Ozonolysis of a-pinene

Much effort this year has been expended on chrysanthemic acid syntheses. Aratani et al. have extended earlier work on asymmetric synthesis (Vol. 6, p. 21) by decomposing various alkyl diazoacetates in 2,5-dimethylhexa-2,4-diene in the presence of chiral copper complexes to yield up to 92% of rrans-chrysanthemic acid in 88% dextrorotatory enantiomeric excess. Mitra has used ozonolysis of (+)-a-pinene to obtain, stereospecifically, the bromo-ketone (104) which undergoes Favorskii rearrangement to yield the anticipated ester (105) from which (+)-trans-chrysanthemic acid is readily obtained a second paper reports another route from (+)-car-3-ene initially to methyl (—)-c/s-chrysanthemate or to (—)-dihydro-chrysanthemolactone (106), both of which are convertible into (+)-rra s-chrysan-... 

Ozonolysis of (—)-a-pinene 146 in pentane at — 35 °C or on polyethylene at —70°C affords only epoxide 147 and its degradation products 148 and 149 but no ozonide, perhaps due to steric hindrance caused by the two geminal methyl groups <1996T14813>. 

Zhang, D., Zhang, R. Ozonolysis of a-pinene and p-pinene kinetics and mechanism. J. Chem. Phys. 122, 114308-114319 (12 pages) (2005)... 

Ozonolysis of pinenes contributes to OH radical and SOA formation. The latter has been speculated to be responsible for the formation of "blue haze". Hence, it is of vital importance to quantitatively understand the roles of ozonolysis of a- and jS-pinenes on both OH and SOA formation in the troposphere. The O3 reaction with both pinenes follows the Criegee mechanism, similar to that of iso-prene. The initial step proceeds through cycloaddition of O3 to the C=C double bond of each pinene, forming a primary ozonide (POZ). The available reaction energy is retained as the internal energy of the product, resulting in formation... 

The clue to the structure of a-pinene is the ozonolysis. Working backwards shows the alkene position. 

Warscheid B, Hoffman T. On-line measurement of a-pinene ozonolysis products using an atmospheric pressure chemical ionisation ion-trap mass spectrometer. Atmos Environ. 2001 35 2927 0. 

Ozonolysis followed by reductive workup gives a mixture of aldehydes and ketones whose structures depend on the groups bonded to the sp -hybridized carbon atoms. Thus, as a synthetic method, the process is limited by the requirement of having the appropriate aUcene. This reaction also wastes part of the starting material because usually only one of the cleavage products is desired and the two carbonyl compounds must be separated. Nevertheless, the method proves useful in specific cases, such as the oxidative cleavage of a-pinene. In this case, the methanal byproduct is a gas that escapes from solution and does not contaminate the bicyclic ketone product. 

Several reports have been received of explosion during work-up of the products obtained from ozonolysis of pinene, despite prior treatment with reducants. A safe alternative procedure is given in [3],... 

In the synthetic procedure, verbenone 118, the air oxidation product of pinene, is first treated with t-BuOK. followed by the addition of prenyl bromide to give a C-ll alkylated product. Selective ozonolysis of the more electron-rich double bond provides the aldehyde 119 with 85% yield. The A ring of taxane is then created through photorearrangement of the aldehyde 119, yielding the chrysanthenone derivative 120 (85% yield, over 94% ee). 

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>. 

Decarbonylation of the ozonolysis product of ot-pinene gives a methyl trimethylcyclobutyl ketone. Addition of acetylene to this, followed by the Carroll reaction, gives (trimethylcyclobutyl)heptadienone. The cyclobutane ring is opened by acid to give a methylated /-ionone which, on cyclization, produces irones. Once again, the Greek prefixes have the same significance as in the ionone series. 

