Chemistry Reference
In-Depth Information
hν
hν
UV light
hν
2
NO
2
CHO
light
dark
O
N
O
NO
2
R
R
Many other examples can be found in the literature. Most familiar isomerization reaction is that of
trans
-stilbene to
cis
-stilbene, shown above. It was observed that the quantum yield of stilbene
cis-
trans
isomerization decreased with an increase in viscosity of the medium [
89
]. In addition, it was
also found that in a polymeric matrix, the photo-isomerization is not inhibited, provided that it occurs
above the glass transition temperature of the polymer. An example of a fragmentation of a molecule is
the decomposition of disulfides upon irradiation with ultraviolet light of the appropriate wavelength:
hν
2
S
S
S
The same reaction takes place in peroxides. Ketones and aldehydes cleave by the mechanism of
the Norrish reaction.
