Photolysis of Carbonyls

The photolysis of carbonyl sulfide is a laboratory method for the production of monoatomic sulfur, a short-Hved species (29). 

In this case, the grafting reactions start with the photolysis of carbonyl groups. 

The photolysis of carbonyl compounds is one of the most intensively studied areas of photochemistry. Since CIDNP studies have been concerned mostly with aldehydes and ketones we shall confine these brief introductory remarks to such compounds. More extensive reviews are available (e.g., Simons, 1971). 

It may be of interest to note that electronically excited sulfur atoms can participate in a chemical reaction to yield 1A9 sulfur molecules.34 The flash photolysis of carbonyl sulfide yields S(1/)), which reacts with more COS according to... 

Sulfur atoms are produced by photolysis of carbonyl sulfide. At low COS pressure and at high pressures of inert gas, the S(1D) atoms initially formed are collisionally deactivated to S(3P) atoms (A = 26.4 kcalmole-1) so that no insertion into C—H bonds is observed.12 Instead the S(3P) atoms add nonstereospecifically to olefins.13... 

A study of the gas phase reactions of sulfur atoms with ethylene and propylene lias been recently carried out by Strausz and Gunning (98). Atomic sulfur, presumably in the (lD) metastable state, was generated by photolysis of carbonyl sulfide in the wavelength region 2550-2290 A., and the study was restricted to 25°C. Pure carbonyl sulfide yields carbon monoxide and sulfur as the main products. When ethylene and propylene are added, the carbon monoxide yield is decreased, tending to a value one half as large as in the absence of the olefins. Cyclic sulfides are simultaneously formed by addition of S atoms to the two olefins. The mechanism which accounts for the main features of the process is... 

It is important to understand the sources and loss mechanisms of stratospheric sulfate aerosols. These aerosols are linked to the decrease in ozone at mid-latitudes because they hydrolyse N2O5, reducing the amount of NOx that would otherwise limit the efficiency of chlorine-catalysed ozone depletion. In addition these aerosols scatter light, cooling the planet [127]. Their concentration increases dramatically following major volcanic eruptions however they are always present at background levels. The source of these background aerosols is a matter of debate. In 1976 Paul Crutzen presented the idea that sulfate aerosols result from the photolysis of carbonyl sulphide [128] ... 

In almost all of the gas-phase kinetic-mechanistic studies on sulfur atom reactions made to date, the source has been the in situ photolysis of carbonyl sulfide (COS). The reasons for this choice are not far to seek. Carbonyl sulfide is a stable, readily available gas. Its absorption spectrum is located in a convenient spectral region and the carbon monoxide formed in the photodissociation provides an excellent internal monitor for sulfur atom production. 

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