3- -3-Methyl-2-pentene, ozonolysis

Ozonolysis of 2,3-Dimethyl-2-pentene. A solution of 2,3-dimethyl-2-pentene (1.04 grams, 10.6 mmoles) in 20 ml pentane was ozonized to 60% theoretical yield at —40°C. The product mixture was analyzed by GPC using an 8-ft, 10% XF-1150 column of temperature 85 °C and flow rate 150 ml/minute. The mixture contained 0.503 mmole acetone diperoxide, 0.210 mmole l,l,4-trimethyl-4-ethyl-2,3,5,6-tetraoxacyclohexane, and 0.12 mmole of methyl ethyl ketone diperoxide. Total yield of diper-... 

We also have examined one final type of olefin. This type of olefin, represented by 2-methyl-3-ethyl-2-pentene, 14, is also capable of giving cross diperoxides although in this case the diperoxide products are not capable of existing as stereoisomers. Ozonolysis of 14 gave three diperoxides, 9, l,l-dimethyl-4,4-diethyl-2,3,5,6-tetraoxacyclohexane, 15, and 3-pentanone diperoxide, 16. 

Y.M.Slobodin et al.ZhurObshKhim 23,1873-7 (1953 ) CA49,192(1955)(Dimeric acet peroxide was obtained together with other products on ozonolysis of 5—chloro—2—methyl—2—pentene)... 

Ozonolysis of a cyclic alkene leads to oxidative cleavage, but the two carbonyl fragments are connected, so there is only one product rather than the two observed from ozonolysis of 2,3-dimethyl-2-butene or 2-methyl-2-pentene. When cycloheptene, for example, is treated with ozone and then with zinc and acetic acid, oxidative cleavage leads to the a,(o-dialdehyde 146 (1,7-heptanedial or 1,7-heptanedicarboxaldehyde). 

By use of matrix isolation infrared spectroscopy, it has been shown that the mechanism of ozonolysis of (Z)-3-methyl-2-pentene (mp) is similar to that for ozonolysis of simple alkenes. Indirect evidence for formation of one or both possible Criegee intermediates is presented. Eight fundamental vibrations of the c/s -isomer of the primary ozonide of mp are observed. UV irradiation led to the product arising from O atom addition to mp. Second-order rate coefficients for the ozonolysis of -butyl methacrylate, ethyl cro-tonate and vinyl propionate under atmospheric pressure have been determined and the effects of substituent groups on the overall rate coefficients have been analysed. Free energy relationships are presented and atmospheric lifetimes are discussed. ... 

An alternative method of synthesis comprises ozonolysis of the acetate (255) and reaction of the enol lactone obtained (258) with the Grignard derivative from 5-chloro-2-methyl-l-pentene. The allylation of compound (259) led to a mixture of Cio epimers in a ratio of 2 1. The epimer present in largest amount had the natural lOp -configuration, as was shown by its conversion into the 3,16-diketone (257) [845]. 

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