that jS-peroxyalkoxy radicals are explosively unstable. 

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