Rate coefficient hexene

Figure 6 Energy transfer rate coefficients from excited cyclohexane molecules to solutes as a function of the A energy difference (1) isooctane, (2) w-heptadecane, (3) cyclooctane, (4) tram-, 2-dimethylcyclohexane, (5) isopropylcyclohexane, (6) cis-l,2-dimethylcyclohexane, (7) decalin, (8) 1-decene, (9) 2-hexene, (10) tetramethylethylene, (11) benzene. (From Ref. 135.)...

Fig. 5-2. Plot of relative disappearance rates for hydrocarbons observed in smog chambers versus OH rate coefficients (in units of cm3/molecules s) from independent measurements. Key (1) n-butane, (2) isobutane, (3) n-pentane, (4) isopentane, (5) n-hexane, (6) 2-methylpen-tane, (7) 3-methylpentane, (8) cyclohexane, (9) ethane, (10) propene, (11) 1-butene, (12) isobutene, (13) ds-2-butene, (14) frans-2-butene, (15) 1-pentene, (16) methyl-l-butene, (17) cis-2-pentene, (18) 1-hexene, (19) 3,3-dimethylbutene, (20) cyclohexene, (21) toluene, (22) o-xylene, (23) m-xylene, (24) p-xylene, (25) 1,2,3-trimethylbenzene, (26) 1,2,4-trimethylben-zene, (27) 1,3,5-trimethylbenzene. Open circles from Wu el al. (1976) relative to c/s-2-butene, upper scale hatched circles from Lloyd etal. (1976) and Pitts eial. (1978) relative to n-butane, lower scale.

Acetylformoin (3-hydroxy-hexane-2,4,5-trione CH3-CO-CH(OH)-CO-CO-CH3) is a suspected major product of the OH initiated oxidation of 3-hexene-2,5-dione, itself a product of the OH initiated oxidation of p-xylene. This compound has been synthesised in its isomeric enediol form 3-hexene-3,4-diol-2,5-dione. The rate coefficients for the reaction with OH radicals was found to be (2.7 0.7) X 10 ° cm s" The residual FTIR spectrum of its OH initiated photooxidation was found to be identical to that obtained from the OH initiated oxidation of 3-hexene-2,5-dione, the major product has been tentatively identified as hexane-3,3-diol-2,4,5-trione (CH3 CO-C(OH)2-CO-CO-CH3). These results suggest that acetylformoin readily enolises and then rapidly reacts with OH radicals to give products of the type observed for the OH initiated oxidation of 3-hexene-3,4-diol-2,5-dione. 

The reactions of NO3 with hexenols have been studied by Atkinson et al. (1995) and Pfrang et al. (2006a) (table II-D-34). The rate coefficient values reported for cis-3-hexen-l-ol are in good agreement with an average value of A = 2.7 x IQ-i cm ... 

Table II-D-32. Rate coefficient (fc, cm molecule s ) for the reaction of OH with cw-3-hexen-l-ol (CH3CH2CH=CHCH2CH20H)...

The reaction of O3 with 4-hexen-3-one has been studied by Grosjean and Grosjean (1999), by monitoring O3 decay in the presence of excess ketone and an OH scavenger. Their data lead to a rate coefficient of = 6.4 x 10 cm molecule" s near 294 K see table V-E-10 for details. 

Table V-E-IO. Rate coefficients (k,cnV molecule" s" ) for reaction of O3 with 4-hexen-3-one [CH3CH2C(0)CH=CHCH3]...

OH rate coefficients have been determined for three members of this series 4-oxo-2-pentenal [CH3C(0)CH=CHCH0], 3-hexene-2,5-dione [CH3C(0)CH=CHC(0)CH3], and 3,4-dihydroxy-3-hexen-2,5-dione [CH3C(0)C(0H) (0H)C(0)CH3]. All data have been obtained using relative rate methods and are summarized in table V-E-17. Bierbach et al. (1994) determined k = 6.2x 10" cm molecule" s" for reaction of OH with a mixture of cis- and trans -oxo-2-pentenal, while Wiesen et al. (1995) report k = 2.7 X 10" cm molecule" s" for reaction of OH with 3,4-dihydroxy-3-hexen-2,5-dione. Data are available for both the cis- and truns-isomers of 3-hexene-2,5-dione (Tuazon et al., 1985 Bierbach et al., 1994). There is reasonable agreement between the two determinations, and average values of k = 7.2 x 10" cm molecule" s" and A = 5.1 x 10" cm molecule" s" are obtained for the cis- and trans- species. 

Davis, M.E., M.K. Gilles, A.R. Ravishankara, and J.B. Burkholder (2007a), Rate coefficients for the reaction of OH with (E)-2-pentenal, (E)-2-hexenal, and (E)-2-heptenal, Phys. Chem. Chem. Phys., 9, 2240-2248. 

Also from this study the difference in the rate of bromination of alkenes and alkynes is quite evident. Thus the bimolecular coefficient (k2) for styrene is 2 x 103 times that for phenylacetylene and k2 for 3-hexene is 1-4 x 105 times the value for 3-hexyne. Since the first two compounds are believed to react via carbonium ions and the latter two via bromonium ions there seems to be an extra factor of 102 in the stability of bromonium ions from alkenes relative to those from alkynes. 

In a study by Corma and coworkers, the rate of epoxidation of 1-hexene on Ti,Al-P matched, for a homogeneous series of solvents, the trend of adsorption. However, it was twice as fast in acetonitrile than in methanol, in contrast to partition coefficients which are ordered in the reverse direction [77, 167]. The relationship for cyclohexanol oxidation was more complex, the rate increasing with the polarity of aprotic solvents and decreasing with polarity increase in protic ones [77]. 

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