Abstract. The atmospheric fate of a series of saturated alcohols (SAs) was
evaluated through kinetic and reaction product studies with the
main atmospheric oxidants. These SAs are alcohols that could be used as fuel
additives. Rate coefficients (in cm3 molecule−1 s−1)
measured at ∼298 K and atmospheric pressure (720±20 Torr) were
as follows: k1 ((E)-4-methylcyclohexanol + Cl) = (3.70±0.16)
×10-10, k2 ((E)-4-methylcyclohexanol + OH) = (1.87±0.14) ×10-11, k3 ((E)-4-methylcyclohexanol +
NO3) = (2.69±0.37) ×10-15, k4
(3,3-dimethyl-1-butanol + Cl) = (2.69±0.16) ×10-10, k5 (3,3-dimethyl-1-butanol + OH) = (5.33±0.16)
×10-12, k6 (3,3-dimethyl-2-butanol + Cl) = (1.21±0.07) ×10-10, and k7 (3,3-dimethyl-2-butanol +
OH) = (10.50±0.25) ×10-12. The main products
detected in the reaction of SAs with Cl atoms (in the absence/presence of
NOx), OH radicals, and NO3 radicals were (E)-4-methylcyclohexanone for the
reactions of (E)-4-methylcyclohexanol, 3,3-dimethylbutanal for the reactions
of 3,3-dimethyl-1-butanol, and 3,3-dimethyl-2-butanone for the reactions of
3,3-dimethyl-2-butanol. Other products such as formaldehyde,
2,2-dimethylpropanal, and acetone have also been identified in the reactions
of Cl atoms and OH radicals with 3,3-dimethyl-1-butanol and
3,3-dimethyl-2-butanol. In addition, the molar yields of the reaction
products were estimated. The products detected indicate a hydrogen atom
abstraction mechanism at different sites on the carbon chain of alcohol in
the case of Cl reactions and a predominant site in the case of OH and
NO3 reactions, confirming the predictions of structure–activity
relationship (SAR) methods. Tropospheric lifetimes (τ) of these SAs
have been calculated using the experimental rate coefficients. Lifetimes are
in the range of 0.6–2 d for OH reactions, 7–13 d for NO3 radical
reactions, and 1–3 months for Cl atoms. In coastal areas, the lifetime due to
the reaction with Cl decreases to hours. The calculated global tropospheric
lifetimes, and the polyfunctional compounds detected as reaction products in
this work, imply that SAs could contribute to the formation of ozone and
nitrated compounds at local, regional, and even global scales. Therefore,
the use of saturated alcohols as additives in diesel blends should be
considered with caution.
Rate Constants and Branching Ratios in the Oxidation of Aliphatic Aldehydes by OH Radicals under Atmospheric Conditions
