Ozonolysis isoprene

Kuwata, K. T Valin, L. C. Converse, A. D. Quantum Chemical and Master Equation Studies of the Methyl Vinyl Carbonyl Oxides Formed in Isoprene Ozonolysis. J. Phys. Chem. A 2003, 109, 10710-10725. 

As with many polymers, polyisoprene exhibits non-Newtonian flow behavior at shear rates normally used for processing. The double bond can undergo most of the typical reactions such as carbene additions, hydrogenation, epoxidation, ozonolysis, hydrohalogena-tion, and halogenation. As with the case of the other 1,4-diene monomers, many copolymers are derived from polyisoprene or isoprene itself. 

Gutbrod, R., E. Kraka, R. N. Schindler, and D. Cremer, Kinetic and Theoretical Investigation of the Gas-Phase Ozonolysis of Isoprene Carbonyl Oxides as an Important Source for OH Radicals in the Atmosphere, J. Am. Chem. Soc., 119, 7330-7342 (1997a). 

Gutbrod, R., S. Meyer, M. M. Rahman, and R. N. Schindler, On the Use of CO as Scavenger for OH Radicals in the Ozonolysis of Simple Alkenes and Isoprene, European Community (LABVOC), Project No. EV5V-CT91-0038, Wiley, New York, 1997b. 

Sauer, F., C. Schafer, P. Neeb, O. Horie, and G. K. Moortgat, Formation of Hydrogen Peroxide in the Ozonolysis of Isoprene and Simple Alkenes under Humid Conditions, Atmos. Enriron., 33, 229-24f (f999). 

A detailed structural and conformational study by DFT and ab initio methods has been reported for the ozonolysis of isoprene <2002JA2692>. The O-envelope conformers of the primary ozonides have the lowest energy. 

Details of the preparation of methyl (-)-cis-chrysanthemate from (+)-car-3-ene have appeared (Vol. 5, p. 15 is misleading).159 Both ( )-cis- and (+)-trans-chrysanthemic acids are again reported from (+)-car-3-ene via ozonolysis 160 this work is very similar to that reported (Vol. 5, p. 15) by Sukh Dev and illustrates the lamentable delay from receipt to publication in some journals. The decomposition of ethyl diazoacetate in 2,5-dimethylhexa-2,4-diene in the presence of the chiral copper complex (72) leads to cis- and frvms-chrysanthemic acids in 60—70% optical yield the degree of asymmetric induction is dependent upon the steric bulk of R1 and R2 in (72).161 cis-Chrysanthemic acid has also been prepared from 3,3-dimethylcyclopropene, isoprene, and 2-methylpropenylmagnesium bromide followed by treatment with carbon dioxide.162... 

The same authors published a detailed report on the calculations of the oxygen insertion into unactivated C-H bonds by dioxiranes using DFT theory and on comparison of the transition structures for stepwise routes via radical pairs with the concerted pathway <2003JOC811>. The articles dealing with the mechanism of OH formation from ozonolysis of isoprene and a- and /3-pinene provide DFT and ab initio calculation results also for the dioxirane formation <2001CPL(358)171, 2002JA2692, 2005JCP114308>. 

Yamamoto and Nakamura have reported a synthesis of rose oxide from the dimer 922 of isoprene. Prins reaction (formaldehyde) yielded the dihydropyran 923, which underwent specific ozonolysis and hydrogenation to the known (and naturally occurring) ketone 924. Conversion of the latter to rose oxide (909) is well known (Vol. 2, p. 168, Ref. 586). 

Pedersen T. and K. Sehested Rate constants and activation energies for ozonolysis of isoprene, methacrolein and methyl-vinyl-ketone in aqueous solution significance to the in-cloud ozonation of isoprene, Int. J. Chem. Kin. 33 (2001) 182-190. 

The reaction has been extended to include buta-1,3-dienes. Thus 86 affords the phosphonic dichlorides 87 (R = H or Me) (reaction carried out in benzene with decomposition of the complex by SO2), apparently confirmed through ozonolysis to give formic acid . Conflicting reports suggest that the addition to buta-1,3-diene (but not isoprene) occurs in the presence of AC2O to give (4-chlorobut-2-enyl)phosphonic dichloride, a result... 

Since ozonolysis of Gutta percha gives the same product as natural rubber, the only structural formula for Gutta percha (from our list of possibles) would be the trans isomer of natural rubber. Hence, Gutta percha is also known as poly-trans-isoprene ... 

A compound named y-terpinene, an isomer of a-terpinene, is isolated along with the a isomer from the oils of a number of plant products. Upon ozonolysis, followed by an oxidative workup, yterpinene yields two compounds, one of which is 4-methyl-3-oxopentanoic acid. The second compound is an acid which decarboxylates upon heating and gives acetone. Two structures consistent with the data are possible for yterpinene. What are they On the basis of the isoprene rule, one of them can be discarded as highly improbable. What is the structure of y-terpinene ... 

Macromolecules of CBR consist of isobutylene orders fragments (blocks) that are statistically divided by chlorine-containing isoprene units of various structure [27, 176, 262]. Under BR chlorination total unsaturation of macromolecules and especially content of internal C=C bonds are decreased that is easily defined by split ozonolysis [263]. Reaction of BR chlorination is occurred according to scheme [27,263,264] ... 

The hypothesis of partial valence gave a convenient explanation for the behavior of natural rubber. The overall formula CsHg already proposed by Faraday in 1826 pointed to one double bond per unit. Harries confirmed this conclusion by ozonolysis of natural rubber and subsequent hydrolysis of the ozonides. Since he also found Cs Hg to be the overall formula, he did not think that he would have to consider any end groups. From the observed low molar masses he concluded initially that there were rings of two isoprene units (Figure 1-2). Later, he concluded that there were five to seven isoprene units per cyclic molecule. 

Montaudo, G., Scamporrino, E., Vitalini, D., and Rapisardi, R., Fast Atom Bombardment Mass Spectrometry Analysis of the Partial Ozonolysis Products of Poly(isoprene) and Poly(chloroprene), /. Polym. Sci, Polym. Chem., 30, 525, 1992. 

Macromolecules of chlorinated BR consist of fragments of isobutylene sequences (blocks) divided by the chlorine-containing isoprene units of various structures at random [8, 25]. BR chlorination results in a decrease of the total unsaturation of the macromolecules and particularly, the content of the internal C = C bonds, which is easily determined by split ozonolysis [26]. The reaction of BR chlorination proceeds as follows (Figure 3.6) [27, 28] ... 

Table 7 Product yields in the gas-phase ozonolysis of isoprene (units are mol-% mole of product formed per mole of isoprene reacted).

This summary will indicate that, even for the simplest of the molecules, isoprene, there remain uncertainties about the degradation pathways. One problem concerns poor carbon balance in almost all of the studies of attack by OH, NO3 and O3 Another concerns the effect of humidity on product distributions. Yet a further question hangs over the significance of the ozonolysis reactions as a source of OH radicals. Almost nothing is known about the mechanisms and specific pathways of reactions of the terpenes, and there are substantial experimental obstacles to investigation of these systems. Much further work is clearly warranted, in order to determine whether ozone is only lost in its reaction with biogenic VOCs or whether the reactions might constitute a source of atmospheric ozone when NOx is present. 

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