Organic Chemistry

Polar stratospheric clouds increase
the rate of ozone destruction.
These clouds form over Antarctica
during the cold winter months.
Ozone depletion in the Arctic is less
severe because it generally does not
get cold enough for the polar
stratospheric clouds to form.

NGrowth of the Antarctic ozone
hole, located mostly over the
continent of Antarctica, since 1979.
The images were made from data
supplied by total ozone-mapping
spectrometers (TOMS). The color
scale depicts the total ozone values
in Dobson units. The lowest
ozone densities are represented
by dark blue.

missing 9PYBAA

354 CHAPTER 9 Reactions of Alkanes • Radicals

THE CONCORDE AND OZONE

DEPLETION

Supersonic aircraft cruise in the lower strato-

sphere, and their jet engines convert molecular oxygen and ni-

trogen into nitrogen oxides such as NO and Like CFCs,

nitrogen oxides react with stratospheric ozone. Fortunately, the

supersonic Concorde, built jointly by England and France,

makes only a limited number of flights each week.

NO 2.

spray cans (deodorant, hair spray, etc.) because of their odorless, nontoxic, and non-

flammable properties and because they are chemically inert and thus do not react with

the contents of the can. Such use now, however, has been banned.

Chlorofluorocarbons remain very stable in the atmosphere until they reach the

stratosphere. There they encounter wavelengths of ultraviolet light that cause the ho-

molytic cleavage that generates chlorine radicals.

The chlorine radicals are the ozone-removing agents. They react with ozone to form

chlorine monoxide radicals and molecular oxygen. The chlorine monoxide radicals

then react with ozone to regenerate chlorine radicals. These two propagating steps are

repeated over and over, destroying a molecule of ozone in each step. It has been calcu-

lated that each chlorine atom destroys 100,000 ozone molecules!

Cl + O 3 ClO + O 2

ClO + O 3 Cl + 2 O 2

h

C

Cl

F

FCClCl

Cl

F

F +

Movie:

Chlorofluorocarbons

and ozone