Fig. 7-17. Compounds identified in the aerosol derived from a-pinene (a) by photooxidation in the presence of nitrogen oxides and (b) by ozonolysis yields in percent are shown in parentheses. [From Schwartz (1974) as reported by Grosjean (1977) and Hull (1981), respectively.]...

Gao, S., Keywood, M., Ng, N.L., Surratt, J., Varutbangkul, V., Bahreini, R., Flagan, R.,C., and Seinfeld, J. H. (2004b) Low-molecular-weight and oligomeric components in secondary organic aerosol from the ozonolysis of cycloalkenes and a-pinene, J. Phys. Chem. A. 108, 10147-10164. 

Either direction of cleavage of the primary ozonide from a-pinene would produce a carbonyl oxide with ten carbon atoms. Fragmentation of this intermediate might well lead to a number of hydroperoxides we could detect, but only MHP was observed from gas-phase ozonolysis. As in the case of isoprene, neutralisation of the sample from aqueous ozonolysis before analysis indicates that significant amounts of HAHPs are formed in water. These are still under investigation. 

Fig. 5 SOA mass yields from a-pinene ozonolysis vs total SOA mass (Cqa)- Increasing mass fractions with increasing Cqa are consistent with progressive partitioning of more volatile products at higher loadings, as shown...

Fig. 8 Measured AMS pToF distributions for diesel POA particles injected into a smog chamber containing SO A from a-pinene ozonolysis. POA particles are evident as a distinct mode at 180 mn for only 5 min (upper panel) after which they vanish into the SOA seeds (initially at 300 nm, ultimately at 400 nm, lower panel). Both the timing and coincident size distributions of the ultimate particle distribution confirm that mixing of POA into SOA occurred via evaporation of fresh POA and subsequent condensation and full (volume) mixing into the SOA seeds...

Fig. 10 SOA product volatility distributions for a-pinene and limonaketone in dark green and mass yields vs Cqa as dark green curve. Precursors with similar volatility, structure, and chemistry have similar yields. Product volatility distribution and yields fOTD-limonene ozonolysis are shown as light green bars and a light green curve (and gray data points). Oxidation of the additional exocyclic double bond in limonene results in substantially less volatile SOA products and correspondingly higher SOA yields...

SOA material formed by either pathway may be surface-active. For example, organic acids including c -pinonic acid, which is formed via the oxidation of the biogenic VOC a-pinene, are traditional SOA products which have been shown to be surface-active [92-96]. Alkene ozonolysis has also been shown to yield water-soluble surface-active organic compounds [97]. 

Chamber (Caltech Indoor Chamber Facility) experiments have also been carried out by Lee et al. to monitor the time evolution and yields of gas-phase VOCs produced by the ozonolysis of ten different terpenes [197] six monoterpenes (a-pinene, (3-pinene, 3-carene, terpinolene, a-terpinene and myrcene), two sesquiterpenes (a-humulene and p-caryophyllene) and two oxygenated terpenes (methyl chavicol and linalool). Several gas-phase oxidation products were identified including formaldehyde, acetaldehyde, formic acid, acetone, acetic acid, nopinone and pinonaldehyde. 

The ozonolysis of the monoterpenes, biogenic species of molecular formula CioHm (e.g., a- and /3-pinene), provides a significant source of secondary organic aerosol. A number of multi-functional organic acids, such as norpinic acid from j8-pinene ozonolysis, and pinonic acid and pinic acid from a-pinene ozonolysis, have been conclusively identified as components of the organic aerosol formed (e.g., Presto et al., 2005 and references therein). As summarized in table VI-F-1, these acidic species possess very low vapor pressures (typically < 10 " Pa at 298 K, Bilde and Pandis, 2001), and thus have a strong tendency to partition to the condensed phase, where they are removed via depositional processes. The low vapor pressures preclude any studies of their gas-phase kinetics. However, the structure-activity relations (SARs) of Kwok and Atkinson (1995) can be used to estimate rate coefficients of about (1-5) xl0 cm ... 

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