Photolysis of heptanal.

Photolysis of heptanal is investigated from an experimental and theoretical point of view. Photoexcited heptanal is believed to undergo rapid intersystem crossing to the triplet manifold and from there undergoes internal H-abstraction to form biradical intermediates. The favored gamma-H abstraction pathway can cyclize or cleave to 1-pentene and hydroxyethene, which tautomerizes to acetaldehyde.

Photochemical sources of organic acids. 2. Formation of C5-C9 carboxylic acids from alkene ozonolysis under dry and humid conditions.

The dependence of organic acid generation by alkene ozonolysis on relative humidity, thermalized Criegee intermediate scavengers, and alkene structure is investigated. Carboxylic acids generated from the ozonolysis of 1-hexene, 1-octene, 1-decene, trans-3-octene, and 1-methylcyclohexene were analyzed as trimethylsilyl (TMS) derivatives. Experiments were performed under dry (relative humidity (RH) < 1%) and humid (RH = 65%) conditions with cyclohexane or n-butyl ether as an OH scavenger.

Photochemical sources of organic acids. 1. Reaction of ozone with isoprene, propene, and 2-butenes under dry and humid conditions using SPME.

Formation of C4 and smaller carboxylic acids from gas-phase ozonolysis of several alkenes under dry (relative humidity (RH) < 1%) and humid (RH = 65%) conditions have been investigated. We have developed a technique based on solid-phase microextraction (SPME) and gas chromatography/mass spectrometry (GC/MS) to quantify the acids, as well as other products, and applied it to the reactions of ozone with propene, trans-2-butene, 2,3-dimethyl-2-butene, and isoprene. Acetic acid yields from propene and trans-2-butene ozonolysis in the presence of an OH scavenger were 2.