Pentenes, ozonolysis

The same reaction that gave 2 4 4 trimethyl 2 pentene also yielded an isomeric alkene This second alkene produced formaldehyde and 4 4 dimethyl 2 pentanone on ozonolysis Identify this alkene... 

FIGURE6 15 Ozonolysis of 2 4 4 trimethyl 2 pentene On cleavage each of the doubly bonded carbons becomes the carbon of a carbonyl (C=0) group... 

Mixon, 47). Ozonolysis of the nonene mixture (which could not be separated by fractionation) indicated that it consisted of the following nonenes 2,3,4,4-tetramethyl-l- and -2-pentene, 50 and 10% respectively ... 

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-... 

An example of the ozonolysis of an olefin of type 1 is provided by the ozonolysis of 2,3-dimethyl-2-pentene, 12. In this case the diperoxides 9, 10, and 11 are produced from a single olefin. A nomenclature consistent with that used for ozonides would describe 10 as the parent diperoxide and 9 and 11 as cross diperoxides. 

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)... 

Annelation of the A ring is accomplished by reaction of the appropriate 4-pentenal 525 with the kinetic enolate generated from 524 followed by ozonolysis of the olefin and cyclization of the resulting ketoaldehyde with potassium graphite-titanium trichloride. Oxidation of the alcohol under Swem conditions gives 527. 

In continuation of a long-standing study, we set out under LACTOZ to determine the products of ozonolysis of 1-pentene, 1-hexene and 1-heptene at gas-phase concentrations of 140 ppm at 100 % relative humidity. It was necessary to develop our HPLC system further in order to do this. We later extended the study to the ozonolysis of lower alkenes and of some terpenes at ca. 4 ppm in dry air. 

The product in highest yield in the ozonolysis of 1-pentene in humid air (where the concentration is also considerably higher) is 1-PHP . MHP and EHP are also seen, the yields decreasing with the chain length. The HMHP probably results from the reaction of water with CH2OO, though some of it may come from reaction of formaldehyde with H2O2, while the BMHP observed must arise from addition of... 

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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